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THE PERFORMANCE OF NATURAL AND SYNTHETIC FIBERS IN LOW STRENGTH
MORTAR: A PILOT STUDY OF SIX SELECTED FIBERS.
By
FELICITY AKU AMEZUGBE
A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN BUILDING CONSTRUCTION
UNIVERSITY OF FLORIDA
2013
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© 2013 Felicity Aku Amezugbe
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To my parents, husband, advisors and family
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ACKNOWLEDGMENTS
First of all, I give thanks to the Almighty God for giving me life and strength to
carry out this study. I acknowledge the support of National Science Foundation (NSF)
Civil, Mechanical and Manufacturing Innovation (CMMI) Hazards Mitigation and
Structural Engineering through a collaborative research award - “Resilient and
Sustainable Engineered Fiber-Reinforced Earthen Masonry for High Wind Regions”
(Project Number: 1131175). Sincere appreciation goes to my mentor, advisor and thesis
committee chair; Dr. Esther Obonyo for her guidance during the entire project. Special
thanks go out to my committee members; Dr. Ian Flood and Dr. Chris Ferraro for their
guidance and support. My gratitude goes to Peter Donkor for his help during the project
especially during the making and testing of the entire mortar specimen and also to
Malarvizhi Baskaran for her support during this project. I also wish to thank all the
faculty members and staff of the Rinker School of Building Construction, University of
Florida.
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TABLE OF CONTENTS
page
ACKNOWLEDGMENTS .................................................................................................. 4
LIST OF TABLES ............................................................................................................ 8
LIST OF FIGURES .......................................................................................................... 9
LIST OF ABBREVIATIONS ........................................................................................... 12
ABSTRACT ................................................................................................................... 13
CHAPTER
1 INTRODUCTION .................................................................................................... 15
Background ............................................................................................................. 15 Statement of Problem ............................................................................................. 15 Aims and Objectives of Study ................................................................................. 16
Justification of Study ............................................................................................... 16 Outline of the Thesis ............................................................................................... 17
2 LITERATURE REVIEW .......................................................................................... 18
Overview ................................................................................................................. 18
Mortar ..................................................................................................................... 19 Uses of Mortar .................................................................................................. 21 Mortar and Compatibility................................................................................... 21
Mortar Mix Types .............................................................................................. 22 Mortar Mix Type M ..................................................................................... 22
Mortar Mix Type S ...................................................................................... 23 Mortar Mix Type N ..................................................................................... 23 Mortar Mix Type O ..................................................................................... 23
Fiber for Construction Applications ......................................................................... 24 Natural Fiber ........................................................................................................... 24
Coconut Fiber ................................................................................................... 25 Sisal Fiber ........................................................................................................ 26
Synthetic Fiber ........................................................................................................ 27 Recycled Polyethylene Terephthalate (PET) Fiber ........................................... 27 Polypropylene Fiber Strands ............................................................................ 28 Engineered Microfiber ...................................................................................... 29 Synthetic Hair Fiber .......................................................................................... 30
Discussion .............................................................................................................. 30 Fibers in Cement Based Materials .......................................................................... 31
Fiber Reinforced Mortar.................................................................................... 31
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Fiber Reinforced Concrete ............................................................................... 34
3 RESEARCH METHODOLOGY ............................................................................... 36
Research Approach ................................................................................................ 36
Experimental Approach........................................................................................... 36 Experimental Data Entry ......................................................................................... 37
Mortar Types .................................................................................................... 37 Mix Design ........................................................................................................ 38
Mortar Testing ......................................................................................................... 38
American Society for Testing and Materials (ASTM) C39: Compressive Strength of Cylindrical Concrete Specimens ................................................. 38
ASTM C496: Splitting Tensile Strength of Cylindrical Concrete Specimens .... 41 Materials for Mortar ................................................................................................. 43
Portland Cement .............................................................................................. 43 Fine Aggregates ............................................................................................... 43
Water ................................................................................................................ 44 Fiber Types ...................................................................................................... 45
Mix Design .............................................................................................................. 45 Nominal Lengths of Fibers ...................................................................................... 47 Hand Mixing ............................................................................................................ 47
Cylinder Casting Procedure .................................................................................... 50
4 RESULTS AND DISCUSSION ............................................................................... 52
Compressive Test ................................................................................................... 52 Tensile Test ............................................................................................................ 54
Compressive Strength Test .................................................................................... 56 Tensile Strength Test .............................................................................................. 58 Comparison of Compressive and Tensile Strength ................................................. 60
5 CONCLUSION AND RECOMMENDATIONS ......................................................... 63
Overview ................................................................................................................. 63
Summary of Main Findings ..................................................................................... 63 Conclusions ............................................................................................................ 64 Recommendations for Further Research ................................................................ 64
APPENDIX
A MORTAR PREPARATION ...................................................................................... 66
B WEIGHT OF MORTAR SPECIMEN ....................................................................... 67
C COMPRESSIVE TESTS ......................................................................................... 68
D TENSILE TESTS .................................................................................................... 70
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LIST OF REFERENCES ............................................................................................... 71
BIOGRAPHICAL SKETCH ............................................................................................ 75
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LIST OF TABLES
Table page 3-1 ASTM Minimum Compressive Mortar Strength .................................................. 37
3-2 Proportions specification using masonry cement based on ASTM C270 ........... 38
3-3 Mix Design by Percentage .................................................................................. 46
3-4 Mix Design in Weight .......................................................................................... 46
4-1 Compressive Maximum Load (lbs.) .................................................................... 52
4-2 Compressive Test Maximum psi ......................................................................... 53
4-3 Tensile Maximum Load (lbs.).............................................................................. 54
4-4 Tensile Test Maximum psi .................................................................................. 55
4-5 Percentage Change from Controlled Specimen ................................................. 57
4-6 Percentage Change from Controlled Specimen ................................................. 59
4-7 Percentage Change between Compressive and Tensile Test of Mortar Specimen ........................................................................................................... 61
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LIST OF FIGURES
Figure page 2-1 Illustration of different sizes of fibers on crack bridging. (Betterman et al
2004). ................................................................................................................. 18
2-2 Slump of Concrete, Mortar and Grout (Masonry Advisory Council 2012) ........... 20
2-3 Variation of the workability with mixing time (mortar of the same initial workability). (Bartos 1993) .................................................................................. 21
2-4 Typical stress-strain with a 2 percent fiber........................................................ 24
2-5 Coconut Fiber ..................................................................................................... 26
2-6 Sisal Fiber........................................................................................................... 26
2-7 Recycled PET Rope ........................................................................................... 28
2-8 Shredded Recycled PET Fiber ........................................................................... 28
2-9 Polypropylene fiber strands ................................................................................ 29
2-10 Engineered Microfiber ........................................................................................ 29
2-11 Synthetic Hair Fiber ............................................................................................ 30
2-12 Typical effect of fiber addition in concrete. ......................................................... 35
3-1 Sketch showing typical failure modes of compression testing: (a) splitting; (b) shear (cone); and (c) splitting and shear ............................................................ 39
3-2 Schematic diagram for conducting compressive strength .................................. 40
3-3 Hardened mortar specimen failure in the compression machine after destructive testing. .............................................................................................. 40
3-4 Schematic diagram for conducting tensile strength ............................................ 41
3-5 Hardened mortar specimen failure in the compression machine before tensile strength testing. .................................................................................................. 42
3-6 3x6" Cylinder Mold.............................................................................................. 42
3-7 Cement ............................................................................................................... 43
3-8 Sieved Fine Aggregates ..................................................................................... 44
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3-9 Water .................................................................................................................. 44
3-10 A: Coconut fiber, B: Sisal fiber, C: Synthetic hair, D: Polypropylene Strands ..... 46
3-11 Nominal Lengths of Fibers (A) Coconut fiber, (B) Sisal Fiber, (C)Synthetic Hair Fiber, (D) Polypropylene Fiber, (E) Recycled PET Fiber, (F) Engineered Micro Fiber.......................................................................................................... 47
3-12 Hand Mixing of Mortar ........................................................................................ 48
3-13 Filling of mortar in Cylinder molds ...................................................................... 48
3-14 Fresh mortar in cylinder molds ........................................................................... 48
3-15 Set Mortar in Cylinders molds............................................................................. 49
3-16 Stripping of cylinder molds from the set mortars. ................................................ 49
3-17 Stripping Rod ...................................................................................................... 49
3-18 Cylinder casting procedure ................................................................................. 50
3-19 Set mortar specimen. (A) Recycled PET Fiber, (B) Controlled Specimen (No Fiber), (C) Coconut Fiber, (D) Micro Fiber, (E) Synthetic Hair Fiber, (F) Sisal Fiber (G) Polypropylene Fiber. ........................................................................... 51
4-1 Compressive Test Result ................................................................................... 53
4-2 Average Compressive Test Result ..................................................................... 54
4-3 Tensile Test Result ............................................................................................. 55
4-4 Average Tensile Test Result............................................................................... 56
4-5 Compressive Strength in order of performance .................................................. 57
4-6 Compressive Test Percentage Change from Controlled Specimen .................... 58
4-7 Tensile Strength in order of performance ........................................................... 59
4-8 Tensile Test Percentage Change from Controlled Specimen ............................. 60
4-9 Comparison of Compressive and Tensile Strength ............................................ 61
4-10 Percentage Change between Compressive and Tensile Test of Mortar Specimen ........................................................................................................... 62
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A-1 Mortar Preparation Process A: Fiber Types, B: PET Fiber Mix, C: Sisal Fiber Mix, D: Synthetic Hair Fiber Mix, E: Coconut Fiber Mix and F: Polypropylene Fiber Mix ............................................................................................................. 66
B-1 Weight of Mortar Specimen with. A: Recycled PET Fiber, B: Control Specimen ( No Fiber, C: Polypropylene Fiber, D: Coconut Fiber, E: Synthetic Hair Fiber and D: Sisal Fiber. ............................................................................. 67
C-1 Failures in Mortar after Compressive Test in A: Controlled Specimen, B: Micro Fiber, C: Polypropylene Fiber and D: Synthetic Hair Fiber ....................... 68
C-2 Failures in Mortar after Compressive Test in a: Recycled PET Fiber, B: Controlled Sample (No Fiber), C: Recycled PET Fiber and d: Sisal Fiber .......... 69
D-1 Failures in mortar after tensile test in A, B and C: Polypropylene Fiber and D: Synthetic Hair fiber ......................................................................................... 70
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LIST OF ABBREVIATIONS
ASTM American Society for Testing and Materials
FA Fly Ash
FRC Fiber Reinforced Concrete
FRM Fiber Reinforced Mortar
FRP Fiber Reinforced Polymer
GFRM Glass Fiber Reinforced Mortar
GFRP Glass Fiber Reinforced Polymer
HPFRC High-Performance Fiber-Reinforced Concrete
HCP High-Performance Concrete
lbs. Pounds
IYNF International Year of Natural Fiber
MK Metakaolin
PET Polyethylene Terephthalate
PVA Polyvinyl Alcohol
Psi Pound per square inch
SIFCON Slurry Infiltrated Fiber Concrete
SF Silica Fume
SFRC Steel Fiber Reinforced Concrete
Vf Volume fraction
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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science in Building Construction
THE PERFORMANCE OF NATURAL AND SYNTHETIC FIBERS IN LOW STRENGTH MORTAR: A PILOT STUDY OF SIX SELECTED FIBERS.
By
Felicity Aku Amezugbe
May 2013
Chair: Esther Obonyo Cochair: Ian Flood Major: Building Construction
In recent years, option of using fibers in mortar and other cementitious materials
has become a growing trend. Several types of fibers have been added to mortar to
improve its mechanical properties. There are other types of fibers which have not been
explored in this respect. This pilot study explored the use of six different types of fibers
and a control sample in mortar to assess the fiber’s impact on compression and tension.
The objective of this research was to experimentally and theoretically quantify
and compare the strength of mortars which contain recycled Polyethylene Terephthalate
(PET) fiber, polypropylene fiber strands, coconut fiber, sisal fiber, synthetic hair fiber,
engineered microfiber and unreinforced fiber in low strength mortar.
This research was performed in phases;
Conducting a literature review of published studies that relate to fiber additions in mortar.
Analyzing the advantages and disadvantages of using recycled PET fiber, polypropylene fiber strands, coconut fiber, sisal fiber, and synthetic hair fiber in mortar.
Developing a mortar mix design enhanced through the addition of recycled PET fibers, coconut fibers and engineered microfibers.
Quantifying the enhancement in compressive and tensile strength in the various fibers.
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Analyzing the difference in performance of the fiber types in the mortar specimen.
Forty two mortar mixes were designed and made using the various types of
fibers and controlled specimen. Compressive and tensile strength (psi) tests were
performed on the samples. Their strengths were compared and analyzed. The
compressive test results showed polypropylene fiber performing best with 798 psi and
least performed is the controlled specimen with no fiber with 516 psi. The tensile test
results showed polypropylene fiber performing best with 848 psi and least performed is
the controlled specimen with no fiber with 340 psi. There was significant difference
between the synthetic polypropylene fiber and the non-fiber mortar. It performed almost
150% better than the controlled non-fiber mortar.
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CHAPTER 1 INTRODUCTION
Background
Sustainability issues have become prevalent in the past years especially in
sustainable construction practices. There has been some substantial effort to educate
the public on its importance in both the long and short run. Sustainable construction
practices are both ecologically friendly and are also cost efficient as they are often
based on the use of locally available materials. Sustainable construction practices
include the use of green materials such as compressed earth bricks. The rising demand
in energy consumption coupled with concerns over the greenhouse effect has driven the
construction industry to substitute conventional construction approaches through using
alternate approaches, sources and structural systems (Silva et al 2008).
There are some concerns over the mechanical properties of non-conventional
approaches which have resulted in a growing interest in modifying the compositions of
such materials. This pilot study leverages on an NSF funded project directed at
engineering fiber-reinforced earthen masonry for resistance to high winds. The scope of
this study will be limited to the fiber options for mortar. Natural and synthetic fibers can
be an effective way to improving the performance of masonry. For example, Oliverira
(2010) observed that addition of PET fibers to mortar mixes controlled plastic shrinkage
cracking.
Statement of Problem
The feasibility of using selected fibers will be investigated in mortar. The
fundamental rule is that mortar should have strength and movement characteristics that
are compatible with the masonry unit. This implies that the standard mortar (for
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example, Class N) is may be too strong for most compressed earthen masonry units.
Earthen masonry is brittle. The ideal mortar for earthen mortar should be compatible to
form a composite unit that will behave desirably within a walling system. Compressed
blocks for the study are at least 300 psi– 600 psi therefore the ideal mortar in addition to
being equally brittle should have compressive strength values in that range.
Aims and Objectives of Study
The aim of this research was to theoretically and experimentally quantify and
compare the performance to compare the performance of natural and synthetic fibers in
low strength mortar using easily accessible fibers like recycled PET fiber, coconut fiber,
sisal fiber, synthetic hair fiber, engineered microfiber and polypropylene fiber strands.
This research is performed in phases;
Conducting a literature review of published studies that relate to fiber additions in mortar.
Analyzing the advantages and disadvantages of using natural and synthetic fibers in mortar.
Developing a mortar mix design enhanced through the addition of recycled PET fibers, coconut fibers and engineered microfibers.
Quantifying and analyzing the enhancement in compressive and tensile strength in the various fibers.
Analyze the difference in performance of the fiber types in the mortar specimen.
Justification of Study
This research will contribute to efforts directed at advancing scientific knowledge
with respect to using natural and synthetic fibers in earthen masonry construction.
The fiber addition in mortars has been used to control plastic shrinkage cracking, therefore, it will be an option to explore the use of recycled PET fiber, polypropylene fiber strands, coconut fiber, sisal fiber and synthetic hair fiber as additional constituents for mortar.
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For the past four decades, plastic wastes have become a canker in most areas especially in developing countries. As part of this research, being able to use recycled PET fibers in mortar will go a long way to manage the waste and at the same time increase its use as a construction material.
The use of natural fibers such as coconut fibers will increase the awareness of its importance and provide employment for people in areas where they are produced.
The cost and non-availability of engineered microfibers in less endowed or low income regions has also been a motivation to conduct this research so that the micro fibers can be substituted for readily available and inexpensive recycled PET fibers and coconut fibers especially in those low income regions.
Outline of the Thesis
The study is organized in five chapters.
Chapter 1 – Introduction: This essentially includes a background of the study,
problems statement, aim of the study and objectives towards achieving aim.
Chapter 2 - Literature Review: This chapter seeks to inform on previous and
other well-known research conducted in natural and synthetic fibers in cementitious
materials such as mortar and concrete.
Chapter 3 – Research Methodology: The methods of data collection for analysis
will be treated into details in this section.
Chapter 4 – Results and Discussion: This chapter provides the results of the
laboratory experiments performed on the mortar specimens with respect to compressive
and tensile strength.
Chapter 5 –Conclusion and Recommendations: This section analyzes the
laboratory results and provides a conclusion of the research and results. Further
research studies will be discussed in this section.
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CHAPTER 2 LITERATURE REVIEW
Overview
In addition to providing background information on mortar, this chapter reviews
information on previous and well known studies that relate to using synthetic and natural
fibers as construction materials, their effects in mortar and concrete.
According to Betterman et al (1994), the interest in the use of microfibers in
cement based materials is motivated by the effect of fiber dimensions on the tensile
properties of composite materials. That research also concluded that microfibers can
significantly enhance the tensile strength of the composite as illustrated in Figure 2-1.
Figure 2-1. Illustration of different sizes of fibers on crack bridging. (Betterman et al
2004).
According to Silver (2004), in order to improve mortars and concrete behavior,
the fibers must be easily dispersed in the mixture, have suitable mechanical properties
and durable in highly alkaline cement matrix. In general, fiber length used in the
concrete and mortar production varies from 0.25 to 2.5 inches (American Concrete
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Institute (ACI) Guide for Specifying, Proportioning, and Production of Fiber-Reinforced
Concrete 2008). By combining fibers of varying sizes into a matrix, improvement in both
the peak and post peak toughening can be expected (Betterman et al 1994).
Ochi et al (2007) raised a problem with the mixing of PET fiber with mortar. This
research investigated both the hand mixing and machine mixing. Oliveira and Castro-
Gomes (2010) developed an experimental study with a typical render mortar mix
proportion by volume of 1:1:6 cement, hydrated lime and natural sand. The research
introduced different volumes of fibers; 0%, 0.5%, 1.0% and 1.5% into dry mortar and
after hand mixing and careful observation, neither fiber balling nor any abnormalities
were observed.
Mortar
Mortar is an applicable paste used to hold together blocks or bricks. Mortars are
usually cement and sand with either lime or a plasticizer added to improve workability.
In recent years, new types of mortars have been developed including thin bed mortars
for use with accurately dimensioned units and mortars with improved thermal properties
(Hendry 2001). The first mortars were made from mud or clay. These materials were
used because of availability and low cost. The Egyptians utilized gypsum mortars to
lubricate the beds of large stones when they were being moved into position (McKee
1973).
In a majority of masonry formulations, Ordinary Portland Cement (OPC) is the
principal binding agent (Bediako et al 2011). Mortars are often ordered based on
compressive strength; but even more important properties are bond strength and
flexibility (Rodriguez 2012). Even though mortar makes up as little as seven percent of
the total volume of a masonry wall, it plays a crucial role in the performance of the
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structure. It not only bonds the individual units together, but also seals the building
against moisture and air penetration. It is critical to appreciate mortar’s properties and
how the ingredients in mortar affect performance. Three important properties of mortar
are workability, bond and compressive strength (Masonry Advisory Council 2012).
Mortar usually has a slump of between five inches to eight inches as illustrated in Figure
2-2.
Figure 2-2. Slump of Concrete, Mortar and Grout (Masonry Advisory Council 2012)
The amount of fibers added to a mortar mix is measured as a percentage of the
total volume of the composite (mortar and fibers) termed volume fraction (Vf). Vf typically
ranges from 0.1 to 3% (Mishra 2012). The volume of fiber added to the mortar affect the
slump of the mortar. Figure 2-3 shows an example of varying volume of fiber added to
mortar and the workability with mixing time.
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Figure 2-3. Variation of the workability with mixing time (mortar of the same initial
workability). (Bartos 1993)
Uses of Mortar
Mortar is used for the following;
To bind masonry units like stones, bricks and hollow cement blocks.
To give impervious surface to roof slabs and walls (plastering).
To give neat finishing to concrete works.
For pointing masonry joints.
For preparing hollow blocks.
As a filler material in ferro-cement works.
(Bhavikatti 2010)
Mortar and Compatibility
As previously indicated, a key goal for this study was ensuring that the fiber-
reinforced mortar is compatible to the masonry units. Compatibility is a primary goal in
mortar for historic masonry retrofitting. Faria (2004) described and analyzed the results
of an experimental study with ten formulations of current mortars - including some that
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can hardly be considered as adequate conservation procedures - allowing a direct
comparison in terms of some of the most relevant characteristics. The design of a
compatible repair mortar is also dependent on the functional role it performs within the
structure, which should be considered as a whole. Functional requirements derived from
the role or the function of the mortars in the masonry element and the role of the
masonry element in the building (Balen et al 2005) are listed below.
Mortar Mix Types
There are many types of mortar mixes. Mortar mix types are classified based on
their compressive and bonding properties and flexibility. These are three very important
characteristics of mortars, because they hold and provide the strength on masonry
units. Mortars are often ordered based on compressive strength; but even more
important properties are bond strength and flexibility. Choosing a mortar mix will be
based on its use, adhesion and sealing requirements.
Mortar Mix Type M
Type M mortar mix has the highest amount of Portland cement and it is
recommended primarily for walls bearing heavy loads. Type M mortar mix is used
primarily for heavy loads, masonry below grade, foundations, retaining walls and
driveways. Mortar mix type M will provide with at least 2,500 pound per square inch
compressive strength. A type M mortar with its high strength yet poor adhesion and
sealing can be a bad choice for one area of the job and just what is needed in another.
Type M is preferred with stone because the strength of the mortar simulated that of the
stone being used.
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Mortar Mix Type S
Offering a high compressive strength over 1800 psi, and with high tensile bond
strength, mortar mix type S is the ideal product to be used in masonry at or below
grade. It performs extremely well to fight soil pressure, wind or under seismic
conditions. This mortar mix can be used for below grade areas, for example masonry
foundations, manholes, retaining walls, sewers, and brick patios and brick pavements.
Type S mortars are required to have a minimum of 1800 psi and their mixes usually give
you strengths of from 2300 to 3000 psi.
Mortar Mix Type N
A mortar mix type N is usually recommended on exterior and above-grade walls
that are exposed to severe weather and high heat. Type N mortar mix has a medium
compressive strength and it is composed of 1 part Portland cement, 1 part lime and 6
parts sand. A type N mortar is described as a general purpose mortar mix, used in
above grade, exterior and interior load-bearing installations. It is also the preferred
mortar mix for soft stone masonry. This is the mortar most often used by home owners.
Type N mortar typically achieves 28 day strength in the range between 1500 and 2400
psi.
Mortar Mix Type O
Mortar mix type O is referred as that mix with a low compressive strength, about
350 psi, used on interior or non-load –bearing walls. Its exterior use should be limited
due to its low structural capacity. In the appendix for ASTM C 270, Type O mortar is
listed as an alternative to Type N for areas exposed to freezing. Type O Mortar mix is
ideal when repointing due to its consistency and can be applied easily. . It is used in
above grade, non-load bearing situations in both interior and exterior environments.
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Type O mortar provides a psi in the range between 750 and 1200, sometimes up to
2000 (Rodriguez 2012).
Fiber for Construction Applications
The first laboratory results were presented by Betterman et al. (1995) about
microfiber reinforced mortar. The results of the tests showed that there was significant
tensile strength with two combinations of fiber, i.e. 4 mm (0.16”) and 12 mm (0.47”) long
as per Figure 2-4.
Figure 2-4. Typical stress-strain with a 2 percent fiber.
Natural Fiber
The United Nations General Assembly declared 2009 as the International Year of
Natural Fiber (IYNF). The IYNF came together to emphasis the positive qualities of
natural fibers, raise awareness and stimulate demand for natural fibers, to encourage
appropriate policy responses from governments to the problems faced by natural fiber
industries, to foster an effective and enduring international partnership among the
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various natural fibers industries; and to promote the efficiency and sustainability of the
natural fibers industries.
According to official website of International Year for Natural Fibers (2009),
approximately, 500,000 tons of coconut fibers are produced annually worldwide, mainly
in India and Sri Lanka. Its total value is estimated at $100 million. India and Sri Lanka
are also the main exporters, followed by Thailand, Vietnam, the Philippines and
Indonesia. Around half of the coconut fibers produced is exported in the form of raw
fiber” (Majid 2010). “New environmental legislation as well as consumer pressure has
forced the manufacturing industries to search for new materials that can substitute for
conventional non-renewable reinforcing material materials, such as carbon or glass
fibers. On account of this, coconut and oil palm have attracted scientists and
technologist for applications in consumer goods, low-cost housing and other structures”
(Justiz-Smith et al 2008). The subsequent paragraphs will focus on coconut and sisal
fibers which were identified for this study as examples of readily accessible natural fiber
options.
Coconut Fiber
Coconut fiber is one of the natural fibers abundantly available in tropical regions,
and is extracted from the husk of coconut fruit. Coconut fibers reinforced composites
have been used as cheap and durable non-structural elements (Majid 2010). A matured
tree can produce 50 to 100 coconuts per year. Coconut fibers measure up to 35 cm
(13.8 inches) in length with a diameter of 12-25 microns. There are two types of
coconut: brown fiber as shown in Figure 2-4, which is obtained from mature coconuts,
and finer white fiber, which is extracted from immature green coconuts.
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Figure 2-5. Coconut Fiber
Sisal Fiber
Sisal fiber is obtained from agave sisalana, a native plant of Mexico. The hardy
plant grows well in a variety of hot climates, including dry areas which are unsuitable for
other crops. After harvest, its leaves are cut and crushed in order to separate the pulp
from the fibers. The average yield of dried fibers is about 1 ton per hectare, although
yields in East Africa reach 2.5 tons. Sisal is used in twine and ropes, but competition
from polypropylene has weakened demand. It is used as reinforcement in plastic
composite materials. World production of sisal and a similar agave fiber, henequen, is
estimated at around 300 000 tons, valued at $75 million. The major producers are Brazil
(120,000 tons), Tanzania (30,000 tons) and Kenya (25,000 tons).
Figure 2-6. Sisal Fiber
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Synthetic Fiber
Synthetic fibers are fibers created from chemical processes- usually through
extrusions; and they account for about half of all fiber usage with applications in every
field. According to the American Concrete Institute (ACI) report on the Physical
Properties and Durability of Fiber-Reinforced Concrete (2010), the use of fibers in
concrete to improve pre-cracking and post-cracking behavior has gained popularity.
Since 1967, several different fiber types and materials have been successfully used in
concrete to improve its physical properties and durability. The ACI (2010) also reported
on other research results showing the ability of fibers to improve durability and physical
properties of concrete and mortar. The subsequent paragraphs identified some feasible
options.
Recycled Polyethylene Terephthalate (PET) Fiber
In the United States, 80% of post-consumer plastics waste is sent to the landfill,
eight percent is incinerated and only seven percent is recycled (Environmental
Protection Agency (EPA) 2003). Brazil consumes 471 kilotons of PET and only 55.6%
of that is recycled, which makes Brazil one of the largest PET recyclers in the world and
the most effective in finding applications for the recycled material (Reis and Carneiro
2011). In 2010, it was reported that PET bottles were produced about 150,000 tons in
Turkey. Due to the rapid increase on the use of PET bottles, solid waste problem is on
the raise. In order to find a solution to this problem, some works on the re-using of PET
wastes have been accelerated (Akcaozoglu and Atis 2011).
The current worldwide production of PET exceeds 6.7 million tons per year and
shows a dramatic increase in the Asian region due to recent increasing demands in
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China and India. In Korea, the production of PET bottles has grown to 130,000 tons per
year (Kim et al 2009).
PET does not create a direct hazard to the environment, but due to its
substantial fraction by volume in the waste stream and its high resistance to the
atmospheric and biological agents, it is seen as a noxious material (Reis and Carneiro
2011).
Figure 2-7. Recycled PET Rope
Figure 2-8. Shredded Recycled PET Fiber
Polypropylene Fiber Strands
Synthetic fibers show most success in practical applications and experiments
since they have qualities that other fibers do not, for example; they are chemically inert;
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do not corrode; allow easy jetting of the concrete; are lighter than steel fibers of the
same number and allow a better control of the plastic shrinkage cracking (Foti 2011).
Of the synthetic fibers available in the United States, polypropylene is the most widely
used in ready mixed concrete and mortar. Polypropylene fibers are hydrophobic, so
they don’t absorb water and have no effect on concrete mixing water requirements.
Figure 2-9. Polypropylene fiber strands
Engineered Microfiber
The industry accepted microfiber will be acquired from the manufacturing
industry. The fibers come will come in specified lengths. The nominal length of the
engineered micro fiber is 0.5 inches. Figure 2-9 shows a sample of the engineered
microfiber.
Figure 2-10. Engineered Microfiber
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Synthetic Hair Fiber
Synthetic fibers are used in most of the research on masonry reinforcement, but
the synthetic fibers are only available to a limited extent and moreover cost-intensive.
Hairs are used as a fiber reinforcing material in concrete to study its effects on the
compressive, crushing, flexural strength and cracking control to economize concrete
and to reduce environmental problems created by the decomposition of hair. Hair is
used as a fiber reinforcing material in concrete for the following reasons:
1. It has a high tensile strength which is equal to that of a copper wire with similar diameter.
2. Hair, a non-degradable matter is creating an environmental problem so its use as a fiber reinforcing material can minimize the problem.
3. It is also available in abundance and at a very low cost.
4. It reinforces the mortar and prevents it from spalling. Human hair is strong in tension; hence it can be used as a fiber reinforcement material. (Jain and Kothari 2011).
Figure 2-11. Synthetic Hair Fiber
Discussion
Two main benefits of fiber for this study are;
To control plastic shrinkage cracking in mortar.
To make mortars compatible with compressed blocks in order to form a composite unit.
31
As previously stated, mortar must be compatible with the masonry units in
question. For this project the masonry units are fiber-reinforced compressed earth
blocks. Based on the foregoing, both natural and synthetic fibers can be feasible options
for enhancing the performance of mortar for use in compressed earthen masonry. A
comparative analysis of recycled PET fiber, coconut fiber, sisal fiber, synthetic hair fiber,
engineered microfiber and polypropylene fiber strands was done through the
experimental work discussed in the subsequent sections.
Fibers in Cement Based Materials
Fiber Reinforced Mortar
In Armwood et al 2008, the authors used two types of fibers polyvinyl alcohol
(PVA) fibers and novel organic fibers, such as corn silks with several specimens with
different type, size and volume fraction of fibers and tested for compression and flexure.
When compared to the plain mortar, the FRMs both increased and decreased in
compressive strength. The inclusion of fibers does not prevent the mortar from reaching
the specified minimum strength of 750 psi for the ASTM C270 Type N mortar. They
concluded that the addition of fibers to the mortar did not significantly affect
compressive strength but corn fiber showed a surprising increase in bond strength.
Skourup and Erdogmus (2009) studied the various FRM mixtures using polyvinyl
alcohol (PVA) fibers and FRM-clay unit prisms. The FRMs used were developed
specifically for masonry applications such as the rehabilitation, reconstruction, and
strengthening of existing masonry structures; therefore, mixtures with low compressive
strength and high ductility were desired. Results showed that increased toughness,
ductility, and energy absorption can be achieved using FRMs in masonry joints without
significantly altering the compressive capacity or aesthetics of the structure.
32
Youjiang et al 1989 reported on an experimental study of synthetic fiber
reinforced mortar. The fibers used included aramid, high-strength high-modulus
polyethylene and polypropylene, and they were randomly mixed in the matrix at volume
fractions below 3%. Concrete, a heavily used construction material has low tensile
strength and low toughness. Their research demonstrated that fiber reinforcement at
low fiber volume fractions can significantly improve the tensile behavior of concrete.
Tensile properties of the composites were measured by the direct tensile test under
both monotonic and cyclic loading.
An article by Parto and Kalantari (2012), described a laboratory study on the
compressive strength of windblown sand by stabilizing it with ordinary Portland cement
(OPC) and polypropylene fibers (PPF).The results showed that when polypropylene
fibers are mixed in windblown sand-cement mortar, they will be evenly distributed in a
matrix, relax the stress concentrations around crack tips, prevent crack expansion and
enhance windblown sand-cement mortar mechanical properties, moreover, the inclusion
of polypropylene fiber reinforcement within windblown sand-cement mortar could
increase the compressive strength of cement mortar; however utilizing high content of
fiber (beyond 0.2 %) has no positive effect on compressive strength.
De Gutiérrez et al 2005, conducted a research to determine the effect of
pozzolans such as silica fume (SF), fly ash (FA), and metakaolin (MK) on the properties
of fiber-reinforced mortars. Different types of natural and synthetic fibers were used. A
super plasticizer was used to keep the same workability as that of the control mortar.
Results of the mechanical and durability properties of the fiber-reinforced mortars were
reported. The results showed that a loss of resistance due to embedding fibers in mortar
33
is compensated for by the increase in strength caused by silica fume or metakaolin
additions to the mortar. In general, these materials, especially SF and MK, improve the
mechanical performance and the durability of fiber-reinforced materials, especially those
reinforced with steel, glass or sisal fibers.
Kosa et al (1991) compared the durability properties of four types of fiber
reinforced cement composites. The four composites were conventional steel (SFRM),
polypropylene, glass fiber reinforced mortar (GFRM), and slurry infiltrated fiber concrete
(SIFCON). Results indicate that polypropylene reinforced mortar has the best overall
durability, while glass fiber reinforced mortar shows the poorest overall performance.
Steel fiber reinforced mortar showed noticeable reduction in flexural strength and a
dramatic reduction in toughness. For SIFCON, the reduction in strength and toughness
were both moderate. While cement mortar was used in this study because of the nature
of the thin specimens tested, the conclusions should generally apply to fiber reinforced
concrete where the coarse aggregate is of sufficient quality and not to contribute to
corrosion.
Udoeyo and Adetifa (2012) used water- retted kenaf fibers as reinforcement in
mortar composites of size, 650 mm × 450 mm × 8 mm. Three fiber contents (0.5 %, 1.0
% and 1.5 %) and four fiber lengths (20 mm, 30 mm, 40 mm and 50 mm) were
considered in the study. Physical and mechanical characteristics of the composites
were evaluated according to ASTM and other appropriate standards. The results of the
experimental program showed that although the bending capacity of kenaf fiber-
reinforced mortar sheet decreased with increase in fiber content, the flexural toughness
and the impact resistance of the composite were enhanced with higher content of the
34
fiber, compared with the control composites (composite without fiber). The water
absorption and the fire resistance of the composite were also observed to be within
acceptable limits specified by relevant standards.
Fiber Reinforced Concrete
Fiber-reinforced concrete (FRC) is concrete containing fibrous material which
increases its structural integrity. It contains short discrete fibers that are uniformly
distributed and randomly oriented. FRC is made of hydraulic cement or cements; water;
fine and coarse aggregate; and short, uniformly dispersed discontinuous fibers. Fibers
may be of steel, glass, polymeric materials, carbon, cellulose, and so forth and their
lengths vary from 3 to 64 mm (0.12 to 2.52 in.). The diameters may vary from a few μm
to about 1 mm (0.04 in.). The sections may be round, oval, polygonal, triangular,
crescent shaped, or even square depending on the manufacturing process and the raw
material used. The two broad categories of fibers are micro and macro. Microfibers
have diameters or equivalent diameters less than 0.3 mm (0.012 in.), and macrofibers
have diameters or equivalent diameters greater than 0.3 mm (Banthia et al 2012).
Fibers include synthetic and natural fibers; each of which lend varying properties to
concrete. In addition, the character of fiber-reinforced concrete changes with varying
concretes, fiber materials, geometries, distribution, orientation, and densities.
The Federal Highway Authority report (1989- 1994) on High-Performance Fiber-
Reinforced Concrete (HPFRC) presented the results from the addition of either short
discrete fibers or continuous long fibers to the cement based matrix. FRP bars and
tendons reach their ultimate tensile strength without exhibiting any yielding of the
material. FRP bars are weaker in compression than in tension. However, the
35
compressive strength of GFRP is not a primary concern for most applications. The
compressive strength also depends on whether the rebar is smooth or ribbed.
From the above literature on fiber reinforced mortar and concrete, it can be
deduced that fiber addition in mortar improves the strength of the mortar and the
masonry structure as a whole. The shape and texture (smooth or ribbed) of the fibers
also account for its performance in fiber reinforced mortars and concrete. PET fibers
additions in cementitious matrix have been an alternative to control of plastics shrinkage
cracking. The plastic shrinkage cracks are widely evident in render mortar, which have
thick and large areas of exposure (Oliviera 2011). Figure 2-12 shows a typical effect of
fiber addition in concrete (Kumar and Sharma 2009).
Figure 2-12. Typical effect of fiber addition in concrete.
36
CHAPTER 3 RESEARCH METHODOLOGY
Research Approach
The methodology followed in this research was determined by the objective of
the study and the hypotheses statements listed in Chapter 1. The steps taken to
conduct the thesis research and to obtain quantifiable results were as follows:
1. A literature review was performed on sustainable building materials for the construction industry as well as the ethical basis for providing developing countries with the knowledge and means to employ sustainable building materials, particularly on mortar.
2. The data needed for the analysis was identified. Data was sought from the existing ASTM standards and from the extensive literature reviews.
3. The sources of data were identified. Fine aggregates were acquired locally, ordinary portland cement, natural and synthetic fibers were acquired from a local hardware store. Pipe borne water was from the Soils and Concrete Laboratory in the Rinker School of Building Construction.
4. Standard ASTM for mortar testing for the seven selected mortar samples with various fiber components (coconut, sisal, recycled PET, Polypropylene strands, microfiber and synthetic hair fibers including a controlled sample with no fiber) was identified.
5. The seven mortar types were mixed and poured into 6 cylinders of 3 x 6 inch size for each mix type, resulting in a total number of 42 cylinders and tested in the laboratory by ASTM standards to obtain the data.
6. Analytical and descriptive statistics was used to assess the significance of the laboratory results sought.
Experimental Approach
This chapter discusses the structured process for conducting the research. The
quantitative method was used in data collection. The structured experiments and testing
was conducted in the Soils and Concrete Laboratory at the M.E. Rinker School of
Building Construction at the University of Florida.
37
Experimental Data Entry
The following ASTM standard methods for testing concrete were conducted in
the laboratory setting to make the three sustainable mortar mixtures, to determine their
compressive strength, to determine their tensile strength of the seven mixtures after
twenty-eight (28) days of curing. Detailed results of the testing are contained in Chapter
4: Data Collection, Results and Discussion.
Mortar Types
Masonry mortar types are specified by American Standard Testing Method
(ASTM) C 270, Specification for Mortar for Unit Masonry. Mortars were evaluated by
ASTM C 780, Preconstruction and Construction Evaluation for Mortars for Unit
Masonry. Following ASTM standards, Table 3-1 shows the minimum required
compressive strength of the mortar types in pound per square inch (psi).
The mortar type to be used will be a type O mortar. Type O mortar has a
compressive strength of 350 psi and has high tensile bond strength too.
Table 3-1. ASTM Minimum Compressive Mortar Strength
Type PSI
Type M 2,500 psi
Type S 1,800 psi
Type N 750 psi
Type O 350 psi
Type K 75 psi
38
Mix Design
A mix design was chosen based on the ASTM C 780 for a Type O mortar.
Mortars sampled were made in 3x6 inches cylinders. The molds were filled three times
and tapped four times on a solid based after addition of each increment. Figure 3-1
shows a sample of a 3x6 inch cylinder mold.
Table 3-2. Proportions specification using masonry cement based on ASTM C270
No Mortar Type
Parts by Volume
Portland or blended cement
Masonry cement type Fine Aggregates
M S N
1 M 1 - - 1 4½ to 6
- 1 - - 2¼ to 3
2 S ½ - - 1 33/8 to 4½
- - 1 - 2¼ to 3
3 N - - - 1 2¼ to 3
4 O - - - 1 2¼ to 3
Mortar Testing
American Society for Testing and Materials (ASTM) C39: Compressive Strength of Cylindrical Concrete Specimens
The test was done in compliance with ASTM C39. This test is also known as
destructive testing of hardened concrete. The strength of the mortar to be tested is
affected by the length to diameter (L/D) ratio of the cylinder and the condition of the
ends of the cylinder samples is noted to determine the failure mode of the concrete
(Figure 3-1). The loading rate of the compression machine is typically between 20-50
psi/sec. (see Figure 3-3).
39
The results of this test method are used as a basis for quality control of mortar
proportioning, mixing, and placing operations; determination of compliance with
specifications; control for evaluating effectiveness of admixtures; and similar uses. The
maximum load at failure in pounds was then recorded and the compressive strength
was calculated as f’ = P /(D 2 *π/4)
Where
P is the maximum load at failure in pounds
D is the diameter of the cylindrical specimen in inches
π/4 is the area of the surface of cylinder
Figure 3-1. Sketch showing typical failure modes of compression testing: (a) splitting; (b) shear (cone); and (c) splitting and shear
40
Figure 3-2. Schematic diagram for conducting compressive strength
Figure 3-3. Hardened mortar specimen failure in the compression machine after
destructive testing.
41
ASTM C496: Splitting Tensile Strength of Cylindrical Concrete Specimens
The test was done in compliance with ASTM C496. This ASTM test method
covers the determination of the splitting tensile strength of cylindrical concrete
specimens. This method consists of applying a diametral compressive force along the
length of a cylindrical specimen. This loading induces tensile stresses on the plane
containing the applied load. Tensile failure occurs rather than compressive failure.
Plywood strips are used so that the load is applied uniformly along the length of the
cylinder. The maximum load is divided by appropriate geometrical factors to obtain the
splitting tensile strength. The mortar cylinders were placed in the compression machine
with bearing strips - 2 each, 1/8 in. thick plywood strips, 1 in. wide (the length shall be
slightly longer than that of the specimens). The bearing strips were placed between the
specimen and the upper and lower bearing blocks of the testing machine. Figure 3-4
presents the procedures of conducting tensile strength test in the laboratory. (see
Figure 3-5).
Figure 3-4. Schematic diagram for conducting tensile strength
42
Figure 3-5. Hardened mortar specimen failure in the compression machine before
tensile strength testing.
The load was applied continuously at a constant rate of 100 to 200 psi/minute of
splitting tensile stress until failure occurred. The maximum load at failure in pounds was
then recorded and the splitting tensile strength was calculated f’ = 2P / π l*d where
P is the maximum load at failure in pounds
l and d are the length and diameter of the cylindrical specimen in inches.
Figure 3-6. 3x6" Cylinder Mold
3”
6”
43
Materials for Mortar
The materials to be used to prepare the mortar for testing are Portland Cement,
Fine Aggregates, Natural and Synthetic Fibers and water.
Portland Cement
Ordinary Portland Cement conforming to ACI standard was used for this
experiment and locally available fine aggregates was used. In a majority of masonry
formulations, Ordinary Portland Cement (OPC) is the principal binding agent (Bediako
et al 2011). Fresh and dry cement from properly sealed bags where used for the mix.
Figure 3-7. Cement
Fine Aggregates
Good grade fine aggregates passing through 20 mm and retained on 4.75 mm
sieve size was considered for the investigation. The sand was free from clayey
materials so as not to cause expansion and contraction when the water dries up in the
mortar.
44
Figure 3-8. Sieved Fine Aggregates
Water
Water is a major component in the mix of mortar. Too little or too much water will
significantly affect the mix and the overall strength of the mortar. Using the optimum
weight or volume of water during the mix is very important. “Water is imperative for two
reasons. One is to hydrate the cement and the second is to create a workable
substance. Hydration of the cement is necessary to form bonds with the aggregate
which in turn give concrete its strength” (Chopra et al 2007).
Figure 3-9. Water
45
Fiber Types
Recycled PET Fiber
Polypropylene Fiber Strands
Coconut Fiber
Sisal Fiber
Synthetic Hair Fiber
Engineered Microfiber
Mix Design
Proportioning of a mortar mix comprises of determining the relative quantities of
materials to be used in production of mortar for a given purpose. Approximately 19
pounds of mix was prepared per batch using a specific fiber type.
The main objectives of the concrete mix design can thus be started as production
of concrete, which shall be,
Satisfying the requirements of fresh concrete (workability).
Satisfying the properties of hardened concrete (strength and durability).
Most economical for the desired specifications and given materials at a given site.
Performing most optimally in the given structure under given conditions of environment.
The concrete mix design is based on the principles of;
Workability of fresh concrete.
Desired strength and durability of hardened concrete which in turn is governed by water-cement ratio law
Conditions at the site, which helps in deciding workability, strength and durability requirements. (Garg 2003)
46
Table 3-3. Mix Design by Percentage
Component %
Cement 10.0%
Sand 89.9%
Fiber 0.2%
Table 3-4. Mix Design in Weight
Component Ibs
Cement 1.9
Sand 17.1
Fiber 0.038
Figure 3-10. A: Coconut fiber, B: Sisal fiber, C: Synthetic hair, D: Polypropylene
Strands
47
Nominal Lengths of Fibers
The nominal lengths of the fibers were approximately an inch long, except for the
polypropylene fiber strands which were approximately 2 inches long. Short fibers are
used as admixtures in cement-based materials for structural and functional reasons
(Chung 2005).
Figure 3-11. Nominal Lengths of Fibers (A) Coconut fiber, (B) Sisal Fiber, (C)Synthetic
Hair Fiber, (D) Polypropylene Fiber, (E) Recycled PET Fiber, (F) Engineered Micro Fiber
Hand Mixing
Mixing was done on a mixing board to avoid contamination. The raw materials
were combined and mixed to an even color prior to adding water. Water was then slowly
added with the continuous turning of the mix until a thick creamy mortar is obtained. It is
important that mortars are used within an hour of mixing and should not be re-tempered
by the addition of water.
48
With regards to the curing of mortar specimen for all stabilized formulations, the
mortar samples remained in a room to cure for a 28 days minimal period.
Figure 3-12. Hand Mixing of Mortar
Figure 3-13. Filling of mortar in Cylinder molds
Figure 3-14. Fresh mortar in cylinder molds
49
Figure 3-15. Set Mortar in Cylinders molds
Figure 3-16. Stripping of cylinder molds from the set mortars.
Figure 3-17. Stripping Rod
50
Cylinder Casting Procedure
Figure 3-18. Cylinder casting procedure
51
Figure 3-19. Set mortar specimen. (A) Recycled PET Fiber, (B) Controlled Specimen
(No Fiber), (C) Coconut Fiber, (D) Micro Fiber, (E) Synthetic Hair Fiber, (F) Sisal Fiber (G) Polypropylene Fiber.
52
CHAPTER 4 RESULTS AND DISCUSSION
A total of 48 specimens molds was be made; 12 each for the recycled PET fiber,
coconut fiber, sisal fiber, synthetic hair fiber, polypropylene fiber strands, microfiber and
non-fiber respectively. Testing was done 28 days after casting. The compressive and
tensile tests were carried out on the mortar specimen.
Compressive Test
The compression test determines behavior of materials under crushing loads
(Saikia et al 2011). The mortar samples will be compressed and the deformations at the
different loads will be recorded. The compressive strain and stress will be calculated
using the stress-strain diagram. The Stress-strain diagram will be used to determine
compressive strength, yield point, limit and proportional limit. The compressive strength
will be measured on a universal testing machine.
Table 4-1. Compressive Maximum Load (lbs.)
SPECIMEN A B C
No Fiber 3575 3735 3620
Coconut Fiber 4114 4645 4485
Sisal Fiber 5630 4745 5790
Recycled PET 5375 5455 5040
Polypropylene Fiber 6505 5330 5070
Microfiber 3830 4140 3925
Synthetic Hair Fiber 4185 5340 4460
53
Table 4-2. Compressive Test Maximum psi
SPECIMEN/ psi A B C Average psi
No Fiber 506 529 512 516
Coconut Fiber 582 658 635 625
Sisal Fiber 797 672 820 763
Recycled PET 761 772 713 749
Polypropylene Fiber 921 754 718 798
Microfiber 542 586 556 561
Synthetic Hair Fiber 592 756 631 660
Figure 4-1. Compressive Test Result
No FiberCoconut
FiberSisal Fiber
RecycledPET
Polypropylene Fiber
MicrofiberSyntheticHair Fiber
A 506 582 797 761 921 542 592
B 529 657 672 772 754 586 756
C 512 635 820 713 718 556 631
0
100
200
300
400
500
600
700
800
900
1000
psi
Specimen
Compressive Strength Test Result
54
Figure 4-2. Average Compressive Test Result
Tensile Test
The tensile test subjects the specimen to a uniaxial tension until it fails. The
universal testing machine will be used in for the tensile test. This test is used to predict
how materials react under different types of forces.
Table 4-3. Tensile Maximum Load (lbs.)
SPECIMEN/ lbs. A B C
No Fiber 2340 2635 2235
Coconut Fiber 3375 3650 3620
Sisal Fiber 4420 4070 3850
Recycled PET 4035 2985 2925
Polypropylene Fiber 5955 5835 6175
Microfiber 3150 3105 3560
Synthetic Hair Fiber 4930 4380 3435
No FiberCoconut
FiberSisal Fiber Recycled PET
Polypropylene Fiber
MicrofiberKanekalon
Fiber
Average 516 625 763 749 798 519 660
0
100
200
300
400
500
600
700
800
900
psi
Specimen
Average Compressive Strength
55
Table 4-4. Tensile Test Maximum psi
SPECIMEN/ psi A B C Average
No Fiber 331 373 316 340
Coconut Fiber 478 517 512 502
Sisal Fiber 626 576 545 582
Recycled PET 571 423 414 469
Polypropylene Fiber 843 826 874 848
Microfiber 446 439 504 463
Synthetic Hair Fiber 697.81 619.96 486.20 601.32
Figure 4-3. Tensile Test Result
No FiberCoconut
FiberSisal Fiber
RecycledPET
Polypropylene Fiber
MicrofiberSyntheticHair Fiber
A 331 478 626 571 843 446 698
B 373 517 576 423 826 439 620
C 316 512 545 414 874 504 486
0
100
200
300
400
500
600
700
800
900
1000
psi
Specimen
Tensile Strength Test Result
56
Figure 4-4. Average Tensile Test Result
Compressive Strength Test
From the compressive test results as shown in Figure 4-5, this was arranged in
order of performance; with Polypropylene fiber performing best with 798 psi and least
performed is the controlled specimen with no fiber with 516 psi. The graph shown in
Figure 5-1 does not show any significant difference between the synthetic and natural
fibers performance. For instance, synthetic polypropylene fiber performed best with the
natural sisal fiber preforming second best with a 763 psi.
No FiberCoconut
FiberSisal Fiber Recycled PET
Polypropylene Fiber
MicrofiberSyntheticHair Fiber
Average 340 502 582 469 848 463 601
0
100
200
300
400
500
600
700
800
900
psi
Specimen
Average Tensile Strength Test Result
57
Figure 4-5. Compressive Strength in order of performance
From Table 4-5 and Figure 4-6, the percentage change in strength from the
controlled specimen of non-fiber mortar is used as the baseline are shown.
Table 4-5. Percentage Change from Controlled Specimen
Specimen psi % change
Polypropylene Fiber 798 54.6
Sisal Fiber 763 47.8
Recycled PET 749 45.1
Synthetic Hair Fiber 660 27.9
Coconut Fiber 625 21.1
Micro fiber 561 8.8
No Fiber 516 0.0
798 763 749
660 625
561
516
0
100
200
300
400
500
600
700
800
900
PolypropyleneFiber
Sisal Fiber Recycled PET Synthetic HairFiber
Coconut Fiber Micro fiber No Fiber
psi
Specimen
Compressive Strength in order of Performance
58
Figure 4-6. Compressive Test Percentage Change from Controlled Specimen
Tensile Strength Test
From the tensile test results as shown in Figure 4-7, this was arranged in order of
performance; with Polypropylene fiber performing best with 848 psi and least performed
is the controlled specimen with no fiber with 340 psi. The graph shows a significant
difference between the synthetic polypropylene fiber and the non-fiber mortar. It
performed almost 150% better than the controlled non-fiber mortar. As shown in Figure
4-8, the percentage change in the performance in tensile strength is more significant
than the compressive strength.
798 763 749
660 625
561
516
54.6
47.8 45.1
27.9
21.1
8.8
0.0 0.0
10.0
20.0
30.0
40.0
50.0
60.0
0
100
200
300
400
500
600
700
800
900
PER
CEN
TAG
E C
HA
NG
E %
PSI
SPECIMEN
Compressive Test Percentage Change
psi % change
59
Figure 4-7. Tensile Strength in order of performance
From Table 4-6 and Figure 4-8, the percentage change in strength from the
controlled specimen of non-fiber mortar is used as the baseline are shown.
Table 4-6. Percentage Change from Controlled Specimen
Specimen psi % change
Polypropylene Fiber 848 149.3
Synthetic Hair Fiber 601 76.9
Sisal Fiber 582 71.2
Coconut Fiber 502 47.7
Recycled PET 469 38.0
Micro fiber 463 36.2
No Fiber 340 0.0
848
601 582
502 469 463
340
0
100
200
300
400
500
600
700
800
900
PolypropyleneFiber
Synthetic HairFiber
Sisal Fiber Coconut Fiber Recycled PET Micro fiber No Fiber
psi
Specimen
Tensile Strength in Order of Performance
60
Figure 4-8. Tensile Test Percentage Change from Controlled Specimen
Comparison of Compressive and Tensile Strength
Compressive and tensile strength test Figure 4-9 shows the change between the
bars. The polypropylene fiber was the only mortar specimen which had an increase in
psi from the compressive to the tensile. For the rest, there was a decrease in psi from
compressive to tensile. It can be noted that recycled PET fiber had the most difference
in change from the compressive test of 749 psi to the tensile test of 469 psi whiles
polypropylene fiber had the least change in difference from the compressive test of 798
psi to the tensile test of 848 psi.
848
601 582
502 469 463
340
149.3
76.9 71.2
47.7
38.0 36.2
0.0 0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
0
100
200
300
400
500
600
700
800
900
PER
CEN
TAG
E C
HA
NG
E %
PSI
SPECIMEN
Tensile Test Percentage Change psi % change
61
Figure 4-9. Comparison of Compressive and Tensile Strength
Table 4-7. Percentage Change between Compressive and Tensile Test of Mortar Specimen
Specimen Compressive Tensile % change
Polypropylene Fiber 798 848 5.9
Sisal Fiber 763 582 -31.0
Recycled PET 749 469 -59.6
Synthetic Hair Fiber 660 601 -9.7
Coconut Fiber 625 502 -24.4
Micro fiber 561 463 -21.2
No Fiber 516 340 -51.6
Polypropylene Fiber
Sisal FiberRecycled
PETSythetic Hair
FiberCoconut
FiberMicro fiber No Fiber
Compressive 798 763 749 660 625 561 516
Tensile 848 582 469 601 502 463 340
0
100
200
300
400
500
600
700
800
900
1000
psi
Specimen
Comparison of Compressive and Tensile Strength
62
Figure 4-10. Percentage Change between Compressive and Tensile Test of Mortar
Specimen
798 763 749
660 625
561
516
848
582
469
601
502 463
340
5.9
-31.0
-59.6
-9.7
-24.4 -21.2
-51.6
-70.0
-60.0
-50.0
-40.0
-30.0
-20.0
-10.0
0.0
10.0
0
100
200
300
400
500
600
700
800
900
PER
CEN
TAG
E C
HA
NG
E %
PSI
SPECIMEN
Percentage Change between Compressive and Tensile Test of Mortar Specimen.
Compressive Tensile % change
63
CHAPTER 5 CONCLUSION AND RECOMMENDATIONS
Overview
This research was focused on the use of natural and synthetic fibers in low
strength mortar. The research was directed at theoretically and experimentally quantify
and compare the performance to compare the performance of natural and synthetic
fibers in low strength mortar using easily accessible fibers like recycled PET fiber,
coconut fiber, sisal fiber, synthetic hair fiber, engineered microfiber and polypropylene
fiber strands.
The specific objectives were to;
Conduct a literature review of published studies that relate to fiber additions in mortar.
Analyze the advantages and disadvantages of using the selected natural and synthetic fibers in mortar.
Design a mortar mix design enhanced through the addition of recycled PET fibers, coconut fibers and engineered microfibers.
Quantify the enhancement in compressive and tensile strength in the various fibers.
Analyze the difference in performance of the fiber types in the mortar specimen.
Summary of Main Findings
From the preceding chapter it was evident that the engineered polypropylene
fiber performed best in both compression and tension with 798 psi and 848 psi
respectively and the control samples (no fiber) performed least both in compression and
tension with 516 psi and 340 psi respectively. The best performing natural fiber was the
sisal fiber with a compression strength of 763 psi and tensile strength of 582 psi.
Synthetic hair fiber also showed a significant tensile strength of 601 psi, thus performed
second best.
64
Conclusions
From the results of the pilot study, it can be said that the addition of the natural
and synthetic fiber in low strength mortar significantly increased the compressive and
tensile strength of the mortars. The controlled specimen with no fibers performed least
with 516 psi and 340 psi for compression and tension respectively.
The pilot study also indicated that it is possible to satisfy the code requirements
given that the minimum compressive strength needed for a Type O mortar is 350 psi. As
this is a pilot study further work will be done to validate these initial findings.
There are factors that can be attributed to the performance of the fibers types in
the mortar. The fibers had a nominal length of approximately an inch except for the
polypropylene fiber which was approximately 2 inches long. The length of the
polypropylene fiber could have contributed to its performance, more so, the
polypropylene fiber was corrugate, and hence, it enhanced the bond of the fiber and
mortar.
Recommendations for Further Research
Through the course of this study, several opportunities for further research were
noted to expand the amount of data for natural and synthetic fibers in mortars. The
results of this study lead to the following recommendations;
Compressive and tensile tests should be performed on the mortar specimen in order to find out its strength on days 7 and 14 respectively because a 7 day test may help detect potential problems with mortar quality or testing procedures at the laboratory but this is not a basis for rejecting mortar.
Other natural and synthetic fibers like jute, silk nylon can be used as components for the mortar mixes.
Different quantities of fibers can also be used in the mortar mixes so as to find out the optimum fibers to be added to the mortar specimen in order to achieve maximum strength.
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Mortars can be made using types M,S and N mortar. In this way, further analysis will be performed if mortars with higher cement ratio will improve the strength of the mortars when fibers are added to it.
Mortar specimen can also be made in 4x6 inch and 6x12 inch cylinders to compare the change in strength and the effects the size of the cylinder can affect the strength in testing.
Test can be conducted in various laboratories. Tests made by different laboratories on the same mortar specimen should not differ by more than about 13% of the average of the two test results.
Conduct a cost benefit analysis on using different types of fibers in large scale construction.
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APPENDIX A MORTAR PREPARATION
A B
C D
E F Figure A-1. Mortar Preparation Process A: Fiber Types, B: PET Fiber Mix, C: Sisal
Fiber Mix, D: Synthetic Hair Fiber Mix, E: Coconut Fiber Mix and F: Polypropylene Fiber Mix
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APPENDIX B WEIGHT OF MORTAR SPECIMEN
A B
C D
E . F Figure B-1. Weight of Mortar Specimen with. A: Recycled PET Fiber, B: Control
Specimen ( No Fiber, C: Polypropylene Fiber, D: Coconut Fiber, E: Synthetic Hair Fiber and D: Sisal Fiber.
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APPENDIX C COMPRESSIVE TESTS
A B
C D Figure C-1. Failures in Mortar after Compressive Test in A: Controlled Specimen, B:
Micro Fiber, C: Polypropylene Fiber and D: Synthetic Hair Fiber
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A B
C D
Figure C-2. Failures in Mortar after Compressive Test in a: Recycled PET Fiber, B: Controlled Sample (No Fiber), C: Recycled PET Fiber and d: Sisal Fiber
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APPENDIX D TENSILE TESTS
A B
C D Figure D-1. Failures in mortar after tensile test in A, B and C: Polypropylene Fiber and
D: Synthetic Hair fiber
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BIOGRAPHICAL SKETCH
Felicity Aku Amezugbe was born in Ho, Ghana and lived in Tema, Ghana all her
life until she moved to the United States in 2011 to further her studies. In 2009, she was
awarded a Bachelor of Science in building technology from the Kwame Nkrumah
University of Science and Technology in Kumasi, Ghana. She graduated with a Master
of Science in building construction from the University of Florida - M. E. Rinker School
of Building Construction in Spring 2013.
