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Mortar as Grout for Reinforced Masonry Phase 1 Report April 2005 RBA Project 8379
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Page 1: Mortar as Grout for Reinforced Masonry - Association · PDF fileMortar as Grout for Reinforced Masonry Phase 1 Report ... The material standard in the United States for masonry grout

Mortar as Grout for ReinforcedMasonry

Phase 1 Report

April 2005

RBA Project 8379

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Mortar as Grout for ReinforcedMasonry

Phase 1 Report

Prepared for:

International Masonry Institute

National Lime Association

Bricklayers and Allied Craftworkers Local No.1, New York, NY

National Concrete Masonry Association Research and EducationFoundation

Prepared by:David T. Biggs, P.E.Ryan-Biggs Associates, P.C.291 River StreetTroy, New York 12180(518) 272-6266(518) 272-4467 (fax)[email protected]

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TABLE OF CONTENTSPAGE

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Historical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Codes and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Previous Research Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

TESTING CONCEPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

MATERIAL CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Mortar Fill and Pourable Mortar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Concrete Masonry Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Compressive Strength of Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

TESTING RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Pull-Out Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Failure Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Bond Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

ANALYSIS OF RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Pull-Out Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Tests of Bond Between Fill Material and CMU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

CONCLUSIONS/RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

APPENDIX A Sand Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1APPENDIX B Grout and Mortar Fill Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1APPENDIX C Concrete Masonry Unit Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1APPENDIX D Pull-Out Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1APPENDIX E Bond Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1APPENDIX F References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1

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EXECUTIVE SUMMARY

Mortar used as grout for reinforced masonry for grout in commercial construction is a topic of majorinterest to many masons that use low-lift grouting techniques. While not specifically allowed bymodel codes and standards, it is commonly used on projects. Residential standards in the UnitedStates have allowed Type S and Type M mortar tempered to a “pourable” consistency for groutingfor many years. A pourable consistency has a slump of approximately 6 inches. This reportdocuments Phase 1 testing of a research program aimed at evaluating mortar as a substitute forgrout for use with vertical reinforcement.

Phase 1 includes a series of pull-out tests and bond shear stress tests performed on prism-sizedsamples. This phase was intended to evaluate only vertical reinforcing using small-scale samplesto determine if full-scale testing is recommended and the possible parameters of that testing.

Samples were constructed at facilities of Bricklayer and Allied Craftworkers, Local 2 in Albany, NewYork. Testing was performed at commercial laboratories in Watervliet, New York, Scotia, NewYork and at the National Concrete Masonry Association.

Several mixes were compared using reinforced CMU:1. Type N and Type S mortars as commonly mixed for setting units.2. Type N and Type S mortars that were tempered to a pourable consistency.3. ASTM C 476 grout.4. Type S mortar tempered to the consistency of grout.

Type N mortar did not provide acceptable results, primarily due to its low strength. Type S mortar performed better in the pull-out tests than the “pourable” mortars that are allowedin residential codes. However, based upon the tests results, Type S and Type M mortar could bean acceptable substitute for grout provided the mix achieves at least 2000 psi compressive strengthwhen tested as a grout prism.

Phase 2 full-scale testing is recommended using Type S and Type M mortars in a modified low-liftapplication.

The test results suggest some topics for additional consideration. Some of these include:1. The strength of the fill material (mortar, pourable mortar, or grout) that encases the

reinforcement affects the development length of the reinforcement. MSJC formulas for lapsplices do not adequately account for the strength of the fill material.

2. The shrinkage characteristics of the fill material should be evaluated to determine theirimportance in achieving adequate bond shear strength.

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INTRODUCTION

The Masonry Standards Joint Committee (MSJC)1 requires grout for use in reinforced masonry forcommercial construction. Grout is used to fill cells of hollow masonry and fill cavities of compositeconstruction. However, the majority of its use is to encase reinforcement. For residentialconstruction, some model codes allow the use of “pourable” mortars. “Pourable” mortars arecreated by adding sufficient water to the mortar so that the mix can be poured into the masonry.

In spite of codes and standards, it is common in some regions of the United States for variousmasonry contractors to substitute mortar for grout in commercial construction. The mortar is usedas traditionally mixed without additional water added. Dependent upon the jurisdiction, the mortarsubstitution requires the acceptance of the designer as well as the building official. The logic forthe substitution is that mortar and grout have similar constituent materials and therefore shouldperform similarly.

Masonry contractors who prefer to use mortar as grout along with the low-lift technique cite thefollowing reasons:

1. Reduces installation costs for low-lift applications when the masonry is to be grouted.2. Reduces the number of mixers used since industry standards generally require separate

mixing of mortar and grout. 3. Eliminates contamination of core cells that can occur when using two different materials.4. Increases the chance of placing consistent material by grouting course by course in walls

when there are numerous mechanical trade penetrations, reduced overhead clearance,and general access restrictions to the top of the wall.

5. Improves delivery of materials on high-rise buildings for infill walls. Contractordistribution of different materials is reduced.

For contractors that prefer the high-lift grouting technique, using mortar as grout is generally notdone or limited to filling at openings with embedded hardware such as door jamb anchors. The material standard in the United States for masonry grout is ASTM C 4762. Within the standard,there are two types of grout: fine grout and coarse grout. Fine grout has sand aggregate, portlandcement, and lime; coarse grout uses pea gravel in addition to the sand.

The material standard for mortar is ASTM C 2703. The standard allows three cement options formixing mortar. These include:

1. Portland cement and lime.2. Masonry cement.3. Mortar cement.

In all three options, sand is used as the aggregate.

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Purpose of this Report

This report documents the research that was initiated to examine the performance of portlandcement and lime-based mortars in reinforced masonry as an alternative for grout to encase verticalreinforcement. Portland cement and lime-based mortar is evaluated since it most closely replicatesthe constituent materials of fine grout. Natural sand was used as the aggregate.

The study is limited to concrete masonry units (CMU) used in a modified low-lift groutingapplication.

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BACKGROUND

Historical

A. Grouting began in the United States after the 1933 Long Beach California earthquakedamaged many unreinforced brick buildings. The use of reinforcement in the walls madegrout necessary. Initially, all grouting was performed course by course. Six-foot lengths ofreinforcement were used; four feet were grouted each day and two feet were left for a lapsplice. In northern California, masonry contractors wanted to speed up construction andproposed constructing the masonry full height and then grouting the wall full height. Withlimitations, the method was accepted by the State of California 4.

From this beginning, two grouting techniques were developed for the United States: low-liftand high-lift. Low-lift grouting occurs incrementally with the installation of the masonry.Standards limit this grouting to a maximum pour of 5 feet.

High-lift grouting allows the masonry to be constructed and grouted in pours greater than 5feet using lifts that are a function of the grout type and the size of the cell or cavity to befilled. In the 2005, the MSJC changed its criteria so that the maximum lift heights couldincrease from 5 feet to as much as 12 feet 8 inches. Pour heights were not changed.

B. Amrhein 5 reported that grout slumps for high-lift grouting were determined by the Office ofthe State Architect, Structural Safety Section, Circular Number 10, Clay Brick Masonry, HighLift Grouting Method. The circular stated “The slump of the grout should be varieddepending upon the rate of absorption of the masonry units and temperature and humidityconditions. The range should be from 8 inches for units with a low rate of absorption (30 to40 grams per minute) up to 10 inches for units with a high rate of absorption (80 to 90 gramsper minute).” Thus, high-slump grout was developed for high-lift grouting to flow into thevoids of the masonry units and around reinforcement. This became the grout standard forboth low-lift and high-lift grouting.

The absorption rates noted are interesting in that industry recommendations are to pre-wetbricks before construction whenever the initial rate of absorption (IRA) exceeds 30 grams perminute per 30 square inches 6. Thus, if the bricks are pre-wetted and the IRA is reduced toless than 30, the California information would seem to justify lower slump grouts.

C. Isberner7 reported in 1982 that grout had not been extensively researched. He states “..it isunfortunate we disallow certain practices and materials on little or no evidence. Some pastand recent research, however, shows there is much to be learned regarding the role of groutin reinforced masonry”. Furthermore, “Although many grouted reinforced masonrystructures are now in existence, the specifics of grout design and use are relativelyunfounded.”

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He suggested that “Grouts be designed, specifically, to develop the specification strength atthe required test age when acceptable test molds and specimens are used.” He also notedthat test data indicates that low water content grouts (2 to 3 inch slump) could developcompressive strengths in the 2000 psi range. Lastly, Isberner recommended research toshow alternative methods of grouting reinforced masonry.

D. In many areas of the country, high-lift grouting is not commonly used. Thus, the questionarises as to whether a high-slump grout is necessary for those applications that use low-liftgrouting techniques. If not, is mortar satisfactory for grout for low-lift applications?

There have been no reported incidences found in the literature of structural failures attributedto mortar being used as grout for vertical reinforcement. Failures associated with groutingare generally attributed to missing or inadequate filling of masonry. The properties of thegrout were not reported.

Codes and Standards

In the 1982 Uniform Building Code 8, mortar was acceptable as a substitute for grout for chimneysand fireplaces. This was subsequently deleted in the 1985 edition.

Residential codes from the Council of American Building Officials (CABO)9 allowed Type S or TypeM mortar with water added to be used as grout. CABO became part of the International CodeCouncil, and its International Residential Code (IRC)10 also allows Type S or Type M mortar withwater added to be used as grout.

Previous Research Work

A. To support the use of mortars in residential construction, previous research11 was done in1991 by the National Concrete Masonry Association (NCMA) to evaluate mortar as finegrout. They used Type S and Type M mortars with sufficient water added to create a“pourable” mixture that achieved a slump of 7 to 9 inches. The pourable mortars werecompared to three grout mixes with similar slump. The three grout mixes contained onlycement and sand. The aggregate ratios in the grouts were varied to achieve compressivestrengths similar to the mortars.

The test setup was not described; it was noted a No. 5 bar was pulled in tension from thespecimens and tension bond strengths were calculated.

Comparing the data for pourable Type S, PCL (portland cement- lime based) mortar andASTM C 476 fine grout:

1. The compressive strength for the grout was 10 percent higher than for the pourablemortar.

2. The grout only achieved tension bond strengths 6 percent higher than the pourableType S mortar.

The report concluded that further research was necessary but that pourable mortars “couldbecome an effective substitute for grout.”

B. In 1998, a report prepared by Brown12 at Clemson University reported using mortar as groutin reinforced hollow clay walls. The tests obtained tension bond strengths between the

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reinforcement and grout developed from three methods of filling the cell space aroundreinforcing in hollow clay units and compared them with each other. The three methodsincluded grouting with standard grout, “slushing” with mortar, and “souping” with mortar. Theauthor indicated that “slushing” involved filling the cells of the masonry with mortar as thewalls were laid. “Souping” mortar involved adding sufficient water to produce a slump ofabout 10 inches.

Specimens were tested in pull-out mode; some were tested in direct tension, and others weretested to evaluate lap splices. The direct tension pull-out tests developed flexural tensioncracks in the masonry along the center of the rebar that clearly reduced the pull-out strength.The report noted that this phenomenon would not be expected in actual walls and was simplya result of using a test specimen that produced an effect that was not anticipated. Theyindicated the results of the pull-out tests should not be considered other than for comparisonwith each other.

The mortar used to fill the masonry was a Type S masonry cement mortar. The compressivestrength from mortar cubes was between 1,076 and 1,802 psi for the “slushed” mortar. The“souped” mortar tested as grout achieved a strength of over 4,500 psi. The grout strengthswere unusually high at over 11,000 psi.

No general conclusions were listed. However, a notable observation was that of the 36 testsconducted, 35 produced tension bond strengths that developed tensile bar strengthsexceeding the allowable tensile strength of the rebar. The single test that did not achieveallowable stress was observed after testing to be poorly consolidated.

The “slushed” mortar samples produced results in the pull-out tests slightly less than the“souped” mortar samples. The grout tests resulted in the highest pull-out results. However,the ratio of the compressive strength of the grout to the “souped” mortar was approximately2.44, whereas the ratio of the pull-out strengths was 1.45. Thus, the mortars performed verywell in comparison to the grout.

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TESTING CONCEPT

Goals

While the compressive strength of masonry is important, the primary concern of this study is howthe masonry, and in particular, the mortar that is used to fill the cells (referred to as mortar fill), islikely to respond to tension in the reinforcement. The ability of the masonry to develop tension inthe reinforcement is related to the ability of the mortar fill to bond to the CMU and the reinforcement.This research is intended to study mortar as grout in reinforced masonry by testing the pull-outstrength of vertical reinforcement and the bond strength of the mortar fill to the units. The study is being performed at an elemental level rather than with full wall tests. The results willbe used to determine if further large-scale testing is appropriate and worthwhile.

Definitions

For the purpose of this research, the following definitions are used.

Mortar fill: ASTM C 270 mortar used as mixed with no water added.

Pourable mortar: ASTM C 270 mortar with water added to produce a pourable consistency.

Grout: ASTM C 476 grout with a slump of 8 to 11 inches.

Fill material: The generic term used for mortar fill, pourable mortar, and grout to makespecimens.

Tests

Two types of tests were performed.

A. Pull-Out TestsNo specific ASTM test was used for this work. Small scale tests were developed in 1996 byRyan-Biggs Associates (RBA) for specific projects to compare the performance of mortar fillto grout when prism-type samples containing a reinforcing bar are exposed to pull out of thereinforcement. That testing concept is the basis for this portion of the research and is similarto the procedure used by Richart 13 to test for tension bond strength.

The tests used were not intended to represent actual wall performance but were selected asmore representative than pure tension tests of lap splices.

A key component of the current study is to create a test that forced a failure in the fill materialunder pull out mode. From those results, it would be possible to compare the performanceof the mortar fill and pourable mortar with the grout. It was decided to place the masonryunits in compression rather than use tension samples. While neither the previous tensiontests nor this work adequately represents walls subjected to flexure, it was decided that theproposed tests would serve to adequately compare mortar fill, pourable mortar, and groutunder similar test conditions. Therefore, from these tests a decision could be made as towhether further full-scale tests were warranted that represent flexural walls and tension testsfor shear walls.

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Figure 1 Pull-Out Test Specimen

In this portion of the study, the performance of the mortar fill is to be judged based upon its:

1. Capacity to develop tension in the reinforcement.2. Capacity to develop tension in the reinforcement relative to code requirements.3. Capacity to develop tension in the reinforcement in comparison to grout.

Testing was performed at Materials Characterization Laboratory, a commercial testinglaboratory in Scotia, New York.

Pull Out Procedure

1. Samples were prepared as shown in Figure 1 with two CMU stack bonded. They wereprepared by a journeyman mason from Bricklayers and Allied Craftworkers (BAC) Local#2 in Albany, New York. The jacking plate was added prior to the test and was set dryon the sample.

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2. Samples were constructed inside the BAC facilities (Photograph 1). The air temperatureat the time of construction was approximately 75°F, with a relative humidity ofapproximately 85 percent.

For consistency, all samples were made similar to ASTM C101914 prisms by rodding thefill material 25 times for each lift. Each sample had three lifts.

3. Each sample was created from a sawn half unit of 8-inch CMU; units had either a squareend or a sash block end. Construction was similar to ASTM C 1019 which containsinformation related to constructing prisms.

Samples were first constructed two units high and allowed to cure for 21 days. Theywere subsequently filled with mortar fill, pourable mortar, or grout and allowed to air dryfor 7 days; no moisture was applied. After 7 days, they were transported to the testingfacility and allowed to continue air curing. Due to the large number of samples and thepresence of reinforcement, the samples were air cured rather than being placed in aplastic bag as recommended by ASTM. The fill material in the samples were 31days oldwhen tested.

4. Samples were tested in a tensile testing machine. Photographs 2 and 3 show the testconfiguration. The top jacking plate was fitted with spacer bars to allow the bearing ofthe steel on the face shells and webs of the CMU and not on the fill material so as not torestrict slippage of the fill material from the CMU.

Photograph 1

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Figure 2 - Pull-Out Specimen in Test Frame

Figure 2 shows the test setup graphically and the free-body diagram of the load application.

5. Test results were recorded for load versus reinforcement slippage and elongation untilmaximum load was applied. The test equipment pulled the reinforcement at a constantrate of 0.2 inches per minute.

6. Samples were photographed and the types of failure categorized.

Photograph 2 Photograph 3

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Photograph 5

B. Tests of Bond Between Fill Material and CMU

No specific ASTM test was available to measure this bond property. The test method in thisstudy followed the procedure outlined in the Department of State Architect of Californiarequirements in California State Chapter 2405(c)3.C. The test method is described inConcrete Masonry Association of California and Nevada document, “RecommendedGrouting Procedure for Hollow Concrete Masonry Constructed Under CAC Title 24.”

Prism samples were prepared similar to thepull-out test samples except without thereinforcing bar. After approximately 40 days,prisms were delivered to the NationalConcrete Masonry Association in Herndon,Virginia. Core samples (6-inch nominal)were taken from the prisms (Photograph 4)and tested in their laboratory.

The intent was to test for bond shearstrength between the fill material and theCMU. Theoretically, these results shouldcorrelate with the results of the pull-out teststhat were observed to fail by pull out of the fillmaterial.

The test is performed with a guillotine apparatus. Each face shell is sheared off in separatetests to derive the bond shear strength (Photograph 5). The arrows indicate the shearingplate elements. The right plate remains stationary; the left plate drops down and shears theface shell from the core sample.

Photograph 4

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Variables

Bedding Mortar:

All samples were constructed with mortar mixed according to ASTM C 270, Type S, proportionedby volume. The proportions were one part portland cement to one-half part lime to four and one-half parts sand by volume (1:0.5:4.5).

Mortar Fill:

Two variations were used with the Proportions method of ASTM C 270:

Mix N: Type N mortar mixed by proportions 1:1:6. Mix S: Type S mortar mixed by proportions 1:0.5:4.5 (same as bedding mortar).

These mixes were mixed with no additional water. This is similar to the “slushed” mortar in theClemson research.

The mortar fill was mixed in a gasoline-powered mortar mixer. Slump measurements were takenwith a concrete slump cone in accordance with ASTM C14315. The mortar fill was placed into theprisms within 30 minutes of mixing. No retempering was done.

Pourable Mortar:

Two variations were used with the Proportions method of ASTM C 270. These included:

Mix NSL: Type N mortar mixed by proportions 1:1:6 with water added, producing aslump of 6 inches.

Mix SSL: Type S mortar mixed by proportions 1:0.5:4.5 with water added, producinga slump of 6 1/4 inches.

These mixes had water added to create a pourable consistency. The previous research at NCMAused a 7 to 9 inch slump; the Clemson work used a 10 inch slump.

The pourable mortar was mixed in a gasoline-powered mortar mixer. Slump measurements weretaken with a concrete slump cone in accordance wtih ASTM C143. The pourable mortar wasplaced into the prisms within 30 minutes of mixing.

Grout:

Two variations were used:

Mix G: ASTM C 476 fine grout mixed by proportions 1:0.1:3.3 with a slump of 10 1/4inches. The proportions are: portland cement, lime, and sand aggregates.

Mix ModG: ASTM C476 fine grout modified with extra lime to proportions of 1:0.4:4.2with a slump of 9 ½ inches. Effectively, this is a Type S mortar with a groutslump.

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Mix G is the basis for comparison for the other mixes since grout is currently recommended bycodes and standards for commercial construction. However, recognizing that grout usuallyproduces much higher strength than is normally associated with mortars, a modified mix (ModG)was created with increased lime content to produce a mix with a compressive strength close to2,500 psi, which was anticipated for the Type S mortar mix. Mix ModG does not comply with theproportions method of ASTM C 476 by virtue of its higher lime content but does conform to thestrength requirements of that standard.

ASTM C 476 specifies a grout slump of between 8 inches and 11 inches. While ASTM allows thegrout to be mixed by proportions, MSJC requires the grout have a minimum strength of 2,000 psi.

Grout was mixed in a gasoline-powered mortar mixer. Slump measurements were taken with aconcrete slump cone in accordance with ASTM C 143. The grout was placed in the prisms within30 minutes of mixing.

Concrete Masonry Units:

Two types of 8-inch CMUs were used for the pull-out tests and bond shear tests. Both weremanufactured by Zappala Block, Inc., of Rensselaer, New York. One type was a regular (normalweight) CMU meeting ASTM C 9016. The second type of CMU was the same as the first with theexception that Block Plus-W10, a liquid integral water-repellent admixture by AddimentIncorporated, Atlanta, GA, (now a subsidiary of W.R. Grace ) was included in the mix in an attemptto provide a lower water absorption rate.

There is no ASTM test to evaluate the rate of absorption in CMU, only total absorption. Thus, it isnot possible to quantify the effect of the integral water-repellent on the rate of absorption.

The face shells of the units were tapered with the top 1 7/16 inches thick and the bottom 1 1/4inches thick. The webs were also tapered with the top 1 1/4 inches thick and the bottom 1 1/2inches thick.

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MATERIAL CHARACTERIZATION

Sand

Test samples were prepared using natural sand from the sand pit of William M. Larned and Sonsin Schenectady, New York. The sand is regularly used locally on masonry projects based uponthe ASTM C14417 testing and certification by Construction Technologies Inc. of Schenectady, NewYork (Appendix A).

Sieve analyes were performed on two additional samples by Ryan-Biggs Associates and ChemicalLime Company for conformance with ASTM C 144. Subsequently, the sand tests were comparedto ASTM C 40418. All three analyses indicated a fine-grained sand. The test results byConstruction Technologies Inc. and Ryan-Biggs Associates indicated the sand met C 144, whilethe Chemical Lime test indicated it did not. Copies of these analyes are included in Appendix A. The results are not inconsistent. Two sieve tests indicated the samples were at the high end of therange for nearly all sieve sizes. The third test indicated that the material exceeded the high endof the range on two sieve sizes. It is not unreasonable that the one sample would exceed the highend of the range for a specific sieve size for this material. Based upon the performance of the sandin the local market and the two passing tests, conformance with ASTM C 144 and its gradationrequirements was assumed.

While the mortar fill sand was tested for compliance with ASTM C 144, grout aggregates arerequired to meet ASTM C 404. By comparing standards, natural sands meeting ASTM C 144 alsomeet the standards for fine aggregates in accordance with ASTM C 404.

Grout

Grout prisms were made in accordance with ASTM C 1019 to determine compressive strength.The air temperature was approximately 70°F with a relative humidity of approximately 55 percentat the time of grout mixing and placement.

Prisms were kept moist with damp paper towels until block molds were removed after two days.The prisms were then wrapped with damp paper towels and placed in plastic bags, palletized, andtransported to the lab by RBA. At the lab, they were placed in a water storage tank in accordancewith ASTM C 51119 to finish the curing process.

Three samples of each mix were tested at 7, 14, 28, and 90 days. A summary of the results isshown below in Table 1. Individual test results are in Appendix B.

All mixes achieved approximately 85 percent of their 28-day strength within 7 days. Between 28and 90 days, the mixes gained less than10 percent greater strength.

Mix G, the typical grout mix, averaged 3,677 psi at 28 days. The modified grout, Mix ModG,averaged 2,323 psi at 28 days. Both mixes had one unusually low test with the 28-day strengthsthat can not be explained. The table gives values denoted with a * that ignore the low values.These values seem more representative of the actual strength when compared to the 7, 14, and90 day strengths. At 90 days, the average values (low values) were 4,187 (4,140) and 3,073(2,940), respectively. Both mixes, G and Mod G, easily surpass the 28-day minimum compressivestrength of 2,000 psi recommended in the MSJC.

The modified grout mix (Mod G) was originally selected to develop a mix that was a high-slump

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grout with a strength close to 2,500 psi at 28 days. That was achieved.

Mix 7 Days 14 Days 28 Days 90 Days

G3080 4050 3010 4200

3160 3460 4180 4220

2790 3950 3840 4140

Mean 3010 3820 3677 (*4010) 4187

Std Deviation 195 316 602 34

COV (%) 6.5 8.3 13.3 1.0

ModG2490 2470 2760 3240

2400 2630 1380 3040

2360 2400 2830 2940

Mean 2416 2500 2323 (*2795) 3073

Std Deviation 67 118 818 153

COV (%) 2.8 4.7 35.2 5.0

Table 1 - Grout Compressive Strengths

Mortar Fill and Pourable Mortar

Since the mortar fill and pourable mortar are being used as grout, samples were also made inaccordance with ASTM C 1019, which is intended for grout and is not the traditional method fortesting mortars. The air temperature was approximately 70°F with a relative humidity ofapproximately 55 percent at the time of mortar fill mixing and placement.

Prisms were kept moist with damp paper towels until the block molds were removed after two days.The prisms were then wrapped with damp paper towels and placed in plastic bags, palletized, andtransported to the lab by RBA. At the lab, they were placed in a water storage tank in accordancewith ASTM C 511 to finish the curing process.

Three samples of each mix were tested at 7, 14, 28, and 90 days. A summary of results are shownbelow in Table 2. Individual tests results are in Appendix B.

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Of the mortar fills, Mix S meets the MSJC minimum compressive strength of 2,000 psi for grout; MixN does not. Of the pourable mortars, neither Mix NSL nor Mix SSL meets the MSJC minimumcompressive strength of 2,000 psi for grout.

Mix 7 Days 14 Days 28 Days 90 Days

N1190 1450 1550 1460

1240 1460 1220 1360

1320 1320 1530 1620

Mean 1250 1410 1433 1480

Std Deviation 66 78 185 131

COV (%) 5.3 5.5 12.9 8.9

NSL1270 1460 1680 1620

1300 1560 1360 1590

1320 1350 1570 1140

Mean 1297 1457 1537 1450*

Std Deviation 25 105 163 269

COV (%) 1.9 7.2 10.6 18.6

S2040 2010 2600 2160

2020 2000 2620 2550

2180 2400 2420 2160

Mean 2080 2137 2547 2290*

Std Deviation 87 228 110 225

COV (%) 4.2 10.7 4.3 9.8

SSL1780 2010 1690 2230

1800 1720 1890 2250

1690 1940 1820 2140

Mean 1757 1890 1800* 2207

Std Deviation 59 151 101 59

COV (%) 3.4 8.0 5.6 2.7

Table 2 - Mortar Fill Compressive Strengths Tested in Accordance with ASTM C 1019

None of the mixes meet the minimum slump requirements of ASTM C 476.

The increase in water content going from a mortar consistency to a pourable mixture had little affect

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on the strength of the N mix going to the NSL mix. However, the increase in water content reducedthe compressive strength in the SSL mix from the S mix.

Individual results did not conform to the usual strength gain trend for Mix NSL at 90 days, Mix S at90 days, and Mix SSL at 28 days. These could not be explained and either raised or lowered themean values. These values are noted with a * in Table 2.

The mortar used as bedding mortar and mortar fill was also characterized by Chemical LimeCompany. The results are part of Appendix A. They provide mortar cube strengths that will bediscussed later.

Concrete Masonry Units

The units were normal weight and manufactured in accordance with ASTM C 90. Manufacturer’sdata indicates the average net compressive strength is approximately 3,138 psi based upon ASTMC 14020 testing (Appendix C).

Reinforcement

Twenty-four-inch lengths of No. 5 reinforcement meeting ASTM A 61521 were used for the pull-outtests. The fabricator reported that the actual yield strength was 61,500 psi and the actual tensilestrength was 98,500 psi. For analysis purposes, the yield capacity was based upon 60,000 psiyield strength and 90,000 psi tensile strength consistent with ASTM A 615 minimum requirements.This produces a yield capacity of 18.6 kips and a tensile capacity of 27.9 kips.

Compressive Strength of Masonry

Using the Unit Strength method, Section 1.4B.2.b., Table 2 of the 2002 MSJC Specifications22, thecompressive strength of the masonry was determined based upon Type S mortar in combinationwith the CMU unit strength of 3,138 psi. This gives a calculated compressive strength of themasonry equal to 2,178 psi. While the grout strength is not included in the development of thisvalue, the MSJC Specification requires that the grout meets either ASTM C 476 or the groutcompressive strength equals or exceeds f'm but not less than 2,000 psi.

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For this study, the compressive strength of the masonry ( f'm) was taken conservatively as 2,178psi or the mortar fill strength, whichever is less, as shown in Table 3.

Mix Compressive Strength (psi) fromTables 1 and 2

Assumed f'm (psi)(CompressiveStrength of Masonry)

Mortar fill N 1,433 1,433

Mortar fill S 2,547 2,178

Pourable mortar NSL 1,537 1,537

Pourable mortar SSL 1,800 1,800

Grout G 4,010 2,178

Grout ModG 2,795 2,178Table 3 - Compressive Strength of Masonry

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TESTING RESULTS

Pull-Out Tests

Loads

Complete results are provided in Appendix D. Photographs of the tests are included on a disk thataccompanies this report. Figure 3 shows a summary of the test results for the regular CMU with thevarious mixes. For reference, the yield strength of the reinforcement is plotted. As previouslynoted, the reinforcement has a minimum yield strength of 18.6 kips and a minimum tensile strengthof 27.9 kips.

Figure 4 shows the summary of the results for the CMU with water-repellent admixture. Individualtest results are in Appendix D.

Figure 3 - Pull-Out Loads versus Mix Type for Regular CMU

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Mix G and Mix ModG gave comparable results.

Figure 4 - Pull-Out Loads versus Mix Type for Water-Repellent CMU

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Figure 5 superimposes the results for all tests. In all tests, the CMU with water-repellent admixturegave higher results.

Figure 5 - Pull-Out Loads versus Mix Type for CMU

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Failure Types

Failure mechanisms took several forms. For the purpose of these descriptions, fill material is eithermortar fill, pourable mortar, or grout. Failures can be classified as:

1. CMU cracking; fill material cracking (Photograph 6).

2. CMU cracking; little or no fill cracking but slippage of the fill material from the core (Photograph 7).

3. No CMU cracking; s p a l l i n g a r o u n dre in fo rcemen t and reinforcement slippage

Photograph 6

Photograph 7

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(Photograph 8).

Cracking was identified as outwardly visible cracking. In some samples, cracking occurred internalto the fill material. This was evident in those samples where the face shells broke away exposingthe fill material and the tensile failure of the fill material near the mortar joint level.

Cracking of the CMU is considered a preferred method of failure in that the stress is beingtransferred to the units. Referring back to Figure 2, it is noticeable that the CMU has tapered faceshells. For the fill material to be pulled out of the top of the specimen, it is possible some of themasonry cracking results from the “wedging” action of the fill material as it slips within the taperedcore. Had the sample been constructed upside down, the fill material would have been locked intothe lip created by the overhanging upper unit at the bed joint. In either configuration, there wouldhave been some mechanical advantage to preventing the fill material from pulling through.

Fill material slippage or slippage of the reinforcement is not a preferable mode of failure. Fillmaterial slippage was a dominant mode of failure for Mix N with regular CMU (four tests) and alsooccurred with Mix SSL (two tests) and Mix ModG (one test). With the water-repellent CMU, Mix N(one test) and Mix S (one test) also had fill slippage. Fill material slippage is a result of bond failurebetween the fill material and the units. Shrinkage of the fill material reduces the bond to the CMUand increases the possibility of fill material slippage from tension in the reinforcement.

Reinforcement slippage, independent of significant cracking, was the dominant mode of failure forMix NSL with water-repellent CMU (six tests) and also occurred with Mix N with water-repellentCMU (one test).

Visible in Photograph 7 is shrinkage at the interface of the CMU and fill material. This may haveoccurred because the samples were initially air dried before being sent to the lab for moist curingand not covered with a plastic bag as recommended by ASTM C 1019. However, it is moreindicative of how real samples are constructed and may perform.

Photograph 8

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Bond Tests

Six-inch-diameter core samples were taken from the prisms as recommended by the Californiastandard. The cells of the CMU were narrow and did not have sufficient width to take the 6-inchcores without coring a portion of the unit. Photograph 9 shows one of the samples after testing; theembedded portion of the web is visible in the sample.

Twelve prisms were made, one for each fill material type and CMU type. One core was taken fromeach prism. Each core produced two samples. This resulted in 24 bond shear test samples.Subsequently, two additional tests were taken from the Mix S prism of the water-repellent CMU.

Loads

Table 5 shown later has a summary of test results. Photographs of tests are provided on the disk.The test results were highly variable. Therefore, it is difficult to draw conclusions with only twoshear values for each type of fill material.

Failure Types

Failure mechanisms took several forms and can be classified as interface or combined. Thespecimens exhibiting interface failures sheared at the joint between the fill material and unit. Thesurface was generally smooth with little mortar fill, pourable mortar, or grout remaining. This wasthe predominant mode of failure.

For the combined failure, the mortar fill, pourable mortar, or grout remained partially intact with theCMU and the shearing went through both the fill material and the interface. There were combinedfailures observed in 5 of the 24 samples.

The initial Mix S samples from the water-repellent CMU tested lower than expected, and a secondset of samples was retested. During the retest, one face shell debonded during the coringoperation and was conservatively recorded as a zero-capacity sample.

Photograph 9

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ANALYSIS OF RESULTS

Pull-Out Tests

2002 MSJC - Allowable Stress Method

Equation 2-8 of the MSJC gives the development length for the reinforcement, Thisl 0.0015d Fd b s= ⋅value assumes a minimum grout strength of 2,000 psi. For the No. 5 reinforcing bar, the bardiameter db = 0.625 inches. For the Grade 60 reinforcement with the allowable stress, Fs = 24,000psi, the calculated ld = 22.5 inches. The test specimens had an actual embedment for the reinforcement of 15.6 inches. This lengthwas selected to try to produce the failure mechanism in the fill material.

There is no MSJC procedure within the Allowable Stress method for calculating the capacity of apartially developed reinforcing bar. However, we assumed that there is a linear relationshipbetween embedment length and the stress in the reinforcement. Therefore, using Equation 2-8 withour reduced actual embedment of 15.6 inches, we solved for the reduced allowable stress, fs =16,640 psi. This results in a reduced allowable force in the bar of 5,159 lbs. A factor of 2.5 is usedto obtain an anticipated ultimate load of 12,898 lbs.

Figures 7 and 8 replicate the test results shown in Figures 3 and 4 and superimpose the anticipatedultimate loads that were calculated. Mix S, Mix SSL, and the grout mixes achieved the anticipatedultimate load. Mix N in water-repellent CMU achieved the anticipated ultimate load also.

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Figure 7 - Pull-Out Loads versus Mix Type for Regular CMU

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Figure 8 - Pull-Out Loads versus Mix Type for Water-Repellent CMU

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2002 MSJC - Strength Design

With the introduction of a Strength Design method in the 2002 edition of the MSJC, a new formulafor development length was produced. It includes factors for the size of the reinforcement (( ) andcover over the bars (K). Bar diameter (db) and specified compressive strength (f'm) are alsovariables. The new formula is .l 0.13d f / K f'd b

2y m= γ φ

( = 1.0 for a No. 5 bar. K = clear cover or five bar diameters, whichever is less. In this case, thefive bar diameters criteria applies and K = 3.13 inches. The capacity reduction factor, N, equals 0.8.

Figure 9 shows the variation in required development length versus masonry strength for the No.5 bar. The six mixes are superimposed along with the actual embedment length of the sample.

Since three mixes (Mix S, Mix G, and Mix ModG) had compressive strengths that exceeded themaximum f'm previously determined by the unit strength method, they are plotted also. However,by the standard, the development length for those three mixes would be based upon the maximumf'm value in the figure.

Using the 2002 MSJC - Strength Design criteria, all of the mixes required a development length thatexceeds the actual length used in the test samples. Theoretically, the ultimate load capacity of thereinforcement should not have been developed and the failure should have occurred in the fillmaterial.

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Figure 9 - Required Development Length versus Compressive Strength ofmasonry (f’m) for No. 5 Reinforcement Centered in 8-inch CMUBased Upon MSJC Strength Design

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2005 MSJC

Recent developments in the MSJC have again resulted in changes to the development length. Thedevelopment length is the same for both Allowable Stress and Strength Design. The new formulais . For the No. 5 bar used in the test, the variables are the same as usedl 0.13d f / K f'd b

2y m= γ

in the 2002 Strength Design. The primary changes are that the capacity reduction factor wasdropped and ( was changed to 1.3 for No. 6 and No. 7 bars.

Figure 10 shows the variation in the required development length versus specified compressivestrength for the No. 5 bar. The six mixes are again superimposed along with the actual embedmentlength of the sample.

As with the 2002 MSJC - Strength Design criteria, the strengths of three mixes (S, ModG, and G)exceeded the maximum f'm previously determined by the unit strength method. While all of themixes are plotted, the development length for the three mixes (S, ModG, and G) would again bebased upon the maximum f'm value in the figure.

Therefore, using the 2005 MSJC criteria, all of the mixes required a development length thatexceeds the actual length used in the test samples and the ultimate load capacity of thereinforcement should not have been developed. Using the actual strength of Mix G as the criterion,it is conceivable that the ultimate load capacity of the reinforcement could be achieved by pull out.

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Figure 10 -Required Development Length versus Compressive Strength ofmasonry (f’m) for no. 5 Reinforcement Centered in 8-inch CMU Basedupon 2005 MSJC

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CODE SUMMARY

For the No. 5 bar, Table 4 indicates the results for the three versions of the MSJC standard. TheLength column is the required development length for the specific standard. The Load is in kipsand represents the force that would be expected to be developed by the actual embedment. Themasonry compressive strengths from Table 3 were used to calculate the development lengths forthe 2002 MSJC - Strength Design and 2005 MSJC methods.

Mix 2002 MSJC - ASD 2002 MSJC -Strength

2005 MSJC

Length(inches)

Load(kips)

Length(inches)

Load(kips)

Length(inches)

Load(kips)

Mortar fill N 22.5 12.8 32.0 9.1 25.6 11.3

Mortar fill S 22.5 12.8 26.0 11.2 20.8 14.0

Pourable mortar NSL 22.5 12.8 30.9 9.4 24.7 11.7

Pourable mortar SSL 22.5 12.8 28.6 10.2 22.9 12.7

Grout G 22.5 12.8 26.0 11.2 20.8 14.0

Grout ModG 22.5 12.8 26.0 11.2 20.8 14.0

Table 4 - Development Lengths

Figure 11 superimposes the tested pull-out values with the calculated values from the three codecriteria. By all criteria, pull-out loads obtained with Mix S, Mix SSL, Mix G, and Mix ModG exceededthe calculated capacities for all three design methods. In addition, the pull-out loads obtained withMix G and Mix ModG exceeded the yield strength of the reinforcement as well.

Mix N with water-repellent units achieved the calculated capacities for the three design methods;Mix NSL did not.

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Figure 11 - Pull-Out Loads versus Mix Types

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Tests of Bond Between Fill Material and CMU

These test results are provided in Appendix E and are summarized in Table 5. The Average BondShear Stress is calculated from the individual test results on the front and rear face shells. TheEffective Pull-out Capacity is calculated from the Average Bond Shear Stress times the surfacearea of the perimeter of the CMU cell for the sample (358.64 in2).

The Tested Pull-out results from Figures 3, 4, and 5 are listed along with the calculated Pull-outBond Stresses resulting from the pull-out tests.

Mix MasonryUnit

BondShearStress-FrontShell(psi)

BondShearStress -RearShell(psi)

AverageBondShear Stress(psi)

EffectivePull-OutCapacity(lbs)

TestedPull-out(lbs)

Pull-outBondStress(psi)

N Reg 29.6 37.4 33.5 12,015 12,297 34.3

N WR 28.8 24.9 26.9 9,630 14,257 39.8

S Reg 144.8 105.9 125.4 44,956 15,261 42.6

S WR#1 49.1 63.1 56.1 20,120 16,265 45.4

S WR#2 0 93.1 46.5 16,677 16,265 45.4

NSL Reg 141.7 9.3 75.5 27,078 9,682 27.0

NSL WR 17.9 167.4 92.7 33,228 11,402 31.8

SSL Reg 21.8 197.8 109.8 39,379 14,333 40.0

SSL WR 191.6 70.9 131.3 47,072 15,816 44.1

G Reg 204 105.1 154.6 55,428 21,924 61.1

G WR 206.4 338 272.2 97,623 21,977 61.3

ModG Reg 199.3 24.9 112.1 40,204 20,665 57.6

ModG WR 160.4 88.8 124.6 44,687 19,656 54.8

Table 5 - Bond Shear Tests

This testing is not incorporated into ASTM. It is primarily used in California where therecommendation from the Office of the Architect of the State of California is that 100 psi is anacceptable bond shear stress.

Overall, the bond shear stress results were highly variable.

The bond shear stress for tests exceeded 100 psi for Mix S with regular units and Mix G with

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regular and water-repellent units. Mixes NSL, SSL, and ModG with regular and water-repellent unitsall had one of the two tests exceed 100 psi. The average bond shear stress of Mix S with regularunits and Mixes SSL, G, and Mod G with regular and water-repellent units exceed 100 psi.

Two sets of samples were tested for Mix S with water-repellent units (WR) because the results ofthe first tests appeared to be lower than anticipated. The second test gave one higher result, butthe other test from the front face shell debonded during the coring operation.

In all cases except for Mix N, the average bond shear stress exceeded the calculated bond stressesfrom the pull-out tests. That correlated well with the pull-out tests in that most did not fail in bond.That was interesting because most of the samples when viewed from the top appeared to haveshrinkage around the perimeter of the fill material.

From observations of the pull-out tests, we note that there were fill material pull outs (bond shearfailure with the CMU) for individual samples comprised of N Reg, N WR, S WR, SSL Reg, andModG Reg.

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COMMENTS

General

1. Pourable mortar Mix SSL is currently allowed by the International Residential Code.

2. The pull-out tests for Mix S versus Mix SSL indicate that mortar fill performs better than“pourable” mortars with a 6 inch slump.

3. The bond tests for Mix S versus Mix SSL indicate that mortar fill performs better than“pourable” mortars with a 6 inch slump with regular CMU but not the CMU with water-repellent.

4. In the Clemson tests, “pourable” mortars had higher compressive strengths than the mortarfills. As was seen in Table 3, in this study there was little difference in compressive strengthfor Mix N as a result of adding water to make it pourable (Mix NSL). In contrast to theClemson study, this study produced a significant reduction in the compressive strength ofMix S by adding water to create a pourable consistency (Mix SSL).

5. Test results indicate that Mix G performed the best of all mixes. While mortar fill Mix Sachieved 64 percent of the grout strength of Mix G, it had 70 percent of the pull-out strengthfor regular CMU and 74 percent of the pull-out strength for the CMU with water-repellent.

6. Table 6 compares the 28-day strengths of Mix N and Mix S when tested as mortar cubesversus the grout prisms. The results are included in Appendix A from Chemical LimeCompany. The mortar cubes tested in accordance with ASTM C 78023 overstate thestrength of mortar used as fill material.

Mortar (mixed byproportions)

Mortar Cubes (ASTM C 780)

Grout Prisms(ASTM C 1019)

Ratio

Type N 2421 psi 1433 psi 0.59

Type S 4132 psi 2547 psi 0.61

Table 6 - 28-Day Compressive Strengths for Type N and Type S Mortars

This is not unexpected. ASTM C 780 indicates that mortar samples made as cylinders willtest to approximately 85 percent of the values obtained using cubes due to the variation inaspect ratio of the samples. In this study, the prisms tested to approximately 60 percent ofthe cube samples made in compliance with ASTM C 780. The reduction can generally beexplained as a result of the increased water content of the prisms providing lowercompressive strengths.

Therefore, mortar fill should be evaluated in accordance with ASTM C 1019.

7. The use of sand meeting ASTM C 144 appears to be acceptable for mortar fill.

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Based upon the Pull-out Tests:

1. The mortar fill performed better than the “pourable” mortars with a 6 inch slump that areallowed by residential codes for the conditions tested in this study.

2. The mortar fill mixes achieved higher pull-out values when the CMU contained the water-repellent admixture. The pull-out strengths of the grout mixes were relatively unchangedby the use of CMU with water-repellent admixture.

3. The pull-out load results increased with increasing compressive strength of the fill material.

4. The compressive strengths of Mix N and Mix NSL were less than 1,600 psi when measuredby ASTM C 1019. In general, these mixes did not achieve adequate pull-out values.

5. The pull-out loads achieved with mortar fill Mix S exceeded the required calculated loadsfor all three design methods in the codes. The compressive strength of the mix exceeded2,000 psi and was closer to 2,500 psi.

6. The pull-out loads achieved with pourable mortar Mix SSL exceeded the required calculatedloads for all three design methods. The compressive strength of the mix was approximately1,800 psi.

7. The pull-out loads achieved with grout mixes Mix G and Mix ModG exceeded the requiredcalculated loads for all three design methods. The compressive strength of the mixesexceeded 2,800 psi.

8. The pull-out loads achieved with the grout mixes (Mix G and Mix ModG) exceeded the yieldstrength of the reinforcement. This was well beyond what was anticipated or requiredbased upon the three MSJC design methods. All three methods had calculated pull-outloads well below the yield value.

9. The use of water-repellent admixture in the CMU had little affect on the pull-out test resultsfor the grout mixes. It appears the grout water content was sufficiently high that thedifference in loss of water through absorption into the units had a negligible effect.

10. While Type M mortar fill was not tested, it is likely that, based upon the results for mortarfill Mix S, it too would have produced pull-out loads that exceed the three design methods.

11. The 2002 and 2005 MSJC formulas produced results for development length that are moreconservative when based upon the compressive strength of the masonry (f'm) as determinedby the unit strength method rather than the fill material strength.

12. Pull-out strengths for Mix S and Mix SSL were acceptable in spite of the observed shrinkageof the fill material.

Based upon the Bond Tests:

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1. The coring operation to obtain the bond shear samples is highly operator dependent.Based upon the speed of the coring, the angle of the core relative to the surface, and thequality of the core drill, it is possible to introduce stress into the sample and, in the extremecase, to “spin-off” the face shell. The reduction in the tested shear stress due to thesampling is unknown.

Standard procedure is to take a second sample if one is damaged by the coring operation.

2. The fill material exhibited shrinkage, but the mortar fill shrinkage seemed greater.

The shrinkage and the coring operation apparently resulted in significant shear stressdifferences from one face shell to the other in samples Mix NSL, Mix SSL, Mix G, and MixModG with regular CMU and Mix NSL, Mix S, Mix SSL, Mix G, and Mix ModG with water-repellent units.

3. While the California standard does not have a minimum standard for its grout bond test, 100psi is considered acceptable. The grout mixes developed the highest bond shear stresses.The other mixes did not give consistent results.

4. The effect of coring a portion of the web of the CMU was considered insignificant. Theresults were not consistently greater due to a portion of the unit in the sample.

5. With only two bond shear tests for each mix, there was too much variability in the resultsto draw any reliable conclusions about the shear bond characteristics of the fill materials.

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CONCLUSIONS/RECOMMENDATIONS

Overall, the goals of the research were achieved. Mortar fill was evaluated to compare it withpourable mortar and grout as a means to encase reinforcement in vertical applications. The resultsare:

1. The elemental test results indicate that mortar fill could be an acceptable alternative to finegrout for modified low-lift applications of reinforced masonry. The specifics of themodifications for installation techniques need to be developed but could include the liftheight, the method of consolidating the mortar fill, the board life of the mortar, retempering,and splicing the reinforcement.

2. While high-slump grout may be necessary for high-lift grouting operations, the high-slumpmaterial may not be required for low-lift grouting applications. Type S and Type M mortarfill and “pourable” mortars offer an alternative worth further consideration.

Mix N and Mix NSL did not perform adequately. It appears the compressive strength of thematerial is too low for use as a fill material. The minimum MSJC value of 2,000 psi for thegrout seems reasonable.

3. Mortar fill performed better than “pourable” mortar in the pull-out tests.

4. The development length of reinforcement based upon the MSJC criteria (2002-StrengthDesign and 2005) should be based upon the lesser of the compressive strength of themasonry (from unit strength method or prism test method) or the 28-day mortar fill strength.The minimum mortar fill strength should be 2,000 psi.

5. A reduction in the absorption of the concrete masonry units improved the pull-out strengthof the mortar fill. Lower absorption of the units was created by the use of an integral water-repellent additive. The improved strength is likely due to the higher compressive strengthof the fill due to reduced water loss from the mix. Whereas the grout has excess water torelease to the units, the water retention from the mortar fill is helpful in the hydration of themortar. It could also be due to reduced shrinkage.

This is somewhat consistent with Isberner’s statements that low slump material can provideadequate strengths. However, the mix needs to be appropriately designed.

6. No definite conclusions can be drawn from the grout bond shear stress tests based uponthe variability of the results and the small sampling.

7. The sampling process for the bond shear stress test weakens the sample. The resultsseem to be affected by the sampling. A test program that compares the bond shear testmethod to push-through samples of fill material might provide some insight into the effectsof the coring operation.

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8. Full-scale wall tests that evaluate flexural and axial capacity should be performed basedupon the following criteria.

A. Mortar fill with a minimum compressive strength of 2,000 psi when tested inaccordance with ASTM C 1019. This should be Type S and Type M mortars.

B. For consistency with this study, the mortar fill would be portland cement and lime-based mortar meeting ASTM C 270.

C. Wall specimens should be constructed in a modified low-lift application. A procedure should be developed for the installation that should be consideredmandatory if the use of mortar as grout is proposed to MSJC. The procedure shouldinclude lift height, consolidation method, board life of the mortar, retempering, andreinforcement splicing. Consolidation of the mortar fill must be complete andconsistent.

D. The results should be compared to those for walls constructed using the low-liftmethod using fine grout.

E. The bond shear strength tests should be repeated with a larger sampling to furtherexamine the shrinkage characteristics of the mortar fill and its impact on bond shearstress.

9. Several additional issues became evident during this research and should be evaluatedfurther.

A. The performance of the ModG mix indicates that Type S and Type M portlandcement and lime mortars mixed to a grout consistency could provide a suitablesubstitute for ASTM C 476 grout.

B. The unit strength method for determining the compressive strength of the masonryis based upon the CMU strength and the mortar type. It does not involve the mortarfill or grout strength. This study indicates that the development length and laplengths for reinforcement should be evaluated using the mortar fill or grout strength.

C. In this study, the reinforcement always developed in a shorter length than calculatedusing the compressive strength of the masonry based upon the unit strengthmethod. One distinct possibility is that the unit strength underestimates thecompressive strength of the masonry sufficiently to require significantly longer lapsthan would be necessary had the compressive strength of the masonry beendetermined using the prism test method. MSJC should reconsider the lap lengths and development lengths for reinforcement.To avoid overly conservative lap lengths, the compressive strength of the masonryused in the determination of lap lengths should not be based upon the unit strengthmethod; it should be based upon grouted prisms.

D. It is the author’s opinion that research on lap lengths is needed that tests samplesin flexure in comparison to pure tension samples. It would be appropriate todetermine different lap lengths based upon the application.

E. Shrinkage effects of mortar fill and grout should be evaluated further relative to bondwith regular and low absorption units. Grout aids or other admixtures could beconsidered that increase bond.

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F. The use of water-repellent additives or other admixtures in mortar fill should beevaluated for their affect on the material when used as a grout.

G. The importance of the bond shear strength should be evaluated in light of theexistence of core insulation that has received the acceptance of BOCA EvaluationServices for grouted masonry. The insulation is U-shaped and debonds the groutfrom the face shells and one web leaving the grout only bonded to one web.

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ACKNOWLEDGMENTS

Peer Review Group

The peer review team for the research program:

John Buck , Bricklayers and Allied Craftworkers Local 2. Brian Trimble PE, Brick Industry Association (formerly International Masonry Institute - Mid-

Atlantic Region). Gene Abbate, International Masonry Institute - Empire State Office. Diane Throop PE, Consultant; Chair of MSJC Construction Practices Subcommitee. Robert Thomas, National Concrete Masonry Association. Margaret Thomson, Chemical Lime Co.; MSJC member. Dr. Arturo Schultz, University of Minnesota; MSJC member. Tom Murray, Colonie Masonry Corporation of Albany, Inc. Arthur Del Savio, Del Savio Construction Corp. Donations

Major funding for this research was provided by:

International Masonry Institute, represented by Mr. Gene Abbate.

National Lime Association, represented by Mr. Eric Males and Ms. Margaret Thomson.

Bricklayers and Allied Craftworkers, Local No.1, New York, New York.

National Concrete Masonry Association Research and Education Foundation representedby Mr. Robert Thomas, P.E., Vice President of Engineering.

Donated materials and services were provided by:

Dimension Fabricators, Scotia, New York, represented by Mr. Scott Stevens, President -reinforcement.

V. Zappala and Co., Rensselaer, New York, represented by Ralph Viloa Jr. - concretemasonry units.

Glens Falls Lehigh Cement Co., Glens Falls, New York, represented by Mr. Peter Maloney -portland cement.

Graymont Dolime (OH), Inc., Genoa, Ohio, - hydrated lime.

Chemical Lime Co., Henderson, Nevada, - mortar characterization represented by Ms.Margaret Thomson and Mr. Richard Godbey.

Bricklayers and Allied Craftworkers - Local No. 2, Albany, New York, represented by Mr.John Buck and Mr. Bart McClellan - masonry sand; fabrication of samples.

Subcontractors

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Evergreen Testing and Environmental Services, Inc., Menands, New York, - compressiontesting.

Materials Characterization Laboratory Inc., Scotia, New York, - pull-out tests.

National Concrete Masonry Association, Herndon, VA - grout bond shear tests.

Ryan-Biggs Associates, P.C.

Thanks to Don Trojak for coordinating the testing and assisting with the sample preparation;Ross Shepherd for graphics; Jill Shorter for report preparation assistance; Jack Healy forreviewing the report; and Barbara Meagher for editing.

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ASTM C144: Size Distribution of Sand: Sieve Analysis

0

2040

6080

100

#4 #8 #16

#30

#50

#100

#200

Sieve Sizes

Perc

ent P

assi

ng C-144 Low

C-144 High

PercentPassing

APPENDIX A - SAND TEST RESULTS

RYAN-BIGGS ASSOCIATES, P.C.

MATERIAL SOURCE: Mason Sand from Wm. Larned & Sons Inc.MATERIAL DESCRIPTION: Sand, fine/medium, trace Silt/Clay

MATERIALPROJECT USE: Mortar and Mortar FillRBA Project Number: 8379DATE: October 15, 2004

Sieve Percent C-144 C-144 PercentSize Retained Low High Passing#4 0 100 100#8 0 95 100 100#16 4 70 100 96#30 27 40 75 73#50 67 10 35 33#100 86 2 15 14#200 96 0 5 4

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APPENDIX B - GROUT AND MORTAR FILL TEST RESULTS

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APPENDIX C - CONCRETE MASONRY UNIT TEST RESULTS

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APPENDIX D - PULL-OUT TEST RESULTS

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APPENDIX E - BOND TEST RESULTS

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APPENDIX F - REFERENCES

1. Building Code Requirements for Masonry Structures (ACI 530-02 / ASCE 5-02 / TMS 402-02), Masonry Standards Joint Committee, 2002.

2. ASTM C 476-02, “Standard Specification for Grout for Masonry,” ASTM International, WestConshohocken, PA.

3. ASTM C 270-02, “Standard Specification for Mortar for Unit Masonry,” ASTM International,West Conshohocken, PA.

4. 2005 Personal correspondence from James E. Amrhein, former Executive Director ofMasonry Institute of America, Los Angeles, CA

5. Grout...The Third Ingredient, James E. Amrhein, MASONRY INDUSTRY magazine, June1980

6. Technical Note 9B - Manufacturing, Classification, and Selection of Brick, Part 3 RevisedDecember 2003, Brick Industry Association, Reston, VA

7. Grout for Reinforced Masonry, A.W. Isberner, Jr., ASTM STP: Masonry: Materials,Properties, and Performance, ASTM International, West Conshohocken, PA., 1982

8. 1982 Edition, Uniform Building Code, International Code Council, Falls Church, VA.

9. One and Two-Family Dwelling Code, Council for American Building Officials, InternationalCode Council, Falls Church, VA.

10. 2000 International Residential Code, International Code Council, Falls Church, VA, 2000.

11. Reinforcement Bond Strengths in Portland Cement-Lime Mortars, Masonry Cement Mortars,and Fine Grout, NCMA research and Development Laboratory, Hedstrom and Thomas,June 1991.

12. Feasibility of Using Mortar in Lieu of Grout for Reinforced Hollow Clay Wall Construction,Russell Brown, Clemson University, 1998. Unpublished, but cited with permission of theWall Committee of the National Brick Research Center.

13. Bond Tests Between Steel and Mortar in Reinforced Brick Masonry, F.E. Richart, StructuralClay Products Institute, February, 1949.

14. ASTM C 1019-02, “Standard Test Method for Sampling and Testing Grout,” ASTMInternational, West Conshohocken, PA.

15. ASTM C 143-03, “Standard Test Method for Slump of Hydraulic Cement Concrete,” ASTMInternational, West Conshohocken, PA.

16. ASTM C 90-02, “Standard Specification for Loadbearing Concrete Masonry Units,” ASTMInternational, West Conshohocken, PA.

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17. ASTM C 144-02, “Standard Specification for Aggregate for Masonry Mortar,” ASTMInternational, West Conshohocken, PA.

18. ASTM C 404-97, “Standard Specification for Aggregates for Masonry Grout,” ASTMInternational, West Conshohocken, PA.

19. ASTM C 511-03, “Standard Specification for Mixing Rooms, Moist Cabinets, Moist Rooms,and Water Storage Tanks Used in the Testing of Hydraulic Cements and Concretes,” ASTMInternational, West Conshohocken, PA.

20. ASTM C 140-02a, “Standard Test Methods for Sampling and Testing Concrete MasonryUnits and Related Units,” ASTM International, West Conshohocken, PA.

21. ASTM A 615, “Standard Specification for Deformed and Plain Billet-Steel Bars for ConcreteReinforcement,” ASTM International, West Conshohocken, PA.

22. Specifications for Masonry Structures (ACI 530.1-02 / ASCE 6-02 / TMS 602-02), MasonryStandards Joint Committee, 2002.

23. ASTM C 780-02, “Standard Test Method for Preconstruction and Construction Evaluationof Mortars for Plain and Reinforced Unit Masonry,” ASTM International, WestConshohocken, PA.


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