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MASONRY
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TECHNICAL TEAM
Coordination:• Prof. Fernando Branco ([email protected])• Prof. Jorge de Brito ([email protected])
Contents:• Prof.ª Inês Flores-Colen • Arq.ª Natasha Redin• Arq.º Pedro Dias• Arq.º Vítor Ferreira• Prof. João Correia• Prof. Jorge de Brito (translation)• Prof. Pedro Paulo
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TABLE OF CONTENTS
1. INTRODUCTION1.1. The brick masonry construction1.2. Field of application1.3. Advantages1.4. Limitations1.5. Types and definitions1.6. Chapter conclusions
2. ANOMALIES AND THEIR CAUSES2.1. Introduction2.2. Anomalies (physical/mechanical source)2.3. Anomalies (chemical source)2.4. Anomalies (biological source)2.5. Chapter conclusions
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CHAPTER 1
INTRODUCTION
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1. INTRODUCTION
BRICK MASONRY
Subchapters:
1.1 The brick masonry construction
1.2 Field of application
1.3 Advantages
1.4 Limitations
1.5 Types and definitions
1.6 Chapter conclusions
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1.1 The brick masonry construction
1. INTRODUCTION
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Brick remained throughout the centuries one of the main constructionmaterials. In the XX century, stone masonry walls were replaced bybrick walls, going from a single-leaf stone or brick wall until the recentdouble-leaf walls incorporating various components (insulation, watervapour retarders, bottom gutter, air cavity ventilation, water drainageand thermal bridge correction).
1.1 The brick masonry construction
Present walls are linked to more efficient, thinner and lighter structural systems thanin the past
1. INTRODUCTION
1940’s 1950’s1940’s 1960’s 1970’s 1980’s
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Assemblage of stones, bricks or other materials that, convenientlylaid and locked by superimposition using mortars, are used for theexecution of building walls.
Masonry:
1.1 The brick masonry construction
“It is estimated for our country that masonry works, including their renders,correspond to around 13% to 17% of the overall construction value.” - in Regulationand Standardization of Masonry Construction - Studies Planning, from LNEC
1. INTRODUCTION
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Ceramic brick masonry is made of bricks (solid or hollow) andtheir laying and/or coating mortars.
Their perform a load-bearingrole (structural masonry) ora filling role (mere panels inbetween structural elements).
The red clay bricks are themasonry elements with greaterproduction in Portugal, with manyceramic companies spread allthe national territory.
1.1 The brick masonry construction
Production in Portugal
1. INTRODUCTION
Production tonnes/year
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NP 834 defines the acceptance criteria of ceramicbricks in terms of their aspect, touch, mechanicalstrength, efflorescence susceptibility, soluble saltsand durability.
Bricks shape:
NP 80 defines the normalized shape of the bricksand their size tolerances.
Characteristics and tests:
Types of bricksBricks sizes
1. INTRODUCTION
Brickuncoated
Solid Horizontal holes
Perforated Vertical holes without socket
Vertical holes with socket
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1.2 Field of application
1. INTRODUCTION
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The first civilizations from Western Asia, especially those from the Tiger and Euphrates valleys (Sumer, Babylon and Assyria), had very scarce timber and stone reserves for construction, but had available great amounts of alluvial clay for the production of bricks, both fired and baked under the sun.
1.2 Field of application
Minaret of the Great Mosque of Samarra (in Universal
Architecture - Islam)
1. INTRODUCTION
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The application of bricks was common in the Greek and Romantimes. The latter used them in several ways, particularly to buildarches and vaults.
In the V century, the destruction of theRoman civilization by the Barbarianscaused the loss of the art of makingbricks.
In Central Europe, for centuries,Brick construction was almost inexistent.The few constructions made usedbricks stolen from Roman ruins.
1.2 Field of application
Roman construction
1. INTRODUCTION
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In the Middle Ages, around the XII century, the manufacture ofbricks restarted in Holland and in some areas of Germany, wherethe stone and timber available for construction was scarce. Fromhere it expanded to the British Isles and the North of Europethrough the Flemish merchants.
In Italy, the alluvial clays of theLombardy plain provided thebricks for some of the mostdecorative buildings of theGothic and Renaissance periods.
1.2 Field of application
Construction in Reggio Emilia (Italy)
1. INTRODUCTION
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Until the beginning of the XIX century, the brick manufacturingprocess was manual. In the middle of that century, with theincrease in populations and the beginning of the industrialrevolution, the brick with horizontal holes as an industrial productfor construction emerges, initiating a large scale production.
Since then, there has been a noticeable expansion of brickmasonry, due to this element’s aptitude to guarantee the comfort ofconstruction.
1.2 Field of application1. INTRODUCTION
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In the beginning of the XX century, the masonry load-bearing wallswere relegated to second place in favour of other constructionsolutions.
With the evolution of steel and reinforced constructions, the use ofbrick was not discontinued and, even though it has alreadyperformed more important structural roles, it is still widely useful,and its replacement is not foreseen in the near future.
To make external walls, masonry essentially starting playing asecondary role of filling the panels. The publication of Eurocode 6relative to masonry structures may lead to a greater future use ofstructural masonry.
1.2 Field of application1. INTRODUCTION
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Saint Anthony, Padua, Italy
Buildings/monuments: Bullfighting arena, Lisbon
1. INTRODUCTION
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Bridges:
1. INTRODUCTION
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1.3 Advantages
1. INTRODUCTION
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Brick masonry, as long as it is designed and executed according tothe adequate codes and construction rules, are capable ofperforming an appropriate load-bearing and hygrothermal role,even under adverse in use conditions.
1.3 Advantages
Relative to other traditional walls:• Economical execution;• Easy assemblage;• Easy to open grooves;• Reasonable thicknesses and self weight;• Incombustible constituent material;• Good hygrothermal behaviour;• Is complies with the minimum demands ofacoustic insulation;
• Liable of rational reuse.
1. INTRODUCTION
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1.4 Limitations
1. INTRODUCTION
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• Greater execution complexity for double-leaf walls;
• Qualified workmanship required; • Difficult to integrate and make compatiblethe various construction elements(current wall area, external coating andsingularities).
The lack of standardization in the national production of accessories and elements to detail the singularities of the double-leaf walls leads to improvisation and deficient construction quality situations.
Thermal correction in a blinds boxle
1. INTRODUCTION
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1.5 Types and definitions
1. INTRODUCTION
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From a structural viewpoint: filling masonry or structural (or load-bearing) masonry.
a) Classification from a structural viewpoint:
1.5 Types and definitions
Filling or structural masonry?
1. INTRODUCTION
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In Portugal, “masonry is predominantly used to fill in between the structural meshes of external walls and to execute partition walls” - in Regulation and Standardization of Masonry Construction - Studies Planning, from LNEC.
Filling masonry:
Double-leaf wall
1. INTRODUCTION
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The use of structural masonry has different importance in variousEuropean countries.
Hotel with 12 floors, in reinforced masonry with double-leaf walls of ceramic bricks, EUA
1.5 Types and definitions
Structural masonry:
Duplex structure with three floors made with ceramic blocks, Switzerland
1. INTRODUCTION
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In Portugal, even though load-bearing masonry have been moredominant in the past, presently their use is little relevant. The fewexamples of structural masonry correspond generally to smallbuildings, practically without design.
Recent studies have shown that this solution can be economicaland functionally interesting for buildings of moderate size.
GNR station, in Ourique
1.5 Types and definitions1. INTRODUCTION
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Structural masonry differs from current masonry, not only in thedesign method and planning, but also in the construction methodsand detailing and, naturally, in the materials used.
To improve the shear and flexural strength and increase theductility of the walls, it is frequent to use steel reinforcement in thehorizontal joints and in vertical confinement elements.
1.5 Types and definitions
Structural masonry (non-paralepipedic shape)!
1. INTRODUCTION
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From a composition viewpoint: single-leaf, double-leaf or mixedwalls.
Internationally, there is in variouscountries a trend for thedevelopment of façade with single-leaf solutions as analternative to the execution ofdouble-leaf walls. In Portugal,some studies have been madeof new shapes and constructivesystems that ensure the variousfunctional requirements.
b) Classification from a composition viewpoint:
1.5 Types and definitions
Insulation in the wall’s air cavity
1. INTRODUCTION
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Mixed walls
Walls that incorporate various types ofconstituents: stone and brick masonrywalls.
1.5 Types and definitions
Mixed technique: solid brick to make the vault, filling with rubble stone
masonry and part of the arch with regular stone
masonry - Monastery of S. Martinho de Tibães
1. INTRODUCTION
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1. INTRODUCTION
Pombaline system (cage)• Masonry made of stone and solid ceramic brick, with a timber truss;• Walls with an important role in the structures’ global interlocking, decisive
for the performance against horizontal loads;• Thickness around 0.90 m at the ground level, successively thinned up to
the highest floor.
The timber truss, embedded in the masonry mass,withstands the seism.
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Classify the masonry used in external walls in Portugal from a structural and composition viewpoint
1. INTRODUCTION
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In Portugal, external masonry are double-leaf and for filling purposes, made with ceramic brick with many horizontal holes and with small mechanical strength, very frequently using insulation in the air cavity, especially in the coldest regions.
1.5 Types and definitionsDouble-leaf filling masonry
1. INTRODUCTION
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There are other factors that influence the behaviour of walls:• Type of laying mortar;• Assemblage type of the elements of the wall;• Number of wall leaves and their connections, between themselvesand with the structure;
• Type of coating of the wall;• Existence of complementary elements of thermal insulation, watertightness and vapour diffusion control;
• Location of the wall;• Position of the wall relative to the ground.
c) Other classifications:
1.5 Types and definitions
The mortar must be able to accommodate the dimensional variations and the physical properties of the brick, after it has been laid.
1. INTRODUCTION
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EC6, devoted to structuralmasonry walls, classifiesthem according to the type ofthe constituent materials and,complementarily, according tothe type of leaves and theirconnections.
d) Classification according to EC6:
1.5 Types and definitions
Types of masonry walls according to EC6, using
various types of bricks
1. INTRODUCTION
Single-leaf walls Double-leaf walls
Uncoated wall Double-leaf walls
Discontinuous joints walls Curtain walls
Walls with no
longitudinal joint
Walls with no
longitudinal joint
Walls with longitudinal
joint
Uncoated units
Longitudinal joint
Cladding wall
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In terms of the actions they can be subjected to and the structural role they play, EC6 classifies the walls as:• Load-bearing walls;• Bracing or shoring walls;• Walls subjected to shear;• Partition walls; • Walls subjected to lateral loads.
From a strongly structural viewpoint, EC6 and EC8 also make a distinction between unreinforced, reinforced, prestressed and confined masonry.
1.5 Types and definitions
Reinforced masonry-cracking prevention
1. INTRODUCTION
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1.6 Chapter conclusions
1. INTRODUCTION
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. Since human beings started building shelters clay was a materialoften used. The use of bricks goes back to faraway times;
. It is estimated, for Portugal, that masonry works, includingrenders, correspond to around 13% to 17% of the overallconstruction value;
. Masonry, if designed and executed according to the technicalrules, are able to play an appropriate load-bearing andhygrothermal role, even in adverse working conditions;
. Generally, masonry can be classified from the structural (filling orstructural) or composition (double-leaf, single-leaf or mixed)viewpoint.
1. INTRODUCTION
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SOLID BRICK MASONRY
LOAD-BEARING NON LOAD-BEARING
EXTERNAL/INTERIOR EXTERNAL/INTERIOR
GROUND LEVEL HIGHER GROUND LEVEL HIGHER
FACADE GABLE SEPARATION PARTITION
DOUBLE-LEAF SINGLE-LEAF DOUBLE-LEAF SINGLE-LEAF
WITH AIR CAVITY
WITHOUT INSULATION WITH INSULATION
1.6 Chapter conclusionsConjugation of various classification types:
HOLLOW BRICK MASONRY
NON LOAD-BEARING
EXTERNAL INTERIOR
GROUND LEVEL HIGHER GROUND LEVEL HIGHER
FACADE GABLE SEPARATION PARTITION
DOUBLE-LEAF SINGLE-LEAF
WITH AIR CAVITY
WITHOUT INSULATION WITH INSULATION
1. INTRODUCTION
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. The industrialization of construction, the short deadlines ofconstruction and the growing size of buildings have definitelyrelegated to a second plan the development of load-bearingmasonry (in the inverse proportion of the development ofreinforced concrete);
. The recent publication of Eurocode 6 and its future application,will allow a new boom of the use of structural masonry;
. In Portugal, the present situation corresponds to filling double-leafwalls, made with ceramic brick with many horizontal holes andmechanically weak, very frequently using insulation in the aircavity;
. There are several research studies developed within thePortuguese universities related with the use of structural single-leaf walls.
1. INTRODUCTION
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CHAPTER 2
ANOMALIES AND THEIR CAUSES
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Subchapters:
2.1 Introduction
2.2 Anomalies (physical/mechanical source)
2.3 Anomalies (chemical source)
2.4 Anomalies (biological source)
2.5 Chapter conclusions
2. ANOMALIES AND CAUSES
ANOMALIES
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2.1 Introduction
2. ANOMALIES AND CAUSES
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The materials characteristics (design), the execution and the maintenance actions are decisive factors for the good performance of masonry during its service life, minimizing the occurrence of anomalies.
The main anomalies that occur in brick masonry are related with cracking or water action related phenomena. It is stressed that these two phenomena are not independent, and each of them may cause or worsen the other.
In this chapter, the anomalies are divided in three main groups: anomalies with a physical/mechanical, chemical and biological source.
2. ANOMALIES AND CAUSES
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Anomalies classification:
Anomalies with aphysical/mechanical
source
Anomalies with achemical source
Anomalies with abiological source
Cracking
Crushing
Disaggregation
Spalling
Erosion
Anomalies due to humidity
Efflorescence/cryptoflorescence
Swelling
Stains
Loss of colour
Moulds and fungi
Disintegration of the joints
Vegetation growth
Moulds/fungi
Other biologicalagents
2. ANOMALIES AND CAUSES
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Actions that may cause anomalies:
• Excess weight;• Foundations settlement;• Seismic actions;• Temperature changes;• Freeze/thaw cycles;• Cryptoflorescence;• Extreme temperatures;• Water absorption;• Pollution;• UV rays.
The actions originate the causes that lead to given consequences, the anomalies (action - cause - effect).
2. ANOMALIES AND CAUSES
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Incorrect stocking of bricks on site
Design and execution errors:
The brick masonry performance is strongly influenced by the design (detailing and materials characteristics) and execution (specialized workmanship) quality.
Opening of grooves
2. ANOMALIES AND CAUSES
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Brick is a porous material with great water absorption capacity.
Brick:
Humidity absorption causes the masonry’s expansion (3 to 4
times greater than the expansion due to temperature).
2. ANOMALIES AND CAUSES
ValuesCharacteristics of the ceramic material
Apparent bulk density
Open porosity
Water absorption by
cold immersion
Water absorption by
capillarity (1 min)
Saturation coefficient
Linear thermal expansion
Expansion due to humidity
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g2.1 Introduction
Main agent causinganomalies⇩- Rain;- Ground humidity;- Condensation;- Leakages;- …
Disaggregation in the long run; Reduction of the thermal insulation.
Cracking
Water action
Disaggregation
2. ANOMALIES AND CAUSESWater absorption:
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g2.1 Introduction
Natural ageing:
Lack of maintenance associated to the long age of the buildingsworsens most of the anomalous situations, contributing decisively to the materials degradation state and very often to the very collapse of the structure.
Various forms of manifestation:
• Water leakage;• Materials detached from the walls;• Areas where the masonry is exposed
(degradation of the external coatings and/or finishes);
• Dispersed cracking in the walls;• Degradation of the frames of the
external windows/doors;• Corrosion of the metal elements.
2. ANOMALIES AND CAUSES
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2.2 Anomalies (physical/mechanical source)
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)A) Cracking:
Cracks result from the inability of brick masonry walls to withstand the bending, shear or tensile stresses due to external or internal causes. Cracks can be classed according to whether they refer to load-bearing walls (with structural-related problems) or filling walls.
2. ANOMALIES AND CAUSES
The cause of cracks is stresses acting on the masonry sections, due to external or internal actions. Cracks have the same cause, whether in load-bearing walls or non load-bearing walls.
Detail 1
Element
Mortars weaker than the masonry element
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g2.2 Anomalies (physical/mechanical
source)A) Cracking (cont.):EXTERNAL CAUSES :(external actions)
• Deformation of the structure;• Action of the loads;• Imposed displacements;• Humidity.
INTERNAL CAUSES :(internal actions)
• Cryptoflorescence;• Freeze/thaw cycles;• Thermal expansion;• Oxidation of metal elements.
Cracking caused by internal causes
Cracking caused by external causes
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)In frame structures,Mostly in buildings with a concrete structure, creep and the consequent deformation of the structural elements may impose high stresses to the masonry, mostly in the windows lintels, cantilevered sections and other locations where stresses concentrate.
A) Cracking (cont.):
2. ANOMALIES AND CAUSES
More frequent cracking in partition wallsCONTRACTION OF
THE WALL
THERMAL CHANGES
FOUNDATIONS SETTLEMENT
FLEXURAL DEFORMATION OF THE PAVEMENTS
lower pavement more deformable
upper pavement more deformable
lower and upper pavements with identical deformations
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g2.2 Anomalies (physical/mechanical
source)a) Cracking due to excessive deformations of the support:
The brick masonry walls have a relatively low elastic deformation capacity.
Main causes:• Deflections of the reinforced concrete
elements, increasingly flexible with slenderer cross-sections;
• Characteristics of the masonry (size of the bricks, type of the joint, characteristics of the laying mortar and size of the spans).
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)Examples of cracking:
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)a) Cracking due to excessive deformations of the support:Examples of cracking:
Lower pavement more deformable than the upper one
Upper pavement more deformable than the lower one
Lower and upper pavements with identical deformations
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)b) Cracking due to differential settlements:
The most damaging anomalies occur when the settlements are differential, causing distortions that may damage both the structural elements and the filling walls.
It is frequent with this type of anomaly that diagonal cracks occur starting from
the wall openings given the stresses concentration that occurs in those areas
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)b) Cracking due to differential settlements(cont.):
Main causes:• Ground consolidation;• Heterogeneity of the foundation soil;• Foundations on landfills;• Use of different types of foundations;• Deficient design of the foundations elements, among others.
Building founded on a non consolidated soil
Building founded on a stable landfill
Cracks due to settlements gradually evolve.
2. ANOMALIES AND CAUSES
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g4.2 Anomalies (physical/mechanical
source)c) Cracking due to loads application:
The brick masonry wall, by itself, has a limited capacity to absorb loads directly applied to them.Once the tensile strength of the bricks is reached, cracks start to occur in the wall.
Solid brick wall
Due to the greater strength of the solid brick, the crack tends to propagate through the mortar going round the brick (for low stresses).
Hollow brick wall
Aspect of thecracks
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)c) Cracking due to loads application (cont.):
Main causes:• Vertical loads;• Loads binary;• Concentrated loads;• Eccentric loads;• Among others.
At the design level, this aspect should have been taken into account, preventing the beams from loading directly the masonry walls or excluding details such as accessories fastened to the walls (clotheslines).
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)c) Cracking due to loads application (cont.):
Examples of cracks due to the application of loads on the masonry:
Cracks caused by vertical loads acting in the same direction
Crack in the masonry caused by the application of an eccentric load
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)d) Cracking due to insufficient support of the masonry:
Anomaly frequent in external walls (normally double-leaf walls) due to insufficient support in each floor.
Main causes:• External correction of thermal bridges due to the concrete structure;• Execution of big panels of uncoated brick.
It is recommended to support the brick in at least 2/3 of its width, increase the thickness of the external leaf and clamp it to the interior leaf.
2. ANOMALIES AND CAUSES
Section
Plan
Interior
Exterior
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g2.2 Anomalies (physical/mechanical
source)e) Cracking due to temperatures changes:
Temperature changes, seasonal and daily, cause dimensional changes (expansions and contractions), and may lead to masonry expansion and structure movements.
Main causes:• Physical properties of the materials (differentthermal expansion coefficients);
• Extent of the temperature changes (amplitudeand speed of the thermal phenomenon);
• Type of structure (restriction degrees);• Lack of expansion joints.
Cracking in masonry due to compression caused by
thermal expansion of the slab
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)e) Cracking due to temperatures changes (cont.):
External walls are more susceptible to this phenomenon (especially those facing South and West), because there is a greater thermal gradient. On the other hand, of the roof is not adequately protected in order to minimize the respective thermal-related movements, it is relatively frequent for the last floor walls to be more affected.
Cracks in the last floor walls due to expansion of the slab
2. ANOMALIES AND CAUSES
Wall
Wall
Wall
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g2.2 Anomalies (physical/mechanical
source)B) Crushing:
Crushing is associated to situations of excessive compressive stresses. It is a localized anomaly, normally associated to cracking.
Main causes:• Increase of concentratedloads;
• Decrease of the wall’sstrength capacity.
Crushing and cracking of the masonry caused by the
application of a concentrated load
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)C) Bulging/deformations:All grounds have elastic and plastic deformations (settlements) under the action of loads. Bulging/warping manifests itself by lack of verticality, loss of planeness or angular distortion of the surfaces. It is normally associated with cracking.
Main causes:• Insufficient characteristics of the foundations;• Incapacity of the ground to withstand the loads.
Possible settlement situations
2. ANOMALIES AND CAUSES
Uniform settlement
Rotation Non-uniform settlement
Angular distortion
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g2.2 Anomalies (physical/mechanical
source)D) Disaggregation:
Corresponds to the loss of cohesion translated by the easy detachment of particles even for low intensity mechanical actions.This anomaly occurs more explicitly in uncoated masonry walls.
Main causes:• Cracking evolution;• Climatic actions (e.g. wind);• Damping of the materials;• Seismic actions.
Disaggregation caused by damping of the materials
2. ANOMALIES AND CAUSES
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source)
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)E) Spalling:
Anomaly resulting from the development of internal cracks in the brick (interior disaggregation). It is more frequent in uncoated solid brick masonry (they have no coating to protect them).
Main causes:• Temperature changes;• Freeze/thaw cycles;• Cryptoflorescence.
Spalling of bricks
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)F) Erosion:
Anomaly resulting from the wear of the brick due to climatic and atmospheric agents that generate a transforming action on all the materials exposed to them.
Wear of a wall during its service life
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)1 - Identify the anomalies and corresponding causes
2. ANOMALIES AND CAUSES
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2 - Identify the anomalies and corresponding causes
2. ANOMALIES AND CAUSES2.2 Anomalies (physical/mechanical
source)
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g2.2 Anomalies (physical/mechanical
source)Cracking
Differential settlementsDeformation of the structure(pavements)
2. ANOMALIES AND CAUSES
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g2.2 Anomalies (physical/mechanical
source)Disaggregation
Cracking
Erosion
Spalling
Application of loads (loads binary)
Action of atmospheric agents
Cryptoflorescence
2. ANOMALIES AND CAUSES
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2.3 Anomalies (chemical source)
2. ANOMALIES AND CAUSES
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A) Anomalies due to humidity:
The anomalies in brick masonry wallsdue to the action of humidity are normally classified as a function of the humidity’s source.
Humidity manifests itself in diverseways:• Construction humidity;• Condensation humidity (vapour);• Precipitation humidity (rain);• Rising damp (ground).
2.3 Anomalies (chemical source)2. ANOMALIES AND CAUSES
CONSTRUCTION WATER
CONDENSATION BY COOLING
INTERSTICIAL CONDENSATION
SALTS CONCENTRATION
FUNGI AND MOSSES
CONDENSATION ON THE PAVEMENT
RUNOFF WATER
GROUND WATER
INFILTRATION FROM THE SUBSOIL
ENTRY OF SOLUBLE SALTS FROM THE GROUND
CONDENSATION DUE TO LACK OF THERMAL INSULATION
LATERAL ENTRY OF DRIVING RAIN
CRACKINGAGGRESSIVE AGENTS
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a) Construction humidity:
This type of humidity results from the construction of the buildings and normally decreases gradually until it disappears, and manifests itself by stains, fungi or efflorescence, reducing the thermal insulation.
Main causes:• High water content used in the execution of the masonry;• Water that reaches the materials during their execution (rain or other random causes).
2.3 Anomalies (chemical source)2. ANOMALIES AND CAUSES
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b) Condensation humidity:
It results from the water vapour that is condensed on the exposed surfaces or inside the construction elements. It occurs when the hot and humid air from a location comes in contact with a cold area (thermal bridge). This anomaly may be permanent or temporary.
2.3 Anomalies (chemical source)
Main causes:• Deficient thermal insulation;• Low ambient temperature;• Deficient ventilation.
Condensations
2. ANOMALIES AND CAUSES
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c) Precipitation humidity:
External humidity (rainwater driven by wind) that infiltrates through the masonry elements, pores and eventual cracks. It manifests itself at any level of the masonry, after intense rain periods.
2.3 Anomalies (chemical source)
Critical areas:• Brick joints;• Low section of the walls;• Various crack types;• Connection masonry/structure;• Connection masonry/windows.
2. ANOMALIES AND CAUSES
Roof
Exposed area
Rain
Protected area
Roof protection
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d) Humidity due to random causes:
The humidity problems may be due to random causes, such as:• Damage of the rainwater drainage systems;• Forgotten open tap;• Nature itself (e.g. the humidity caused by climbing plants).
2.3 Anomalies (chemical source)
Clogging of the drainage system (downspouts)
2. ANOMALIES AND CAUSES
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e) Ground humidity:
Rising damp is the most current type of humidity and comes from the ground, due to the capillarity of the materials. It manifests itself by stains, efflorescence, cryptoflorescence or moulds at the bottom of the construction (ground floor walls).
2.3 Anomalies (chemical source)
Main causes:• Rising damp, through the foundations
and/or walls, of the water in the ground;
• Hydrostatic pressure in basement walls, when the groundwater level is higher than the element level.
2. ANOMALIES AND CAUSES
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B) Efflorescence:
Crystalline deposit of water soluble salts (sulphates, sodium, potassium, calcium, magnesium and aluminium carbonates, chlorides) on the brick masonry surface. It manifests itself by light/white coloured stains. It is anti-aesthetical, difficult to remove and usually harmless.
It the crystallization occurs underthe surface, causing cracking,swelling or detachments, it iscalled cryptoflorescence.
4.3 Anomalies (chemical source)
Swelling of a render due to cryptoflorescence
2. ANOMALIES AND CAUSES
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B) Efflorescence(cont.):
2.3 Anomalies (chemical source)
Formation mechanism:• Dissolution of the salts that exist in
the masonry or the ground;• Migration of the water, dragging the
salts to the surface;• Evaporation of the water on the
surface crystalizing the dissolved salts (crystallization).
2. ANOMALIES AND CAUSES
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g2.3 Anomalies (chemical source)
Superficial layer non adherent to the substrate; generally it precedes the fall of the material. The word swelling is used in particular for rendered or tiled surfaces. Sometimes, the designation detachment is also used for the total loss of adherence.
Main cause: chemical processes unleashed by humidity.
C) Swelling:
Swelling of a renderSwelling of a tile
2. ANOMALIES AND CAUSES
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g2.3 Anomalies (chemical source)
This anomaly manifests itself by a decrease of the reddish brick colour in uncoated brick masonry, caused by exposure to the atmospheric agents with emphasis on the incidence of UV rays.
E) Loss of colour:
2. ANOMALIES AND CAUSES
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g2.3 Anomalies (chemical source)
Colour changes (variation of one or more parameters that define the colour) in a circumscribed and contrasting area with the adjoining ones.
Besides efflorescence, stains may include:• Deposits of calcium carbonate;• Deposits of silicates;• Stains of rust;• Stains of pollution;• Stains of humidity;• Stains of microorganisms.
D) Stains:
Rust stains
2. ANOMALIES AND CAUSES
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g2.3 Anomalies (chemical source)
This anomaly is infrequent, except in highly industrialized areas. It manifests itself by the disintegration of the mortars matrix, with eventual attack of the brick, caused by acids (e.g. sulphurous acidsattack the cementitious matrix).
F) Disintegration of the joints:
Disintegration of the joints
2. ANOMALIES AND CAUSES
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1 - Identify the anomalies and corresponding causes
2.3 Anomalies (chemical source)2. ANOMALIES AND CAUSES
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2 - Identify the anomalies and corresponding causes
2.3 Anomalies (chemical source)2. ANOMALIES AND CAUSES
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g2.3 Anomalies (chemical source)Swelling Stains due to rising damp
Stains due to salts
Deposits of calcium carbonate
Stains due to infiltrations humidity
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g2.3 Anomalies (chemical source)
StainsEfflorescence Efflorescence
Dirt deposition
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2.4 Anomalies (biological source)
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g2.4 Anomalies (biological source)
Presence of biological manifestations such as mosses and higher rank plants.
Main causes:• Biophysical processes - plantsand trees feed on nutrientsthat masonry contains; theirroots cause mechanical attack.
a) Vegetation growth:
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g2.4 Anomalies (biological source)
Development of biological microorganisms (algae, bacteria and lichens), that develop fertile grounds for the development of fungi.
They lead to chemical attacks,mostly in surfaces with porous,humid and poorly ventilated materials.
They cause changes of colour andaspect, moulds emergence andrelease of chemical substances.
b) Moulds/fungi:
Faulty ending of a downspout that caused the emergence of stains and moulds
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g2.4 Anomalies (biological source)
c) Other biological agents:
Birds (pigeons) exert a physical action on the masonry surfaces (in particular the stone surfaces), through pecking, nail marks and nesting (sand grains help their digestion). The excrements of living beings, by forming phosphoric acid and sulphur, attack the surfaces.
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g2.4 Anomalies (biological source)
Anomalies due to the biological agents action, in walls with timber elements.
It is related with the presence of humidity (seasonal humidity, ruptures of downspouts and roof gutters, broken rooftiles, etc.) and corresponds to the rotting of the timber included in the bearing walls due to the rot fungi (lichens, algae, roots - biological attack) or to the attack of insects (termites and woodworms), affecting their mechanical strength.
c) Other biological agents:
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2.5 Chapter conclusions
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. Most of the anomalies affect the visual aspect of masonry, its mechanical properties, the physical properties of materials and the habitability conditions and the durability of buildings;
. When surveying anomalies, a distinction must be made between the anomalies of bricks, laying and coating mortars (renders).
. In order to simplify the classification of the anomalies, the criterion used was grouping according to the source of its main aggressive agent;
. The anomalies were classified according to three distinct sources: physical or mechanical (loads action), chemical (water action) and biological;
2.5 Chapter conclusions2. ANOMALIES AND CAUSES
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. The relationship between the anomalies and their sources is a complex issue, due to the diversity of sources and inter-relation of the various aggressive elements;
. In the following tables a causes-anomalies relationship between the most frequent anomalies, their probable causes and the corresponding correlation;
. The absence of maintenance and repair aggravates the existing anomalies, leading inevitably to the emergence of others.
2.5 Chapter conclusions2. ANOMALIES AND CAUSES
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g2.5 Chapter conclusions
EXTERNAL ACTIONS
INTERNAL ACTIONS
ANOMALY CAUSE
DISINTEGRATION OF THE JOINTS ACIDS
SWELLING STRESSES IN THE INTERFACES
EROSION EXTERNAL ACTIONS
DETACHMENT INTERNAL CRACKS
BULGING DEFORMATION
CRACKING DEFORMATIONS
SETTLEMENTS
CRIPTOFLORESCÊNCIAS
INTERNAL CRACKS
CLIMATIC AGENTS
INDUSTRIAL POLLUTION
Summary of some anomalies and causes:
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g2.5 Chapter conclusions
ANOMALY CAUSE
HUMIDITY WATER
EFFLORESCENCE SALTS
SUPERIORLATERALINFERIOR
GROUNDMORTAR
WATER
LOSS OF COLOUR UV RAYS
STAINS
UV RAYS
CARBONATES DEPOSITSSILICATES DEPOSITS
HUMIDITY STAINSMICROORGANISMS STAINS
RUST STAINSPOLLUTION STAINS
Summary of some anomalies and causes (cont.):
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g2.5 Chapter conclusions
Correlation causes/anomalies:NÃO MECÂNICAMECÂNICA NÃO MECÂNICAMECÂNICA
CAUSAS
ANOMALIAS
CAUSAS
ANOMALIAS
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Dilatação térmica
Oxidação
Águaterreno
Sais solúveis
Gelo / degelo
Deformada (fundações)
Ácidos
Água chuva + vento
Acção de cargas
Deformação da estrutura
Águavapores
Raios UV
Poluição, etc.
Dilatação térmica
Oxidação
Águaterreno
Sais solúveis
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Acção de cargas
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U
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P- designC- executionU- use
TM- solid brickTV- hollow brick
2. ANOMALIES AND CAUSES
CR
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MECHANICAL NON-MECHANICALANOMALIES
CAUSES
SOU
RC
E
Deformation of the structureAction of loads
Settlement (foundations)
Waterrain + windWatervapours
Waterground
Freeze/thaw cycles
Thermal expansion
Oxidation
Soluble salts
UV rays
Pollution, etc.
Acids