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TRANSCRIPT
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Masonry
Francisco AguíñigaAssistant Professor
Civil Engineering ProgramTexas A&M University – Kingsville
CEEN 3144 Construction Materials
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Masonry construction
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Masonry construction today
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Masonry evolution
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Clay brick and tileConcrete Masonry Units (CMU)AdobeMortarGroutSteel reinforcement
Masonry materials
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Raw materialHydrated silicate of alumina
Manufacture of fired clayStiff mud
Wire cut process (12 to 15% water by weight)
Soft mudForced through a die (20 to 30% water by weight)
Press processGrind, add 7 to 10% water by weight, press (500 to 1500 psi)
Clay Brick and Tile
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Building brickFacing brickHollow brickStructural clay load-bearing wall tileStructural clay facing tileCeramic glazed facing tilePaving brickSound-absorbing clay masonry
Brick types
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Most common brickPhysical properties
ColorTextureForm and dimension
Engineering propertiesDurabilityInitial rate of absorptionCompressive strengthStiffnessFlexural strengthThermal conductivity and expansionAcoustical characteristics
Building brick (ASTM C62)
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Physical properties
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Physical properties
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Severe weathering (SW)Moderate weathering (MW)No weathering (NW)
Durability
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Grade requirements for different exposures
Durability
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Absorption is a measure of the ability of a brick to form a good bond with mortarASTM C67 - absorption % of brick
Immerse sample for 24 hr in cold waterRecord cold water absorbed as % of dry weight of the unitImmerse same sample in boiling water for 5 hrRecord hot water absorbed as % of dry weight of the unitCalculate cold water/boiling water ratio (C/B), known as saturation coefficient
Water absorption
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C/B represents the portion of the total pore space readily filled with waterC/B < 80% - Good freezing protection
Water absorption
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Pores or small openings function as capillaries - draw water into the unit
Called rate of absorption – suctionImportant effect on tensile bond between brick and mortar
ASTM C67
Initial rate of absorption
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Some effects of high initial rate of absorption
Difficult to lay brick, water removed too rapidly from mortar bed – loss of workabilityBrick layer tends to tap brick as he shoves it into place – disruption of bond between brick and mortarWater drawn from mortar by brick so fast that there is not enough water left for proper curingVery high suction leads to walls that are not watertight
Initial rate of absorption
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Tensile bond strength
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Obtained as described in ASTM C67Compressive strength can be affected by
Physical properties of the clayMethod of manufactureDegree of burnig
Other important factors include Compressive strength of mortar, grout, and prism assemblage
Compressive strength of a composite prism (brick + mortar + grout) is less that those of the clay unit itself
Compressive strength
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Modulus of elasticity (between 1.4 and 5 Msi) increases with compressive strength up to about 5000 psiThe modulus of a composite prism (Brick + grout + mortar) is less that that of the clay unit itself
Stiffness
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ASTM C216Durability
Only SW and MW exist
Stringent aesthetic requirementsColor, texture, and form
Compressive strengthSimilar to ordinary brick (2500 psi min for MW and 300 psi min for SW)
Facing brick
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Similar shape to concrete blocksAbout 25% of the volume are voidsFeatures
Very high compressive strengthFace shell is thick enough to provide stability and sound mortar bedsRequirements for cross beds are similar to concrete blockCell sizes and areas allow for reinforcement and insulating fill placementProvides valid fire ratings either hollow or grouted
ASTM C652 – two grades SW, and MW
Hollow brick
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Hollow brick
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Hollow brick
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Structural clay load-bearing wall tile
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Structural clay load-bearing wall tile - ASTM C34
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Used in steps, sidewalks, platforms, accessible areasASTM C62 or ASTM C216Grades – only SWColor – Generally terra cotta red
Paving brick
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Paving brick
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Wall patterns
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Wall patterns
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Mortar joints
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IngredientsPortland cement ASTM C150Hydrated lime ASTM C207 Type SPoozonals ASTM C618Other constituents
Air entraining, coloring, water repellentsAggregates (normal weight ASTM C33, and lightweight ASTM C331)
ASTM designationsHollow and solid load-bearing capacity ASTM C90Concrete building brick ASTM C55Non load-bearing concrete masonry units ASTM C129
Concrete Masonry Units
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Moisture requirements
Concrete Masonry Units
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Concrete M. Units
Block dimensions
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Minimum thickness of webs
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Strength and absorption
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Joint types
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Purpose of mortarFill irregularities between masonry unitsProvide resistance to penetration of light, wind, and waterBond the units togetherPerhaps add strength
Early mortars – mud, bitumen or tarNew mortar – limeMortar requirements by modern codes
Provide well-bonded and weather resistant wall
Mortar
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IngredientsCement
Portland cement (UBC Standard 26-1 or ASTM C150)Masonry cement (UBC Standard 24-16)Mortar cement (UBC Standard 24-19)
Water – clean, free of alkali (mixing and curing)LimeSand
Mortar
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Calcium oxide (CaO)Hydrated calcium oxide Ca(OH)2
Serves mainly as a plasticizing agent –cement provides the basic strengthIncreases water retentivity - reduces bleeding and segregationFabrication
Limestone is pulverized, blended, and heated to 2500°F
Lime
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Properties of sand significantly influence the workability and strength of mortarGrading requirements ASTM C144 and UBC Standard 24-21Fine sand is preferable over coarse sand
Sand
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Generally neither necessary nor recommended
Water reductionWater retentionWater proofing
Admixtures
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Mix proportions