Masonry Cement and Mortar Lecture #18 Masonry Cement and Mortar

MORTAR binder = mortar Masonry = mortar + masonry units

MORTAR definitions differences w/ other cementitious mixtures classes components types properties

MORTAR cementitious materials sand water lime portland cement sand water used with individual masonry units bonding bedding / seating leveling sealing irregularities providing strength providing aesthetic qualities

MORTAR lime added weak link in masonry construction workability adhesive properties extensibility weak link in masonry construction thin layer stronger (compression) than thick layer

GROUT cement fine and coarse aggregate sand water high slump no segregation used to bond two masonry wythes together (walls one unit thick) filling cores and voids binding reinforcing steel and wythes providing load carrying capability ASTM C476 fine and coarse grouts f’C - less in non-absorbent molds match with masonry f’C

Differences w/ other cementitious mixtures component materials mortar cement, lime, water, fine aggregate grout cement, water, fine aggregate, small-sized coarse aggregate portland cement concrete cement, water, fine aggregate, coarse aggregate proportions

Differences w/ other cementitious mixtures structural performance PCC is structural material, resists mainly compressive stresses mortar, grout are binders, develop strong & durable bond w/ masonry unit workability & placement methods PCC placed in non-absorbent forms, minimum water, w/c ratio very important to performance mortar, grout placed in absorptive forms, much more water, w/c ratio less important

Classes cement/cement-lime mortar lime mortar masonry cement mortar cement, lime, sand, water most common masonry cement mortar proprietary ingredients workable low bond strength, not durable - most commonly used but least desirable lime mortar lime, sand, water slow strength gain calcium carbonate formation seldom used in permanent construction

Components portland cement sand lime water admixtures durability high early strength high compressive strength bond strength sand filler strength lime workability water retentivity elasticity bond strength extensibility water flow required for hydration admixtures

Components portland cement Type I - general use when special properties not required Type II - when moderate sulfate resistance or moderate heat of hydration required Type III - when high early strength required Air entrained portland cements tend to reduce bond strengths

Components hydrated lime [Ca(OH)2] chalk or limestone (CaCO3) burned at 900 0C in kiln to produce quicklime (CaO) water added to quicklime Types (ASTM C207) N - normal, unhydrated oxides & plasticity not controlled S - special, commonly used NA - normal air-entraining, not recommended SA - special air-entraining, not recommended

Components aggregates natural or manufactured gradation (ASTM C144)

Components water admixtures clean potable free of deleterious materials acids alkalies organic materials admixtures color workability reduced water penetration accelerated curing use w/ caution air-entraining chlorides

Types (MASONWORK) ASTM C270 Type M (paving brick) proportion specifications - RECOMMENDED property specifications established with laboratory testing, trial & error same letter designations, but Type N (proportion) = Type N (property) (proportion - higher compressive strength) Type M (paving brick) high strength general use below grade OR in contact w/ ground

Types (MASONWORK) Type S (structural masonry, reinforced brick) high strength reinforced masonry areas subject to high wind Type N (normal, common) general use below grade OR in contact w/ ground

Types (MASONWORK) Type O (interior) Type K (restoration) low strength non-bearing applications not subject to severe weathering Type K (restoration)

Types (MASONWORK) Proportion Specifications

Determine quantities and absolute volumes for an N Type Mortar Vsand = 1.0 ft3 Vlime= 0.5 to 1.25 Vc Vsand=2.25 to 3 (Vc+Vl) 1 ft3 of damp loose sand will yield 1 ft3 of mortar. (due to bulking of wet sand)

Types (MASONWORK) Property Specificationsa a Laboratory prepared mortar only b When structural reinforcement is incorporated in cement-lime mortar, the maximum air content shall be 12% c When structural reinforcement is incorporated in masonry cement mortar, the maximum air content shall be 18%.

Selecting Mortar Types considerations structural requirements exposure wall type workability no single type for all purposes DO NOT change mortar types within same structure uneconomical NEVER use mortar stronger in compression than required shrinkage, debonding

Laboratory vs. Field Mortar CANNOT COMPARE field mortar more water required (lost in evaporation or to masonry unit) laboratory mortar less water, lower initial flow different curing conditions

Properties plastic properties hardened properties other properties influence hardened properties workability initial flow flow after suction water retentivity hardened properties determine performance bond strength durability extensibilty compressive strength other properties color

Workability easily spread adhere to vertical surface difficult to measure directly no standard test or quantitative measure indicators include flow, water retentivity, resistance to segregation affected by properties of components

Flow (ASTM C109) cone formed on flow table raised & dropped 25 times in 15 seconds flow = ratio of increase in diameter

Water Retentivity (ASTM C91) ability to resist loss of water to absorbent masonry unit flow after suction (vacuum for 1 min)/ initial flow low retentivity will bleed moisture unless brick has high suction (IRA) high retentivity will create dry surface low bond strength for low or high retentivity paired with average masonry unit

Bond Strength most important physical property difficult to measure directly, simulate construction Bond Strength Suction (IRA)   Air Content   Elapsed Time   Mortar Flow   Brick Texture rough  Retempering  Pressure   Movement after set  Water Retentivity   Max Bond cement: lime 1:1 to 1:1/4 Type S mortar

Bond Strength

Other Hardened Properties durability not significant if properly prepared no air-entraining components extensibility max et at rupture elongation before cracking lime contributes

Other Hardened Properties compressive strength f (cement content, w/c) cubes (ASTM C109) cylinders, briquettes Proportion f’c Cement   Lime   Water   Flow  

Other Properties color colored aggregates - PREFERRED colored pigment