Building Materials

BRICKS

Clay heated @ < 640 deg C -- only Physical change @ 700 -1100 deg C --- chemical change, alumina & silica fuse together

resulting in compound which is strong & stable Brick @ > 1300 deg C -- above materials get vitrified (bricks lose shape)

Brick size = 20 X 10 X 10 cm. – Nominal, Actual = 19 x 9 x 9 cm.

Frog in a brick.

Types of bricks (based on manufacturing process) : Wire-cut & Pressed brick

Brick classification General physical requirements Class I, II, III (color, burnt, shape,

water absorption 24 hrs in cold water by weight [20, 22, 25]), Efflorescence.I.S. Classification based on strength 10, 7.5, 5, 3.5.

Test for bricks compressive strength, water absorption [sat. coeff., IRA], Efflorescence,

Cement – process of manufacture

TriCalcium Silicate 3CaO.SiO2 ~ C3SDiCalcium Silicate 2CaO.SiO2 ~ C2STriCalcium Aluminate 3CaO.Al2O3 ~ C3ATetraCalcium Aluminoferrite 4CaO.Al2O3.Fe2O3 ~ C4AF

C3S + C2S constitute 65-75% by weight of cement and hydrate to form Ca(OH)2 (~25%) and Calcium Silicate hydrate (~50%) (also called tobermorite gel).

C3S ---- responsible for initial set and early strengthC2S ---- increase in strength at ages beyond a weekC3A ---- responsible for heat of hydration and also contributes slightly to early strength Reducing C3A increases sulfate resistanceC4AF --- reduces clinkering temp. Hydrates rapidly but contributes very less to strength

responsible for coloring effects.

Type I ---- normalType II --- moderate sulfate resistantType III – high early strengthType IV – low heat of hydrationType V --- high sulfate resistantType I,II,III A --- air-entraining variety

Type I ---- general use; where special properties are not requiredType II --- general use; moderate sulfate resistance and heat of hydrationType III – when high strength required. Has similarity chemically with Type I

but particles are ground finer. typical use cold or underwater structuresType IV – when low heat of hydration is required, typical use massive structuresType V --- when high sulfate resistance is required.

Air-entraining materials --- improved resistance to freeze-thaw; scaling caused by chemicals applied for snow/ice removal

White cement --- original color, grey comes in due to iron and manganese oxide, usedfor architectural purpose, curtain walls, tile grout and so on.

Types of Ordinary portland cement used in India: grade 33, 43, 53

Fineness – greater cement fineness increases rate at which cement hydrates and accelerates strength development typically during the first week.

Soundness – ability of the hardened paste to retain volume after set. (free lime and magnesia responsible for lack of soundness). More sound less shrinkage.

Consistency – ability to flow. Depends on water-cement ratio.Setting time – affected by gypsum content, cement fineness, w/c ratio, admixturesCompressive strength – measured by 2 inch mortar cube. Compound composition and

fineness of cement affects it.Heat of hydration – heat generated when cement and water react. Increase in w/c ratio, fineness of cement, curing temp increases heat of hydration.Specific gravity --- 3.15

Fineness measurement of cement (sq. cm per kg. of cement)

Blaine’s air permeability test Wagner’s turbidimeter

Conduction calorimeter –Heat of hydration

Materials to supplement cement

Contributes to the properties of hardenedconcrete through hydraulic or pozzolanic activity or both

Pozzolan :- Sliciceous or aluminosiliceous material that in finely divided form and presenceof moisture, chemically reacts with calcium hydroxide released by hydration of portlandcement to form calcium silicate hydrate and othercementitious material

Fly Ash

Byproduct of combustion of pulverized coal in electric power generating plantsDuring combustion, coal’s mineral impurities (clay, feldspar, quartz, shale) fuse in suspension and are carried away from combustion chamber by exhaust gas. The fused Materials cool and solidifies into spherical glassy particles.

Silica, alumina, iron, calcium 1.9-2.8

Granulated blast-furnace slag

Non-metallic hydraulic cement consisting essentially of silicates and aluminosilicates ofcalcium developed in a molten condition simultaneously with iron in blast-furnace. Molten slag rapidly chilled by quenching in water glassy sandlike granulated material

Silica Fume

Byproduct obtained as a result of reduction of high purity quartz with coal in an electric-arcfurnace in the manufacture of silicon or ferro-silicon alloy

Aggregates

• Natural sand/gravel deposits : deposited glacial formations, river deposits, or along beaches of lakes and seas. E.g. : limestone, granite, sandstone, etc.

• Crushed rock : Igneous rocks e.g. : basalt, granite. Sedimentary rocks e.g. : limestone, gypsum, shale, dolomite, sandstone Metamorphous rocks e.g. : slate, marble, quartzite, gneiss.

• Slag and mine refuse : Blast furnace slag, Industrial materials such as certain types of light volcanic rock, plastics used to produce lightweight concrete.

• Pulverized concrete and bituminous pavements substitute for natural aggregates which are costly; bituminous layers can be recycled and used in pavements.

• Other recycled and waste material : Crushed glass, rubber pellets, bricks, building rubble…

• Fine aggregates-

4.75 mm (sieve No.4) to 75 microns (Sieve No.200)

• Coarse aggregate-

Greater than 4.75 mm (no.4)

• Fines-

Less than 75 microns (no.200)

Classification

Grading of Aggregates(Sieve analysis - ASTM C 136)

- Variation in grading can seriously affect the properties of concrete.- The cement required for concrete is proportional to void content of combined agg.- ASTM C33 grading for Fine-Aggregates (refer table in pg. 34)

- Fine agg. must not be more than 45% retained between any two consecutivestandard sieves

- Fineness modulus 2.3 to 3.1 (do not vary between 0.2 from agg. source) (higher FM --- coarser aggregate)

Sieve #Sieve Size

(mm)

Weight Retained

(g)Percent Retained

(%)

Percent Finer (cumulative

percent passing)

(%)

Percent Coarser (cumulative %

retained)(%)

3/8" 9.5 0 0 100 0

#4 4.75 60 2.84 97.16 2.84

#8 2.26 150 7.11 90.05 9.95

#16 1.18 400 18.96 71.09 28.91

#30 0.60 500 23.70 47.39 52.61

#50 0.30 510 24.17 23.22 76.78

#100 0.15 488 23.13 0.09 99.91

Pan - 2 0.09 0 100.00

Total 2110      

Fineness Modulus = 2.71

Average sieve size= No 30

Particle size distribution graph of fine aggregates

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10

Sieve Opening (mm) logarithmic scale

Per

cen

t F

iner

(%

)

Min. value

Max value

Sample

• Absorption, Porosity and Permeability Absorption relates to the particle’s ability to absorb a liquid. Porosity is a ratio of the volume of the pores to the total volume of the

particle. Permeability refers to the particle’s ability to allow liquids to pass through.

• Surface TextureThe pattern and the relative roughness or smoothness of the

aggregate particle. Plays a big role in developing the bond between an aggregate and a cementing material. A rough surface texture gives the cementing material something to grip, producing a stronger bond, and thus creating a stronger hot mix asphalt or Portland cement concrete.

• Strength and ElasticityStrength is the measure of ability of an aggregate particle to stand up to pulling or crushing forces. Elasticity measures the “stretch” in a particle. High strength and elasticity are desirable in aggregate Base and surface courses. These qualities minimize the rate of disintegration and maximize the stability of the compacted material.

• Strength and Elasticitymeasure of ability of an aggregate particle to stand up to pulling or crushing forces. Elasticity measures the “stretch” in a particle. High strength and elasticity are desirable in aggregate base and surface courses. These qualities minimize the rate of disintegration and maximize the stability of the compacted material.

• Density and Specific GravityDensity is the weight per unit volume of a substance. Specific gravity is the ratio of the density of the substance to the density of water. Helps in determining the amount of asphalt needed in the hot mix asphalt.

• Aggregate voidsThere are aggregate particle voids and voids between aggregate particles. Most aggregate particles have voids, which are natural pores that are filled with air or water. It influence the specific gravity and absorption of the aggregate materials.

• Specific gravity and water absorption

• Abrasion Resistance

• Soundness

• Impact Value Test

• Particle size and shape

• Aggregate voids

Physical tests of Aggregates

Specific gravity (Relative density)- ratio of the weight of the aggregate to the weight of an equal absolute volume

of water (water displaced on immersion).- These specific gravity of aggregates can be determined both at oven-dry state

and at SSD state.- Specific gravity at oven dry state --- Apparent SG- Specific gravity at SSD state --- Bulk SG- typically values range from 2.4-2.9 for natural aggregates

Absorption capacity & Moisture content

- AC = (SSD weight – OD weight) * 100 / (OD weight)- MC = (Sample weight – OD weight) * 100 / (OD weight) - If MC of sample > AC WET else DRY- If WET then Surface Moisture = MC – AC- Fine agg have higher surface moisture (surface tension) (2-6%)

compared to Coarse agg (0.5-2%)- Typically coarse agg. AC = 0.2-4% fine agg = 0.2-2%- Bulking is increase in total volume of moist fine agg over same dry weight (due to surface tension). Finer the sand – higher bulking.

Concrete

Concrete is itself a composite material. It is composed of aggregate and is chemically bound together by hydratedPortland cement.

Aggregate = Sand + Gravel.

Maximum size of gravel:Building construction = ¾ of an inchBridge = 1 to 1 ½ inches

Concrete = Sand + Gravel + Water + Cement

-1 0 1 2 3 4 5 6 7

x 10-3

-0.5

0

0.5

1

1.5

2

2.5

3

strain

stre

ss (

ksi)

cyclic tension compression response envelope

Workability• Consistency• Mobility• Compactibility

Workability depends on• Proportion of aggregates• Physical characteristics of aggregate and cement• Equipment for mixing, transporting and compacting• Size and shape of structure

Workability increases with• high cement content (not so sensitive)• increased quantity of fine materials• decrease in amount and surface area of coarse aggregates• increase in water content

Problems of workability• Segregation• Bleeding

Curing of fresh concrete to make hardened concrete

Concrete curing should be done at 70 deg F for at least 7 days and kept continuously moist after initial set. (ACI 5.11). It gains 75% of its final strength In roughly 28 days.

Moisture and Temp. => Influences process of concrete curing

Problems of improper curing: Shrinkage

• associated with loss of moisture from the gel particles of the paste

Effects:• if unrestrained, shortening of members => loss of prestress• if restrained, induced tension, cracking.• if asymmetric (eg. slabs on grade), curling and cracking

Reduction of shrinkage:low w/c ratiohigh aggregate contentproper curinghigh pressure steam curing over normal curing (better results)water reducing admixtures decrease shrinkageretarding admixtures increase shrinkage

• strength• durability• modulus of elasticity• creep• shrinkage• impermeability

• Mix proportions• curing conditions• environment

Creep: Time dependant increase in deformation due to sustained loading. can occur in all types of loading : compression, tension, torsionThe earlier the age at which loading is applied, the larger the creepcreep higher in wet conditions than in dry conditionsAfter load withdrawn : immediate recovery – elastic ;

delayed recovery – creep recovery

Air entrained concreteProduced by using 1) air entraining cement or 2) air entraining agent. Air entraining agent enhances the incorporation of bubbles of various sizes by

lowering surface tension of mixing water.Effects of increase in entrained air on concrete properties:

Bleeding --- significantly reducedBond to steel ---- reducedcompressive strength --- reduced approx 2-6% per % point increase in airflexural strength --- reduced approx 2-4% per % point increase in airfreeze-thaw resistance --- significantly improvedmodulus of elasticity --- decreasesslump ---- increasessulfate resistance --- significantly improvedunit weight --- decreaseswater demand --- decreases for same slumpworkability --- increases

Factors affecting air-content:cement content, fineness increase --- decreases air contenthigh alkali cements entrain more air than low alkali cementssmaller aggregate size --- air content increases (no change beyond 1.5 in)more amount of fine aggregates ---- increases air content

Factors affecting air contentmixing water increase ---- generates air bubbles --- more air contentincrease in vibration --- reduction in air contentfor constant amount of air-entraining admixture --- increase in slump increase

air content up to about 6-7 in.concrete temp increase ---- less air entrained

Concrete admixtures

Ingredients in concrete other than portland cement, water and aggregates which areadded to the mixture immediately before or during mixing.

Types of admixtures:Air entraining admixtureswater reducing admixtures --- water/cement ratio reduced --- strength increase

(plasticizer(8-15%), super-plasticizer (15-30%))Retarding admixture --- retard rate of setting of concrete --- control heat

of hydration --- hot weather applicationAccelerating admixtures --- accelerate strength development at early stage

---- cold weather applications and underwater applicationsWaterproofing admixtures --- cause capillary contraction resulting in impervious

concrete (Aquaproof, cico, impermo)Mineral admixtures

cementitous material --- granulated blast furnace slag, hydrated lime.

pozzolonic material --- siliceous or aluminosiliceous material,in presence of water reacts with CaOH2 to form compound possessing cementitious properties -- fly ash, silica fume

nominally inert materials --- raw quartz, dolomite, limestone

LimeQuicklime

Hydrated lime / slaked lime

Carbonation of hydrated lime results in calcium carbonate cementing properties

Sand added to lime increase in bulk (leads to economy)to make mortar porous, so that air can circulate resulting in better carbonation

Eminently hydraulic lime : structural work such as arch, domeSemi-hydraulic lime : constructing masonryFat lime & Dolomite lime: finishing coat in plastering, white washKankar lime : masonry limeSiliceous Dolomite lime : undercoat and finishing coat of plaster

Fibers in concrete

Mortar and Plaster

Primary property : Bonding agent under different loading condition

Table1. Mix proportions by volume for mortar

Mortar type Sand Cement Lime

M 3 ½ parts 1 part ¼ parts

S 4 ½ parts 1 part ½ parts

N 6 parts 1 part 1 part

O 9 parts 1 part 2 part

Masonry mortar

Strength of mortar depends on strength of blocks it is binding. Should not be too off.

Cement-sand mix ratio (Cement mortar)Damp-proof course -- 1:2General brickwork -- 1:6Stone masonry – 1:6Brickwork below ground – 1:3 – 1:4Cement plaster Brickwork plaster (inside + outside) – 1:5R.C. Plaster – 1:4

Timber

HardwoodTrees with broad leaves, enclosed nuts, and are found in high densitiesMostly deciduous trees that drop their leaves annuallyExamples include Aspen, Birch, Elm, Maple

SoftwoodTrees that are cone-bearing, leaves are needlesDo not shed their needles annually Examples include Pine, Spruce, Cedar, Fir, and Douglas Fir

KnotImperfection or defect that can be seen throughout in a boardCaused from the branches or limbs that grow from the trunkShould not be placed in tension

Green TimberRefers to lumber that has greater than a 15% absorption capacityRecently Harvested; “fresh”Resists splitting and cracking easily

Air-Dry TimberRefers to lumber that has between 12%-15% absorption capacityResists splitting easily as wellMost desirable stage to work with

Oven-Dry Timber Usually refers to timber with less that a 12%

absorption capacitySplits easily

Weathering

Rotting

Seasoning of wood: Heat treatment as well as chemical treatment of wood to preventits deterioration and restore strength

Chemicals used include waterborne and oil-borne creosote.

Failure in timber structures

shearFlexure

Compression

Industrial timber products: Plywood Particle board (chipboard)HardboardFiberboardBlockboardGlulam

Cast Iron and Steel

Bitumen, Asphalt & Tar

Tar – dark colored product obtained from destructive distillation of organic substances like coal, wood and bituminious shales.

Asphalt: A black or dark brown non-crystalline solid or

viscous material, composed principally of high molecular

weight hydrocarbons, having adhesive properties, derived

from petroleum either by natural or refinery processes and

substantially soluble in carbon disulphide.

Asphalt = bitumen + inert mineral matter

Bitumen is the binding materialin asphalt

• Asphalt is simply the residue left over from petroleum refining.• Crude oil is heated in a large furnace to about 340° C (650° F) and

partially vaporized.  It is then fed into a distillation tower where the lighter components vaporize and are drawn off for further processing.

• The residue from this process (the asphalt) is usually fed into a vacuum distillation unit where heavier gas oils are drawn off.  Asphalt cement grade is controlled by the amount of heavy gas oil remaining.  Other techniques can then extract additional oils from the asphalt. 

Refining of Asphalt

• Depending upon the exact process

and the crude oil source, different asphalt

cements of different properties can be produced. 

Additional desirable properties can be obtained

by blending crude oils before distillation or

asphalt cements after distillation.

Types of Bitumen:Straight run Bitumen – bitumen distilled to a definite viscosity of penetration such that

no further treatment like heating is requiredBlown bitumen – Liquid bitumen + pass air under pressure to remove volatile compounPenetration grade – basic form, has to be heated before applicationCutback bitumen – bitumen + petroleum distillatesBitumen Emulsion – product in liquid form formed in aqueous medium and stabilizing

`agentsPlastic Bitumen – bitumen thinner + suitable filler plastic formCutbacks – bituminious material in solventResidual bitumen – solid substance at normal temp, obtd. as residue during distillation

of high resin petoleum

Modified bitumen – bitumen combined with plastic

Fiber reinforced polymers

Geosynthetics

Crumb rubber

Plastics

Foams and Honeycomb materials

Glass

Composites