Materials of Construction Dr. TALEB M. AL-ROUSAN CEMENT TYPES Materials of Construction Dr. TALEB M. AL-ROUSAN

Types of Cement See Table 2.8 for compound composition of cement types BS Description ASTM Description Ordinary Portland cement Type I Rapid Hardening Portland cement Type III Low-heat Portland cement Type IV Modified cement Type II Sulphate-resisting Portland cement Type V Portland blastfurnace (slag cement) Type IS High slag blastfurnace cement White Portland cement Portland-pozzolan Type IP, P, I(PM) See Table 2.8 for compound composition of cement types

Ordinary Portland Cement (Type I) Most common in general concrete constructions where is no exposure to sulphate in the soil or in ground water and where the special properties of other types are not required. Modern cement has higher C3S content and greater fineness which leads to higher 28-days strength with smaller later gain of strength. Excellent general cement and most widely used in concrete including Pavement, bridges, reinforced concrete buildings, tanks, pipe, masonry, and precast concrete products.

Modified Portland Cement (Type II) Known as Moderate Sulphate resistance cement. Recommended where moderate sulphate attack may occur such as structures or elements exposed to soils or ground waters (Slabs on ground, pipes, concrete posts). Developed to overcome the problem of having, in some applications, a very low early strength. Has higher rate of heat development than Type IV. Has similar rate of gain of strength to that of Type I. Recommended for structures where a moderately low heat generation is desirable. Concrete exposed to sea water is often made with type II. Some times used in all aspects.

Rapid Hardening Portland Cement (Type III) Similar to (Type I) & covered with same standards. Has same setting time. Cost is marginally greater than Type I Has higher C3S, and higher fineness. Strength develops rapidly Used when: Formwork is to be removed early for re-use. Sufficient strength for further construction is required quickly. Can be used satisfactorily for constructions at low temperature and reduces curing period. Should not be used in mass concrete construction or large structural sections because of high rate of heat development.

Low-heat Portland Cement (Type IV) Has lower content of C3S & C3A Slower development of strength, but the ultimate strength is not affected. Used where the rate and amount of heat generated from hydration must be minimized. Used for massive concrete structures such as large gravity dams because its low heat of hydration. Type IV is rarely available.

Sulphate Resisting Cement (Type V) Has low C3A content to avoid sulphate attack from outside the concrete (i.e. soils or ground waters). Sulphate + Ca(OH)2 + Hydrated C3A = Calcium Sulphoaluminate (ettringite) + Calcium Sulphate (Gypsum). Gypsum causes disruption of concrete due to increase in volume). Salts active (Mg & Na sulphates) Mg sulphates has more damaging effects than other sulphates. The hydrated Mg silicate when formed has no binding properties Sulphate attacks accelerate by alternate wetting & drying. Used only when necessary (marine structure for example).

Compound Composition of Cement Types C3S C2S C3A C4AF Type I 59 15 12 8 Type II 46 29 6 (Max 8) Type III 60 (Max 15) Type IV 30 (Max 35) (Min 40) 5 (Max 7) 13 Type V 43 36 4 (Max 5)

Portland Blastfurnace Cement (Type IS) Also known as (Slag cement) Made by blending Portland cement clinker with granulated blast furnace slag (25-70% of the mass of the mixture). Blast furnace slag: Waste product in the manufacture of iron. Slag contains lime, silica, & alumina but with different proportions than cement. Similar to (Type I) in: fineness, setting times, & soundness. Has lower early strength than (Type I) but later strengths are similar. Used in : mass concrete because of lower heat of hydration. Sea water construction because of better sulphate resistance (lower C3A). Slag with low alkai content can be used with aggregate suspected of alkali reactivity. Common in countries where slag is widely available.

Super-sulphated Slag Cement Not a Portland cement. Made by intergrinding a mixture of (80 – 85%) of granulated slag with (10 – 15%) of calcium sulphate and (5%) of Portland cement clinker. Has low heat of hydration. High resistance to sea water & sulphate attack, peaty acids & soils.

White & Colored Portland Cement Is a true Portland cement that differs mainly in color. Use for architectural purposes (walls, precast, cement paint, tile grout, and decorative concrete). Also used because of its low content of soluble alakis staining is avoided. Made of selected materials of which china clay which contains little iron and magnesium oxides (give the cement the gray dark color) . Cost is high

Portland-pozzolan Cement (Type IP, P, & I (PM)) Made by blending pozzolans (15- 40% of total mass) with Portland cement. Pozzolan: A siliceous or siliceous and aluminous material which in it self possesses little or no cementitious value but will chemically react with lime( liberated by hydration of Portland cement) in the presence of moisture at ordinary temperatures to form compounds possessing cementitious properties. This cement gains strength slowly therefore require longer curing periods, but the long-term strength is high. Has slow hydration & low rate of heat development.

Portland-pozzolan Cement (Type IP, P, & I (PM)) Cont. Type IP: used for general construction Type P: used when high strength at early ages are not requied Type I (PM) (Pozzolan-Modified Portland cement): used in general construction Portland fly ash cement (PFA) used in: Rolled concrete, Concrete with low heat characteristics, Concrete requiring good chemical resistance Pozzolan is cheaper than Portland cement. Pozzolan S.G (1.9 – 2.4) while S.G for Portland cement is (3.15) so replacement by mass should be carefully conducted.

Other Portland Cements Developed for special uses Masonry cement Hydrophobic cement Anti-bacterial cement

Expansive Cements A cement that expands slightly during early hardening after setting. Developed to overcome the problem of drying shrinkage (avoid cracking). Magnitude of expansion can be adjusted so that expansion and shrinkage are equal & opposite. Type M (high-energy expanding cement): quick setting, rapid hardening, and high resistance to sulphate attack. Type K: magnitude of expansion is more reliable than Type M. Type S: has high C3A

Expansive Cements Cont. Types of concrete: Expansive Cement Concrete & Shrinkage Compensating Concrete. In these concretes slump loss occurs faster, and resistance to sulphate attack may weaken. Concretes can be used to: Compensate for volume decrease due to drying shrinkage. Induce tensile stresses in reinforcement (post tensioning). Stabilize long term dimensions of post tensioned concrete. Expansive cements may be used in special applications such as prevention of water leakage.

Pozzolans Pozzolan: A siliceous or siliceous and aluminous material which in it self possesses little or no cementitious value but will chemically react with lime( liberated by hydration of Portland cement) in the presence of moisture at ordinary temperatures to form compounds possessing cementitious properties. Typical materials of this type: Volcanic ash (original pozzolan) Fly ash (PFA) Opaline and shales and cherts. Burnt clay

High-alumina Cement (HAC) Developed to resist sulphate attack and became used as a very rapid-hardening cement. HAC has higher cost because of high cost material (bauxite), high firing temperature, and high hardness clinker. HAC produce higher rate of heat development than Type III HAC is slow setting but the final set follows the initial set more rapidly than in Portland cement.

HAC Through the hydration of HAC a crystal change occurs which is encouraged by higher temperature and higher lime and alkalinity. This crystal change is known as conversion. Conversion of HAC leads to loss of strength due to reduce in density (increase porosity). Refractory HAC concrete has good chemical resistance and resist thermal movements and shocks . Can withstand temperatures as high as 1600 – 1800 oC when using special aggregates