Presentation on theme: "Types of Portland Cement Different types of portland cement are manufactured to meet various physical and chemical requirements for specific purposes."— Presentation transcript:
Types of Portland Cement Different types of portland cement are manufactured to meet various physical and chemical requirements for specific purposes. Portlant cements are manufactured to meet the specifications of ASTM C150. ASTM C150 provides for ten types of portland cement: Type INormal Type IANormal, air-entraining Type IIModerate sulfate resistance Type IIAModerate sulfate resistance, air-entraining Type II (MH) Moderate heat of hydration and moderate sulfate resistance
Types of Portland Cement Continued Type II (MH) A Moderate heat of hydration and moderate sulfate resistance, air-entraining Type IIIHigh early strength Type IIIAHigh early strength, air-entraining Type IVLow heat of hydration Type VHigh sulfate resistance
Type III: Type III portland cement provides strength at an earlier period than normally expected. Type III is chemically similar to Type I cement, except that its particles have been ground finer. It is used when forms need to be removed as soon as possible or when the structure must be put into service quickly. In cold weather its use permits a reduction in the length of the curing period. Type IV: Type IV portland cement is used where the rate and amount of heat generated from hydration must be minimized. It develops strength at a slower rate than other cement types. Type IV cement is intended for use in massive concrete structures, such as large gravity dams, where the temperature rise resulting from heat generated during hardening must be minimized. Type V: Type V portland cement is used in concrete exposed to severe sulfate environments (principally where soils or ground waters have a high sulfate content). It gains strength more slowly than Type I cement. The high sulfate resistance of Type V cement is attributed to a low tricalcium aluminate content, not more than 5%.
Air-Entraining Portland Cements Specifications for four types of air-entraining portland cement (Types IA, IIA, II (MH)A, and IIIA) are given in ASTM C150. They correspond in composition to ASTM Types I, II, II(MH), and III, respectively, except that small quantities of air- entraining additions are interground with the clinker during manufacture. These cements produce concrete with improved resistance to freezing and thawing. When mixed with proper intensity and for an appropriate duration, such concrete contains minute, well-distributed, and completely separated air bubbles. Air entrainment for most concrete is achieved through the use of an air-entraining admixture, rather than through the use of air-entraining cements. Air-entraining cements are available only in certain areas, so it is advisable to check on local availability. White Portland Cements White portland cement is a portland cement that differs from gray cement chiefly in color. It is made to conform to the specifications of ASTM C150, usually Type I or Type III. The manufacture of white cement is accomplished by limiting the amount of iron and magnesium oxides in the raw materials. These two oxides are responsible for portland cement’s characteristic gray color. White portland cement is used primarily for architectural purposes in structural walls, precast and glass fiber reinforced concrete (GFRC) facing panels, terrazzo surfaces, stucco, cement paint, tile grout, and decorative concrete. Its use is recommended wherever white or colored concrete, grout, or mortar is desired and should be specified as white portland cement meeting the specifications of ASTM C150, Type [I, II, III, or V].
Problems Associated with cold weather Frost damage in case of immature concrete
External sulphate attack When sulphates from Ground water Sea water Sewerage pipes Enter into concrete and react with Ca(OH) 2. Forming calcium sulpho aluminates.
Problems associated with Calcium sulpho aluminates 1.Reduction in PH value of concrete 2.Chances of reinforcement corrosion 3.Expansion and subsequent cracking http://thehelpfulengineer.com/index.php/2010/10/carbonation-of-concrete-corrosion/
www.cementaustralia.com.au Compressive strength development of concrete containing SRC
Blended Hydraulic Cements Blended hydraulic cements are produced by intimately and uniformly inter-grinding or blending two or more types of fine materials. The primary materials are portland cement, slag cement, fly ash, silica fume, calcined clay, hydrated lime, and pre-blended combinations of these materials. Blended hydraulic cements must conform to the requirements of ASTM C595 Specification for Blended Hydraulic cements. Special Cements Special cements are produced for particular applications. Masonry and Mortar Cements Masonry and mortar cements are hydraulic cements designed for use in mortar for masonry construction. They consist of a mixture of portland cement or blended hydraulic cement and plasticizing materials (such as limestone or hydrated or hydraulic lime), together with other materials introduced to enhance one or more properties such as setting time, workability, water retention, and durability. These components are proportioned and packaged at a cement plant under controlled conditions to assure uniformity of performance.
Special Cements Continued Expansive Cements (also called shrinkage compensating concrete) Expansive cement is a hydraulic cement that expands slightly during the early hardening period after initial set. It must meet the requirements of ASTM C845, Standard Specification for Expansive hydraulic Cement. When expansion is restrained, for example by reinforcing steel, expansive cement concrete can be used to: 1.Compensate for the volume decrease associated with drying shrinkage, 2.Induce tensile stress in reinforcement (post-tensioning), and 3.Stabilize the long-term dimensions of post-tensioned concrete structures in comparison to the original design dimensions. Oil-Well Cements Oil-well cements are used for oil-well grouting. (This procedure is often called oil-well cementing). Oil-well cements are usually made from portland cement clinker or from blended hydraulic cements. Generally they must be slow-setting and resistant to high temperatures and pressures.
Special Cements Continued Rapid Hardening Cements Rapid hardening, high-early strength, hydraulic cement is used in construction applications, such as fast-track paving, where fast strength development is required (design or load-carrying strength in about four hours). They are classified according to ASTM C1600, Standard Specification for Rapid Hardening Hydraulic Cement. Cements with Functional Additions Functional additions can be inter-ground with cement clinker to beneficially change the properties of hydraulic cement. These additions must meet the requirements of ASTM C226, Standard Specification for Air-Entraining Additions for Use in the Manufacture of Air-Entraining Hydraulic Cement, or ASTM C688, Standard Specification for Functional Additions for Use in Hydraulic Cements. ASTM C226 addresses air-entraining additions while ASTM C688 addresses the following types of additions: water-reducing, retarding, accelerating, water-reducing and retarding, water-reducing and accelerating, and set-control additions. These additions can be used to enhance the performance of the cement for normal or special concrete construction, grouting, and other applications.
Special Cements Continued Water-Repellent Cements Water-repellent cements, sometimes called water-proofed cements, are usually made by adding a small amount of water- repellent additive such as stearate (sodium, aluminum, or other) to cement clinker during final grinding. Manufactured in either white or gray color, water-repellent cements reduce capillary water transmission provided there is little to no hydrostatic pressure. However, they do not stop water-vapor transmission. Water-repellent cements are used in tile grouts, paint, stucco finish coats, and in the manufacture of specialty precast units. Regulated-Set Cements Regulated-set cement is a calcium fluoro-aluminate hydraulic cement that can be formulated and controlled to produce concrete with setting times ranging from a few minutes to one hour and with corresponding rapid early strength development. It is a portland-based cement with functional additions that can be manufactured in the same kiln used to manufacture conventional portland cement. Regulated-set cement incorporates set control and early-strength- development components. The final physical properties of the resulting concrete are in most respects similar to comparable concretes made with portland cement.
Special Cements Continued Geopolymer Cements Geopolymer cements are inorganic hydraulic cements that are based on polymerization of minerals. The term more specifically refers to alkali-activated alumino-silicate cements. These cements often contain industrial by-products, such as fly ash. They have been used in general construction, high-early strength applications, and waste stabilization. These cements do not contain organic polymers or plastics. Ettringite Cements Ettringite cements are calcium sulfo-aluminate cements that are specially formulated for particular uses, such as the stabilization of waste materials. They can be formulated to form large amounts of ettringite to stabilize particular metallic ions within the ettringite structure. Ettringite cements have also been used in rapid setting applications, including use in coal mines.
Special Cements Continued Calcium Aluminate Cements Calcium aluminate cement is not portland cement based. It is used in special applications for early strength gain (for example, to achieve design strength in one day), resistance to high temperatures, and resistance to sulfates, weak acids, and seawater. Portland cement and calcium aluminate cement combinations have been used to make rapid setting concretes and mortars. Typical applications for calcium aluminate cement concrete include: chemically resistant, heat resistant, and corrosion resistant industrial floors and repair applications. Calcium aluminate cement concrete must be used at low water cement ratios (less than 0.4). Magnesium phosphate Cements Magnesium phosphate cements is a rapid setting, early strength gain cement. It is usually used for special applications, such as repair of pavements and concrete structures, or for resistance to certain aggressive chemicals. It does not contain portland cement.
Selecting and Specifying Cements When specifying cements for a project, the availability of cement types should be verified. Specifications should allow flexibility in cement selection. Limiting a project to only one cement type, one brand, or one standard cement specification can result in project delays and it may not allow for the best use of local materials. Cements with special properties should not be required unless special characteristics are necessary. In addition, the use of SCMs should not inhibit the use of any particular portland or blended cement. The project specifications should focus on the needs of the concrete structure and allow use of a variety of materials to accomplish those needs.