Last edited 08 May 2019

Types of cement

Contents

[edit] Introduction

Cement is a material with adhesive and cohesive forces that bind together other solid material matter into a compact durable form. Cement is a powdered mineral substance containing lime or gypsum which when mixed with water forms a paste that will set and harden into a hard and brittle material. It is used as a binder in making concrete, mortar and plaster.

There are natural and artificial cements:

Cement is extensively used in all building and civil engineering construction works, particularly in structural elements where high strength is needed. This includes bridge abutments, piers, retaining walls, towers and in large structures such as suspended bridges, silos, chimneys; and in structures that are exposed to the action of water, such as dams and reservoirs.

[edit] Portland cement

Portland cement is produced by finely pulverising clinker that is obtained by calcining to incipient fusion, an intimate and properly-proportioned mixture of argillaceous and calcareous materials. Ordinary Portland Cement (OPC) is categorised by its physical requirements which include fineness, soundness, setting time (initial and final) and compressive strength. For each cement category there are required compressive strengths in MPa; Category A 32 – 37.5, B 37.5 – 42.5, C 42.5 – 47.5, D 47.5 – 52.5, E 52.5 – 57.5 and F 57.5 – 62.5

Changing the chemical composition of OPC using additives or other types of raw materials changes the characteristics of cement to suit the desired use in a given environment.

[edit] Rapid hardening Portland cement

RHPC is manufactured by adding lime content into an OPC clinker; rapid hardening cement attains the strength in one day which a normal ordinary Portland cement attains in three days. For workability, it needs a lot of water which later causes shrinkage. Concrete made with rapid hardening cement is used on those structural elements that are severely exposed to frost, because it matures more quickly. Its properties include an initial setting time of 30 minutes, final setting time of 10 hours, compressive strength in 1 day of 16N/mm², and in three-days 27.5 N/mm².

RHPC is used for the construction and repair of roads and bridges, and for those components onto which load is applied within a short time of concrete casting.

[edit] Super-sulphated Portland cement

SSPC is manufactured by finely grinding and blending a mixture of granulated blast furnace slag with calcium sulphate and 33-grade Portland cement. The water resistance of concrete made with supersulphated Portland cement is higher compared to ordinary Portland cement. This is due to the absence of free calcium oxide hydrate. Its properties include low heat hydration, resistance to chemical attacks, particularly sulphates, compressive strength after three days of 15N/mm, after seven days of 22N/mm2, after 28 days of 30N/mm2.

SSPC is used in hydraulic engineering installations and constructions such as installation of reinforced cement concrete (RCC) pipes in ground water, concrete structures in sulphate-bearing soils, sewers carrying industrial effluents and concrete exposed to concentrated sulphates of weak mineral acids. SSPC is not used in constructions that are exposed to extreme changes in temperature e.g. freezing and thawing conditions.

[edit] Sulphate-resisting Portland cement

SRPC is produced by grinding and blending a mixture of calcareous and argillaceous, silica, alumina and iron oxide-bearing materials.

It has fineness of 400m²/kg, a cement expansion limit 5mm, initial setting 30 minutes and final setting ten hours. Compressive strength after three days 10N/mm², after seven days 16N/mm², and after 28 days 33N/mm²

SRPC is used where the prevailing temperature is below 40C, and in conditions where concrete is exposed to deterioration due to sulphate attack e.g. concrete in contact with soils or water containing excessive sulphates, such as in sea water or near to a coast.

[edit] Portland Slag Cement

Portland slag cement is manufactured by an intimate and uniform blending of Portland cement and finely granulated slag.

Its properties are the same as that of the Ordinary Portland cement i.e. compressive strength at 3 days of 10N/mm², at seven days 16N/mm² and at 28 days 33N/mm², initial and final setting 30 minutes to 10 hours respectively.

[edit] Low Heat Portland cement

LHPC is manufactured for decreasing the heat that is produced during the hydration process of common Ordinary Portland Cement. The rate of strength development is slow but the ultimate strength is the same as that of the Ordinary Portland Cement.

Less heat is evolved in setting, initial setting of 60 minutes and final setting 10 hours, compressive strength at three days of 10 N/mm², 7 days 16 N/mm² and 28 days 35 N/mm².

Suitable for large mass concreting works such as dams and raft foundation works.

[edit] Portland puzzolana cement

PPC is manufactured by finely and uniformly blending Portland cement and fine puzzolana (burnt clay, shale or fly ash). Puzzola has no cementitious properties itself but combines with lime to form a stable lime-puzzolana compound which has definite cementitious properties.

It has greater resistance to chemical attack, making it suitable for marine work; greater water resisting properties than ordinary Portland cement, and has a lower rate of strength development but its ultimate strength is the same as that of Ordinary Portland cement

Due to its low heat evolution property, Portland Puzzolana cement is used for mass concrete works, such as in dam construction and in areas where concrete will be exposed to extreme temperatures, such as in incinerators.

[edit] Quick-setting Portland cement

QSPC is manufactured by reducing the quantity of gypsum and adding a small percentage of aluminium sulphate, ground into a finer powder than ordinary Portland cement.

Initial setting time five minutes and final setting time 30 minutes

Used when cement concrete is being poured under water or in running water.

[edit] Others

See also:

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