Ordinary Portland Cement

Topics: Portland cement, Concrete, Cement Pages: 6 (1932 words) Published: October 18, 2009
Case Study: Ordinary Portland Cement

Is a material with adhesive and cohesive properties which is capable of bonding mineral fragments into a compact-solid whole •Ordinary Portland Cement (OPC)
Is a hydraulic cement. It is used in the making of concrete with property of setting and hardening, of which when the chemical properties reacts with water. OPC Does not disintegrate in water as it sets and hardens in water •Reason of widely usage in Malaysia

Is because raw material used in the making of Portland cement can be easily found and is available all over the world. Apart from that OPC is the cheapest among all other cementitious material available. Malaysia does not have much problem of existing sulfates in soil or groundwater, therefore usage of OPC is optimum to eliminate unnecessary cost spending

The properties of concrete depend on the quantities and qualities of its components. Cement is the most active component of concrete and usually has the greatest unit cost; therefore, its selection and proper use are important in obtaining most economically the balance of properties desired for any particular concrete mixture. Table 1: Properties of cement according to their types

Cement typeUse
I1General purpose cement, when there are no extenuating conditions II2Aids in providing moderate resistance to sulfate attack
IIIWhen high-early strength is required
IV3When a low heat of hydration is desired (in massive structures) V4When high sulfate resistance is required
IA4A type I cement containing an integral air-entraining agent IIA4A type II cement containing an integral air-entraining agent IIIA4A type III cement containing an integral air-entraining agent (Source: Cement-Part 1: Compositions, Specifications and Conformity Criteria for Common Cements; Malaysian Standard, MS 522: Part 1:2007) Table 2: Effects of cements on concrete properties

Cement PropertyCement Effects
PlaceabilityCement amount, fineness, setting characteristics StrengthCement composition (C3S, C2S and C3A), loss on ignition, fineness Drying ShrinkageSO3content, cement composition
PermeabilityCement composition, fineness
Resistance to sulfateC3A content
Alkali Silica ReactivityAlkali content
Corrosion of embedded steelCement Composition (esp. C3A content)

OPC is Type I Portland cements. It provides adequate levels of strength and durability. The Cement composition and fineness play a major role in controlling concrete properties. Fineness of cement affects the placeability, workability, and water content of a concrete mixture much like the amount of cement used in concrete does. Finer powder is better than coarse as it helps to coat the surface of grains of sand or other inert material completely. The Cement composition affects the permeability of concrete by controlling the rate of hydration. However, the ultimate porosity and permeability are unaffected. The More finely cement used and the greater surface been exposed in proportion to its mass, the more rapid the rate of hydration and the greater react of the proportion of cement. •Soundness

Soundness refers to Cement paste that has set(hardened cement), and the expansion occurrence need to be determine. The Cement paste should not undergo a large change in volume and Sometimes after a period of time (month or years have elapsed), it will undergo a change in volume. This May cause cracks due to the slow hydration or due to reaction of cement paste with foreign compound present •Setting time (change of cement from the fluid state to a rigid stage) •Workability of cement is affected by the water content, temperature and admixture used in concrete mix. There are two stages of Setting time which are (i) initial set (ii) final set. •For initial set, paste’s degree of stiffness point must be determined to establish the length of time for paste to still be in plastic and workable state. •...
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