Types of Cement
Wondering what type of cement best suits your project? Refer to this basic guide to cement types to identify which of our cement products will make your project a success. This guide covers the three major cement categories, Portland cements, which dominate the market, Blended cements, which are starting to make their presence increasingly felt in the cement field, and Expansive cements, which are often used in bridges and other important load bearing applications where cracking must be minimized.
Both Portland cement and Blended cements are hydraulic cements, which means that they require the addition of water in order to form the bonds which make them set hard and strong. Once formed, the bonds are not soluble in water, which means that hydraulic cements can be used in situations where they will be exposed to water (such as rain water, drainage water, or sea water) without fear of them breaking down and washing away.
There are six main types of hydraulic cements, and both Portland and Blended cements can be categorized into these types.
Type GU – General Use. Suitable for general applications, except those where ground water may be involved, or where moderate to low heat of hydration is required. Heat of hydration is a term referring to the amount of heat that is given out as bonds are formed within the cement. The reactions which form the bonds in cement are exothermic, which means they give out heat. In some projects, such as large scale dams, it is advantageous to use a cement that has a low heat of hydration, as cements which release a great deal of heat whilst setting and hardening can cause major problems.
Type HE – High Early Strength. High early strength cements set and harden quickly, and can be used as load bearing structures much more quickly than their counterparts. These types of cement are ideal for projects which must be finished quickly.
Type MS – Moderate Sulphate Resistance. Moderate sulphate resistance makes cement suitable for use in applications where the concrete will be exposed to normal levels of sulphates which are present in ground water.
Type HS – High Sulphate Resistance. High sulphate resistance is useful for projects where the cement will be exposed to unusually high levels of sulphates.
Type MH – Moderate Heat of Hydration. Moderate heat of hydration cements are suitable for large applications, such as small bridges, or retaining walls.
Type LH – Low Heat of Hydration. Low heat of hydration cements are designed for relatively rare major construction projects.
Blended cements are produced by blending two types of materials together to produce a new type of cement. Portland cement, natural pozzolanic compounds, blast furnace slag, silica fume, calcined clay, and fly ash are all common components of blended cements. Blended cements have been developed in response to various needs and market pressures, including the need to find means of recycling materials left over from other processes, such as the production of iron, which leaves blast furnace slag. Blended cements also have certain properties that make them more useful in some cases than ordinary Portland cement, and they quite often reduce the cost of cement as well.
There are five main types of blended cement:
Type IS – Portland blast furnace slag cement, where Portland cement has been ground with blast furnace slag. Blast furnace slag content is usually between twenty five and seventy percent of Type IS cement by mass.
Type IP or P – Portland pozzolan cement, where Portland cement has been ground with pozzolanic material. Pozzolan content is usually between fifteen and fourty percent of total mass.
Type I (PM) – Pozzolan modified Portland cement.
Type S – Slag cement.
Because there are no restrictions on the makeup of blended cements, they can be designed with specific properties in mind to fit specific construction applications.
Expansive cements are a type of hydraulic cement which expand as they begin to harden. Expansive cements are designated with an ASTM label of E-1, and come in three categories, K, M, and S, though in certain regions, such as the United States, only K may be available. E-1(K) cement contains lime, calcium sulphate, anhydrous tetracalcium trialuminosulfate, and Portland cement as its main ingredients.
Expansive cements are exceedingly useful in construction applications where structural cracks must not develop. Normal cement types shrink during drying, which can cause problems in some construction applications. Expansive cements compensate for this shrinkage by expanding slightly. There are three main uses for expansive cements the first one being crack resistance, the second being induction of tensile stress in reinforcement applications, and the third being as a means to ensure that dimensions of post tensioned concrete structures remain static.
There are many different types of cement available on the market today, but by far and away the most popular type of cement is Portland Cement, which comes in a range of specifications to suit various conditions. The basic ingredients of Portland cement are calcium and silicone, along with iron, aluminum, and very small amounts of other substances. Gypsum is also a component of Portland cement, added at the very end of production in order to control the rate at which the cement will set. Gypsum (the lay term for calcium sulfate) has been used since Egyptian times to regulate setting of cement like substances.
ASTM Standards For Portland Cement
As has been mentioned, there are various types of Portland cement which posses different properties which make them suitable for different applications. The American Society for Testing and Materials has classified eight different types of Portland Cement.
Type I Portland Cement
Type I Portland cement is general purpose cement with no particularly special attributes. It is suitable for use in general applications, however it should not be used in applications where the cement will be in contact with the ground, or with ground water, as these substances tend to contain sulphates which can attack the cement and make it expand and distort out of shape.
Type II Portland Cement
Type II Portland cement has some sulphate resistance, and releases less heat during setting and hardening than Type I Portland cement. Type II cement is therefore suitable for construction projects which involve exposure of the cement to ground water, such as pavements and drainage systems. Type II cement can also be used for large scale work such as retaining walls and other such masses.
Type III Portland Cement
Type III Portland cement develops strength much quicker than other types of Portland cement. The trade off is that its final strength tends to be slightly less than other forms of Portland cement which take longer to set and harden. Type III Portland cement is very useful for projects which must be completed quickly.
Type A Portland Cement
Type A Portland cement refers to Type IA, Type IIA, and Type IIIA Portland cements. These cements are simply cement types of the aforementioned categories which have had special additives added to them which cause small pockets of air to be trapped inside the cement in a uniform fashion. This provides greater freeze/thaw resistance to the cement, preventing it from cracking in conditions which experience large variances in temperature.
Type IV Portland Cement
Type IV Portland cement is a relatively rare type of Portland cement which is specially designed to release heat slowly during setting and hardening. Designed for use on very large scale projects, such as dams, Type IV Portland cement can generally only be obtained by special order in very large quantities.
Type V Portland Cement
Type V Portland cement was designed to be used in high sulphate conditions, where Type I and Type II Portland cement cannot successfully be used. It is not typically necessary to use Type V Portland cement, except in extreme conditions. Most applications requiring contact with water are adequately satisfied with Type II Portland cement.
White Portland Cement
Whilst not truly a separate type of cement, white Portland cement is a unique kind of Portland cement that can be produced to meet the specifications of most types of Portland cement. It is different from ordinary Portland cement in that it has a white coloration, instead of a dull grey one. This effect is achieved by limiting the amount of iron and magnesium oxide in the mix during production. White cement can also be colored to achieve various effects, and is quite popular as an alternative to the traditional drab grey coloration of ordinary Portland cement, especially in projects which have a strong aesthetic component.
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