Let's Talk about Concrete

Concrete is versatile, durable and economy viable material. That’s why it’s the world’s most used construction material. The USA uses about 340 million cubic yards (260 million cubic meters) of ready-mixed concrete annually. It is used in driveways, highways, streets, homes, parking lots, parking garages, bridges, high-rise buildings, dams, floors, sidewalks, and many other applications.

Specification of Cement for Use in Concrete

There are numerous different properties and applications of cements for use in concrete. They include: portland, hydraulic, blended, and cements. To assist in determine which cement is most viable for your construction needs and to optimize mix performance and economy it’s very important to know what is available… Well, we have come a long way from Joseph Aspdin’s patent in 1824!

When cement is specified for a construction, consideration should be given to all types of material available on site. The specification must be flexible, and should allow either portland or blended cement types. Consideration should always be given to the use of available pozzolans (local resources) and ground-granulated blast furnace slag, which provide the desired concrete properties. Ideally, the specification will allow any cement that matches the performance requirements of the given project. Cements with unique or special properties should not be required unless it’s absolutely necessary.

Case when no special properties are required

The specification should permit the Types I and II of portland cement, blended cements, or any other cement meeting the requirements of a GU hydraulic type of cement. The use of slags or pozzolans should be permitted if possible. It may not be possible to use high levels of slags or pozzolans (or Types P or S of blended cements), in most applications because these concretes have a tendency to set, gain strength and harden at a slower rate. This is especially correct in cold weather.

Heat of hydration requirements

Type II portland cement meeting the moderate heat option can be used where moderate heat of hydration is required as well as a blended cement with the MH suffix, or any other hydraulic cement meeting the requirements of MH Type. The temperature requirements of the concrete may be met by use of other cements such as a Type I portland cement in cojunction with sufficient amounts of slag or pozzolan.

Low heat of hydration requirements can be met using a Type IV portland cement (although it’s not produced in the USA). A portland-pozzolan cement which matches the low-heat option (Type P(LH) cement), or any other hydraulic cement that meets the requirements of Type LH will also provide a low heat during hydration process. Low heat can also be achieved via using suitable supplementary materials.

Where sulfate resistance is required

Moderate sulfate resistance should be provided by the appropriate blended or portland cement or by any other type of hydraulic cement meeting the requirements of MS Type. The sulfate resistance of concrete can be improved by the appropriate use of slag or pozzolans.

High sulfate resistance will be achieved with a Type V portland cement or any hydraulic cement that meets the requirements of HS Type. Many blended Type IP or IS blended cements will match the requirements for high sulfate resistance. But also there is no specific classification for these cements in ASTM C595. Sulfate-resistant concrete may also be mixed by using other cements such as a Type I portland cement in conjunction with sufficient amounts of appropriate slag or pozzolans.

High early strength requirements

High early strength requirements can be met by both Type III portland cement or a Type HE of hydraulic cement. Blended cements may contain highly reactive pozzolans like silica fume may also meet these requirements for high early strength. But there is no specific classification for similar cements in ASTM C595.

Resistance to ASR

When potentially reactive aggregate is being used you need some level of protection against damaging ASR expansion. This may be achieved by specifying either the option for low-reactivity with pyrex glass for blended cements, the low-alkali option for portland cement, or by specifying any other type of hydraulic cement that meets option R. Last is also based on a performance test using pyrex glass. Resistance to ASR may be conferred on a concrete by incorporating appropriate amounts of special slag or pozzolans.

Several types of portland cement may not be readily available in your area. Type I portland cement usually furnished when a specific cement type wasn’t set. Type II cement is usually available. Especially it’s true for areas of the country where medium sulfate resistance is necessary. Cement Types I and II represent about 90% of the whole cement produced. Some cements are designated as Type I/II (both Type I and II). It means that they meet specification requirements that are true for both types. White cement and Type III cement are usually available in large metropolitan areas. Type IV cement is being manufactured only when it’s specified for particular projects (for instance, massive structures like dams). Therefore it’s usually not readily available. Type V cement is available just in particular regions where it is needed to resist highly sulfate aggressive environments.

Blended cements are available in most regions of the U.S. But certain types may not be readily available in some areas. The properties that are conferred on concrete through the use of blended cements can be attained by combining a normal portland cement with appropriate types and levels of supplementary cementing materials at the cement mixer.

When cements with special properties aren’t available, adjustments to the types and proportions of materials in the concrete mixture can usually be made to obtain the desired properties by the use of available materials.