Historical Perspective for Concrete and Precast Concrete Building Construction

The Egyptians were using early forms of concrete over 5000 years ago to build pyramids. They mixed mud and straw to form bricks and used gypsum and lime to make mortars.

The ancient Romans used a material that is remarkably close to modern cement to build many of their architectural marvels, such as the Colosseum, and the Pantheon. The Romans also used animal products in their cement as an early form of admixtures. Admixtures, additions to the mix used to achieve certain goals, are still used today,

Joseph Aspdin of England is credited with the invention of modern Portland cement. He named his cement Portland, after a rock quary that produced very strong stone.

Types of Cement and What They Do

Portland Cement is a type of cement, not a brand name. Many cement manufacturers make Portland cement.

The Wide World of Cements

There are many different properties and applications of cements for use in concrete including portland, blended, and hydraulic cements.

Types of Portland Cement

Portland cements are hydraulic cements composed primarily of hydraulic calcium silicates. ASTM C150, Standard Specification for Portland Cement, recognizes eight types of portland cement.

Types of Blended Cements

Blended hydraulic cements are produced by intimately and uniformly intergrinding or blending two or more types of fine materials. The primary materials are portland cement, ground granulated blast furnace slag, fly ash, silica fume, calcined clay, other pozzolans, hydrated lime, and pre-blended combinations of these materials.

Types of Hydraulic Cements

All portland and blended cements are hydraulic cements. Hydraulic cement is merely a broader term. ASTM C1157, Performance Specification for Hydraulic Cements, is a performance specification that includes portland cement, modified portland cement, and blended cements. ASTM C1157 recognizes six types of hydraulic cements.

Impact of Hot Cement on the Concrete Mix

Hot cement describes clinker that has, through the process of grinding, gained additional energy stored in the form of heat. Once the clinker is ground, this hot cement is stockpiled in storage silos where the elevated temperature, especially in warm climates, is not readily abated. Many attribute slump loss, strength reduction, or other concrete-related problems to the temperature of the cement upon batching. However, research has shown that cement’s ultimate effect on the concrete mixture’s temperature is quite minimal.

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Effect of Cement Characteristics on Concrete Properties

Cement, together with water, creates the paste that binds aggregate together to form concrete. Concrete quality depends upon the quantity and quality of the aggregate and the paste, as well as the bond between the two. Therefore, the properties of concrete are influenced by the properties of cement. Whether it is the clinker composition, the fineness of the individual cement grains, or the amount with which it is used in the concrete, the type and proportion of cement affect both the fresh and hardened properties of concrete. An understanding of cement characteristics can provide insight to many of the issues arising in concrete construction.

Cement Standards and Specifications

Product specifications and test methods are typically developed by national standards development organizations, such as ASTM in the U.S. and CSA in Canada. Full consensus standards are developed with the participation of all parties who have a stake in the standards’ development and/or use.

Specifying Cement for Use in Concrete

When a cement is specified for a project, consideration should be given to the types of material available in that location. The specification should be flexible, allowing either portland or blended cements. Consideration should always be given to the use of locally available pozzolans and slag cements, provided the desired concrete properties can be achieved. Ideally, the specification should allow any cement that meets the performance requirements of the project. Cements with special or unique properties should not be required unless absolutely necessary.