Why is it called "portland" cement?
Joseph Aspdin, an English mason who patented the product in 1824, named it portland cement because it produced a concrete that resembled the color of the natural limestone quarried on the Isle of Portland, an island in the English Channel.

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. More

» 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. More.

» 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: More.

Role of Portland Cement in Concrete

Strength and durability are the two key properties that owners look for in their concrete structures. But what makes concrete strong? How does it become durable? These properties are produced through the chemical reaction between hydraulic cement and water—hydration.

In the presence of water, portland cement hydrates to form new solids that become the foundation of hardened cement paste in concrete. Calcium silicates hydrate to form calcium hydroxide and calcium-silicate-hydrate. The calcium-silicate-hydrate (C-S-H) gel is the most important cementing component of concrete. It is responsible for the engineering properties of concrete including setting, hardening and strength development. The structure of the C-S-H at the microscopic scale is important for the durability of concrete. More on the role of portland cement in concrete.

Cement’s Role in Sustainability: Alternative Fuels (Waste Fuels)

Cement manufacturing is energy intensive, due to the high temperature processing required. As with any industry burning fossil fuels, the cement industry also generates combustion by-products and other gaseous emissions. However, less than half of the emissions produced by the cement industry are attributable to the combustion of fuels.

Although coal, petroleum coke, and other fossil fuels have been traditionally used in cement kilns, many cement companies are turning to energy-rich alternative fuels. Many plants meet a substantial portion (20% to 70%) of their energy requirements using alternative fuels. Currently, solid, liquid, and gaseous wastes, whether or not classified as environmentally hazardous, are fired in cement plants with total success and with destruction rates that exceed 99.99999%.

Slightly more than 65% of all U.S. cement plants now incorporate alternative fuels in their energy consumption strategy. In 2007, the energy obtained from waste fuels increased to 9.4% of the total energy demand at cement plants. More on alternative (waste) fuels.

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. More.

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. More.

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. More.

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. More.

Are all Hydraulic Cements Created Equal?

In 2004 PCA conducted a survey to determine characteristics of commercially available cements. Included in the report released in 2008 (free download: PCA R&D Serial No. 2879), are results of that survey, which includes data on portland, blended, and ASTM C1157 hydraulic cements, as well as masonry, plastic (stucco), and mortar cements. The report contains information on chemical and physical characteristics and compares current data with historically available data so that any trends can be observed.

An important characteristic used for comparing cements for general construction is ASTM C109 compressive strength. Survey results show that cements manufactured to meet ASTM C150, C595, and C1157, tend to have strengths that are relatively similar. This may not be too surprising since they compete in the same marketplaces. More on the comparison of cements.


The Power of Microscopy

With only a basic assemblage of equipment, microscopical analysis can be easily performed on portland cement clinker to determine phase identities, sizes, conditions, and mutual relationships. Study of a polished section or thin section of clinker quickly reveals several details of crystal size, morphology, abundance, and distribution, leading almost intuitively to interpretations relating these data to certain features of the raw material and burning conditions. For example, if nests of tightly packed belite crystals form in silica-rich areas of the clinker, then coarse quartz grains may be in the raw feed. Alite crystal sizes of 10 to 15 micrometers may indicate an undesirably rapid rate of temperature rise in the clinker as it passes through the kiln. Large clusters of free lime suggest coarse limestone particles.

Some of the many aspects of portland cement production in which microscopy can play an analytical and quality-control role include:

Analysis of Raw Materials