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
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
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
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.
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
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
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
Quarry rock analysis
Raw mix analysis
Clinker and Cement Examination
Phase changes and concentration
Grinding and storage
Prediction of cement performance
Analysis of Other Materials
Dust mineralogy and chemistry
Constitution of coal ash and slag
Gypsum and other sulfates