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 Cement
There are many different properties and applications of cement for use in concrete including Portland, blended, and hydraulic cement.
Types of Portland Cement
Portland cement is hydraulic cement, composed primarily of hydraulic calcium silicates.
ASTM C150, Standard Specification for Portland Cement, recognizes ten types of portland cement:
- Type I and Type IA*
General purpose cements suitable for all uses where the special properties of other types are not required.
- Type II and Type IIA*
Type II types of cement contain no more than 8% tricalcium aluminate (C3A) for moderate sulfate resistance.
- Type II (MH) and Type II (MH)A*
Type II (MH) cement have both a moderate heat of hydration characteristic, based on a requirement that the sum of C3S+4.75 C3A <100%, and moderate sulfate resistance properties, based on a maximum C3A content of 8%.
- Type III and Type IIIA*
Chemically and physically similar to Type I cements except they are ground finer to produce higher early strengths.
- Type IV
Used in massive concrete structures where the rate and amount of heat generated from hydration must be minimized. It develops strength slower than other cement types.
- Type V
Contains no more than 5% C3A for high sulfate resistance.
Types of Blended Cement
Blended hydraulic cement is produced by intimately and uniformly intergrinding or blending two or more types of fine materials. The primary materials are portland cement, slag cement, fly ash, silica fume, calcined clay, other pozzolans, hydrated lime, and pre-blended combinations of these materials.
ASTM C595, Specification for Blended Hydraulic Cement, recognizes three classes of blended cement:
- Type IS (X)
Portland blast furnace slag cement
- Type IP (X)
- Type IT(AX)(BY)
Ternary blended cement
The letters X and Y stand for the percentage of supplementary cementitious material (SCM) included in the blended cement, and A and B are the Types of SCMs, either S for slag or P for pozzolan. Type IS(X), can include up to 95% slag cement. Type IP(X) can include up to 40% pozzolans. As an example of ternary cement, Type IT(S25)(P15) contains 25% slag and 15% pozzolans.
Types of Hydraulic Cement
All Portland and blended types of cement are hydraulic cement. 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 cement.
ASTM C1157 recognizes six types of hydraulic cement:
- Type GU – General Use
- Type HE – High Early Strength
- Type MS – Moderate Sulfate Resistance
- Type HS – High Sulfate Resistance
- Type MH – Moderate Heat of Hydration
- Type LH – Low Heat of Hydration