WAYS:Concrete p.2

Portland Cement Concrete is a form of artificial stone. It is in fact the mixture of three elements: Cement, Aggregate, and Water

Cement is the product of super heating Limestone. The most common cement in use today is Portland Cement which is produced by heating limestone to about 1400˚C resulting in something called clinker. This clinker is then ground and mixed with gypsum and other compounds to produce cement.

Aggregate is stone material which when mixed with cement and water bind together producing chemical bonds, which strengthen over time. Aggregates can range from sand to gravel and even cobble-sized stones.

Water is the third and in many ways most crucial component of concrete. By mixing cement and aggregates with water a process called hydration takes place. Only through continued contact with water will a concrete mixture achieve its maximum strength. Concrete does not dry, it sets and then hardens only through continued contact with water.

Mixes of concrete must be appropriate for the end purpose. Without enough paste to fill all the voids between the aggregates, concrete will be porous, difficult to place and have rough, honeycombed surfaces. Too much cement paste will be easy to place and will produce a smooth surface; however, the resulting concrete is likely to shrink more and be uneconomical. Such ‘rich’ mixtures are often used in the production of ferrocement forms like boat hulls which need to be strong and flexible.

A properly designed concrete mixture will possess the desired workability for the fresh concrete and the required durability and strength for the hardened concrete.