Written Summary

Written Summary

Please write a ½ page summary on your

experiences from laying out a foundation wall on

Monday.

What is Concrete?

Concrete is a mix of the following ingredients

•Portland Cement

•Aggregate

•Water

Portland CementPortland cement is a fine powder the powder comes from grinding Portland clinker at a

cement processing factory.

Portland cement clinker is made by heating, in a kiln, a homogeneous mixture of raw materials to a sintering temperature, which is about 1450 °C for modern cements. The aluminum oxide and iron oxide are present as a flux and contribute little to the strength.

The major raw material for the clinker-making is usually limestone (CaCO3) mixed with a second material containing clay as source of alumino-silicate. Normally, an impure limestone which contains clay or SiO2 is used. The CaCO3 content of these limestones can be as low as 80%. Second raw materials (materials in the raw mix other than limestone) depend on the purity of the limestone. Some of the second raw materials used are: clay, shale, sand, iron ore, bauxite, fly ash and slag. When a cement kiln is fired by coal, the ash of the coal acts as a secondary raw material.[

citation needed]

One cool thing about cement kilns

Waste materials used in cement kilns as a fuel supplement:[9]

Car and truck tires - steel belts are easily tolerated in the kilns Waste solvents and lubricants Hazardous waste - cement kilns completely destroy hazardous organic compounds Meat and bone meal - slaughterhouse waste due to bovine spongiform encephalopathy contamination concerns Waste plastics Sewage sludge Rice hulls Sugarcane waste Used wooden railroad ties (railway sleepers)

Lets check out a cement kiln

Kiln 1

Kiln 2

How to choose Aggregates

Testing Cement

This machine is used for checking Compression

strength of cement in PSI or Pounds per

square inch.

There are many additives that can be places in cement to change its

properties and reinforce it.

•steel reinforcing bars, •steel fibers• glass fiber•plastic fiber •Rice ?

Accelerators speed up the hydration (hardening) of the concrete.

Retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable.

Air entrainments add and entrain tiny air bubbles in the concrete, which will reduce damage during

freeze-thaw cycles thereby increasing the concrete's durability. However, entrained air is a trade-off with strength, as each 1% of air may result in 5% decrease in compressive strength.

Plasticizers/superplasticizers (water-reducing admixtures) increase the workability of plastic or "fresh" concrete, allowing it be placed more easily, with less consolidating Pigments can be used to change the color of concrete, for aesthetics.

Corrosion inhibitors are used to minimize the corrosion of steel and steel bars in concrete. Bonding agents are used to create a bond between old and new concrete.

Pumping aids improve pumpability, thicken the paste, and reduce separation and bleedi