Современные проблемы промышленного и гражданского строительства на занятиях английского языка. Кузьмина Е.В. - 20 стр.

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be used as a cement replacement in concrete. Polymers are plastics with long-

chain molecules. Concretes made with them have many qualities much superior

to those of ordinary concrete. Silica fume, also known as microsilica, is a waste

product of electric-arc furnaces. The silica reacts with limes in concrete to form

a cementitious material. A fume particle has a diameter only 1% of that of a

cement particle.

Properties of cement.

All types of cement shrink during setting. In a normal concrete the

amount of this shrinkage will depend both on the proportion of cement in the

mix and the quantity of mixing water employed. Provided enough water is

present to enable the chemical action of setting to take place, then the smaller t

amount of water the less shrinkage there will be. The type of aggregate used has

an appreciable effect upon both the amount of water and the amount off

aggregate that can be mixed with given quantity of cement. Strength and

durability of concrete are linked properties in that they are both associated with

the low water-cement ration. In addition to the proportion of cement and the

water cement ratio of a cement product, the method of curing will also affect

the amount of shrinkage. Normally, the slower the drying the less shrinkage

there will be. All cement products are able to a considerable shrinkage during

setting and hardening.

PORTLAND CEMENTS

Portland cement, the most common of the modern cements, is made by

carefully blending selected raw materials to produce a finished material meeting

the requirements of ASTM C150 for one of eight specific cement types. Four

major compounds and two minor compounds constitute the raw materials. The

calcareous materials typically come from limestone, calcite, marl, or shale. The

argillaceous materials are derived from clay, shale, and sand. The materials

used for the manufacture of any specific cement are dependent on the

manufacturing plant’s location and availability of raw materials. Portland

cement can be made of a wide variety of industrial by-products. In the

manufacture of cement, the raw materials are first mined and then ground to a

powder before blending in predetermined proportions. The blend is fed into the