The role of each component material in concrete

Concrete is a widely used structural material. It is an artificial stone made of cement, water, sand, stone, necessary chemical admixtures and mineral admixtures mixed in appropriate proportions, and then uniformly mixed, compacted and cured. However, what role do these materials play in concrete?

The specific analysis is as follows:

1. Cement paste cementitious material: The quality of concrete mainly depends on the cement paste, and its main role is:

a. Wrap the surface of aggregates and fill the gaps of aggregates;

b. Cement paste plays a lubricating role before the concrete solidifies and hardens, so that the concrete mixture has workability suitable for construction, as a lubricating material between aggregates;

c. Make concrete have the required strength, durability and other important skills. The performance of hardened cement paste mainly depends on the performance of cement, water-cement ratio, degree of cement hydration, etc.

2. Aggregate: Aggregate is the main component material of concrete, which accounts for more than 3/4 of the total concrete. Aggregate has both technical role and economic significance in concrete. Its main functions are:

a. Economically, it is much cheaper than cement, and as a cheap filling material, it reduces the cost of concrete;

b. Technically, the presence of aggregates makes concrete have higher volume stability and better durability than pure cement paste;

c. Aggregates can be used as regulating materials to reduce adverse phenomena such as heating and shrinkage of cement paste.

3. Admixtures: Admixtures added to concrete generally refer to admixtures with volcanic ash activity with a dosage greater than 5%. It is added to concrete in an appropriate amount to partially replace cement, which can not only save cement and reduce the cost of concrete, but also improve the workability of concrete mixtures, improve the density, impermeability and chemical corrosion resistance of concrete.

The most commonly used volcanic ash admixture is industrial waste fly ash. Fly ash is a fine powder collected from the flue gas of boilers in coal-fired thermal power plants. Most of its particles are spherical, with a smooth surface and gray or muddy gray. In addition to fly ash, there are also silica ash (a kind of smoke produced when steel mills and ferroalloy plants produce silicon steel and ferrosilicon), granulated blast furnace slag (a fine granular slag formed by quenching molten slag with water or air), and zeolite powder (a volcanic ash aluminosilicate mineral admixture made by grinding natural zeolite).

4. The role of concrete admixtures

Admixtures refer to substances added during the mixing of concrete to improve the performance of concrete mixtures. The amount of admixture is generally not more than 5% of the mass of cement, which is different from admixtures, the amount of admixtures is generally greater than 5%.

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