Concrete Knowledge 100 Questions (3)

13. Why should continuous grain grade stones be preferred for pumping concrete?

Answer: Because the void fraction of single grain size is larger than that of continuous grain size when the stone is quite large and the particle size is the same, the large void fraction should be filled with mortar. The surface area of aggregate per cubic meter of concrete under the same conditions: the use of single grade stones is larger than that of continuous grade stones, and the corresponding amount of cement is also more. And because the use of continuous grade stone than with a single grade stone mixed concrete fluidity is good, conducive to pumping construction. Therefore, it is preferred to use continuous grained stones.

14, the quality of good stones are mainly a few requirements?

A: There are mainly the following items:

(1) The particle size meets the requirements, and the particle size is continuous;

(2) no yellow skin (surface mud) mud eggs, large mud blocks, large particles of stone;

(3) The less the content of needle and flake particles, the better (the content of needle and flake particles used in pumping concrete stones should not exceed 10%);

(4) The less shale content, the better (because of the lower strength of shale and increased flake particle content).

15. How many requirements are there for the quality of good sand?

A: There are the following:

(1) grain size distribution meets the requirements of medium sand;

(2) The particle size is medium sand, the particle content of more than 10mm is less, quite a lot of less than 10%;

(3) No mud egg, large mud lump, the mud content is not more than 3%;

(4) No roots, roots, mud, plastic bags and other sundries.

16. What is fly ash?

A: Fly ash is a fine powder collected by dust removal equipment in the flue gas of pulverized coal furnace in power plants.

17, fly ash according to its technical requirements into several grades? Where do they apply?

A: There are three levels; Class I, II, III; Class I is suitable for concrete C40 and above, Class II is suitable for concrete C15~C40, and Class III is suitable for cement admixtures.

18. Why should fly ash be added to pumping concrete?

Answer: Because the microscopic structure of fly ash is spherical particles, fineness is finer than cement, it also has a certain activity, when it is mixed into cement can replace part of the cement, and can increase the fluidity of concrete mix, greatly improve the pumpability of pumped concrete, but also improve the strength and durability of concrete in the later period.