7. What is cement? How many kinds of cement are commonly used?
A: where by Portland cement clinker, a reasonable proportion of mixed materials, a moderate amount of gypsum
grinding fine made of hydraulic cementitious material called cement. Commonly used cement are:
Portland cement, ordinary Portland cement and composite cement. Portland cement is divided into P·Ⅰ and P·Ⅱ types,
strength grades of 52.5, 62.5. Ordinary Portland cement is divided into ordinary type and early strength type, code-named P·O,
strength grades are 42.5, 42.5R, 52.5, 52.5r. The composite cement code is P·C, strength grades are 32.5, 32.5R, 42.5R, 42.5r.
8. What are several items in cement reinspection?
A: Setting time, stability, strength, fineness (specific surface area).
9. What is aggregate? There are several types of aggregates
A: The material that acts as a skeleton in concrete is called aggregate (also called aggregate). The stones are called coarse aggregate
and the sand is called fine aggregate. Stone is divided into pebbles and gravel, according to the stone is divided into limestone gravel,
granite gravel and so on. Sand can also be divided into river sand, sea sand, mountain sand, artificial sand and so on.
10, sand according to its fineness modulus divided into several categories?
A: Sand can be divided into coarse sand (3.1 ~ 3.7), medium sand (2.3 ~ 3.0) and fine sand (1.6 ~ 2.2) according to its fineness modulus.
11. Why is medium sand preferred for pumping concrete?
Answer: Because of the reasonable gradation of medium sand, the particle content below 0.3mm can reach about 15%,
this part of the particles in the concrete mortar in the pump pipe close to the wall, friction resistance is very small, conducive to pumping.
Coarse sand has high friction resistance and is not conducive to pumping. The surface area of fine sand is large, and the probability of cracking
is high when cement is used more at the same strength.
12, stone particle level with several kinds of?
A: Single grain and continuous grain. Single grain grade: 10 ~ 20,16 ~ 31.5, 20 ~ 40. Continuous grain size: 5 ~ 10,5 ~ 16,5 ~ 25,5 ~ 31.5, 5 ~ 40.