1. What is commodity concrete?
Answer: According to the demand side, with cement, water, sand, gravel, admixtures and mineral admixtures and other components according to a certain proportion, in the mixing station by metering, stirring after the sale and the use of mixing transport vehicles, within the specified time to the demand-side delivery site of the concrete mix.
2. What is cement? How many kinds of cement are commonly used?
A: Where by Portland cement clinker, a reasonable proportion of the mixture, the right amount of gypsum mill made of water rigid cementitious materials known as cement. Commonly used cement: Portland cement, ordinary Portland cement and composite cement. Portland cement is divided into P²ⅰ and P²ⅱ type, the strength level is 52.5, 62.5 grade. Ordinary Portland cement divided into ordinary and early strong type, code-named P²o, strength level of 42.5, 42.5r,52.5, 52.5R.
Composite cement code-named P²c, strength level of 32.5, 32.5R, 42.5, 42.5R.
3. What are the items of the cement recheck?
Answer: Setting time, stability, strength, fineness (specific surface area).
4, what is the aggregate?
Aggregates have several kinds of answer: in the concrete skeleton action material called aggregates (also called aggregate). A stone is called a coarse aggregate, and the sand is called a 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 be divided into river sand, sea sand, mountain sand, artificial mechanism, such as sand.
5, sand according to its fineness modulus divided into several categories?
Answer: Sand according to its fineness modulus is divided into coarse sand (3.1~3.7), medium sand (2.3~3.0), fine Sand (1.6~2.2).
6, Pump concrete Why the first choice of sand?
A: Because the gradation of sand is reasonable, 0.3mm below the particle content can reach about 15%, this part of the mortar in the concrete in the pump tube close to the wall, friction resistance is very small, conducive to pumping.
7, Coarse sand friction resistance is large, not conducive to pumping.
The surface area of fine sand is large, the use of cement at the same intensity is high.
8,How many grains of gravel are there?
A: Single-grain and continuous-granularity. Single-grained: 10~20,16~31.5,20~40.
The continuous grain level is: 5~10,5~16,5~25,5~31.5,5~40.
9,pumping concrete why should priority to the use of continuous-grain stone?
A: Because the maximum size of the gravel in the case of the same size of the single-grain porosity than the continuous granularity of the porosity, large void ratio to be filled with mortar. In the same condition per cubic meter of concrete aggregate surface area: The use of a single particle of stone than the continuous particle size of the larger, the corresponding need for more cement. Because the use of continuous granular stone than the use of a single stone mixed with the concrete of the flow of good, conducive to pumping construction. Therefore, the priority of the use of continuous-grain stones.
10,What is the winter construction?
A: The average temperature of the day is less than 5 ℃ for five days, and the minimum temperature is less than 0 ℃.
11,What measures should we take in the winter construction period?
Answer: The following measures should be taken: (cold area) to the water tank, pool, admixture tank to take insulation cover measures; for steel sand and gravel silo should be closed insulation; When the lowest temperature is lower than -5℃, the remaining sand in the sand bin outside the silo, to prevent freezing. Shovel the frozen sand blocks to the side before feeding each day, then use the unfrozen sand. The admixture uses the antifreeze pump to send the type. The factory concrete mixing material temperature is not less than 6 ℃. The canister can be wrapped in cotton felt.
12, what is the best way to prevent cracks in cast-in-place concrete slabs in spring?
A: The best way is: to cast a section of the plate surface, with vibrator vibration concrete, with wood washboard rubbing flat surface, and then from the front and back with the film on the film, in the joint or finishing with a trowel to the membrane and concrete compaction, to bond securely, to prevent the wind blowing. If the concrete is in need of final coagulation when the line, the application of cutting knife along the bar to prevent the laying of the line of the site, not all uncovered.