Requirements for Concrete Aggregate Conveying by Fine Stone Concrete Pump - Part 1
1. Fine aggregate
Fine aggregates can be divided into river sand, sea sand, mountain sand and artificial crushed sand according to their sources. The concrete using the former has better pumpability; the artificial sand has a rough surface and poor sand shape, so it is necessary to add some natural sand to improve its proportioning properties, but the artificial sand has better water retention, which can reduce the bleeding and segregation of concrete. Fine aggregates can be divided into three types: coarse sand, medium sand and fine sand according to the average particle size. The concrete prepared with medium sand has good pumpability, and its average particle size is 0.25-0.3 mm. If the average particle size is too small (that is, too much fine sand), it is not good, and it will increase the water consumption and cement consumption of concrete. If measured by the fineness modulus F.M of sand, the particle size of fine aggregate with F.M value between 2.4-3.0 can meet the pumping requirements. In pumped concrete, the use of fine aggregate has a great relationship with the porosity of coarse aggregate. The cement mortar must be filled with the voids of coarse aggregates. If the sand ratio is insufficient, the voids must be filled with cement, which will increase the amount of cement, otherwise the aggregate will be easy to segregate; Otherwise, the lubricating effect of the cement mortar will be greatly reduced, and the pumping resistance will be significantly increased, so there is a good sand rate under certain conditions. If the coarse aggregate gradation is reasonable, the larger the aggregate particle size is, the lower the optimal sand rate will be. The sand rate is related to the average particle size or fineness modulus of the sand. The smaller the particle size, the lower the sand rate. The sand rate also decreases with the increase of cement dosage. In the case of high sand rate, as long as the amount of cement increases accordingly, there is no significant effect on the pumpability of concrete.
Qingdao Saintyol DAWIN Machinery Co., Ltd. is an enterprise integrating scientific research, production, sales and after-sales service to develop large-scale construction machinery and equipment. The company's main products are (D) XBS series fine stone concrete pump, (D) HBX series small aggregate fine stone concrete pump, JBT series mixing trailer pump, SPJ series wet spraying machine, CSP series cement foaming machine, shotcrete machine and other concrete conveying equipment.
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