Author: Li Zhufeng, is the most basic tester in our concrete industry, the author is a young man who loves to study, with his own understanding of concrete, the use of sand and stones in concrete, and the concrete to share.
Sand mainly plays a role in filling, lubrication and water retention in concrete.
The finer the fineness modulus of sand, the higher the water consumption, the better the water retention, relatively speaking, the coarser the sand, the lower the water consumption, and the worse the water retention performance.
Stone foam (stone powder) sand control coarse, according to my understanding is that stone foam (stone powder) can be used as a finer aggregate to retain water, lubricate, reduce the gap between sand and cementitious materials;When the sand is fine to a certain extent, the difference between the sand and the coarse aggregate is too far and not enough to fill, it is necessary to add a part of the pebble appropriately to bring the gradation of sand and coarse aggregate (pebble) closer to reduce the porosity of the pebble. The worse the sand gradation, the greater the porosity, and the more cementitious material is needed to fill the voids of the sand. There are more fine stones in the sand, and there are fewer small stones in the coarse sand.
When the strength of the concrete itself does not exceed the bearing strength of the stone, the strength is not enough, and it must be related to the mix ratio, water-cement ratio, admixture, and sand rate.
Due to local environmental restrictions, the stones may not be able to meet the continuous grading required by the national standards, and the broken grading is a matter of course.
As for how to deal with the change of broken gradation, first of all, it depends on which section of the continuous gradation is located, and it is solved by adjusting and reducing the porosity between the stones. The specific adjustment scheme can be determined by experiments, and the approximate scheme is that the gradation at both ends of the break can be solved by adjusting the amount of coarse aggregate, the section with a larger particle size can increase the amount of stones, and the section with a smaller particle size can be solved by increasing 05 seeds, if the sand is coarse, it can be solved by increasing the sand rate.
As for the middle of the continuous gradation, the gap can generally be reduced by opening the overlapping gradation, that is, by splitting the warehouse, and readjusting the dosage. Or 5-31For example, a 5mm stone is broken at the intermediate level of 16mm, and 19mm is 26In the case of 5mm stone content and exceeding, the overlapping gradation part can be reduced as much as possible by reducing the amount of stones, or increasing the amount of large stones to reduce the specific surface area of aggregates.
The smaller the specific surface area of the aggregate, the less water consumption and cementitious material required on the cementing surface, the more surplus the slurry, and the better the fluidity and workability.
The more single the particle size of the stone, the more average the force and the higher the pressure it bears, without increasing the cementitious material, the rational use of a single layer of stone can increase the strength, which is for high grades.
The more stable the stone in the concrete, the higher the bending resistance, how to increase the stability of the stone in the concreteFirst of all, by reducing the specific surface area of the stone, the larger the unit force area, the less likely it is to loosen, and the better the bending effect.