Influence of machine-made sand and gravel powder content on concrete performance

September.09,2021

The machine-made sand mainly refers to the rock, mine tailings or industrial waste particles with a particle size of less than 4.75mm made by mechanical crushing and sieving after soil removal treatment, and does not include soft and weathered particles. It is made by special sand In machine production, the content of stone powder is generally 10% to 15%, and the particle shape of machine-made sand is generally polygonal and the surface is rough. Since the edges and corners of machine-made sand are obvious and contain stone powder, it generally has a greater impact on the working performance of concrete.

Stone powder with a particle size of less than 0.08mm in machine-made sand can improve the workability of concrete. The gradation and particle size of machine-made sand will obviously affect the working performance of concrete. Reasonable use of superplasticizers can make up for the negative impact of stone powder in machine-made sand.

One view is that when the content of stone powder in machine-made sand is between 5% and 10%, the effect on the working performance of concrete is negligible. Another view is that the stone powder in machine-made sand has a positive effect on the strength of concrete. The stone powder in the machine-made sand can fill the pores in the concrete, thereby increasing the compactness of the concrete and improving the strength of the concrete.

According to the conclusions of related experiments, the influence of 5 kinds of stone powder content of machine-made sand on the working performance, compressive strength and impermeability of C60 high-strength concrete is pointed out.

Test Conclusions

1) The content of stone powder in machine-made sand has little effect on the slump of C60 high-strength concrete, but when the content of stone powder exceeds 5%, it will significantly reduce the expansion of concrete, which is not conducive to the work performance of concrete.

2) The content of stone powder in the machine-made sand within 10% has no effect on the compressive strength of C60 high-strength concrete. When the content of stone powder exceeds 10%, the compressive strength of concrete can be improved.

3) The impermeability of concrete decreases gradually with the increase of stone dust content in the machine-made sand within 10%. When the stone dust content exceeds 10%, the impermeability of concrete can be increased. The test results are consistent with the compressive strength. Participate

The machine-made sand mother rock used in the test is limestone with a fineness modulus of 2.7 and an apparent density of 2670kg/m3. Crushed stone: 5～25mm continuous graded crushed stone with apparent density of 2720kg/m3.