Abstract: The mechanism sand concrete with strength grade C50 was designed, and the influences of stone powder content and mother rock type on compressive strength, slump and microscopic performance of mechanism sand concrete were studied. Through EDS energy spectrum analysis, XRD and SEM, the influence mechanisms of stone powder content and mother rock type on performance of mechanism sand concrete were revealed. The results show that the mother rock type has less influence on compressive strength of mechanism sand concrete. With the increase of stone powder content, the compressive strength of mechanical sand concrete increases first and then decreases. When the stone powder content is 9% of the total mass of mechanism sand, the compressive strength of limestone mechanism sand concrete is the best, which is 69.6 MPa. When the stone powder content is 6%, the compressive strength of dolerite mechanism sand concrete is the best, which is 66.0 MPa. When the stone powder content is 12%, the compressive strength of granite mechanism sand concrete is the best, which is 68.3 MPa. The slump of concrete decreases with the increase of stone powder content. The increase of stone powder content suppresses cement hydration to some extent, and increases the amount of unhydration cement and fly ash. When the compressive strength of mechanism sand concrete is optimal, the Ca/Si ratio (CaO/SiO₂ mole ratio) of C-S-H gel is the lowest. The stone powder content and mother rock type do not affect the hydration products of mechanism sand concrete.

Key words: mechanism sand, concrete, mother rock type, stone powder content, compressive strength, microstructure