考虑石粉影响的盾构管片机制砂混凝土配合比设计研究

Study on the Design of Mechanical Sand-Concrete Mixing Ratio for Shield Segment Considering the Effects of Stone Powder

由于机制砂中石粉在混凝土中主要起到填充作用而非骨架作用,将石粉视为机制砂的一部分已经不再适用于盾构管片机制砂混凝土的配合比设计。本研究将石粉视为粉料的一部分,在计算盾构混凝土的水粉比时考虑了石粉的影响,并引入砂浆包裹层厚度以计算混凝土中的骨料含量,同时研究了砂浆包裹层厚度对盾构管片机制砂混凝土的影响。结果表明:采用本研究配合比设计方法设计制备得到的机制砂混凝土的水泥用量较传统设计方法减少约20 kg/m3,电通量和氯离子扩散系数较传统设计方法的分别降低26.7%和25.1%,90 d收缩率降低33.3%。此外,机制砂混凝土的工作性、抗氯离子渗透性能以及抗收缩性能随着砂浆包裹层厚度的增大而显著劣化。

Given that stone powder in mechanical sand mainly acts as a filler in concrete rather than as a framework,treating stone powder as a part of mechanical sand is no longer suitable for designing the mixing ratio of shield segments and mechanical sand concrete.Taking stone powder as a part of the powder,this study considered the impact of stone powder in calculation of the water-powder ratio of shield concrete,introduced the thickness of the mortar coating layer to calculate the aggregate content in the concrete,and also investigated the effect of the thickness of the mortar coating layer on the mechanical sand concrete of the shield segment.As shown by the results,in comparison to the traditional design method,the amount of cement used for mechanical sand concrete designed and prepared through the design method of this study was reduced by about 20 kg/m3,the electric flux and chloride ion diffusion coefficient were reduced by 26.7%and 25.1%,respectively,and the 90-day shrinkage rate was decreased by 33.3%.Furthermore,the workability,chloride ion penetration resistance,and shrinkage resistance of mechanical sand concrete deteriorated significantly as the thickness of the mortar coating layer increased.