隧道高性能多孔水泥混凝土孔隙率特性的试验研究

孔隙率是隧道路面多孔水泥混凝土的重要技术指标之一,保证多孔混凝土试件成型后或路面铺筑后的实测孔隙率与目标孔隙率基本一致,同时保证其具有足够大小的有效孔隙率,是高性能多孔混凝土隧道路面配合比设计的关键。依据隧道路面的功能要求,文章选定目标孔隙率为18%。级配对混凝土强度影响非常明显,随着10～15mm集料比例的增加,强度先增大后减小。当采用玄武岩等吸水率偏大的集料制备多孔水泥混凝土时,在有效孔隙率计算中应考虑集料吸水的影响。矿料级配对孔隙率的影响规律为:随着10～15mm集料比例的增大,计算孔隙率变化幅度很小,且与目标孔隙率(18%)接近;有效孔隙率呈增大的趋势,实测孔隙率先减小后增大;级配2#-2实测孔隙率最小且与目标孔隙率最接近。依据孔隙率及强度试验结果,选取级配2#-2为最佳级配。

Experimental study of porosity properties of tunnel's high performance porous cement concrete

Porosity is one of the important technical indexes of porous cement concrete which is used in tunnel pavement.The key of mix proportion design of tunnel’s high performance porous cement concrete is to make the observed porosity be consistent with the target porosity after forming the porous concrete specimen or paving the pavement,and to ensure that it has enough effective porosity.Based on the functional requirement of the tunnel pavement,the target porosity of 18% is chosen in this paper.Gradation has significant effect on the strength of concrete.With the increase of the ratio of 10-15 mm aggregate,the strength firstly increases and then decreases.When the aggregate with higher water absorptivity such as basalt is adopted to prepare porous cement concrete,the effect of the aggregate’s water absorption should be considered in the calculation of the effective porosity.The affecting principles of the aggregate gradation on the porosity are as follows: with the increase of ratio of 10-15 mm aggregate,the calculation porosity changes slightly,and is close to the target porosity(18%);the effective porosity presents an increasing trend and the observed porosity firstly decreases and then increases;the gradation 2#-2 has the smallest observed porosity which is closest to the target porosity.According to the results of porosity and strength tests,gradation 2#-2 is selected as the optimum gradation.