透水性混凝土强度-渗透性模型试验研究

Strength-permeability Model of Pervious Cement Concrete

高透水性是透水性混凝土的重要特征,现有的透水性混凝土渗透系数测试装置存在试件侧壁渗漏问题,为此提出了一种试件侧面防水涂抹+柔性夹层+套筒刚性壁的防侧漏复合结构,提高了渗透系数测试精度。透水性混凝土的透水性和强度是一对矛盾体,此消彼长,但目前对它们之间关系缺乏系统的研究。通过室内渗透性和强度试验研究了多种因素(如:水灰比、集灰比、孔隙率)对透水性混凝土的强度和透水性的影响,建立了强度孔隙率模型、渗透性孔隙率模型和强度渗透性模型。研究结果表明:透水性混凝土与普通混凝土不同,存在一个最佳水灰比,最佳水灰比对应的强度最大;强度和水灰比成开口向下的二次抛物线关系,而孔隙率和集灰比均与渗透系数成正相关关系;透水性混凝土强度和渗透性关系服从Lorentzian函数,强度随渗透性的增大而逐渐降低,降低速度先快后慢。在工程设计中应根据具体要求,确定最佳的强度和渗透性组合。

High permeability is an important characteristic of pervious concrete.For the existing permeability testing devices of pervious concrete,the specimen sidewall leakage is serious due to the large numbers of open pores on the surface of specimens.To solve the problem,a new permeability testing method for pervious concrete was developed and a composite sidewall structure with waterproof daub,flexible rubber cushion and rigid sleeve sidewall was proposed.Meanwhile,the strength and permeability of pervious cement concrete are incompatible with a reciprocal relationship.However,limited research has been conducted on the relationship between them.Effects of water-cement ratio（W/C）,aggregate-cement ratio and porosity on the properties of pervious concrete,including strength and permeability,were studied.Furthermore,strength-porosity model,permeability-porosity model and strength-permeability model were established.Tests reveal that： a） There is an optimum W/C of pervious concrete,at which strength reaches the maximum;b） The relationship between the strength and W/C shows a downward quadratic curve,and the permeability is proportional to porosity and aggregate-cement ratio;c） The relationship between strength and permeability of pervious cement concrete can be well fitted with the Lorentzian function,and the strength decreases when the permeability increases,but the rate of reduction decreases gradually.The optimum combination of strength and permeability should be determined based on the specific engineering requirements in design.