基于CT技术的天然浮石混凝土孔隙结构试验研究

Research on the pore structure of natural pumice concrete based on CT technology

天然浮石混凝土具有质轻、多孔和隔热的优点,将其应用于渠道工程可改善低温环境对渠道输水效率的不利影响。通过CT扫描试验、Avizo软件和分形几何理论对天然浮石混凝土的孔结构进行分析并阐明孔结构对抗冻性能的影响机理。研究结果表明:天然浮石混凝土的孔隙具有随机分布且孔径大小不一的特点。孔径分布中大孔(R>1000μm)数量占比最少,分布比较分散;中孔(100μm<R<1000μm)数量最多,分布均匀且集中;小孔(R<100μm)数量占孔隙分布总频数的8.2%,分布均匀且密集。相比普通混凝土,浮石骨料内部的孔隙缩短了气泡间距系数,减小了静水压力,故其抗冻性优于普通混凝土。由分形几何理论可知,天然浮石混凝土孔隙的分形维数在1.920~1.923间,孔隙分布的复杂程度较大,但不同截面处孔隙分布的复杂程度差异较小。

In order to study the characteristics of pores and pore size distribution in natural pumice concrete and further analyze the influence of pore structure on frost resistance,it analyzes the structure of natural pumice concrete through CT scan test,Avizo software and fractal geometry theory.The results show that the pores of natural pumice concrete have the characteristics of random distribution and different pore sizes.In the pore size distribution,the number of large pores(R>1000μm)is the least,and the distribution is relatively scattered.The number of mesopores(100μm<R<1000μm)is the most,and the distribution is uniform and concentrated.The number of small pores(R<100μm)is the proportion.The pore distribution is 8.2%of the total frequency,and the distribution is uniform and dense.Under the freeze-thaw cycle,the relative dynamic modulus changes of natural pumice concrete and ordinary concrete are compared.The reason why the frost resistance of natural pumice concrete is better than that of ordinary concrete.The pores inside the pumice aggregate shorten the bubble spacing coefficient,reduce the hydrostatic pressure,and improve its frost resistance.The fractal dimension of the pores of natural pumice concrete is between 1.920~1.923,and the complexity of pore distribution is relatively large,but the complexity of pore distribution at different cross-sections is relatively small.