Water permeability, strength and freeze-thaw resistance of crumb rubber-modified permeable concrete brick based on orthogonal test

Permeable concrete brick (PCB), as a new type of pavement material, is commonly used in sidewalks and parks owing to its environmental benefits. Crumb rubber, as an excellent pavement materials modifier, has many advantages in improving freeze-thaw durability of PCB. In this paper, a kind of rubber-modified permeable concrete brick (RMPCB) was prepared. The effects of water-binder ratio, designed porosity and crumb rubber content on compressive strength, split tensile strength, permeability coefficient and freeze-thaw durability of RMPCB were studied. Nine groups of tests were carried out by orthogonal design; range analysis and variance analysis were used to investigate the effect of three factors (water binder ratio, designed porosity and crumb rubber content) on the test results of RMPCB. The results show that porosity is the dominant factor in the properties of permeable bricks. Higher porosity can significantly increase the permeability coefficient of RMPCB, but weaken its strength and freeze-thaw durability. The split tensile strength and freeze-thaw durability of RMPCB are positively affected when crumb rubber content is 4% of the weight of cement. With the increase of water-binder ratio, the compressive strength of RMPCB first increases and then decreases, but the effect of water-binder ratio on other properties is not significant. The optimal water-binder ratio, design porosity and crumb rubber content for RMPCB are 0.30, 15% and 4%, respectively.