Experimental Study on the Effect of the Freeze–Thaw Cycle in an Acidic Environment on the Mechanical Properties of Grout-Reinforced Rock Specimens

Abstract

A new type of grouting material—FCM (fast cementing material)—is being used in coastal and offshore infrastructure projects, such as harbor and tunnel rehabilitation. In order to investigate how this material performs under different conditions, the compressive strength, failure mode, and surface microscopic changes of different fracture penetration degrees and different crack angles of grout-reinforced specimens formed by the FCM and sandstone were investigated in an acidic environment with pH = 1.1 and after freeze–thaw cycles of 5, 10, 20, and 30 times. In addition, through the preliminary determination of FCM grouting material fluidity and setting time, it was determined that the water-material ratio in this test is 0.3, and the sandstone used has good uniformity. The results show that the strength of the original rock can be matched or even exceeded by the solid grout of FCM and sandstone. Acidic environments and freeze–thaw cycles will erode the specimens, mainly on the surface of the specimens. The fracture penetration degree and crack angle determine the degree of strength reduction of the specimens. The compressive strength of the specimens decreases most rapidly within 10 freeze–thaw cycles. After soaking in acidic solution and a freeze–thaw cycle in an acidic environment, particle shedding occurs on the surface of the grout material and a “honeycomb” area appears on the surface of the sandstone. As the freeze–thaw cycle increases, the particle-shedding area and the honeycomb area increase continuously.