Application of a capillary crystalline material to enhance cement grout for sealing tunnel leakage

Abstract

Abstract This study investigates the feasibility of using a cement-based capillary crystalline material, Penetron Admix (PA), to enhance the performance of a cement grout for sealing tunnel leakage. A series of experiments were carried out to investigate the effects of PA on the viscosity, setting time, concretion rate, permeability and compressive strength of the cement grout. The experimental results show that inclusion of PA into cement grout has no effect on its viscosity and setting time, but can markedly increase the concretion rate, and the compressive strength of the grout concrete and reduce its permeability. Micro structure characterizations by CT scanning indicate that cement-gravel grout concrete samples with additional PA show a compact and smooth structure compared to those without PA; SEM images show that the dendritic crystals are observable under high magnification in the cement grout concrete samples with PA, and the number of crystals increases as the amount of PA increases. Based on the experimental results and the micro structure characterizations, it can be concluded that PA can be used as an additive to improve the rate of concretion, compressive strength, and impermeability of cement grout. To achieve an optimum leakage-sealing effect, the weight ratio of PA to cement of 1.4–1.6% is recommended.