Influence of aluminum sulfate on mobility and adhesion of hydroxyethyl methyl cellulose in cement-based materials for tunnel linings

Cellulose ether allows for high adhesion of fresh cement-based materials for hard rock tunnel linings. Alternatively, accelerator is used when a fast stiffening rate is required to support the surrounding rock. However, the influence of the addition of accelerator on the performance of cellulose ether has not been explored previously. In this study, four types of hydroxyethyl methyl cellulose with different viscosity levels and pure aluminum sulfate were used. The viscosifying property of the hydroxyethyl methyl cellulose in an aqueous solution with varying concentrations and temperatures was first examined. Furthermore, the hydrodynamic diameter and the concentration of hydroxyethyl methyl cellulose in the extracted interstitial fluid of the fresh mixtures was measured by performing the dynamic light scattering (DLS) test and the total organic carbon (TOC) test. In addition, the adhesion of the materials was tested both in the fresh and hardened state. Results indicate that the addition of aluminum sulfate contracts the pores in the fresh material and hinders the mobility of the hydroxyethyl methyl cellulose, especially for the ones with a high viscosity level. It is also shown that both hydroxyethyl methyl cellulose and aluminum sulfate enhance the adhesion of the fresh material, which can be attributed to improved shear resistance.