A Workability Characterization of Innovative Rubber Concrete as a Grouting Material

Abstract

The aim of this study is to assess the workability of an innovative rubber concrete to fill in the gaps in a shield tunnel construction. This grouting material includes porous sand, PVA (polyvinyl alcohol) fiber, cement, and rubber. One advantage of the material is its high toughness, which is good for the postfailure stage of an earthquake event. Evaluations were carried out on the physical properties in terms of the slurry density, consistency, fluidity, bleeding rate, consolidation shrinkage rate, setting time, and unconfined compressive strength (UCS) (i.e., 3 and 28 days). The toughness index was also introduced to evaluate the performance at the postfailure stage. The results demonstrate that the toughness index will increase as the rubber content increases. It increases from 1.0 at 0% to 1.7 at 80% rubber content (28 days’ curing) and from 1.2 at 0% to 2.2 at 80% rubber content (3 days’ curing). The increase in fiber content and fiber length will also increase the toughness index as the fiber will enhance the tensile strength of the matrix. The results show that when the fiber content increases from 0% to 1%, the toughness index increases from 1 to 7 (28 days’ curing) and from 1.1 to 10 (3 days’ curing). Similarly, if the fiber content or fiber length is above the optimum level, the UCS of the material will be compromised. The optimum fiber content is 0.8%, and the optimum fiber length is 6 mm to 9 mm. This study suggests that the balance of physical properties should be considered in designing a satisfactory grouting material based on the specific purpose of the engineering practice.

Preliminary Mechanical Evaluation of Grouting Concrete as a Protective Layer for Tunnelling

“…However, rubber concrete is not a porous material and is not able to sustain large deformation such as the porous material. According to Lu et al [41], the UCS for the grouting material to form the lining layer should be over 0.5 MPa for 3 days and 2.5 MPa for 28 days. However, there is no requirement for the flexural stiffness according to authors' knowledge.…”

“…According to Table 5, cement, sand, and rubber were mixed evenly in a mixer to ensure a relatively good distribution of the materials [41]. Then, the target amount of water was added to the mixture and mixed for 15 min.…”

Experimental Study on Performance of Modified Cement-Based Building Materials under High-Water-Pressure Surrounding Rock Environment

“…The impermeability of PVA to the grouting material was markedly improved, and it increased with increasing amounts of PVA content. Lu et al [21] proposed porous sand, PVA, cement, and rubber grouting materials. The density, consistency, fluidity, exudation rate, consolidation shrinkage rate, setting time, and unconfined compressive strength of the slurry were tested in the laboratory.…”