Experimental and Analytical Investigation on the Interlayer of Roller Compacted Concrete

Abstract

Roller compacted concrete (RCC) is a dry concrete with zero slump and is constructed in layers. RCC dams are generally weak in interlayers. The bond strength and the permeability of the interlayer affect the performance of the dam structure and its safety. In this study, the mechanical characteristics and the permeability of the interface layer of RCC were investigated by considering three key parameters, including water-to-cementitious materials ratio (w/cm) of concrete, water-to-cementitious (w/c) ratio of bedding mortar, and time interval between pouring each layer. More than 300 RCC specimens were prepared. The bond strength of the interlayer was measured using the direct shear test and the direct tensile test. The permeability of the interlayer was evaluated by conducting the water permeability and the sorption tests. Scanning electron microscopy (SEM) was utilized to investigate the microstructure of interlayers. The analysis of variance (ANOVA) was utilized to identify the statistical significance of experimental parameters, which were the w/cm ratio of concrete, w/c ratio of bedding mortar, and time interval on the strength and permeability properties of RCC. Additionally, the relationship between the variables and responses was determined using the response surface method. Finally, the optimal mix design was achieved by multiobjective optimization based on target strengths and water permeability. Joint condition of the RCC layer was affected by the age of the joint and bedding layer. Results showed an increase in the time interval led to a reduction of bond strength and high permeability of the joint. Furthermore, by increasing the cement content of the bedding mortar, the shear and tensile strengths were improved, and the permeability coefficient was reduced considerably.