Investigating the Impact of Cement–Bentonite Ratio on Plastic Concrete Performance in Diaphragm Wall Applications

The failure of the diaphragm wall at Polavaram Dam highlights the urgent need to improve the construction materials used in critical hydraulic infrastructure. With rising climate-induced hydrological loads and coupled hydromechanical stresses, there is an increasing demand for materials that are durable, impermeable, and resistant to cracking and settlement. Plastic concrete, a composite material consisting of cement, bentonite, aggregate and water in controlled proportion, meets these performance requirements while also providing adequate strength to withstand external loads. The present study investigates the influence of varying cement to bentonite (C/B) ratios on the mechanical performance of plastic concrete, specifically focusing on parameters such as strength and stiffness across different curing periods. Objective of study is to evaluate how the different cement–bentonite (C/B) ratio affects mechanical parameters of plastic concrete at different curing periods. All samples were prepared and cured under standard curing conditions, and both destructive and non-destructive laboratory tests, namely unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) were conducted at each curing stage. The results indicate that a higher C/B ratio leads to greater strength development over time, especially at extended curing durations. However, increased cement content also results in higher stiffness, while lower C/B ratios improve the plasticity of the concrete but lead to reduced strength gains. A strong correlation was established between UCS and UPV results, enabling the development of a statistical prediction model to estimate the strength and stiffness of plastic concrete non-destructively. These findings provide valuable insights into the design and application of plastic concrete in diaphragm wall construction.