Investigation of High Plasticity Clay Stabilized with Cement and Zeolite Using Time-Dependent Pressure Wave Velocity

Enhancing the dynamic properties of expansive soils using cementitious materials has attracted the attention of many researchers over the past few decades. Supplementary cementitious materials (SCMs) can be used as partial substitutes for cement owing to their pozzolanic activity that further improves the mechanical performance of cement-stabilized soils upon curing. In this study, the effect of cement and zeolite incorporation on the mechanical behavior of expansive clay was quantified using the pressure wave velocity ($V_p$) indicator obtained from ultrasonic pulse velocity tests performed at different curing times. Furthermore, a polynomial model was developed to establish the relationship between $V_p$ and zeolite replacement levels at specific curing times and cement contents. The results show that a polynomial function captured the decreasing trend of $V_p$ upon the increase in zeolite at curing times below 14 days. Additionally, the developed equation explained the upward trend of $Vp$ owing to the pozzolanic activity of zeolite at later curing times with an accuracy of over 92%. The coefficients of the polynomial model also increased with the increment of the cement percentage which conformed to the consecutive rise in $V_p$. Ultimately, the polynomial coefficients were expressed in terms of cement content and curing time using the Volterra series. Using this model, the optimum percentage of cement replaced with zeolite ($Z_{\mathrm{opt}}$), the efficiency of using $Z_{\mathrm{opt}}$ instead of cement, and the percentage of zeolite replacement to achieve equivalent $V_p$ of cemented clay samples ($Z_C$) were estimated. The findings of this study contribute to promoting geotechnical sustainability by replacing cement with zeolite that has a considerably lower environmental footprint.

Clay is a type of soil that can be found in many construction projects. For instance, many roads and buildings’ foundations are constructed on clay soils. To ensure the necessary strength of the clay under the main structure, the soil should often be stabilized using adhesive construction materials such as cement. Interestingly, a portion of the cement could be replaced with other minerals not only to improve engineering performance but also to promote sustainability by lowering cement consumption. In this study, the effect of zeolite as a partial replacement for cement on the strength of clay soils was experimentally evaluated. The effect of various design parameters, such as cement replacement level and curing time, on the stability of clays was investigated using an advanced technique called the ultrasonic pulse velocity (UPV) test. Furthermore, a simple mathematical model was proposed based on the experimental results to help engineers design the stabilization plan and timely decide about the next steps of the construction process.