Predicting and evaluating the engineering properties of unstabilized and cement stabilized fibre reinforced rammed earth blocks

This paper investigates the effect of coir percentage, length and cement content on the properties of rammed earth blocks in terms of strength, density and durability followed by predicting the properties using statistical regression analysis. X-Ray Diffraction (XRD) analysis was made on unstabilized (US) and cement stabilized (CS) samples to study the effect of cement stabilization on the phase composition. Scanning electron microscopy (SEM) observations are used to analyze the micro-structural interactions of coconut fibre (coir) with soil and soil-cement matrix. Coir of 1% to 5% and 25 mm to 50 mm lengths was used as reinforcement and 10% of cement as stabilizer. The investigation shows that the characteristic dry compressive strength increases up to 1% coir of 25 mm length and gradually decreases with the increase in coir percentage and length. However, tensile strength increases with the increase in coir percentage and length. CSRE blocks reinforced with 1% and 3% coir of 25 mm and 50 mm lengths respectively meet the durability criteria specified by some standards and researchers. XRD analysis revealed the presence of quartz, calcite, albite and small amounts of other minerals on the other hand cement stabilization increased the calcite peaks. Cement stabilization reduces the microstructure porosity of the material thereby improving the strength and durability properties. Coir reinforcement along with cement stabilization increases the efficiency of rammed earth samples. A series of statistical analysis was also conducted to predict the compressive and tensile strengths correlating coir percentage, length, density and cement content. The equations generated from regression analysis represented a strong correlation between the actual and predicted values, which can be used for accurate prediction of rammed earth strength. (C) 2020 Elsevier Ltd. All rights reserved.