Laboratory Investigation and Field Performance Evaluation of Chemically Stabilized Cement Treated Subbase

Abstract

There is a growing concern over the depletion of naturally occurring construction materials for lower unbound pavement layers. Stabilization of locally available materials has attracted considerable research interest. Nanotechnological additives have a good potential in stabilizing materials that are incompatible for pavement construction. The main aim of this research is to evaluate the use of nano-chemical additives on the laboratory and field characteristics of cement treated subbase (CTSB) mixes prepared with locally available soil. Locally available soil, cement, and nano-chemicals were utilized to assess their effect on California bearing ratio (CBR) and unconfined compressive strength (UCS) of chemically treated subbase mixes. The UCS of the soil-aggregate mix treated with cement improved by 103.4% on the addition of nano-chemical additives. The soaked CBR of the mix treated with the optimum dosage of cement and nano-chemical was increased by 219%. The laboratory-based evaluation was followed by construction of field sections utilizing the control subbase (soil-aggregate only), cement-treated subbase, and cement+nano-chemical treated subbase mixes. Deflectometric investigations were performed on the field sections using a light weight deflectometer. X-ray diffraction and scanning electron microscopy tests were carried out to study the microstructure of subbase mixes. Stabilisation using nano chemicals resulted in additional phases of ettringite that caused densification of matrix compared to pristine soil-aggregate mix. Pavement analysis and economic analysis of the different subbase mixes were also performed. The subbase prepared with 3% cement and 1.2 kg/m3 dosage of nano-chemical additive was found to be the optimum considering laboratory and field performance.