Effects of Ground Coal Bottom Ash and Calcium Chloride on the Compaction Properties of Cement Stabilized Cold In-Place Recycling (CIPR) Pavement Base Course

Flexible asphalt pavement relies on a strong road base layer for structural support throughout its service life. Deteriorated pavement conditions require continuous maintenance and rehabilitation, resulting in maintenance costs. Cold In-Place Recycling (CIPR) offers a sustainable and cost-effective solution compared to the conventional method of ‘remove and replace.’ CIPR involves recycling degraded existing pavement materials with a certain depth of aggregate base to form a new base layer, with the addition of stabilizing agents. Proper compaction before curing is crucial since inadequate compaction reduces base density, risking stability and causing rutting and deformation under traffic. This study investigated the compaction properties in CIPR-based pavement construction, integrating stabilizing agent comprising ordinary Portland cement (OPC), ground coal bottom ash (GCBA), and calcium chloride (CaCl₂) to achieve optimal moisture content (OMC), maximum dry density (MDD), and bulk density. Three different ratios of crushed aggregate (CA) and recycled asphalt pavement (RAP) were used, ranging from 25% to 75%, alongside 1% - 4% OPC, 0% - 3% GCBA, and 0% - 3% CaCl₂. It was discovered that the OMC and MDD values were 5.22% and 1.86 Mg/m³ for CA25RAP75, 5.60% and 1.93 Mg/m³ for CA50RAP50, and 5.87% and 1.94 Mg/m³ for CA75RAP25 using the modified Proctor test. Results also found that stabilizing agents minimally affect bulk density, but the percentages of CA and RAP significantly influence it, with design mixes with higher CA content providing higher bulk density. The findings from this study provide initial results on the OMC, MDD, and bulk density values but do not reliably indicate the strength acquired by the proposed design mix. Further strength tests should be considered.