Study on the Effect of Cinder Ash as Auxiliary Additive Mineral in Hydrated Lime Treatment for Expansive Subgrade Soil for Road Construction

Abstract

Abstract Expansive soils are one of a major challenging soil for road construction in all over the world, the swelling and shrinkage behavior of expansive soil response to changes in moisture content and as a consequence it's leading to pavement failure. From the chemical additives, hydrated lime is one of a common improver used to stabilize expansive soils, but the use of it can be expensive and lead economical limitation and also require a long curing time. A Cinder ash is both a naturally and industrially byproduct available mineral which has been the most likely auxiliary additive mineral for hydrated lime stabilization of expansive soils. This research work is designed to analyze the improvement of the problematic sub-grade soil with the conjugation of random distributed local natural cinder ash in the proportion of 20 to 35% with a 2 to 5% proportion of hydrated lime. The subgrade soil treated with the conjugation of cinder ash and hydrated lime indicated appropriate improvement in the engineering properties of the soil compared to the native subgrade soil. However, the test result showed a reduction in moisture content, swelling properties, and liquid limit, which were noted in all cinder ash and hydrated lime composites. The samples of soil and cinder ash are collected from Wolaita region Kindo Didaye Woreda Belle Keble of Ethiopia. The MDD, OMC, CBR, and UCS values of the untreated soil were 1.429g/cc, 25.71%, 2.85% and 36.5kpa respectively. The method of characterization is done as per AAS HTO and ASTM test methods, which are recommended by the Ethiopian Road Authority (ERA). The proportion used to treat expansive subgrade soil for characterization was, 20%, 25%, 30%, and 35% for cinder ash, and 2%, 3%, 4%, and 5%, for hydrated lime are used accordingly. The analysis presented that, MDD increased and OMC decreased with increased percent of cinder ash and hydrated lime. The three-point soaked CBR test indicated that the value increased from 2.7–12.8%, this result shows that the CBR value is increased by 374% from the native soil CBR value when the expansive soil is treated with the mixture of 35% of cinder ash and 5% of hydrated lime. 4.54 kg surcharged swell value is decreased from 3.56–0.38% as a percent of 20 to 35 of cinder ash and 2 to 5 percent of hydrated lime are conjugated on an expansive soil. Besides, the developed simple linear regression analysis of a statistical model indicated a good agreement with the experimental study. Results from the current study concluded that stabilizing problematic subgrade soil with cinder ash and the hydrated lime mix was an economical and environmentally friendly investigation method to improve expansive subgrade soil. It can be shown from the conducted experimental results, developed excel graphs, and statistical model, the improvement method formed conjugation with successful environmental grip between cinder ash and hydrated lime composite was obtained.