Suitability of Waste Paper Ash Blended with Lime to Improve the Strength of Expansive Subgrade Soil

Abstract

Expansive soils have the tendency to behave volume change during wetting and drying conditions which causes significant damage to structures such as buildings and pavements. This behavior of the soil cause large uplift pressure, differential settlement, and upheaval of structures built on them. Avoiding these types of unsuitable soils is mostly impractical. Hence, the aim of the study is to investigate the suitability of waste paper ash blended with lime to improve the strength of expansive sub-grade soil to be used as sub-grade materials. The research design followed the experimental type of study which began by collecting samples. In this study moisture content, Atterberg limits, particle size distribution, soil classification, free swell index, linear shrinkage, specific gravity, compaction (moisture-density relationship) tests, CBR and CBR swell were determined. The sampling technique used for this research was a purposive sampling which is non– probability method. Two expansive soil samples were taken for the study by observation and free swell index tests at a depth of 1.5 m-2 m to remove organic matters. The data processing and analyzing were conducted by using both descriptive and analytical methods. Laboratory test result of waste paper ash shows that specific gravity, liquid limit, plastic limit, plastic index and optimum moisture content were 1.67, 50.8%, 43.7%, 7.1% and 50.1%, respectively. The laboratory test results fulfilled the requirements of class-C fly ash according to ASTM C-618. JIT soil sample has plastic index 39 %, free swell index 88.12 %, linear shrinkage 17.73% and CBR value 2.33%. In addition, the MAR soil sample has plastic index 41.8 %, free swell index 96.83%, linear shrinkage 20.07% and CBR value 1.95%. Since both soil samples were found with high degree of expansion, stabilization was made by mix-ratio of (0, 2%HL+12%WPA, 4%HL+10%WPA, 6%HL+8%WPA, 8%HL+6WPA). As the content of hydrated lime increases and WPA decreases in WPA: HL mix-ratios, LL, PI, MDD, FSI, CBR swell decreased whereas PL, OMC, CBR are increased. All the laboratory test results were compared with standard specifications. It was recommended to investigate the effect of additional curing time and aging effect of soil stabilized by WPA. Additional parameter like unconfined compressive strength, PH value test, volumetric shrinkage and mineralogical tests should also be performed to have more realistic test results.