Effect of the Curing Time and Combination of Corncob (Zea Mays L.) Ash With Swelling Clay on Mechanical Properties of Soil in Forest Road

Abstract

ABSTRACT Swelling soil such as clay soil is known as unsuitable material for forest transportation due to the high volume change and mechanical defects. The aim of this study was to investigate the effects of corncob ash as a biologic additive on mechanical properties of clayey soil in forest roads of Bahramnia forestry plan in Golestan province. Different content of corncob ash and curing time were the treatments of study. Corn wastes were collected from farmlands and nodes of corncob with high silica content were used to produce ash. Soil samples were collected from the road construction area to conduct testing. First set of soil samples without additives and second set contained 5%, 10%, 15%, and 20% of corncob ash. Atterberg limits, standard proctor, and unconfined compressive strength were carried out on 7, 14, and 28 days curing times. Findings showed that the plastic index decreased by increasing corncob ash to 5%. Adding ash up to 5% can cause dramatic increase in plastic index. Addition of ash to the soil decreased dry bulk density and increased optimum moisture content. Maximum dry density (1.73 g cm−3) was recorded in optimum moisture of 28.5% and ash content of 5%. Unconfined compressive strength of samples increased until adding 5% of ash, and then the compressive strength decreased by increasing the ash content. There wasn’t significant difference between the curing times of 14 and 28 days in mechanical properties of soil samples. It was concluded that ash content of 5% and curing time of 14 days were the optimum values which maximum improvements in mechanical properties of swelling clay soil are occurred.