IMPROVEMENT OF CLAYEY SILTY SOIL LAYERS BELOW SUB BASE OF DELTA COUNTRY ROADS BY MIXING WITH PALM FRONDS

The paper aims to minimize greenhouse gas emissions from cement and lime production while removing potential risks associated with inappropriate waste disposal techniques such as rice straw ash (RSA), sugarcane bagasse ash, crumb rubber, and palm frond ash, among others. Even in the face of heavy traffic and adverse weather, the subgrade must be strong and stable. Soil stabilization can be used to improve soil compressive strength and engineering properties of soil and, also weak subgrade layer in order to reduce pavement thickness and increase its lifetime. In this study, the stabilization materials were waste materials in the form of palm frond ash (PFA), which were collected from Beni Suef Governorate, Egypt. The tested soil is from Kafr Tohormos which is a residential area in Boulaq Al-Dakrour district, Giza Governorate, Egypt. The dry soil passing sieve No.40 was mixed with the palm frond ash, with 3%, 7%, 11%, and 15% from the dry weight of soil. Laboratory tests such as moisture content, sieve analysis, specific gravity, consistency limits, compaction test, unconfined compressive strength (UCS), and California Bearing Ratio (CBR) were carried out to identify the basic properties of a clayey silty soil. The findings of this study deduced decreasing in Atterberg limits with an increase in the stabilizing martial up to 11% then increased with more additives. Also, the specific gravity decreased with the increase of PFA percent with an amount of 3% to 15%. Maximum dry density decreased by 10% when adding 15% PFA, and the optimum moisture content increased by 25% when adding 15% PFA compared to their values without adding PFA. A significant change in CBR values which increased from 5% at natural soil conditions to a value of 31% when adding 15% PFA. Moreover, there is an increase in the unconfined compressive strength by 32% when adding 7% PFA.