PILI SHELL ASH AS ADMIXTURE: IT’S EFFECT ON THE MECHANICAL STRENGTH OF SUBGRADE SOIL

This paper investigated the incorporation of Pili Shell Ash as admixture to improve the mechanical strength of soil used as subgrade course in pavement construction. Laboratory tests performed includes Sieve Analysis, Atterberg limits, Compaction and California Bearing Ratio test. Based on the result, the soil samples are classified as Group A – 5 which is a Silty soil. It can be seen that the pure raw soil with a 5% Pili Shell Ash has Plasticity Index less than 12 which signifies that the specimens are for item 200 as specified by Aggregate Sub – Base Course DPWH Standards and Specifications. However, samples with 10%, 15% and 25% Pili shell Ash has Plasticity Index less than 6 which signifies that the specimens are for item 201 as specified by Aggregate Base Course DPWH Standards and Specifications. The moisture content value increases while the maximum dry density decreases as the ratio of the Pili Shell Ash admixture increases. On the California Bearing Ratio Test, the samples with admixtures have the high range of compressive strength while that of pure raw soil has the least. Thus, the results showed that the addition of Pili shell ash improved the mechanical strength of soil.