3RD INTERNATIONAL CONGRESS ON TECHNOLOGY - ENGINEERING & SCIENCE - Kuala Lumpur - Malaysia (2017-02-09)

Change In Oki Peat Soil Cohesion And Friction Angle Due To Additional Geopolymer

Peat soil generally has a small effective cohesion value but has a relatively large friction angle value due to the organic fiber content in peat soil that serves as reinforcement. The addition of geopolymer on peat soils is expected to increase effective cohesion value because the nature of geopolymer which can function as a binder like cement in a mixture of soil cement. Increasing the effective cohesive value would be beneficial to improve the performance of road subgrade constructed from the peat soil as used at peatland OKI (Ogan Komering Ilir) South Sumatra Province. Geopolymer research on the effect of adding OKI peat soil conducted through CU (Consolidated undrained) triaxial testing to measure how much cohesion and friction angle value changes. Triaxial testing performed on compacted cylindrical samples with a diameter of 3.5 cm and height 7.0 cm, compacted at the optimum water content (100% - 120%) with a standard proctor compaction. Radial stress used is 50 kPa, 100 kPa and 150 kPa. Geopolymer used is composed from the 70% Fly Ash, 10% Water Glass, 10% Fire Soda and 10% Water futher content of geopolymer used as a mixture of soil of peat by 0%, 10% and 20%. From result of examination shown that the peat soil effective friction angle is influenced by radial stress where the higher radial stress tends to establish effective friction angle increases. Eeffective friction angle values on radial stress between 50 kPa - 100 kPa is smaller when compared with friction angle on radial stress between 100 kPa - 150 kPa. This is possible because the effect of concentration, orientation, homogeneity and type of peat soil organic fibers. Tests of peat soil with a mixture of 10% and 20% geopolymer showed a relatively constant effective friction angle to the stress radial increasing where the effective friction angle value on radial stress between 50 kPa - 100 kPa relatively equal to the effective friction angle value on radial stress between 100 kPa - 150 kPa. It can also be seen that higher geopolymer content tends to increase effective cohesion value although on the other hand slightly decrease effective friction angle value. This is be understood because the formation of bonds between geopolymer and peat soil matrix. It can be concluded that the addition of geopolymer content on peat soil can increase the effective cohesion value which will support the performance of the road subgrade constructed by peat soil.
Allih Hayyan, Sigit P. Hadiwardoyo, Wiwik Rahayu, Nasuhi Zain