Panich Voottipruex

Flexural Strength Characteristics of Compacted Cement-Polypropylene Fiber Sand

AbstractAn improvement of flexural strength of cement stabilized sand using polypropylene fibers designated as compacted cement-polypropylene fiber-sand (CCFS) is investigated in this research. The studied material performance of the CCFS includes postpeak behavior, toughness, and equivalent flexural strength ratio. The fiber inclusion significantly improves the postpeak flexural behavior, which is a requirement for bound pavement materials. The first peak flexural strength f1 and stiffness of both compacted-cement-sand (CCS) and CCFS are essentially the same for the same cement content. For low fiber content, the fiber inclusion primarily prevents the sudden failure. The CCFS exhibits deflection-hardening behavior and the peak flexural strength (fp) is higher than the first peak flexural strength (f1) for medium to high fiber contents. Two modes of failure are noted: single failure plane and stress transfer–induced multiple cracks. For low to medium fiber contents, the single failure plane is observed fo...

Comparison between cement and fly ash geopolymer for stabilized marginal lateritic soil as road material

ABSTRACT The stabilisation of marginal lateritic soil using cement and fly ash (FA) geopolymer with a liquid alkaline activator was investigated. In this study, soil with satisfactory gradation and percentage of wear was selected. Only the soaked California Bearing Ratio (CBR) value must be enhanced to satisfy the requirement to form a suitable pavement subbase material. Field CBR tests were conducted for both geopolymer- and cement-stabilised soils used as pavement subbase materials. The soaked CBR of cement- and FA-geopolymer-stabilised marginal lateritic soil of various mixing percentages at 14 days satisfied the standard requirements specified by the government agencies in Thailand. Equations were established from field test data to predict the CBR at any testing time. The CBR development of cement-stabilised soil took more time than that of geopolymer-stabilised soil. The appropriate mixing percentages of cement and FA geopolymer with marginal lateritic soil were 3–5 and 4–8%, respectively. Microstructural analysis indicated that the stabilised soil exhibited a denser structure, which corresponded to the CBR increment. The findings of this study will enable the implementation of cement and FA geopolymer as successful stabilisers for pavement subbase materials.

Effective Stress Parameter for Unsaturated Soils under Drying and Wetting Processes

This paper presents a variation of effective stress parameter with matric suction for unsaturated soils using a comprehensive data set of suctioned-controlled shear tests under drying and wetting processes. The effective stress parameter is determined by assuming that the slope of the critical state line in the plane of deviator stress against mean effective stress is independent of matric suction. This study shows a different in relationship between the effective stress parameter and matric suction for drying and wetting processes. The values of effective stress parameter obtained from the experiments were compared with those obtained from the expressions proposed in literature.