The role of rice husk ash, cement and polypropylene fibers on the mechanical behavior of a soil from Guabirotuba formation

Abstract

The main focus of this research was to evaluate the behavior of three different materials added to the Guabirotuba Formation soil, which were: rice husk ash (RHA) [5%, 10%, 15%], Portland cement (PC) [2%, 5%] and polypropylene fiber (PPF) [0.5%]. A geotechnical characterization and compaction tests of the soil and all blends were carried out. Subsequently, unconfined compressive strength (UCS) and splitting tensile strength (STS) tests were performed for specimens subjected to three curing times (7, 28, 90 days). Finally, statistical analysis based on the theory of errors were conducted. The results showed a significant variation of Atterberg limits, where PI went from (14.8 ± 0.1)% in the pure soil to (1.3 ± 0.2)% in B12 (Soil + 5 %PC + 15 %RHA + 0.5 %PPF). On the other hand, the maximum dry unit weight (γdmax) was decrease and the optimum moisture content (OMC) increase as the content of additives and PPF increased. This variation was higher in B12 where the γdmax had a decrease of 1.46 kN/m3 and the OMC increased 10.7 pp concerning to the pure soil. The results of the UCS and STS tests showed that the best blend was B12 where UCS went from (357 ± 6)kPa to (2118 ± 3)kPa in the pure soil and B12, respectively. In the same way, STS went from (39 ± 1)kPa in pure soil to (431 ± 4)kPa in B12. In this way, it was found that the RHA is a potential substitute for a part of the PC used in soil improvement. On the other hand, it was observed that the PPF presented the most important contribution to the reinforcement of the stabilized soil, since the PPFs prevent the development of cracks and improves the strength of the soil when the force was applied.