Use of Rice Husk Ash (RHA) in Flowable Fill Concrete Mix Material

Rice hull (RH) is one of the main agricultural residues obtained from the outer covering of rice grains during the milling process. RH constitutes 20% of about 700 million tons of paddy produced in the world. When burnt, 20% of RH is transformed into rice husk ash (RHA). RHA is a cementitious material, and locally produced RHA in Arkansas contains about 75% silica in an amorphous form and has an extremely high surface area. RHA is also economically beneficial in producing concrete, but its performance as a construction material has been investigated very little. Based on the preliminary data of the research team of this project, locally produced RHA is not capable of producing “regular” concrete of compressive strength of greater than 3000 psi. Rather, low strength concrete such as Flowable Fill Concrete (FFC) can be produced using the “as is” RHA. However, the usage, test protocols and procedures of FFC are different from “regular” concrete. Arkansas Department of Transportation (ARDOT) has ranked this problem statement in its Top 10 Problems for possible solution in 2018-2019. The main objective of the proposed study is to assess the feasibility of the use local RHA in producing FFC. Specific objectives are to: (i) prepare FFC and determine their workability and flow behavior, (ii) evaluate the effect of curing time and environmental conditions on strength properties and durability of RHA-modified FFC, and (iii) evaluate the optimum dosages of RHA as pozzolan in preparing FFC.