Master of Engineering (Hons.)
Department of Civil and Mining Engineering
Semaan, Nelson, Mix design of rice husk ash concrete: an Australian experience, Master of Engineering (Hons.) thesis, Department of Civil and Mining Engineering, University of Wollongong, 1986. http://ro.uow.edu.au/theses/2428
Research carried out in various parts of the world, has. led to the conclusion that rice husk ash (RHA) a pozzolanic material can be used as partial replacement for ordinary Portland cement (OPC) in making concrete.
Recently a new mix design procedure has been established in which two parameters are identified. They are the strength correlation factor, e, and the differential lubrication constant, f, both of which can be obtained by routine laboratory tests. This design procedure has been proved to be reliable for RHA produced at the Asian Institute of Technology. (AIT) in Thailand. The applicability of this new design procedure for the Australian RHA is investigated herein.
Experiments were carried out to find the two parameters for four different types of ash available from the Rice Growers Co-Operative Mills Ltd, Leeton, N.S.W. One of these four types was chosen for detailed investigation; this is known herein as Type C ash.
Conflicting results were obtained in the characteristics of the local RHA which affected the applicability of the said mix design procedure. The values of standard consistence of the Australian RHA are considerably higher than those of the AIT RHA. This rendered the mix design procedure unworkable. Some other differences between the Australian and AIT ashes, such as relative density, fineness and water absorption, also affected the reliability of the mix design procedure.
Based on the experimental data obtained in this study, a new mix design procedure is introduced for the use of Type CRHA in concrete. The proposed design aids consist of graphs for strength and wet densities, as well as tables for workability (slump) and free water content. Illustrative design examples are given.
The performances of the Australian RHA in concrete is examined. It is found that the compressive strength of the RHA concrete with 50% volume replacement of cement by RHA is higher than the comparable ordinary cement concrete by 2% to 11% for the four types of RHA. Type C is the most strength-effective.
Durability tests were also carried out. This led to the conclusion that RHA concrete is less prone to acid attack than comparable OPC concrete. The improvement is considerable.