Asian Research Thesis Index

Abstract

Concrete is being utilized as construction material in the construction industry worldwide. Nevertheless, it has some inherited deficiencies in terms of tensile strength, flexural strength and durability; such deficiencies lead its limitation on application for repair and rehabilitation of existing structures. In order to improve the inbred limitation of concrete, additives like; blast furnace slag, fly ash, rice husk ash, silica flume and other pozzolans are being blended in its production. In fact, inclusion of these materials not only improves the concrete, but also utilizes the abundantly generated wastes thereby contributing to the environmental cleansing. In addition to that lowering of the construction cost and reduction of CO2 emission can be achieved to a relative extent. The utilization of RHA as a cementing material in concrete improves compressive and tensile strength of concrete to a greater extent. Polymeric compounds are being added in concrete to improve strength and durability, but limited utilization of such compounds is reported because of their cost. Hence a new composite, i.e. „Rice Husk Ash PolymerModified Concrete‟ (RHAPMC) is envisaged to use RHA as a supplementary cementing material so as to make concrete more economical and to mitigate some persistent environmental problems. Moreover, for enhancing impermeability of RHA blended concrete a re-dispersible polymer powder is added. The present study is mainly concerned with the techniques necessary to develop and characterize RHAPMC matrix. In the first phase of this study, cement is replaced with extracted locally available RHA which is obtained under different temperatures and burning durations. For in-depth characterization of the extracted RHA, in terms of chemical composition, loss on ignition and strength activity index has been carried out. It has been found that the extracted RHA at a temperature of 800oC for 2hr duration is more efficient as pozzolanic material. Chemical composition, strength activity index and loss on ignition meet the requirement of a pozzolanic material to be used in concrete as per ASTM C 618 standard. Cement was replaced with RHA (800oC-2hr) at dosages of 1 to 15% by weight of cement to study workability, compressive and tensile strength of concrete. A significant strength improvement at 10% replacement of cement with RHA is obvious in experimental outcome but impermeability decreases. In the second phase to improve the impermeability and to further increase strength of RHA blended concrete 1 to 15%dosages of re-dispersible polymer powder (RPP) was added. Workability, compressive strength, tensile strength, bond between steel and concrete, unit weight, water absorption, water permeability, carbonation effect and corrosion potential were investigated. Furthermore, to examine performance of RHAPMC matrix, standard size beams were cast with developed material and load carrying capacity, deflection and mode of failure were examined. It is found that beams cast with RHAPMC improved load carrying capacity with more deflection and prolonged ductile failure as compared to control beams. Based on the conducted research it can be concluded that the investigated physical, mechanical and durability properties of RHAPMC produced with 10% cement replacement by RHA and the inclusion of 5% RPP (by wt. of cement) along with 0.8% super plasticizer (by wt. of total binder) significantly improved than that of control concrete.

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