Use of Wollastonite as a Microfiber Reinforcement in Cement Composite systems

Use of Wollastonite as a Microfiber Reinforcement in Cement Composite systems Use of Wollastonite as a Microfiber Reinforcement in Cement Composite systems The manufacture of portland cement is a highly energy intensive process requiring about 4 GJ of energy per ton of the finished product. Current worldwide cement production is of the order of 3.6 billion tonnes (2011 figures), with China producing as much 57% of that share [1]. Use of supplementary cementitious materials in concrete is therefore an area of interest to construction community for several economic and environmental reasons [2]. Readily available industrial products such as wollastonite may require little additional processing, and have inherent characteristics that makes them suitable for use in cementitious materials. From an economical point of view, use of wollastinote in the ready-mix concrete industry is attractive since of all the constituent materials, cement is the most expensive component. From an environmental perspective, production of cement results in generation of significant amount of green-house gases such as CO2, hence cement replacement by wollostonite would ultimately reduce the green- house gas contribution. An increase in the use of wollastonite in concrete represents an inexhaustible demand since the worldwide usage of concrete is currently more than 20 billion tons per year [3]. The aim of this proposal is to characterize the performance of wollostonite compositions and investigate the effects of using it in the development of new construction products. A study is proposed to address early age and long term properties of cementitious composites reinforced with wollastonite micro-fibers. The proposal addresses the effect of wollasonite on early age properties and strengthening of fresh paste against plastic shrinkage cracking potential. In the area of long term performance, the synergistic nature of using a hybrid cement composite using wollastonite micro-fibers and other fibers such as polypropylene (PP) or steel will be addressed. Significant strength increase has been observed by addition of short wollastonite micro-fibers by other researchers. The results of these studies will be evaluated in order to back-calculate the contribution of wollastonite to the overall load carrying capacity of the composites. Due to the ability to bridge the larger microcracks, the wollastonite's contribution is expected to be limited to increasing the first crack strength and thus allow other fibers to become effective during a later stage of load carrying response. Since the post-peak toughening effects are limited, fracture toughness may be increased by addition of PP, or steel fibers. While the pullout of PP fibers from matrix is the main reinforcing mechanism and results in significant energy dissipation, it is expected that the effect of wollastonite would be in a synergistic nature of increasing the transition level of cracking. Based on the above hypothesis, hybrid composites made with wollastonite and steel or PP fibers are expected to have superior properties as compared to either reinforcement alone.