The Application Research Of Metakaolin In Self-compacting Concrete

This paper mainly studies the effect of low grademetakaolinproduced by calcined kaolin tailings in Guangdong on the properties of self-compacting concrete, which provides experimental evidences for the metakaolin as admixture in the applications and development of self-compacting concrete, so as to adapt to the general requirements of modern architectural technology and human sustainable development direction.This paper systematically studies the effects of the single metakaolin admixture or relatively common fly ash, complex system made up of slag on function of self-compacting concrete working performance, mechanical property and durability.Experimental results show that there are three aspects where the incorporation of metakaolin influences the properties of self-compacting concrete.Firstly, it is the working performance. Polycarboxylate water-reducer is designated after various compatibilitytest comparison of water-reducers and cement. It tests the fluidity of net paste and mortar under the effects of single metakaolin or mixed with fly ash or slag in the presence of Polycarboxylate water-reducer which shows the metakaolin admixture has better performance than single metakaolin. It provides effective test basis to continue the study.What's more, different from normal concrete, self-compacting concrete has better fluidity,passing quality through gaps and filling characteristic in working performance. Therefore it compares the results of the different single metakaolin content with a certain quantity of metakaolin mixed with different content of fly ash or slag on slump extension degrees of self-compacting concrete, T50, The collapse of los degree, U box experiment fill height and air content. And it shows that metakaolin mixed withfly ashhas best performance,metakaolin mixed with slag takes second place, and single metakaolinis the worst.Experimental results show that metakaolin has an adverse effect on self-compacting concrete working performance,fly ash and slag can improve the function of concrete, and fly ashhas better effect than slag.Secondly, it is the mechanical property. The compressive strength and flexural strength are the leading indicators to evaluate the mechanical property of concrete in this paper. Based on the working performance tests above, it conducts compressive and bending tests on the concrete blocks after 7d and 28 d maintenance, which shows compressive and flexural strength of block increase at first and then decreased along with the increase of the mixing amount both in singlemetakaolin and metakaolincompound system. In general, single metakaolin has best performance,metakaolin mixed with slag follows, and metakaolin mixed with fly ash is the poorest.The main reason is that metakaolin has a strong pozzolanic effect;slag has micro-aggregate effect, and it can also stimulate its hydration activity in alkaline solution; although fly ash has some pozzolanic effect, it mainlyimproves its mechanical properties by improving working performance indirectly.The above conclusion, therefore,provides powerful basisfor the third mixture of metakaolin, fly ash and slag mixed experimental study. And it also indicates the applications of self-compacting concrete is the most suitable in third mixture, no matter from the perspective of the working performance, the mechanical properties, or the environmental and economic factors.Thirdly, it is the durability. It tests concreteconfiguration consisted of 12% metakaolin,fly ash and slag on its consolidation of water soluble chloride ion, chloride ion diffusion and sulfate ion erosion.Experimental results show that the performance of the metakaolin in the concrete is better than the fly ash and slag. After microscopic analysis, it is found that its main reason is that internal density of single metakaolin block is the greatest.