Study On Basic Properties Of Spraying PVA Fiber Cementitious Composites

PVA-ECC (Engineered cementitious composites, hereafter referred to as ECC) is an ultra-high toughness cement-based composites using PVA (Polyvinyl alcohol) as its reinforcing fibers, which has gained a relatively rapid development in recent years. Because of its much superior properties, such as multiple cracking property and strain-hardening behavior that the traditional cement-based materials do not have, it has gradually caused widespread concern at home and abroad. Currently, study and application of PVA-ECC is mainly focused on common casting performance, and there is less study on spraying construction performance. Based on the existing research results on common PVA-ECC, this paper carried out initial exploration and study on PVA-ECC with spraying performance. Major contents and research results are listed as follows:(1) Through test of working performance of admixture, rules of influence on working performance caused by different types and amount of admixture have been studied. The results show that:50%fly ash or50%coal ash mixing with kaolin and silica fume, under the condition of adding superplasticizer, PVA-UHTCC that can satisfy simple spraying construction demand can be made up, and several sets of mix proportions can be get out.(2) Through tests on compressive strength and thin plate bending, rules of influence on basic mechanical properties caused by different types and amount of admixture have been studied. The results show that:the increase of admixture will cause unfavorable effect on the compressive strength, but can remarkably improve the bending resistance. Best results can be got on the condition of three kinds of admixture are combined with50%fly ash.(3) Through tests on rapid carbonization and electric flux, rules of influence on durability such as anti-carbonization and chloride penetration resistance caused by different types and amount of admixture have been studied. The results show that:the property of anti-carbonization will be reduced if the amount of fly ash is more than30%, while the chloride penetration resistance will be significantly improved. Anti-carbonization will be improved if silica fume is added in50%fly ash, while anti-carbonization will not be improved obviously when metakaolin is mixed. Both the metakaolin and the silica fume has remarkable effect on resisting penetration chloride, with the former is better than that of the later. The effect can be reinforced after50%fly ash is added, especially for improving the resistance of chloride penetration on early stage.(4) Based on the above-mentioned rules, suggestions on PVA-UHTCC mix proportion that can be referred in spraying construction of a project are made.