Study On Properties Of Carbon Fiber Reinforced Alkali Activated Slag Composite

Compared with traditional cement,alkali activated cementitious materials produce less carbon emissions in the production process,with excellent mechanical properties and durability,it is a promising green cementitious material.However,its short setting time,large drying shrinkage and other defects still restrict its further development and application.Carbon fiber is a kind of high-performance material with high tensile strength,corrosion resistance and chemical stability.Its reasonable introduction can effectively improve the performance of alkali activated cementitious material.In this paper,the preparation of carbon fiber reinforced alkali activated slag composite(CFAASC)as the object,focusing on the improvement of carbon fiber dispersion in alkali activated slag cementitious material matrix.By means of resistivity,fluidity,flexural strength,SEM image and CT scan,the effects of changing feeding sequence,nano silica(NS)fiber modification,polycarboxyate superplaticizer(PCS)matrix modification on the dispersion of carbon fiber were studied,and the improvement method of NS was optimized by using ultrasonic technology,furthermore,the effects of carbon fiber length and content on the fluidity,setting time,drying shrinkage and mechanical properties of CFAASC were analyzed,so as to optimize the properties and preparation methods of CFAASC.The results show that:(1)When the content of alkali is 5%of the slag mass and the ratio of water to AASC is 0.4,the mechanical properties and fluidity of the material are better.The effect of activating slag by alkali solution is better than that by alkali solid particles.The adverse effect of activating slag by alkali solid particles can be eliminated by prolonging the stirring time.(2)The method of mixing carbon fiber with slag after dispersing carbon fiber in water is better than that of dispersing carbon fiber directly in slag slurry.(3)Nano silica and PCs can promote the dispersion of carbon fiber.Ns particle size is very small,which has strong adsorption effect and microparticle effect.It can effectively modify the surface of slag slurry and carbon fiber,so as to promote the dispersion of carbon fiber.PCS,as a surfactant,can not only promote the dispersion of NS,but also improve the fluidity of slag slurry and the dispersion environment of carbon fiber matrix.(4)The effect of low power ultrasonic treatment on the dispersion of carbon fiber is mainly reflected in the promotion of NS dispersion,which is conducive to the adhesion of NS on the surface of carbon fiber to improve its dispersion.30 min NS ultrasonic treatment can effectively improve the dispersion effect of carbon fiber.(5)The fluidity of alkali activated carbon fiber composite decreases with the increase of the length and content of carbon fiber.Low length and high content of carbon fiber are beneficial to reduce the drying shrinkage of CFAASC.The mechanical properties of CFAASC increase first and then decrease with the increase of the length and content of carbon fiber.When the length of carbon fiber is 6 mm and the content of carbon fiber is 1.1%of the quality of AASC,the material performance is the best.(6)According to the physical and mechanical properties of CFAASC,when the best length and content of carbon fiber is selected,the content of NS and PCs is 0.5%of the mass of AASC,and when the mass ratio of water and AASC is 0.38,the material performance is the best.