Study On Modified Basalt Fibers And It's Cementitious Composities Performance Valuation

Cracking and durability of traditional cement-based composite materials have always been the top priority in the field of building materials.With the progress of materials science,fiber-reinforced cement-based composite materials have developed rapidly in recent years.As a new environmental-friendly inorganic material,basalt fiber has sufficient resource reserves and simple production process.The material itself has excellent physical and chemical properties.Adding it to cement-based materials can improve the tensile and flexural strength of materials,so do the problem of cracking and durability.However,as a kind of reinforcing-material,it is criticized that the reinforcing effect is restricted due to its smooth surface.So,in order to improve the surface state,the surface modification of basalt fiber gradually becomes the focus of research.In this paper,the surface of basalt fiber was modified by different sorts of silane coupling agents.On the basis of the analyzing the corrosion resistance of the modified fiber,the effect of reinforcing cement matrix composite was studied,and the related results were analyzed.Test by using CG550(gamma-ammonia propyl triethoxy silane)CG570(gamma-(methyl)acryloyl oxygen propyl silane)three oxygen radicals and Z6518(vinyl triethoxy silane)three kinds of silane coupling agent with the concentration of 0.4% 0.8% and 1.2%respectively to modify the surface of basalt fiber,and the mechanic properties and durability of modified basalt fiber is studied,to explore the performance of the modified basalt fiber itself.The experimental results show that the surface defects of basalt fiber can be made up after surface treatment.After the modification of CG550 and CG570,the mechanical properties of basalt fiber were obviously improved,and the best comprehensive effect was achieved with the concentration of 1.2%CG550 and 0.8%CG570.The tensile strength of basalt fiber increased by 6.2% with the concentration of1.2% CG550.CG570 with a concentration of 0.8% increased the tensile strength of basalt fibers by 5.8%.Basalt fiber can be corroded in acid or alkaline medium,and with the increasing of the concentration of corrosive medium,the mass loss ratio and strength loss of the fiber gradually increase.Under the same HCl concentration,the acid resistance of fiber treated with CG550 and CG570 were obviously improved.When the concentration of HCl is 2mol/L,the mass loss ratio of BF with concentration of 1.2% CG570 decreased by55.6% and the strength maintenance increased by 13.6%,comparing with original fibers.Under the same NaOH concentration,the alkali resistance of fiber treated with CG550,CG570 and Z6518 were also improved.When the concentration of NaOH is2mol/L,the mass loss ratio of BF with concentration of 1.2% CG570 decreased by 50% and the strength maintenance increased by 13.1%,comparing with original fibers.The silane coupling agent acts on the surface of basalt fiber and improves the mechanical properties of the fiber by repairing the defects on the surface of BF.At the same time,the surface of the fiber is denser.So the probability of contact between the corrosive medium and the fiber itself is reduced,and its durability is improved.The mix ratio of basalt fiber cement matrix composite was determined by orthogonal test,and the modified fiber was used to make the cement matrix composite at this ratio.The modified effect of basalt fiber was characterized by the test of mechanical properties,and the relevant action mechanism was analyzed.The experimental results show that according to the influence of the three factors in the order of significance from high to low:W/B,S/B,F/C.After the modification of basalt fiber,the surface attachment makes the fiber become rough,and the surface moisture increases so that the interface between the fiber and the cement mortar is improved.The flexural strength and compressive strength of the basalt fiber reinforced cement matrix composites modified by CG550 and CG570 were improved effectively.Although the overall strengthening effect of the fiber modified with Z6518 on the mortar is not obvious,its early strength increases rapidly.After the basalt fiber was modified with a concentration of 1.2%CG570,the flexural strength on day 28 of mBFRC was 14.8Mpa,which was 20.3% higher than that of the original-fiber group and24.3% higher than that of the pre-treatment group.The compressive strength on day 28 was 62.1MPa,which was 10.7% higher than that of the original-fiber group and 7.3%higher than that of the pre-treatment group.Using basalt fiber modified by silane coupling agent to reinforce cement matrix composites,the main mechanism is to improve the surface wetting property of the fibers,so that the fibers can be better wrapped by cement matrix materials,improving the interface strength.In this way,the mechanical properties of the fiber composites is enhanced.