Experimental Study On Mechanical Properties And Resistance Chloride Penetration Of PVA Fiber Concrete

PVA fiber has a series of advantages such as high strength,high elastic modulus,good hydrophilicity?increased adhesion?,acid and alkali resistance,using safely,etc.Adding PVA fiber to concrete can improve properties such as crack resistance,toughness and durability of concrete materials.At the same time,it has good engineering application prospects.At present,at home and abroad,there are some research results on the influence of the type and specification of fiber on the performance of concrete.However,there are few studies on the characteristics of PVA fiber against cracking and strengthening mechanism of concrete.In this paper,mechanical properties and chloride ion penetration resistance test with PVA fiber reinforced concrete.Combining SEM and NMR techniques to analyze the mechanism of concrete performance improvement and to provide a reliable basis for practical application.PVA Fiber with three kinds of lengths 8 mm,12 mm,18 mm,three kinds of fiber content 0.6 kg/m³,1.2 kg/m³ and 1.8 kg/m³ in concrete was added to prepare a fiber reinforced concrete.Analysing the influence of the fiber content and length on the compressive strength,flexural strength and early crack resistance,and obtain the best fiber content and the optimal length.Study on the resistance to chlorine permeation of 12 mm long PVA fiber concrete under three kinds of dosages.Analysis of microstructure by scanning electron microscopy and nuclear magnetic resonance.The research results are as follows:The addition of PVA fiber to concrete has little effect on compressive strength.When8 mm and 18 mm PVA fibers are added,the compressive strength of concrete decreases.When 12 mmPVA fiber is added,the compressive strength of concrete is increased.When the dosage is 1.8 kg/m³,the increase is 11.9%.The longer the fiber has the greater influence on the flexural strength of concrete,the average increase of the flexural strength of concrete after adding 18 mm PVA fiber is 19.3%²7.9%;the addition of PVA fiber can significantly improve the early crack resistance of concrete.With the increase of fiber content,the total cracking area and maximum crack of concrete are significantly smaller than ordinary concrete.The incorporation of appropriate amount of fiber can improve the microstructure of the concrete,so that the fibers are tightly bonded in the cement matrix,the internal pores of the concrete are reduced,and the integrity and compactness of the fiber concrete are enhanced.When adding 1.8 kg/m³ of 12 mm long PVA fiber,The free chlorine ion content in the concrete is the lowest,chloride ion distribution uniformity and there is no enrichment phenonmenon.When the length is 8 mm,12 mm and the dosage is 1.8 kg/m³,the T₂ spectrum area of the concrete is the smallest and the relaxation time is the least,which is most beneficial to reduce the internal pores of the concrete.