Study On Properties Of Polyacrylonitrile Fiber Concrete

With the development of fiber concrete technology,more and more synthetic fibers are being applied to concrete.Polyacrylonitrile,a kind of synthetic fiber,has the properties of a high modulus of elasticity,breaking strength and good hydrophilicity which allows the polyacrylonitrile fibers to be well dispersed in the concrete and has good adhesion to the concrete matrix.There are still relatively few studies on the performance of polyacrylonitrile fiber concrete.Therefore,it is of great significance to study polyacrylonitrile fiber concrete and promote its application in engineering.This paper first studies the basic mechanical properties of different water-binder ratio polyacrylonitrile fiber concrete.Secondly,the durability of freeze resistance,impermeability and resistance to sulfate dry and wet cycles was studied.Then,the mechanical properties and deformation properties of various concretes under thermal-force coupling are studied and monitored by acoustic emission system for real-time.And from the perspective of energy absorption and release,the whole process of stress destruction of various types of concrete is explained.Finally,the mechanical properties of polyacrylonitrile fiber concrete were studied after high temperature.It can be seen from the research of the basic mechanical properties of polyacrylonitrile fiber concrete,the effect of fiber addition on the compressive strength of concrete is not particularly obvious.It can significantly improve its flexural strength and splitting tensile strength.The mechanical properties of concrete 7d should be increased by more than 28d.Therefore,the addition of fibers is more conducive to improving the early mechanical properties of concrete;In addition,the addition of polyacrylonitrile fiber to concrete is beneficial to increase the tension-compression ratio and Poisson's ratio of concrete,reduce the brittleness of concrete and increase the toughness of concrete.The tensile strain energy and the compressive strain energy are more evenly distributed in the concrete and the mechanical properties of the concrete are improved by adding polyacrylonitrile fiber to the concrete.From the research of the durability of polyacrylonitrile fiber concrete,it can be seen that the addition of fiber can reduce the water penetration height of concrete,improve the impermeability of concrete,inhibit the reduction of dynamic elastic modulus during concrete freeze-thaw cycle and improve the frost resistance of concrete.It can also improve the corrosion resistance of concrete and the growth rate of compressive strength and the performance of concrete's anti-sulfate dry-wet cycle.From the high temperature test of the concrete,it can be found that polyacrylonitrile fiber,steel fiber and polyacrylonitrile&steel fiber are added to the concrete,which is beneficial to reduce the damage of concrete under thermal-force coupling,maintains the integrity of concrete better and improves the mechanical properties and deformation properties of concrete;At the same time,the energy counting rate of acoustic emission has a certain correspondence with the magnitude of stress,and it has a positive correlation,which better reflects the damage of concrete under different stress fields.Throughout the loading,the energy count rate of various types of fiber concrete is wider and denser than that of the reference concrete.The variation of strain energy and energy cumulative count of concrete has consistent.From the high-temperature test of polyacrylonitrile fiber concrete,it can be found that if the fiber is added to the concrete,it is beneficial to improve the compressive strength and tensile strength of the concrete and the relative dynamic elastic modulus of concrete after high temperature,especially for the low water-binder ratio concrete.The high-temperature compressive strength and tensile strength of polyacrylonitrile fiber concrete and reference concrete show a trend of decreasing first and then rising with the extension of the rest time.