Experimental Study On Mechanical Properties Of Basalt Fiber Reinforced Recycled Aggregate Concrete After High Temperatures

Recycled aggregate concrete is a kind of new concrete material which is reformulated using aggregates that is obtained by crushing,screening and washing the waste concrete to replace natural aggregates.It realizes the sustainable utilization of building material resources,which has important significance to promoting ecological harmony.In order to meet the increasing needs of the population housing,high-rise,high-rise and large span buildings rise in response to the proper time and conditions.Fire is a serious threat to the safety of the buildings.Once the building fire caused the collapse of the structure,it will bring great losses to people's lives and property.Improving the fire resistance of the structure has become our focus.If basalt fiber is added into recycled aggregate concrete,the mechanical properties of recycled aggregate concrete after high temperatures will be improved by using basalt fiber properties such as high temperatures resistance,high strength and good chemical stability.Therefore,it is necessary to study the mechanical properties of basalt fiber recycled aggregate concrete after high temperatures.Firstly,the paper studys on the influence of the basalt fiber with different dosages and different mixing methods on basic mechanical properties and the relationship between mechanical properties of basalt fiber recycled concrete after high temperatures(200?,400?,600?)under the condition of the C40 recycled concrete with certain mix proportion.Mixing methods are cement paste wrapped fiber and fiber direct mixing method.Basalt fiber volume rates are 0.1%,0.15%,0.2%.Four basic mechanical properties are mass loss rate,compressive strength,splitting tensile strength,axial compressive strength and static elastic modulus.Furthermore,the paper studys on the effects of the basalt fiber volume rate on the compressive strength,splitting tensile strength and tensile compression ratio of recycled basalt fiber concrete after 25 freeze-thaw and high temperatures.Finally,the formulas of fitting curves about mechanical properties are given.The test results show that the basalt fiber can reduce the mass loss rate of recycled aggregate concrete.Compressive strength reaches maximum value at 200? after high temperatures.With the increase of temperatures,the static elastic modulus and tensile strength decrease.The compressive strength and the splitting tensile strength are improved by basalt fiber,which are higher than axial compressive strength and elastic modulus.When the dosage is 0.15%,the performance is the most obvious.The cement slurry wrapped fiber is better than direct mixing method.The damages are caused by the 25 slow freeze-thaw and high temperature superposition,which are greater than the sum of damage caused by the single action.