Experimental Study On Mechanical Properties Of Basalt Fiber Reinforced Concrete

With the development of science and technology,the civil engineering industry is becoming much more modernized,and the application of green high-performance concrete becomes more acceptable to people,and with the emergence of high-rise large-span structures,the demands for light-weight,high-strength and high-toughness concrete extensively elevate.On the evolving basis of composite material theory,the compounding effect of materials has become an effective way to overcome the intrinsic flaws of materials.The properties of basalt fiber,BF,which is a new type of green high-performance inorganic fiber material,high tensile strength,excellent cracking performance,great integration performance with concrete,high cost-effectiveness,for example,make it a hot research topic in fiber-reinforced concrete（FRC）field.By conducting indoor experiments and tests,the influence of BF’s length and content on concrete’s service performance,and on four mechanical parameters of concrete,which are compressive strength,axial tensile strength,splitting tensile strength and rupture strength,respectively,were analyzed and studied,with an aim to select the optimum portion of BF which can result in the highest performance of this kind of FRC.Besides,the effect of BF on FRC’s toughness was also discusses through analyzing the compressive load-displacement curve and bending load-displacement curve.The results obtained indicated that:1.The dispersion of basalt fiber in concrete is affected by length and volume,the larger the amount of fiber,the longer the fiber length is,the worse the dispersion.2.The addition of basalt fiber has a certain effect on the performance of concrete,especially when the volume of fiber exceeds 0.15%,the fluidity of concrete is significantly reduced,taking the dosage of 0.2%as an example,slump of 12mm,18mm and 24mm test groups decreased by 59%,61.5%and 79.5%respectively,concrete slump but basically no longer expand,but the fluidity of concrete can be improved by increasing the amount of water reducer.3.According to the test results of cube compressive strength and splitting tensile strength,the change rate of 7d strength in most of the test groups is higher than that of 28d,so the effect of basalt fiber on the early strength of concrete is higher than that of the later strength.4.Basalt fiber has no obvious effect on compressive strength of concrete,taking the cube compressive strength as an example,when the amount of admixture is best（all is 0.1%）,the improvement rates of 28d cube compression strength of 12mm,18mm and 24mm test groups are 2.24%,6.5%and 2.87%respectively.but basalt fiber can significantly improve the tensile properties of concrete,under the optimal dosage condition（12mm and 24mm are 0.2%,18mm is 0.1%）,The flexural strength of 28d,12mm,18mm and 24mm test groups are 15.4%,18.66%and 12.86%respectively.5.In the range of test admixture（0.05%⁰.3%）,the mechanical strength of basalt fiber reinforced concrete,tensile pressure ratio,toughness value,flexural peak deflection and toughness value basically increase and then decrease with the increase of fiber content.but the peak displacement of pressure increased with the increase of fiber content.In general,the amount of basalt fiber is the main factor affecting the mechanical properties of concrete,the fiber length has little effect on the compressive properties of concrete,but the increase of fiber length can improve the tensile properties.6.The addition of basalt fiber can improve the load deformation performance and toughness of concrete under compression and bending.When the concrete is pressed,the peak displacement increases with the increase of the dosage,the maximum peak displacement of12mm,18mm and 24mm increases by 20.1%,17.5%and 33.5%respectively,the toughness I₀increased by 1.8 times on average,and the toughness I₁ increased by 1.5 times;When the concrete is bent,the maximum peak deflection of 12mm,18mm and 24mm increased by21.9%,51.3%and 44.4%respectively,when the fiber admixture between 0.1%⁰.15%,the gain ratio of flexural toughness GF_1.0 is about 1.5,and the other is roughly between 1.0¹.3.