Experimental Study On Corrosion Resistance Of Basalt Fiber Concrete In Saline Soil Environment Of Southern Xinjiang

South Xinjiang is located in the south of Tianshan Mountains,the climate is dry,the precipitation is rare,the unique geological environment and climatic conditions,so that the distribution of a large area of saline soil,and the salt in the soil is mainly sulfate and chlorine salt.As a new type of green and energy saving reinforcement material,basalt fiber can improve the mechanics and durability of concrete in different degrees when it is mixed into concrete.In this paper,early age（3d,7d,28d）cube compressive strength test,corrosion test in natural environment and indoor corrosion degradation test（salt erosion-dry-wet cycle and long-term immersion）of basalt fiber concrete with different dosage were carried out.The main research conclusions are as follows:（1）The influence of basalt fiber with the same length（18mm）and different volume content（0%,0.1%,0.2%,0.3%）on the compressive strength of early age concrete cube was explored.The experimental results show that the addition of basalt fiber can improve the early compressive strength of concrete to a certain extent,but it is not the case that the more the fiber content,the better.When the fiber content is 0.1%,the early cube has the best effect of improving the compressive strength.Compared with the ordinary concrete,the compressive strength of the cube at 3d,7d and 28d is increased by 16.04%,20.62%and 11.49%,respectively.（2）Experimental study on corrosion performance of basalt fiber concrete with different volume content（0%,0.1%,0.2%,0.3%）in natural environment conditions was carried out.The experimental results show that the relative quality evaluation parameterω₁of basalt fiber concrete specimens with different mixing amounts increases slightly in the first 180d exposure test,but does not fluctuate greatly in 180d～360d.The evaluation parameterω₂of the relative dynamic elastic modulus at both ends of the specimen has no obvious fluctuation,but shows a small increase from 0d to 270d,and the growth rate accelerates after270d.When the content of basalt fiber concrete is 0.3%,the evaluation parameters of relative mass and relative dynamic modulus of basalt fiber concrete are maintained at about 1.0 as a whole compared with the variation fluctuation of other contents.Therefore,the salt erosion resistance of concrete is better than other contents when the content of basalt fiber is 0.3%.（3）Experimental study on corrosion resistance of basalt fiber concrete with different volume content（0%,0.1%,0.2%,0.3%）indoor composite salt solution（salt erosion-dry-wet cycle,long-term immersion）was carried out.The experimental results show that the variation of the relative quality evaluation parameterω₁of the concrete mixed with fiber is less than that of the concrete without fiber under the condition of salt erosion and dry-wet cycle test.With the increase of the number of salt etch-dry-wet cycles,the relative dynamic elastic modulus at both ends of the specimen fluctuated greatly,and its change rule was that the growth rate was fast in the early stage and slow in the late stage.Under the condition of long-term immersion test,the relative quality evaluation parameterω₁of samples from 0d to 120d showed an overall upward trend.The relative dynamic elastic modulus at both ends is consistent with the change rule of salt erosion and dry-wet cycle,but the speed is slower than that of the former.Therefore,under the two indoor test systems,the corrosion resistance of concrete specimens with basalt fiber content of 0.3%is better than other contents.（4）SEM,XRD,EDS and other microscopic and mineral testing techniques were used to analyze the microstructure characteristics and chemical composition of the corrosion products of concrete specimens in the process of laboratory and external tests.The experimental results show that the corrosion degradation products of basalt fiber concrete in the saline soil environment of southern Xinjiang are acicular ettringite（AFt）and short columnar gypsum.Among them,the corrosion and peeling products under the action of salt-erosion-dry-wet cycle are more than those under the long-term immersion test condition,indicating that the damage is relatively serious.Moreover,the change of microstructure characteristics of basalt fiber reinforced concrete specimen is consistent with the law of macroscopic property deterioration.