Properties of basalt fiber self-compacted concrete at elevated temperature

Inorganic based basalt fibers used in concrete production prevent the development of cracks and increase the service life of concrete structures. Similar to other industrial concrete fibers, basalt fibers can be utilized in self-compacted high strength concrete (SCHSC) with low permeability and proper workability. Because of this feature, basalt fiber concrete can be used in various infrastructure projects such as buildings, highways and bridges. Studies on the mechanical properties of this concrete are non-extensive; therefore, further investigations are considered essential in the direction of the efficiency of self-compacted basalt fiber concrete (SCBFC) in retrofitting deteriorated normal strength concrete. In this study, effect of basalt fiber on the workability of fresh SCHSC has been measured in terms of slump flow, J-ring flow, V-funnel flow and L-box height ratio. In addition, the properties of hardened concrete such as compressive strength, splitting strength, modulus of elasticity, flexural strength and Poisson ratio were investigated for different temperatures between 25oC – 500oC. It was concluded that the fibers decreased the unit weight and compressive strength of the concrete and improved the tensile strength due to the arresting of micro cracks with increasing fiber ratio. The strength of SCHSC which has been exposed to high temperature was observed decrease. Permeability tests have been conducted as well and revealed that 0.25% volume fraction of basalt fibers is optimum value to get reasonable penetration of liquid within this concrete material. In preparation of hybrid prism samples, it was prepared low strength concrete base to represent old and new repaired concrete and the surface of the new repaired concrete was coated with SCHSC. At the interfaces between these two parts, different roughening manners such as drilling (holes), grooving and sand blasting were applied. Slant shear test was performed to investigate adherence strength of samples. Surface improvement by grooving and sand blasting was found better than the other cases with taking into account the applied high temperatures. The effect of independent variables such as basalt fiber volume ratio and environmental temperature on the mechanical properties of concrete were evaluated statistically. According to the analysis outcomes, the roughening type of the interfacial surface was found more important than fiber ratio and temperature changes on slant shear of hybrid concrete. Finally, modelling has been performed with depending on gene expression programming for present experimental results and it is demonstrated that the predicted and experimental values from the models obtained are in suitable distribution on the agreement line with correlation coefficient more than 90%.