Performance Evaluation of Fibers Modified Concrete Using Acoustic Emission Technique

Abstract

The aim of this study is to use acoustic emission (AE) technique for assessing performance of fibers modified concrete specimens subjected to two-point loading. Four different types of M20 grade concrete were produced. The batches were plain concrete (PC), steel fiber reinforced concrete (SFRC 1%), polypropylene fiber reinforced concrete (PFRC 1%) and hybrid fiber reinforced concrete (HFRC) containing a mixture of 0.85% steel fibers and 0.15% polypropylene fibers. Hooked end steel fibers with aspect ratio as 66.67 and polypropylene fibers of 12 mm thickness were used at a volume fraction of 1% each. Hybrid fiber reinforced concrete (HFRC) was produced using mixture of steel and polypropylene fiber at volume fractions of 0.85% and 0.15% each, keeping the total volume fraction at 1%. Different types of concrete prepared was used to cast cubes 150 mm x 150 mm x 150 mm for compressive strength, cylinders 150 mm x 300 mm for split tensile strength and beams 150 mm x 150 mm x 700 mm for flexural strength of concrete. After 28 days of curing the respective tests for mechanical properties of concrete were performed. The study investigates the addition of steel and polypropylene fibers on mechanical properties of concrete. Results indicate that steel fiber addition had a significant effect on mechanical properties of concrete while polypropylene fibers had a slight impact in increasing the compressive strength, tensile strength and flexural strength of concrete. Results for mechanical properties of HFRC were on a higher side as compared to plain concrete but on a lower side when compared to SFRC owing to the low elastic modulus and strength of polypropylene fibers. The beams were tested in two-point loading for flexure along with acoustic emission technique for investigating the propagation of cracking and damage. The AE setup consisted of 8 sensors which were surface mounted on the beam, a pre-amplifier, a data acquisition system and an analysis system. AE technique results aimed at damage assessment and crack monitoring in beam specimens under bending. It was done by studying the AE parameters resulting from the analysis system. The study included locating the damage source, comparing Ib value and AE hits with load history. This study was able to define the progression of cracks in concrete from micro to macro- cracks. The AE parameters were able to act as warning before actual failure of concrete occurred. The results indicate that acoustic emission technique has the capability to predict the failure and cracking phenomenon in concrete.