Early Setting and Hardening of Concrete Containing Flyash Using Non-destructive Techniques

Strength monitoring is a crucial aspect in determining the durability and serviceability of concrete based structures. Strength monitoring can be done using two main approaches which are broadly termed as destructive testing and non-destructive testing. This study focusses on the applicability of non-destructive techniques (NDT) for concrete testing such as acoustic emission technique (AET) and ultrasonic guided wave (UGW) method in order to monitor early age setting properties of concrete which is modified by flyash addition. Experimental investigation was carried out on concrete mixes containing varying amounts of flyash which went up from 0% till 30%. Early setting and hardening of 150 mm*150 mm concrete cube specimens embedded with mild steel rods were monitored using AET and UGW techniques. The aim of the current study was to monitor all the aspects of the setting as well as hardening process of concrete containing flyash using NDT techniques. The results so obtained were then compared to destructive testing results. It was found that AE and UGW were successful in identifying the various stages of concrete setting and hardening. Due to slower reaction of flyash, it was reported that the fluid zone extended over a larger period of about 26–40 h as against that for the control concrete which was found to be 24 h. Further Scanning Electron Microscopy was used to validate the results obtained by NDT testing as well as by compressive strength testing.