Materials Engineer, Roorkee
The time lag (usually 3 to 28 days) between concrete placement and the evaluation of cube strength is a primary deficiency of the current quality control method used in concrete construction. The development of accelerated curing techniques have reduced the lag time to 24 to 48 hours. But even the 24 hours time is sufficient to allow the concrete to set and harden in the form prior to the testing of the accelerated cubes. This paper describes the method for determination of water-cement ratio of the mix discharged from the mixer and conjunction with air-content tests can predict 28-days strength of concrete in 15 minutes, so that any mix found sub-standard should not be allowed for placement.