Experimental studies on behavior of hybrid materials concrete using non-destructive testing (NDT) methods

Abstract

This paper presents the experimental studies conducted on hybrid materials concrete using non-destructive testing (NDT) methods. M−35 grade hybrid concrete was designed by incorporating Fly ash and Alccofine in the ratios of 5 %, 10 % and 15 % as a partial replacements to cement. Further, light weight aggregates were used to partially replace the natural coarse aggregates in the ratios of 5 %, 10 % and 15 %. A cumulative of 13 concrete mixes were prepared to investigate the behavior of hybrid materials concrete under different NDT methods. Ultra-sonic Pulse velocity (UPV) testing was conducted on 150 mm concrete cube specimens in three different conditions, namely direct UPV, semi-direct UPV and indirect UPV. Rebound hammer (RH) test was also performed to study the strength of concrete. The results of concrete under NDT testing were then validated by comparing them with compressive strength values. The experimental results showed that, the increase in fly ash content moderately improved the compressive strength of concrete and the addition of light weight aggregates decreased the compressive strength of concrete. The alccofine addition to concrete has yielded higher compressive strength and better NDT values of concrete. A maximum compressive strength of 45.54 MPa was obtained with 15 % alccofine replacement. The hybrid concrete containing 5 % light weight aggregates, 15 % alccofine and 10 % fly ash yielded a compressive strength of 42.68 MPa, which is 17 % higher than the reference mix. The values obtained from NDT methods were in good agreement with the compressive strength values. The results were also used to develop statistical models and the numerical equations were established for compressive strength in terms of percentage replacement of constituent materials.