Issue 22

A. Namdar, Frattura ed Integrità Strutturale, 22 (2012) 26-30; DOI: 10.3221/IGF-ESIS.22.04 29 Figure 4 : XRD pattern of cement, and cement-kaolin-bentonite mixture, the kaolin-bentonite was submitted to 800 ºC heat for 1 hour. Figure 5 : Concrete compressive strength. C ONCLUSION  The FESEM image indicated changing crystal structure of cement past is responsible for enhancing concrete compressive strength.  The proportion of additive before subjected to heat has different effect on concrete compressive strength compare to when additive is modified under high level of heat.  The quantity of 12% additive produced by 800 ºC heat has shown best result in improving concrete compressive strength.  The amount of 6% additive not subjected to the heat has shown acceptable result in improving concrete compressive strength.  Increasing bentonite-kaolin mixture which was treated by heat in concrete mixed design resulted in better enhancement compressive strength.