Issue 22

A. Namdar, Frattura ed Integrità Strutturale, 22 (2012) 26-30; DOI: 10.3221/IGF-ESIS.22.04 27 M ETHODOLOGY he natural minerals have ability in producing new material or modifying characteristics of materials. In this research work the kaolin and bentonite have been selected for improve concrete compressive strength. The kaolin and bentonite have been mixed in equal weight and subjected to the heat for 1 hour for 600 ºC, 800 ºC and 1000 ºC. The main propose for mixing kaolin and bentonite before submitting to heat is to analysis minerals of kaolin and bentonite interaction in high temperatures. The unheated and new produced materials have been mixed with concrete for 6% and 12% of cement weight (Tab. 1). The compressive strength of concrete for 7 days and 14 days has been tested. To study macro properties of additive-cement mixture X-ray experiment and FESEM have been used. R ESULT AND DISCUSSION n Figs. 1-3 the image of FESEM shows Nano particles of cement past without additive and, when 6% and 12% additive have been used in concrete mixed design. In Fig. 1 the Nano particle have almost plane shape and in Fig. 2 the shape is convert to the lengthy shape and in Fig. 3 this process is increased, and subsequently resulted in improving concrete compressive strength. The additive creates new crystal structure in cement past. The result is indicated that 6% proportion of unheated kaolin-bentonite is improving concrete compressive. And if kaolin-bentonite mixture treated by heat under 800 ºC and in quantity of 12 % of cement weight has been used in concrete mixed design the concrete compressive strength of 7 days is resulted in improving concrete compressive strength in maximum level. It is due to develop new crystal morphology under high temperature condition in bentonite-kaolin-cement mixture and also considerably enhancement bonding of cement. If quantity of bentonite-kaolin mixture treated by heat increased in concrete mixed design resulted in better enhancement compressive strength, and it is not for unheated bentonite-kaolin mixture. Figure 3 : Image FESEM of cement mixed with 12% additive. T I Figure 1 : Image FESEM of cement. Figure 2 : Image FESEM of cement mixed with 6% additive.