Issue 22

A. Namdar, Frattura ed Integrità Strutturale, 22 (2012) 26-30; DOI: 10.3221/IGF-ESIS.22.04 28 The Fig. 4 is highlighted XRD pattern of cement, and cement- kaolin-bentonite mixture, the kaolin-bentonite was submitted to 800 ºC heat for 1 hour. The XRD pattern shown that Ca(OD) is converted to Ca(OH) 2 but no significant change in XRD pattern in increasing kaolin-bentonite mixture from 6% to 12% in concrete mixed design. The Tab. 2 and Fig. 5 show the result of different mixed design for compressive strength of concrete. The result is indicated appropriate proportion of natural minerals mixture can improve concrete compressive strength without and treatment process. Sl No Con type Unheated additive (%) Additive produced by 600 ºC (%) Additive produced by 800 ºC (%) Additive produced by 1000 ºC (%) 1 40 - - - - 2 40 6 - - - 3 40 12 - - - 4 40 - 6 - - 5 40 - 12 - - 6 40 - - 6 - 7 40 - - 12 - 8 40 - - - 6 9 40 - - - 12 Table 1 : Concrete-additive mixture ratio. Sl No Type of concrete Additive (%) 7 days 14 days Stress (N/mm 2 ) Stress (N/mm 2 ) 1 Without additive - 25.77 30.48 2 Natural additive 6 33.65 34.50 3 Natural additive 12 21.87 28.44 4 Additive produced under 600 ºC heat 6 18.70 33.07 5 Additive produced under 600 ºC heat 12 25.14 40.19 6 Additive produced under 800 ºC heat 6 30.95 35.15 7 Additive produced under 800 ºC heat 12 40.32 42.39 8 Additive produced under 1000 ºC heat 6 27.05 31.70 9 Additive produced under 1000 ºC heat 12 31.97 33.44 Table 2 : Concrete compression strength.