Cement, Energy and Environment

22 Physical Parameters PSC 1 PSC 2 PSC 3 PSC 4 PSC 5 Normal Consistency 28 26.75 26.75 26.5 26.5 Soundness Test Le chatelier Expansion (mm) [IS: 4031: Maximum 10mm] 0.00 1.00 0.00 1.00 1.00 Autoclave Expansion (%) [IS: 4031: Maximum0.8%] 0.003 0.004 0.006 0.008 0.012 Setting time Initial setting time (minutes) [IS: 4031: Minimum 30min] 140 145 135 125 125 Final setting time (minutes) [IS: 4031: Maximum 600mm] 190 225 230 215 220 Determination of Compressive Strength Curing time Compressive strength (MPa) 1 Day 17.35 19.10 19.35 19.75 18.75 72±1 Hrs (3 Days) 28.53 32.07 29.03 30.66 29.53 168±2 Hrs (7 Days) 38.00 44.93 42.80 44.37 40.90 672±4 Hrs (28 Days) 57.16 64.63 63.83 63.00 61.30 Table 3: Physical parameters of blended cement. 3.4 Determination of Heat of Hydration The measurement of heat flow and total heat of hydration were measured for 7 days. Fig 6 has demonstrated the Heat flow curve concerning the hydration reaction coordinate (Fig 6. a) and cumulative liberated heat (heat of hydration) concerning the reaction coordinate (Fig. 6.b). The heat flowcurve (Fig. 6.a) has demonstrated the two heat flowmaxima (Peak P1 and Peak P2, Fig 6. a) for all five samples almost in the same time intervals. After those peaks, the curves were found to be declining in nature. This indicates the occurrence of maximum reaction rates of the cement hydration. Although the curves were found to be declining in nature after these peaks, those didn’t meet the baseline or zero (Y axis). This indicates the continuous heat liberation and continuation of cement hydration reaction for all samples. Comparing the nature of the curve of all samples it was found that the PSC 1 has demonstrated the Peak P2 with lower height compared to the other four samples. This indicates that some additional exothermic heat flow happened in the other four samples (PSC 2 to PSC 5). Hence it is clear that the addition of GEOFS (PSC 2 – PSC 5) provides some additional reactivity. Again from the cumulative heat vs time plot (Fig. 6.b), it was found that the cumulative heat of hydration of PSC 1 (for 7 days) is less than comparatively other four samples (PSC 2 - PSC 5). Hence the additional heat of hydration found in PSC 2 – PSC 5 can be considered as contributed by GEOFS reactivity. So the determination of heat of hydration experiment supports the existence of additional reactivity of GEOFS in blended cement hydration. Figure 6: (a) Heat flow curve concerning hydration reaction coordinate (or time) and (b) Plot of cumulative liberated