Page 8 - November-2022

TECHNICAL PAPER

binder mass in PLS00. It is because that the hydration degree of the references both at 90, and 365 days should be attributed
of normal UHPC pastes is only around 30-35 % after 28 days [21] , to MK reaction consuming abundant portlandite derived from
which indicates still a large number of unhydrated cement grains cement hydration . In addition, its peak intensity of Ca(OH) 2
[32]
exist in PLS00 paste at late ages. Therefore, the dosage of of MK-cement paste (P15) at 365 days is obviously less relative
30 % LS substituting cement by binder mass can not obviously to that at 90 days. While the peak value of portlandite in MK-
prevent the rehydration of cement in UHPC paste without MK LS-cement paste (PLS15) at 365 days is comparable to that
with long term water curing in this study. at 90 days. Combining the results of chemically bound water
in section 3.2, it should be concluded that the rehydration
3.3 DTA curves and XRD patterns
of MK blended pastes should include cement hydration and
The differential thermal analysis (DTA) curves as well as XRD MK reaction simultaneously. The peak intensity of protlandite
patterns for UHPC pastes with long term water curing are of control mixtures without MK have outstanding increase on
presented in Figure 4 and Figure 5, respectively. Obviously account of remarkable cement hydration reaction after 90 days.
weaker peak intensity on Ca(OH) 2 in MK contained mixtures Moreover, the areas of endothermic peak between 80-200°C
reflected in DTA curves (450°C) and XRD patterns (18°) than that in DTA curves characterizing the decomposition of calcium

(a) Pastes without LS (b) Pastes blended with LS
Figure 4: DTA curves of pastes under long term water curing

(a) Pastes without LS (b) Pastes blended with LS
Figure 5: XRD patterns of pastes under long term water curing 1-C 3 S, 2-Ca(OH) 2 , 3-ettringite, 4-limestone (LS), 5-monocarboaluminate(Mc)

22 THE INDIAN CONCRETE JOURNAL | NOVEMBER 2022