Zhenping Sun;Yang Yu;Qi Li;
<正>Although low field NMR can provide information on cement hydration and pore structures,magnetic substance in cement and mineral admixtures cause confusion in interpreting NMR results.Knowledge of NMR response of tricalcium silicate,a main phase of cement clinker without magnetic substance will provide direct insight into this problem.Tricalcium silicate(C_3S),synthesized by Pechini method,were probed by transverse relaxation time(T2),longitude relaxation time(T1) and T1-T2 correlation spectrum.T1 and T2 of tricalcium silicate paste decreased with hydration and had stage-like proprieties.A minor population of water,emerging after hydration of 3-4h in T1 and T2 distribution curves and T1-T2 correlation spectrum,was gel water.T1-T2 correlation spectrum had two populations of water near the diagonal of T1/T2=4,with one being gel water mentioned above and the other one being capillary water.T1/T2 of capillary water was higher than that of gel water and it showed tortuosity of gel pore was bigger and interactions between capillary pore surface and hydrogen atom was less intense.An off-diagonal peak,whose T1 was the same as capillary water and T2 the same as gel water,originated from exchange between these two populations of water. Amplitude of this peak increased in the first 14d and it proved that exchange intensified in this period. Originality Low-field NMR provided information of water evolution in tricalcium silicate paste. Although this method had extensively used to study hydration of white cement and Portland cement,seldom researches regarding hydration of tricalcium silicate were performed T1-T2 correlation spectrum prevailed recently and could give information on local physicochemical environment of capillary pore and gel pore and on water exchange between capillary water and gel water. So,in this contribution,we performed low-field NMR experiment on tricalcium silicate at different ages.An inverse Laplace transform method was used to get T1 and T2 distribution curves at different ages.As shown in both T1 and T2 distribution curves,a minor population of water emerged at age of 3-4h.Similar phenomena were observed on T1-T2 correlation spectrum at rough the same age.This population of water was regarded as gel water.In TI-T2 correlation spectrum,an exchange water peak emerged at this age and gradually intensified,which meant exchange between capillary water and gel water increased in the first 14d.
Relaxation time;;Correlation spectrum;;Capillary water;;Gel water;;Exchange water
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