EFFECTS OF THE TEMPERATURE AND RELATIVE-HUMIDITY ON THE STRUCTURE OF C-S-H GEL

This paper describes the structural changes of C-S-H caused by curing at different relative humidities (R. H.) and temperatures using XRD, Si-29 NMR and thermal analysis. The results show that within the relative humidity range studied (9%-100%), the polymerization of C-S-H does not change, but that the local structure becomes more disordered with decreasing R. H. Heating of C-S-H results in increasing polymerization and;structural disorder, and decreasing basal-spacing. It appears that decreasing relative humidity removes interlayer water molecules but that heating removes both water molecules and OH- groups. Thermal behaviors of jennite and 1.4-nm tobermorite are also studied and compared with those of C-S-H.