This study examines the effect of silica fume (SF) as a partial replacement for cement to prevent strength retrogression in hardened paste (HCP) and mortar at elevated temperatures. An experimental procedure was conducted on 320 specimens, replacing 0, 10, 20, 30% by weight with SF. The residual compressive specimens evaluated room temperature (25 °C) 100, 200, 300, 400 °C 7, 28, 56 days. resul...

The role of water in hardened Portland cement paste (hpc) is germane to an understanding of the nature of nanostructure – property relationships. The irreversible dimensional changes of hpc that occur on wetting and drying are dissimilar to those observed for other silicate minerals of interest to cement science. This irreversibility is also observed for the modulus of elasticity parameter. Len...

The origin of different stability crystalline calcium silicate hydrates was investigated. tobermorite crystal has been used as an analog cement hydrate that is being mostly manufactured material on earth. Normal thermally unstable and transforms to amorphous at low pressure. Meanwhile, anomalous with high Al content does not significantly transform under pressure or temperature. Conducted X-ray...

This work is a systematic attempt to determine the possibilities and the limitations of the (43)Ca high field solid state NMR in the study of cement-based materials. The low natural abundance (0.135%) and small gyromagnetic ratio of (43)Ca present a serious challenge even in a high magnetic field. The NMR spectra of a number of cement compounds of known structure and composition are examined. T...