Influence of pozzolanic activity of coal gangue on hydration products in coal gangue-cement system
Qualitative and quantitative analysis of the composition in the paste of complex cements have been determined by means of X-ray diffraction (XRD),differential scanning calorimetry (DSC) and directly-heating method. Results show that the composition of hydration products in coal gangue-cement complex system is similar to that in pure cement system, but the content of hydration products for per unit cement in former is higher than that in later at the early hydration stage. The pozzolanic reaction between coal gangue and cement hydration products mainly occurs in 3d. The content of Ca(OH)2 and that of C-S-H in the paste are related to the activity and the content of coal gangue. The content of C-S-H in high activity coal gangue-cement system is related to the activity of coal gangue rather than the content, but that is opposite in low activity one.
Research on Interaction between Coal Gangue and Cement in Thermal Activated Coal Gangue-Cement System
The rule of interaction between the thermal activated coal gangue and the cement in the thermal activated coal gangue-cement system is revealed by the study of the hydration heat,the content of Ca(OH)2,the chemical combined water content and the reaction degree of thermal activated coal gangue in the system.The research results show that the accelerating effect of thermal activated coal gangue on cement hydration takes place at early stage and thermal activated coal gangue can restrain the cement hydration at the middle stage to some extent.The accelerating effect of cement on the pozzolanic reaction of thermal activated coal gangue exists from start to end.
SURVEY OF NORTH AMERICAN PORTLAND CEMENTS: 1994
A survey of portland cements marketed in North America was conducted in 1994 by the American Society for Testing and Materials (ASTM). The primary purpose of the survey was to acquire new data on cement characteristics and to aid in evaluating standard development needs. The survey includes 387 different cements, with cements from 136 of the 140 cement-producing facilities in the United States and Canada plus several foreign cements from import terminals. The data show that modern cements differ from those produced in the 1950s, with differences in compositional and physical characteristics clearly in evidence. While an overall classification into five basic types is still applicable, the conceptual definitions of those types have changed from previous surveys, and there now are numerous subtypes not previously given officially recognized status. This snapshot of modern cement characteristics should assist ASTM committees in their development of standards relating to portland cement and should provide a basis for consideration of many topics relating to hydraulic cements.