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.
On Study of Development Expansive Coal Gangue Portland Cement by Microwave Technology
Added carbon powder or M mineral powder in unburned kaolinite coal gangue, the mixtures could be changed better expansive mineral additive of Portland cement by microwave irradiation. The microwave activation coal gangue mixtures 5%, 10%, 15%, 20%, 25%, 30% and 35% (by weight) were respectively added intoⅠ42.5 Portland cement. The compressive/flexural strength of various expansive coal gangue Portland cements were determined after 3 and 28 day. The fineness, initial and final setting time, soundness and volume expansive ratio was also measured. 　　　The expansive reasons of coal gangue Portland cement were considered that there were lots of thicker and bigger flaky crystal during hydration processes by scanning electron microscope, and found the Al, Si, O and other elements in flaky crystal by Edax. 　　　The expansive mechanism of coal gangue Portland cement is different from traditional expansive cements theories by microwave irradiation.
Durability of Parking Structures: Analysis of Field Survey
A total of 215 garages in Toronto, Ottawa and Montreal, Canada, have been surveyed to various extents by assessing delamination, half-cell potential, depth of cover, and component condition. In addition, tests were carried out on cores, in which chloride content, compressive strength, and chloride permeability were determined and the air void system was analysed. The evidence indicates that durable garages can be built, and that poor performance must be attributed to design and construction practices whose effectiveness falls short of that required by the environment. It follows that almost all previously built garages will eventually require repair unless upgraded before the chloride concentration of the concrete reaches a critical level. Repair by the "patch and waterproof" method was found to decrease the rate of corrosion of deteriorated garages by approximately 70 percent. Detrimental effects following installation of a waterproofing membrane over concrete with elevated chloride concentration were not observed. No relation was detected between extent of delamination and crack density or compressive strength. Half-cell potential did not prove more sensitive than the chain-drag test in detecting delamination. (Author/TRRL)