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 Experimental Study of Activation Coal Gangue-Portland Cement by Microwave Technology
Added appropriate amount of microwave activation coal gangue intoⅠ42.5 Portland cement, there were not negative influence to Portland cement properties such as fineness, setting time, volume stability, pozzolan activity, strength by physical and mechanical experiments and scanning electron microscopy (SEM) ; though there was micro expansion during hydration and hardening process, the volume stability of microwave activation coal gangue cement mixtures also could satisfy relevant state technology standards; compare to tradition thermal activation coal gangue, microwave activation coal gangue could be changed better cement additives, and could more remarkable reduce product cost and save energy.
Making Concrete "Greener" with Fly Ash
Environmental issues will play a leading role in the sustainable development of the cement and concrete industry in the 21st century. The World Earth Summits in Rio de Janeiro, Brazil in 1992, and Kyoto, Japan in 1997, have made it abundantly clear that unchecked increased emission of greenhouse gases to the atmosphere is no longer environmentally and socially acceptable for overall sustainable development. The primary greenhouse gas emissions discussed in the sessions of the above conferences are carbon dioxide emissions. Other greenhouse gases such as nitrous oxide and methane, are of serious concern, but the amount involved is relatively small compared with that of carbon dioxide. Consequently, developed countries are considering regulations and mandatory quotas on the emission of these gases, and the main thrust is to stabilize these emissions to the 1990 level by the year 2010. Since the manufacture of portland cement contributes significantly to carbon dioxide emissions, this article discusses the increase use of large volumes of fly ash and other supplementary cementing materials in the construction industry and its role in reducing these emissions.