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.
CATARACT: A HISTORICAL PERSPECTIVE.
The earliest extant description of a surgical operation for the cure of cataract is that of Celsus, toho practiced medicine in Rome at the beginning of the Christian era. In his text De Meclicina he described in detail his method of couching, by which he inserted a bronze needle into the eye at the equator on the lateral side of ihe globe and depressed the cataract downward into the lower part of the vitreous where the surgeon hoped it would remain out of the way of vision. The same method had been employed by the Greeks and Hindus for at least several hundred years earlier and ivas to continue as the only operation available until the middle of the eighteenth century when Daviel of Paris described extraction of the lens through the cornea. The early couchers worked on the premise that the crystallin humor we know as the lens was the receptor for vision, and that in certain conditions of disease a suffusion flowed doivn in front of the crystallin humor where it solidified and formed a dense curtain. The purpose of couching was to press the hardened corrupt humor out of the way of the lens. That cataract was opaque material within the lens itself was not recognized until after the middle of ihe seventeenth century. Until then ihe surgeons were not even aware that it was the lens they were dislocating.