Cationic reaction of transition metals with synthetic crystalline calcium sillicates

The action uptake reactions of transition metals of Mn, Fe, Co, Ni, Cu, Zn, Pb, Cd and Hg with some synthetic crystalline calcium silicates such as xonotlite, gyrolite and Beta-wollastonite were studied. The total cations uptake reaction appeared to be a factor combining both partial exchange Ca[2+] - M[2+]and precipitation of M[2+] as carbonates, hydroxy carbonates, hydroxy nitrates or hydroxides during the course of reaction. It was difficult to delineate the extent of the former reaction from the latter. These cations; have negative effect, on basic crystallinity of the solids, Beta-wollastonite was considered the most stable one. The total amounts in meq. of ions up taken by these solids have been found in a descending order : xonotlite > gyrolite > Beta-wollastonite

promotion effect of cerment dust for the Ca [oH] 2-Sio2 Hydrothermal reaction

Understanding of the chemistry of the Ca[OH]2-SiO2 hydrothermal reaction put the bases of the manufacture of sand-lime brick and autoclaved building materials. The effect of partial or complete substitution of Ca [OH]2 with cement dust on the lime-silica hydrothermal reaction was investigated. The pressed samples were prepared by using Ca [OH]2; silica ratio of 10: 90 by wt in which 20, 40, 60, 80 and 100% Ca [OH]2 was substituted by cement dust. The hydrothermal conditions were 10 bar [180 degree] and different periods from 4-24 hour. Major attention focused on the kinetic of the reactions, while other properties such as strength, density and porosity were also studied. The extent of hydration as measured by the chemically combined water, free lime and reacted silica, is enhanced due to the cement dust substitution. The reaction products as characterized by x-ray diffraction analysis and scanning electron microscopy [SEM] are CSH [1] and 11 A tobermorite. The results indicate that the substitution of Ca [OH]2 with cement dust accelerate the tobermorite formation and improve its crystallinity. For industry the results revealed that the substitution of lime with cement dust [by-product of cement industry] up to 50% can be used to prepare sand- lime brick with higher strength and lower cost

Chemical studies on corroded constructions

In Ismailia area [Egypt], it is observed that many buildings are deteriorated, especially in the bathrooms and in the parts which are in contact with water, in very short time. The deterioration is visually seen as white salts on the surface. This phenomena is observed not only on the walls but also on the floor. In this work, this phenomena is studied to know the reason or reasons which lead to the corrosion of the buildings in order to avoid or decrease this problem. The chemical and mineralogical studies showed that the white salts which occur on the surface, when water percolate through the mortar and concrete, are sodium sulfate and traces of calcium carbonate. These salts arise as a results of many factors such as high amount of aggressive ions in the used materials humidity and high porosity of the mortar and concrete