hydration of C3A systems in sodium chloride solutions

This study attempts to generate information about the chemistry of the hydration reaction of tricalcium aluminate [C3A] in 0.1 M sodium chloride solutions for hydration times up to one week at room temperature. The effect of gypsum, lime and alite on the progress of the reaction was investigated and the behavior of the dissolved ions was related to that of the solid phases. It is found that the hydration of C3A in 0.1 M sodium chloride solutions, also in the presence of gypsum, lime and alite has shown quite modification compared to that in water. The calcium chloro aluminate hydrate is a major phase formed in the different systems. It appears as a sole hydration product during the hydration of C3A alone in sodium chloride solutions, shows up together with ettringite phase in the presence of gypsum and predominates the ettringite phase in the presence of lime and alire. The hydration rate and the consumption of C3A in sodium chloride solution occur faster in the presence of gypsum than that in the presence of lime and alite

Chemical and mechanical properties of some Egyptian soils

The thermal and chemical activation of the clay minerals present in the naturally occurring soils may be developed well hardening materials suitable for construction purposes especially low cost housing. These processes have the advantage of making use of the raw materials present in the sites and consume their transport costs. The pozzolanic activity of the burnt clay increases with the increase of the amorphous character and the calcinations of clay at temperature 650-850 degree sign C show increasing pozzolanic properties [1-4]. Lime was also used as an activator for hydration reactivity of burnt clays [5], and the optimal value of the Ca [OH]2 content in lime pozzolans binders was approximately 20%[6]. Also, the use of Ca [OH][2] and CaSO[4], activators lead to best strength of calcined metakaolin [7]. The most common hydrates formed in system clay-CH mixtures are C-S-H and C[4]AH[13], while G[2]ASH[8] and C[3]AH[6] were also detected with clay rich in Al [8-11]. Turriziani [12] mentioned that gehlenite hydrate [C[2]ASH[8]] changes into hydro garnet in the presence of Ca [OH][2]. It has been assumed that the clay-lime reaction separate C-A-H phases but not as expected on stoichiometric grounds. In general the hydration behavior of metakaolin/calcium hydroxide system shows pronounced similarities to ordinary Portland cement hydration especially of heat evolution and set characteristics[7]. The present investigation aims to follow the mechanical properties and the hydration products produced as a result of interaction of lime and the thermally activated clays, also the effect of gypsum and B-anhydrite addition on the lime - bearing system as well as the influence of sodium chloride and magnesium sulfate as mixing solutions on the hydration reaction