Performance of Lime-Metakaolin Pastes and Mortars in Two Curing Conditions Containing Kaolin Wastes

Abstract

Many works have shown that metakaolin is very good pozzolanic material for using in lime mortars and Portland cement mortars. Alternatively, many studies also have shown that kaolin wastes, after some treatment, can become a high quality pozzolans. Most of these studies have discussed about the microstructural characteristics and hardened properties of pastes, mortars or concretes mixes containing metakaolin or kaolin wastes cured in moist environment. In this work pastes and mortars made of metakaolin and hydrated lime (L-MK), which the metakaolin was obtained from the kaolin production waste, were assessed in their hardened state. Two curing conditions were considered: dry and moist environment; and three ages of curing (28, 90 and 180 days) were studied. Pastes were assessed by XRD and TG/DTG. In pastes according to the XRD and TG/DTG results, the main hydrated products found were strätlingite, in moist curing, and monocarboaluminate, in dry curing. Properties like flexural and compressive strengths, water absorbed capillarity and loss mass variation were studied in mortars. The results showed that mortars in dry curing presented lower strengths than one in moist curing. In moist curing mortars presented compressive strength values around 12 MPa and in dry curing this value reached 6 MPa. This fact indicate that the strätlingite maybe is responsible for the high strengths in mortars in moist curing when compares with the strengths of mortars cured in dry environment. Further the results showed that mortars in dry curing presented higher water absorbed and mass loss variation than mortars in moist curing.

Colloidal and Thermal Behaviors of Some Venezuelan Kaolin Pastes for Therapeutic Applications

“…Possibly as a result of the significant iron oxide contents (7.76%), the dispersions formulated with VE12 showed negligible apparent viscosity (0.03 Pa·s), which would prevent the permanence of the product during application. In general, the viscosities measured in these Venezuelan kaolins are high in comparison to other kaolins [34][35][36][37]. Studies on other types of clay used for pelotherapy (bentonites) showed viscosities higher than 1 Pa·s [38,39].…”

The Transformation of Coal-Mining Waste Minerals in the Pozzolanic Reactions of Cements

“…Traces of portlandite and tetracalcium aluminate hydrate were identified at short reaction times [40,41]. However, tetracalcium aluminate hydrate was the prevalent phase in the pozzolanic reaction of coal waste at 900˝C at seven and 28 days; layered double hydroxides formed at day one of the reaction in coal waste at 600˝C to become the prevalent phase at day seven of the pozzolanic reaction.…”

“…Traces of portlandite and tetracalcium aluminate hydrate were identified at short reaction times [40,41]. However, tetracalcium aluminate hydrate was the prevalent phase in the pozzolanic The pozzolanic activity of the coal-mining waste that was activated at 600˝C and 900˝C/2 h had values, at one day, of 65.2%, at 600˝C, and 3.0%, at 900˝C; at seven days, these values were 67.2%, at 600˝C, and 33.1%, at 900˝C, and at 28 days into the reaction reached 72.4%, at 600˝C, and 65.8%, at 900˝C.…”