Ingenieria de Materiales

This article assesses the effect of mix design parameters on the compressive strength and thermal performance of alkali silicate-activated blends of metakaolin (MK) and granulated blast furnace slag (GBFS). A strong interrelationship between the effects of activator composition and the GBFS/(GBFS + MK) ratio is identified through statistical analysis of compressive strength data. Pastes formulated with higher SiO2/Al2O3 molar ratios show improvements in mechanical strength with increasing GBFS addition, associated with the formation of a structure comprising coexisting aluminosilicate ‘geopolymer’ gel and Ca-rich Al-substituted silicate hydrate (C-(A)-S-H) reaction products. The inclusion of GBFS in MK-based geopolymers seems also to improve their performance when exposed to high temperatures, as higher residual compressive strengths are reported for these mixtures compared to solely MK-based systems. Only slight differences in shrinkage behaviour are observed at temperatures of up to 600 °C with the inclusion of GBFS; however, slag-blended pastes exhibit enhanced stability at temperatures exceeding 800 °C, as no variation in the compressive strength and no additional shrinkage are identified. These results suggest that nanostructural modifications are induced in the gel by the inclusion of GBFS into MK-based geopolymers, improving the overall performance of these materials.

... de Pereira. scientia@utp.edu.co. ISSN (Versión impresa): 0122-1701. COLOMBIA. 2007. Serguei Solarte / Michel Ospina / William Aperador / Ruby Mejía de ... ABSTRACT. In this article the effect of rice husk ash on mechanics and durability properties. of concrete was investigated. ...

... ha sido ampliamente estudiado debido a sus excelentes propiedades puzolánicas (Caldarone, et al.,1994; Balogh, 1995; Kakali et al., 2001; Razak y Wong ... En el difractograma se puede apreciar la presencia de ettrin-gita y yeso, donde la intensidad de los picos es muy similar ...

Randomly oriented short fibers have been shown to increase tensile strength and retard crack propagation of cement based materials such as fiber-reinforced mortars for diverse applications, especially in aggressive environments. In the case of reinforced concrete, it is very important to produce a “high quality” cover in order to prevent corrosion of the rebars. In order to obtain a high

ABSTRACT Chloride permeability was determined using a modified version of the ASTM Standard Method. A current passing through a mortar was monitored at regular one minute intervals over a 72 h period for each sample and the ionic flux calculated. This RTC (rapid test coefficient) method was used to determine the chloride diffusion coefficient for normal and blended Portland cement mortars containing silica fume, fly ash, natural pozzolan, activated clay, and granulated blast slag, respectively. The RTC method was applied to determine chloride permeability when silica fume is incorporated into cement mixes. Also, the porosity and absorptivity of these mortars and the corrosion activity of embedded reinforced specimens were measured. A good correlation was found between the coefficient obtained by the RTC method and that determined from the increased chloride concentration, and on the other hand, a good correlation was also found between pozzolanic characteristics and this last chemical parameter and/or its direct and indirect related parameters. The proposed method can be used as a quick tool to evaluate chloride diffusion.