In order to provide a theoretical foundation for the utilization of tailings as supplementary cementitious materials, the pozzolanic activity of muscovite—a typical mineral phase in tailings—before and after mechanical activation was investigated. In this study, significant pozzolanic activity of muscovite was obtained as a result of the structural and morphological changes that were induced by mechanical activation. The activated muscovite that was obtained after mechanical activation for 160 min satisfies the requirements for use as an active supplementary cementitious material, and the main characteristics of the pozzolana were as follows: median particle size (D50) of 11.7 μm, BET specific surface area of 28.82 m2 g−1, relative crystallinity of 14.99%, and pozzolanic activity index of 94.36%. Continuous grinding led to a gradual reduction in the relative crystallinity and an increase in the pozzolanic activity index due to the dehydroxylation reaction induced by mechanical activation, which occurred despite the fact that the specific surface area showed a decreasing trend when the grinding time was prolonged. Mechanically activated muscovite exhibited the capacity to react with calcium hydroxide to form calcium silicate hydrate, which is a typical characteristic of pozzolana. This experimental study provided a theoretical basis for evaluating the pozzolanic activity of muscovite using mechanical activation.

The effect of heating, to temperatures between 400 and 1200ºC, on the dehydroxylation of kaolin and the pozzolanic activity of the resulting amorphous material were determined by a variety of analytical techniques. Mixtures of concrete containing variable amounts of kaolin calcined at 700ºC were analysed and the results compared with those for concrete samples containing two different types of imported metakaolin. As shown in this work, Colombian kaolin can be used effectively as a raw material to obtain a highly active product (metakaolin). The optimum heating temperature for the kaolin is between 700 and 800ºC.

This paper presents results from comparative thermogravimetric, calorimetric and pozzolanic activity analyses of five natural zeolite samples from Bulgaria, Slovakia, Philippines, USA and North Korea. The zeolites actively participate in the hydration processes of cement. Their activity in the early stage of hydration is based mainly on the large surface area of the particles while, in the later stages of activation, chemical reactions occur between the products of the hydration of cement and the soluble SiO2 that is present in the bulk of the zeolites. It has been shown that in all cement pastes which contain zeolite additives, the quantity of portlandite is lower than that in pure cement paste or is even totally absent. The amounts of hydration products are greater when 30% zeolite is used than when 10% zeolite is added (excluding the sample with chabazite). The lowest pozzolanic activity is shown by chabazite, which possessed the lowest SiO2/Al2O2 ratio.

Cement mortars and concretes incorporating clinoptilolite, silica fume and fly ash were investigated for changes in their physical and mechanical properties. It was found that additions of 10% clinoptilolite and 10% Pozzolite (1:1 mixture of silica fume and fly ash) were optimal for improvement of the quality of the hardened products, giving 8% and 13% increases in flexural and compressive strength respectively. The specific pore volume of the mortars incorporating zeolite decreased between the 28th and 180th day to levels below the values for the control composition due to the fact that clinoptilolite exhibits its pozzolanic activity later in the hydration. In these later stages, pores with radii below 500 nm increased at the expense of larger pores. The change in the pore-size distribution between the first and sixth months of hydration occurs mostly in the mortars with added zeolite.

Alkaline activation involves a reaction between aluminium silicates and compounds with alkalis or alkaline-earth elements in a caustic environment and under certain thermal and pressure conditions. It has been used in the production of non-structural building materials and in so-called ‘green’ concrete, as products display high mechanical strength, low chemical reactivity and high resistance to fire. Green concrete could be an eco-efficient alternative to concrete made using ordinary Portland cement (OPC), reducing CO2 emissions substantially. The main goal of this work is to test common clays, glass cullet and other industrial wastes as an alternative to the commonly used binders (metakaolin or fly ash) in geopolymers. Optimized formulations show interesting mechanical strength (approaching 20 MPa) after just 48 h of curing. The addition of F-sand as aggregate minimizes the shrinkage upon curing and the amount of activator required, and increases the density/degree of compaction of the bodies, thus improving their mechanical resistance within certain limits. Curing in ambient conditions also has a beneficial affect on the mechanical strength.