Pastes of blast‐furnace slag were cured for up to 90 d using sodium silicate (waterglass), NaOH, and three different mixtures of Na2CO3–Na2SO4–Ca(OH)2 to activate reactions. The highest slag reactivity was observed for NaOH activation and the least for waterglass, although nonevaporable water indicated similar amounts of hydration products formed. The main hydration products found using X‐ray diffractometry in all systems were calcium silicate hydrate (C‐S‐H) and a hydrotalcite‐type phase. Microanalysis was performed on pastes activated using 50% Na2CO3·25% Na2SO4·25% Ca(OH)2, NaOH, and waterglass; the chemical composition of the C‐S‐H in the waterglass case was different relative to the other two alkalis. For all alkaline agents used, the C‐S‐H seemed finely intermixed with a hydrotalcite‐type phase of Mg/Al = 1.82, on average.

Pastes of pulverised fly ash (PFA) and blast furnace slag (BFS) in proportions of 100-0, 75-25, 50-50, 25-75 and 0-100 (wt-%) were chemically activated using sodium silicate with modulus (SiO 2 /Na 2 O) of 0, 0 . 75, 1, 1 . 5 and 2; the %Na 2 O was added at 4, 6 and 8% relative to the binder weight. The pastes were cured for 24 h at 75uC and then 28 days at 20uC. For 100%PFA pastes, the higher %Na 2 O, the better the strength; 4%Na 2 O was ineffective, whereas the highest strength of 25 MPa was reached using modulus 1. For 100%BFS pastes, the highest strengths were for 4%Na 2 O (80-85 MPa); the optimum modulus was 1 . 5. The addition of BFS to PFA rich pastes was favourable; for 50% blends, the strengths were between the above mentioned figures and the best modulus was 1-1 . 5 (45-48 MPa). The lower glass content of PFA (70%) compared with the BFS (.90%), together with the porous nature of the PFA, were considered to have reduced the strength in PFA blends.

Semi‐crystalline potassium titanates, useful as precursors to produce composite materials and coatings, were synthesized by thermal treatment of powdered TiO2 in molten mixtures of KNO3 and KOH at 450°–550°C. The products obtained had similar structures of laminar crystals, aggregated in particles of about 3 μm of n=TiO2/K2O molar ratio in the range 2.8–6.0. The value of n could be regulated by the temperature of synthesis, the weight ratio of [KOH]/[KNO3] in the molten salt mixture, and the number of water washing operations. The reduction of the TiO2/K2O molar ratio increased the contents of H2O in the composition of potassium polytitanate, from 5.3 to 11.4 and from 0.2 to 8.6 (wt%) in the adsorbed and structural forms. The thermal treatment of the potassium polytitanate precursors obtained resulted in dehydration and chemical interaction with unreacted TiO2 at 500°–750°C, amorphization at 750°–850°C, crystallization of K2Ti4O9 (in some cases K3Ti8O17) at 850°–1090°C, and crystallization of K2Ti6O13 at temperatures >1090°C. The mechanisms of the structural transformation and phase evolution were considered as a function of the TiO2/K2O molar ratio in the potassium polytitanate.

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