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Two types of blast furnace slags (HS N and HS V) with different CaO/SiO2 ratios, were activated by potassium silicate solution (Ms = 1). The results showed that most of the alkali silicate activated slag AAS mortars lost their workability within 10 min. Only an AAS mortar made from slag HS V had an outstanding fluidity even after 20 min. The microstructural evolution of the AAS pastes, as well as their selective dissolution residues after 1 h, were analyzed by an ultrasonic method, TGA, FTIR and solid state 29Si/27Al NMR. By employing a model developed for aluminosilicate glasses, Si(Qn(kAl)) species in the slags were calculated and fitted to their 29Si NMR spectra. The results indicate that slag HS V experienced incongruent dissolution during hydration and that its dispersed glass structure in terms of Si(Qn(kAl)) abundance, was significant with respect to its unusual solidification process.

Retarders are widely used in construction materials to control the setting and hardening. The present study focuses on changes in the rheological behavior, the admixture adsorption and the pore solution composition with a controlled addition of sodium gluconate and ethylenediamine tetra(methylene phosphonic acid) (EDTMP) in cement. The adsorption of the sodium gluconate was influenced by time of addition of dosage. Delayed addition induced a depot effect which was reduced by the ongoing hydration whereas the adsorption of EDTMP was not affected by time of dosage. Nearly the complete admixture concentration was directly adsorbed on clinker phases or first hydration products. For sodium gluconate, an interaction with ferrite containing clinker phases and a calcium complexing mechanism were suggested. In contrast, EDTMP seemed to have no significant influence on the calcium concentration. With regard to the sodium concentration a fast adsorption of sodium gluconate was determined. Furthermore, a competitive adsorption between dissolved sulfate and retarder molecules or a complex formation mechanism is supposed.

Basic oxygen furnace slags (BOFS) are by-products of the steelmaking process. Several researchers have studied the production of Portland cement clinker and metallic iron from BOFS via a reductive treatment. In this study, we applied a carbothermal reduction of BOFS in a technical-scale electric arc furnace and characterised the clinker-like products. Those clinker-like non-metallic products (NMPs) had a chemical and mineralogical composition comparable to clinker for ordinary Portland cement (OPC) and contained large elongated alite crystals as major component. The pure NMPs reacted more slowly and achieved a lower degree of hydration compared with commercial OPC. If the reactivity of the products can be further increased by employing specific adaptations, it can be used as a full clinker substitute for OPC. Nevertheless, it is also an option to use the material without further modifications as a cement component or concrete addition, which contributes to the strength development in both cases.

Alkali silica reaction (ASR) occurred in the alkali activated slag (AAS) concrete was evaluated by a revised mortar prism method. The mortars were made of blast furnace slags activated by alkali silicate solution possessing different modulus (0.5, 0.75, 1 and 2) as well as cations (sodium and potassium) and standard sand with a volume replacement of 25 vol% by borosilicate glass beads. Their changes in length and dynamic elastic modulus were monitored up to 7 months. The results showed that ASR has taken place among some mortars, which were evident under both light microscopy and electron microscopy with EDX analysis. The results also revealed that high alkali content did promote the risk of ASR but the degradation due to ASR was affected in a much more complex way.

In this paper analytical evidence on crystal structure and hydration behaviour of C3A solid solutions with MgO, SiO2, Fe2O3, Na2O and K2O is given. Samples were prepared using an innovative sol-gel process as precursor, examined by X-ray powder diffraction, infra-red spectroscopy and the crystal structure was refined by the Rietveld method. A significant shift of lattice parameters was found for C3A solid solutions with SiO2, Fe2O3 or Na2O but only minor changes were detected for K2O. The hydration of C3A solid solutions in the absence of CaSO4 was accelerated for samples doped with SiO2 or K2O and it was retarded in the case of MgO, Fe2O3 or Na2O. The hydration in the presence of CaSO4 was accelerated when C3A was doped with K2O or Na2O, whereas Fe2O3 strongly retarded the hydration. The doping with SiO2 nearly had no influence on the hydration, the effect of MgO was not straight forward.

The influence of high intakes of Cr, Ni, and Zn on the burning process and the formation of clinker phases is described. Three different raw meals were used and were burned with the metal oxides in four concentrations from 200 to 25,000 ppm. The resulting clinker was analysed for the content of free lime and X-ray diffraction analysis was done. Some of the clinker material was crushed and polished, and quantitative point counting was performed to provide the content of the different clinker phases. These samples were also analysed by scanning electron microscope connected with an energy-dispersive X-ray-spectrometer to detect the composition of the clinker phase. The results show that only very high intakes of heavy metals have measurable effects on the formation and composition of the clinker.

Results are reported on the influence of Cr, Ni, and Zn on the properties of the pure clinker phases C3S, C3A, and C4AF. Part I deals with the most important clinker phase C3S. Samples were prepared with dosages of 0.02, 0.1, 0.5, 2.5, and 5.0 wt.% of Cr, Ni, and Zn (in form of their oxides). The doped C3S was investigated for the content of free lime, the rate of evaporation of the metals, and by X-ray powder diffraction. The rate of heat liberation of ground samples was followed by differential scanning calorimetry for 2 days. The hydration products were investigated by X-ray powder diffraction and scanning electron microscopy combined with an energy-disperse X-ray spectrometer. All in all the heavy metals only have an influence on the structure and reactivity of the C3S when the dosage is much higher than in ordinary portland cement.