Utility properties of novel hybrid cement (H-Cement) are influenced by pozzolanic reaction of fly ash, latent hydraulic reaction of metallurgical slag together with the alkali activation of inorganic geopolymer based on precipitated waste water coming from bauxite residues. Content of Portland cement clinker is at maximum of 20 mass %, the remaining portion consists of inorganic geopolymer. Up to 80% of CO 2 emissions are saved by H-Cement manufacture compared to ordinary Portland cement (OPC). No heat treatment or autoclaving is needed at H-Cement production. The field application of H-Cement is performed by the same way than that of common cements listed in EN 197-1, and is also connected with highly efficient recovery and safe disposal of red mud waste. H-Cement is suitable for ready-mixed concretes up to C30/37 strength class and is specified by beneficial shrinkage-reducing property of the concrete kept in long dry-air cure opposite to common cements. RESUMEN:Características básicas de un cemento híbrido industrial: utilización en hormigón premezclado y aplicaciones como reductor de la retracción. Las propiedades de un nuevo cemento híbrido (cemento-H) vienen determinadas por la reaccion puzolánica de cenizas volantes, la hidráulica latente de las escorias metalúrgicas y la activación alcalina mediante las aguas residuales generadas por el tratamiento de la bauxita para dar un geopolímero inorgánico. La proporción máxima de clínker de cemento en este nuevo material es del 20%, y por ello, en su fabricación se emite hasta un 80% menos de CO 2 que en la producción del cemento portland (OPC). El cemento-H se prepara sin necesidad de tratamiento térmico ni de estancia en autoclave y su aplicación es la misma que los cementos convencionales definidos en la norma EN 197-1. Por otra parte, su fabricación supone la recuperación y la valorización segura de los lodos rojos de bauxita. El cemento-H es apto para la preparación de hormigones premezclados hasta la categoría C30/37, presentando el nuevo material, además, una menor retracción que los cementos convencionales, por lo que su empleo resulta especialmente ventajoso en los hormigones que se curan al aire.

The article deals with studying the antifungal effect of ground granulated blastfurnace slag (GGBS)

This article describes utilization of a cement kiln bypass dust utilization as an added component in a hydraulic road binder. Three experimental binder mixes (BM1–BM3) with variation in the composition of the main constituents (cement clinker, ground limestone and ground granulated blast furnace slag) and constant content of bypass dust (10%) were prepared under laboratory conditions. The properties of binder constituents, fresh experimental binder mixes and hardened specimens were tested according to STN EN 13282-2 for a normal hardening hydraulic road binder. The physical and chemical properties of all binder mixes (fineness: +90 µm ≤ 15 wt.%; SO3 content: <4 wt.%) met the standard requirements. The bypass dust addition led to an increase in the water content for standard consistency of cement mixes (w/c = 0.23) and to a shortening of the initial setting time for two experimental blended cement pastes (BM1 and BM3) compared with the value required by the standard. Only BM2 with the lowest SO3 content (0.363 wt.%) and the highest percentage of granulated blast furnace slag (9.5 wt.%) and alkalis (Na2O and K2O content of 5.9 wt.%) in the binder mix met the standard value for the initial setting time (≥150 min). The results of compressive strength testing of experimental specimens after 56 days of hardening (59.2–63.9 MPa) indicate higher values than the upper limit of the standard requirement for the N4 class (≥32.5; ≤52.5 MPa).

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The article deals with the study of the effects of alternative fuels and raw materials on the cement clinker quality. The clinker quality was expressed by the content of two principal minerals alite C 3 S and belite C 2 S. The additions of alternative fuels ashes and raw materials, in principle, always increased the belite content and conversely reduced the amount of alite. The alternative fuels with high ash content were used such as the meatbone meal, sewage sludge from sewage treatment plants and paper sludge and the used alternative raw materials were metallurgical slags -granulated blastfurnace slag, air cooled blastfurnace slag and demetallized steel slag, fluidized bed combustion fly ash and waste glass. Meat-bone meal, sewage sludge from sewage treatment plants and paper sludge were evaluated as moderately suitable alternative fuels which can be added in the amounts of 2.8 wt. % addition of meat-bone meals ash, 3.64 wt. % addition of sewage sludge ash and 3.8 wt. % addition of paper sludge ash to the cement raw mixture. Demetallised steel slag is suitable for production of special sulphate resistant cement clinker for CEM I -SR cement with addition up to 5 wt. %. Granulated blastfurnace slag is a suitable alternative raw material with addition 4 wt. %. Air cooled blastfurnace slag is a suitable alternative raw material with addition 4.2 wt. %. Waste glass is not very appropriate alternative raw material with addition only 1.16 wt. %. Fluidized bed combustion fly ash appears not to be equally appropriate alternative raw material for cement clinker burning with less potential utilization in the cement industry and with addition 3.41 wt. %, which forms undesired anhydrite CaSO 4 in the cement clinker.