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Concrete with a low Portland clinker content involves the use of mineral additives as a cement component or as a additive in a concrete mix. The main factors influencing the increasing use of mineral additives in concrete technology are the advantageous development of the functional properties of the concrete mix, hardened concrete and a large impact on the ecological effects, including reduction of CO2 emissions. The use of concrete with a low Portland clinker content is part of the strategy for sustainable development of the economy. This paper describes the technological and ecological effects of using silica fly ash and granulated blast furnace slag additives in concretes with a low Portland clinker content. The cement and concrete additives used were mechanically activated, which allowed to reduce the content of Portland clinker in concrete. A new generation superplasticizer was used in the research, enabling a low water-cement ratio to be obtained. The mechanical properties and ecological effects of the production and use of concretes with a low content of Portland clinker were determined, including the reduction of CO2 emissions. Test results confirmed the very good mechanical properties of concrete with a high content of mechanically activated mineral additives. The research also showed an average of 3 times lower CO2 emissions compared to reference concretes made of CEM I Portland cement without additives.

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The paper presents the results of investigation over influence of 0.3% addition of hydroxypropyl methylcellulose (MC) of 40 and 70 Pa·s viscosity on the hydration process of main clinker phases: C3S and C3A and also their mixture, both in presence and absence of gypsum. During the research it has been indicated that methylcellulose inhibits the hydration process of clinker phases, analyzed both separately and in their mixture. Moreover, presence of that additive reduces reactivity of calcium sulphate dihydrate what leads to formation of decreased amounts of ettringite. No significant differences resulting from viscosity of used methylcellulose were observed. Investigation over the influence of that admixture on the hydration process of tricalcium aluminate indicated that addition of methylcellulose inhibits hydration process of C3A with water. Similar influence of that admixture was observed in the case of C3A hydration in presence of gypsum. A lot of gypsum remains in the reaction mixture. Little amounts of ettringite are forming, however, there is no monosulphate. Inhibition of sulphate ions reaction with C3A is slightly higher in the case of methylcellulose of higher plastic viscosity. Also in the hydration examinations of tricalcium silicate methylcellulose addition caused a retardation of alite reaction with water. In first hydration hours of alite with MC addition there were no peaks of portlandite in the XRD pattern. In the presence of gypsum the influence of methylcellulose addition on the hydration course was significantly weaker. Simultaneously no significant differences related to the influence of different plastic viscosity of methylcellulose were observed. Similar course of reactions was observed in the case of hydration of alite and tricalcium aluminate mixture in the presence of gypsum and methylcellulose. After one week of hydration significant amounts of unreacted gypsum are still remaining. However, little amounts of ettringite are created. [ABSTRACT FROM AUTHOR]