Hydration Processes of Four-Component Binders Containing a Low Amount of Cement

Results of research on hydration of four-component binders containing very high amounts of supplementary cementitious materials were presented. The samples were composed of blended pozzolana (a mix of conventional fly ash and spent aluminosilicate catalyst), cement (about 20 wt.% in the binder) and Ca(OH)2. Spent aluminosilicate catalyst was proposed as activating component which can improve properties of low-cement blends, while the role of Ca(OH)2 was to enhance pozzolanic reaction. Early and later hydration periods of such blends were investigated by calorimetry, TG/DTG, FTIR and X-ray diffraction. Initial setting time as well as compressive strength were also determined. It was concluded that enhancement of reactivity and improvement of properties of fly ash–cement binders are possible by replacing a part of fly ash with more active fine-grained pozzolana and introducing additional amounts of Ca(OH)2. The spent catalyst is mainly responsible for accelerating action during the first hours of hydration and for progress of early pozzolanic reaction. Fly ash develops its activity over time, thus synergic effect influences the later properties of composites. Samples containing blended pozzolana exhibit shorter initial setting times and higher compressive strength, as well as faster consumption of Ca(OH)2 compared to the reference. Investigated mixtures seem to be promising as “green” binders, alternatives to cement, after optimizing their compositions or additional activating procedure

Comparative Investigations of Some Properties Related to Durability of Cement Concretes Containing Different Fly Ashes

abstractEN: The results of research of mechanical properties and selected other characteristics influencingdurability of cement concretes containing cement substitutes were presented. Cement concretesperformed with conventional fly ash, fluidised fly ash and their mixture were investigated. The obtainedresults were compared with findings registered for two types of concrete performed withoutcement replacements and with cement concrete containing silica fume. The results have shown thatcement concrete with predetermined 28-day compressive strength of about 50 MPa and good workabilitymay be obtained using different cement replacements. Generally, these cement concretes exhibitedalso favorable properties related to concrete durability, i.e. low permeability and sorptivity,and significant reduction of chloride migration coefficient. Favourable results were obtained for cementconcrete containing mix of conventional and fluidised fly ashes: good workability, compressivestrength after 28th day exceeding 50 MPa, low permeability of water, and low sorptivity, as well aslow coefficient of chloride migration. These features were similar as for cement concrete containingsilica fume.score: 15collation: 154-16