Abstract: AFm phases, called also (Al2O3-Fe2O3-mono), are a common term for the hydration products with general formula [Ca2(Al,Fe)(OH)6∙(X)]∙y H2O, where X means e.g. OH-, SO42-, CO32-. AFm phases are formed when the corresponding phases are present in adequate concentrations in the solution under the room temperature. The incorporation of sulfite anions in the structure of lamellar AFm phase will be shown. The presence of monosulphite in the Portland clinker system was investigated by infrared spectroscopy, XRD and SEM analyses.
Abstract: Blended cements were prepared from belite clinker burned in a model kiln and ordinary industrial alite clinker. The mechanical and physical properties of these blended cements were determined. The difference in the development of hydration heat of belite and alite cements by using calorimetric method was determined also. The results show that strengths of prepared belite cement after 28 days of hydration are equal to those of industrial alite cement. Short time strengths are suitable for blended cements up to 30 % content of belite clinker. These results demonstrate the possibility of separate industrial belite clinker production next to common alite clinker manufactory and production of economically and ecologically advantageous blended Portland cements with suitable technological properties.
Abstract: Reusing and recycling of secondary raw materials from high-volume industrial productions (especially form construction materials and binders fabrications) is very important way of conserving environment and it is also interesting from the economical point of view. The production of common hydraulic binders, especially Portland cement, burdens the environment with considerable amount of combustion gases and consumes energy in massive scale. Alternative (low – energy) binder can be used as Portland cement substitution in applications with lower mechanical properties requirements. Mined limestone wash sediments contain large amount of clay components, but there is also indispensable share of fine calcite. This composition makes these sediments a promising material for the preparation of hydraulic binders as Roman cement or hydraulic lime.
Abstract: The aim of this work is to study the influence of boron and its compounds, boric acid and borax, on the hydration of Portland cement. The samples – cement paste modified by the addition of boron, borax and boric acid in different concentrations were prepared. The results are obtained from the evaluation of calorimetric curves, mechanical properties and phase composition. The goal is to describe the kinetics of targeted retarded process of hydration and to find such addition which would suspend the setting of boron modified system entirely. The comparison of effects of each boron-containing compound is based on its concentration and on its kind.
Abstract: The article discusses the physical mechanical concrete properties of five different concrete recipes. The objective of the composition of the concrete is to use the lowest quantity of Portland cement by adding additives (fly ash, slag and limestone) and the various combinations.
Abstract: Mayenite (C12A7) and calcium dialuminate (CA2) are both components of Calcium aluminate Cement (CAC). The hydration of these phases depends on initial conditions especially on the temperature. Pure phases were synthesized by solid-state reaction. The hydration was carried out at three different temperatures – 20 °C, 30 °C and 60 °C. The course of hydration was investigated by isothermal calorimetry. The results prove, that higher temperature increase reactivity of phases and decrease their initial period of hydration. The X-ray diffraction analysis (XRD) identified the hydration products of CA2 as katoite (C3AH6) and gibbsite (AH3). The hydration products of C12A7 depends on the temperature. At 20 °C the major products are C2AH8 and CAH10. At 30 °C CAH10 disappears and only C2AH8 remains. At 60 °C the only stable hydrates – C3AH6 and AH3 are formed.
Abstract: The paper deals with testing of CO2 diffusivity through poly (vinyl butyral) (PVB) layers and their efficiency to serve as barriers against cement mortar carbonation. Two different types of PVB were tested; PVB sheet made from original extruded PVB polymer and PVB sheet made from PVB dispersion obtained from recycled windshields. The first part of the work was focused on testing CO2 diffusion when polymer sheets were exposed to a CO2 atmosphere (10% v/v CO2) with 0% RH. The excellent barrier capability against CO2 permeability of both types of polymer layers was observed. In the second part, mortar specimens were exposed for 23 days to two different carbonation regimes (laboratory conditions and chamber with CO2 atmosphere (1% v/v CO2) and 60% RH), having been coated or not with recycled PVB dispersion. Compressive strength tests, carbonation depth measurements and acoustic measurements (impact-echo method) were performed. The results showed the alternation of the compressive strength values depending on whether PVB coating was used or not. Both phenolphthalein test and impact-echo method confirmed the protective effect of PVB layer against mortar carbonation.
Abstract: Paper deals with testing of surface photoactivity of fibre-cement composites. Self-cleaning ability, de-NOx activity, visual stability and weathering resistance were tested. Carriers of photoactivity were four different nanopowders with high content of anatase; crystalline form of TiO2. Photocatalytic properties of TiO2 particles are maintained even after mixing with cement in composite matrix. Natural photolysis as reaction of material and UV light is accelerated in presence of a proper form of TiO2 as a catalyst which by producing free radicals is able to oxidize organic matter and even small inorganic particles. Oxidized material is mostly less harmful considering the de-NOx process and decomposition of other gaseous pollutants. By this reaction the surface of composites containing large number of TiO2 particles is able to maintain its original appearance by so called self-cleaning ability.
Abstract: Viscoelastic properties of Portland cement-metakaolin fresh pastes were measured using rotational rheometer. In mixtures 10 % of Portland cement was replaced by various fractions of metakaolin with different particle size distribution. The role of the fineness of metakaolin was revealed characterizing flow, adhesion and creep of the fresh pastes.