Materials Science Forum Vol. 824

Abstract: Parameters of cement pastes with ceramic powder as partial Portland cement replacement up to 40 mass% are presented in the paper. Ceramic powder belongs to the pozzolanic materials. Utilization of pozzolanic materials is accompanied by lower request on energy needed for Portland clinker calcination which generally results in lower production costs of blended binder and lower CO₂ emissions. The ceramic powder is used in cement based pastes composition in amount of 8, 16, 24, 32, and 40 mass% of cement. For the studied ceramic powder, chemical composition is measured by X-Ray Fluorescence. The particle size distribution of ceramics is accessed on laser diffraction principle. Bulk density, matrix density, and total open porosity are measured for 28 days cured paste samples. The obtained results demonstrate that ceramic powder has potential to replace a part of Portland cement in composition of cement based composites.

Abstract: In this article Portland-slag cement was step by step replaced with pozzolana (fine red-clay ceramics) in concrete. This is first step of research that is why the only measured characteristics were consistency of mixtures and compressive strength. There were designed four mixtures with increasing replacement of Portland cement by 10 % each (CR, C1, C2, C3) where complete activity of pozzolana was assumed. Mixtures C4, C5 and C6 were designed with respect to presumed just partial activity of the used pozzolana (set as 40 %). The water/cement coefficient was decided to be taken according to the consistence of the mortar.

Abstract: Basic physical properties, pore structure, hygric properties and frost resistance concrete containing supplementary cementing materials. The amount of SCMs was kept constant to replace 10% of cement. Experimental results show that bulk density and matrix density of studied material vary only slightly except the mixture with fine natural pozzolana which achieved lower values in comparison with the reference material. This is in agreement with open porosity and transport of liquid water - its highest values manifest the worst performance of fine natural pozzolana among the studied materials. Frost resistance was found to be satisfactory for all mixtures except material with fine natural pozzolana and with fly ash.

Abstract: Physical and mechanical behaviour of cement pastes with partial Portland cement replacement by fine milled waste glass is researched in the presented paper. The tested pastes contain milled borosilicate glass in amount of 5, 10, 20, and 30 mass% of cement. The chemical composition of borosilicate glass and used Portland cement is accessed by XRF (X-Ray Fluorescence) analysis. For the milled glass, pozzolanic activity and particle size distribution are measured. Here, modified Chapelle test is used for evaluation of pozzolanic activity. Particle size distribution is measured on laser diffraction principle. Basic physical properties and mechanical properties are determined for samples cured 28 and 90 days in water in order to evaluate the kinetics of hydration process. The obtained results revealed the possible applicability of the tested borosilicate glass in the composition of cement-based composite materials.

Abstract: Floor screed with different amount of pozzolanic admixture was studied. There were designed 3 mixtures with different amount of the pozzolana. The basic physical properties, mechanical properties and frost resistance were determined. The water /cement coefficient was decided to be taken according to the consistence of the mortar. The mixtures were designed with respect to their application as screed. The properties of developed low-cost pozzolanic screed exceeds the reference material.

Abstract: The moisture resistance of the ternary gypsum-based materials with metakaolin was investigated. Materials with metakaolin have lower porosity and higher strength than gypsum-lime binder without metakaolin. While material without metakaolin lost compressive strength in the wet environment, the strength of the ternary binders increased. Therefore it can be concluded that the gypsum – lime mixtures with the metakaolin can be used in the environment with higher humidity, e.g. in the exterior.

Abstract: Exterior renders are protecting the load bearing parts of building constructions against the negative action of surrounding environment such is freezing-thawing action, crystallization of salts in pore system of material, biocorrosion etc. Thus sufficient mechanical properties, namely bending strength and adhesion to load bearing material’s surface, as well as durability properties are required. The paper deals with durability parameters of lime plasters modified by pozzolana and small amount of Portland cement. Such modification provided reduction of rate of liquid water transport what is promising with respect to freezing-thawing resistance of render. The water vapour diffusion coefficient was influenced just moderately.

Abstract: An application of a transient method for investigation of water vapour permeability of autoclaved aerated concrete is presented in the paper. Relative humidity profiles along the longitudinal axis of the rod shaped sample are measured using a transient arrangement of a diffusion experiment. Using an inverse analysis of experimentally accessed relative humidity profiles, water vapour permeability of studied material is calculated as function of relative humidity. In the inverse analysis, the Boltzmann-Matano treatment is used as the most straightforward way to the solution of inverse problems to parabolic water vapour diffusion equation.

Abstract: In this paper, sandstones from particular quarries are studied using pressure plate method and a water vapour adsorption device. Firstly, basic material properties are examined. Moisture storage parameters for hygroscopic and over-hygroscopic moisture transport are determined using desorption isotherms and water retention curves. Using Kelvin equation, the combined desorption isotherms and retention curves are presented in a full range of relative humidity (0 – 100 %). Resulting combined isotherms of tested sandstones show the tendency of moisture storage properties in relation to the porosity of the materials. The measured data gives the information on material desorption capacity when exposed to the water vapour pressure.

Abstract: Pozzolanic materials and their usage in concrete production are nowadays widely spread. Their application as additives is inherent especially for the purpose of high strength concrete. This article deals with evaluation and comparison of the influence of two different supplementary cementitious materials on the properties of high strength concrete: natural pozzolana (NP) and finely crushed brick (FCB). The studied characteristics are basic physical properties with connection to mechanical parameters, and next to this, characterization of water transport. In the scope of this study results revealed better pertinence of finely crushed brick, as the appropriate replacement of cement was found out to be up to 30%, whilst for natural pozzolana only 10% of cement substitution is favourable. The open porosity as the first indicator of both mechanical and water transport properties appeared to be lower in all studied mixtures with FCB than in the case of NP. With increasing ratio of the additive to cement there is significant worsening of mechanical and water transport parameters when NP is involved. The behaviour of mixtures with FCB is better even when high amount of cement is substituted.