Abstract: In laboratory conditions, the effect of minor oxides – MgO and SO3 on formation of Portland cement clinker was observed. The research extended the current knowledge about the effect of these oxides on phase composition and structure of clinker and on alite polymorphism. Mainly means of optical and electron microscopy were used for the research.
Abstract: Polymer cement matrix based materials were designed within the frame of the research presented in this paper. Resistance of these materials to combination of several adverse factors was observed. Considerable proportion of input materials used were components from alternative material resources. Primary binder was replaced with fly ash and blast furnace slag. Dominant proportion of filling mass was taken up by agloporite – porous aggregate produced by self-baking from fly ash. The focus of the research was assessment of degradation of materials after long-term exposition (up to 90 days) to increased concentration of sulphate ions and high temperatures. Degree of degradation was evaluated on the basis of physico-mechanical and physico-chemical tests combined with microstructural analyses.
Abstract: The paper deals with a comprehensive analysis of the influence of applied crystallization additives on the service life of self-compacting concrete (SCC), specifically when exposed to the effects of chemically aggressive environments. Attention is focused not only on the influence of a crystallization additive on the characteristics of the capillary porous structure of SCC, but mainly on its effects in terms of the long-term service life of self-compacting concrete. The effects of individual types of aggressive environments are evaluated on the basis of a set of physico-mechanical and physico-chemical analyses.
Abstract: Fluidized bed ash, which is the youngest industrial waste can be considered on the basis of research, a high-quality secondary raw material base which can be easily used in the production of Portland cements and, in general, other hydraulic binders. Regarding the direct effect of anhydrite on the course of hydrating mixed cement with the fluidized fly ash and the consequent behaviour of the originated cement stone, its reaction with clinker materials on the mentioned Aft (Al2O3–Fe2O3-–tri) phase is clear. The creation of AFt phases, if they originate additionally, due to their morphology, is accompanied by significant volume changes which may lead to deformation up to the destruction of the cement stone. Some foreign publications show the possibility of the transformation of this thermo-dynamically unstable mineral into the further mineral from the group AFt phase, which is thaumasite, Ca3Si (CO3)(SO4)(OH)6.12H2O.
Abstract: This investigation was made to examine how the particle size of lime influence the properties of calcium hydrosilicate materials. Quicklime was sorted in three fractions: 0-1 mm, 1-11.2 mm and 11.2.-22.4 mm. Slaked lime putties were prepared in the laboratory by mixing lime fractions and deionized water under vigorous stirring. The C/H ratio was 1:8. The lime putties were mixed with finely ground sand with the C/S ratio equal to 0.85. The hydrosilicate materials were prepared under hydrothermal conditions: temperature 205 °C, pressure 16 bar. This work focuses on lime putty rheological behaviour and on composition and properties of lime hydrosilicates. It was found that hydrated particles of fractionated lime form smaller aggregates than standard lime. Plasticity increases with the increasing size of fraction. When separate fractions are used, 11.3 Å tobermorite crystallization is slower.
Abstract: In the current restoration practice, the mortars based on aerial or hydraulic lime with siliceous aggregate are used on repair / reconstruction of historical plasters. The resulting properties of lime mortars do not depend only on the type of aggregate, but also on its contamination, origin and a degree of hardening. For this reason, it is needed to know a detailed characteristic of the aggregate and the results obtained for the particular aggregate cannot be generally applied for the similar type of aggregate. This work presents the applicability of Czech local crushed limestone aggregate and limestone fines as a filler to natural hydraulic lime-based mortars. The role of aggregate and limestone fines on the properties of mortars is examined by comparing the mechanical strengths, porosity and frost resistance of the mortars with pure quartz sand and limestone aggregate and its quantity in the mortar. It was found that the limestone aggregate has produced lower strengths, higher total porosity of natural hydraulic lime-based mortars. It has resulted in low frost resistance of the mortars.
Abstract: Application of various pozzolanic materials is the current approach to obtain suitable environmental, economic and durability parameters of composites, in which they are used. Considerable interest is focused on the possibilities of finely ground ceramic powder (CP) exhibiting pozzolanic activity. Present paper is aimed at the experimental study on the monitoring of reaction kinetics in lime-ceramic powder system (1:1). Ceramic powders with controlled grading were used. Reaction capacity was assessed in time by means of thermogravimetry. The dominant effect of the finest fractions (up to 0.030 mm) on the pozzolanic reaction was proved; coarser fractions of used CP exhibited approximately the half reaction efficiency after 28 days of curing.
Abstract: Limestone as a natural rock tends to have various parameters. Variation in parameters, as well as firing temperature have significant impact on key properties of quicklime. Sedimentation volume and reactivity determine quality of quicklime in building industry. This paper is focused on monitoring the reactivity and sedimentation volume of quicklime prepared from various types of limestone at different temperatures. Selection of limestones with high purity collected from various quarries around the world were characterized by porosity, chemical and petrographic composition. To create quicklime, these samples were fired at 4 different temperatures. Reactivity measurements were made on quicklime with specific particle size. Sedimentation volume of hydrated slurry was determined. Obtained results suggest that there is tendency for slower reactivity and smaller sedimentation volume with increased firing temperature.
Abstract: Pozzolanic additives are widely applied as components of cementitious composites as well as mortars based on white lime. They are generally recognized as components improving the durability of resulting material – concrete or mortar. The mechanism responsible for this favorable effect lies in physical and chemical modification of initial binding system. The present paper deals with influence of a pozzolanic additive – ceramic dust (CD) – on pore system of lime – based mortar. The CD was characterized by means of elementary and phase analysis. The range of mortars of varying CD/lime ratio was prepared; their pore size distribution, strength and rate of liquid water and water vapor were determined. The presence of CD caused change in the pore size distribution while the total porosity did not changed significantly. The volume of large pores was reduced and amount of fine pores was increased as consequence of growing CD content. It had positive effect on rate of liquid water transport. Diffusion resistance factor was influenced by the presence of CD towards the lower values; in opposite to the liquid sorptivity the diffusion resistance was controlled by the total porosity. The strength was improved by addition of pozzolanic additive as could be expected. It is in accordance with the reduced volume of capillary pores but obviously the presence of pozzolanic additive in lime converts the binding system to hydraulic and thus the effect of CD on strength cannot be explained just by its influence on pore size distribution.