Abstract: The cement hydration is an exothermic reaction. The hydration heat is characterizing quantitatively the clinker hydration degree. Monitoring its time response makes it possible to determine not only the heat released during a certain time interval but also the concrete mix setting onset, the cement hydration degree (when evaluating the cement applicability after a long storage period) etc. The measurement of the hydration heat or the temperature versus time plot for a hydrating mix makes it possible to identify the effect of the different additives and admixtures on the mix hydration kinetics. This paper deals with the effect of adding two different super-plasticizers (lignin-sulphonate-based and naphthalene-sulphonate-based) on the hydration heat development progress. A set of iso-peribolic calorimeters was used to measure the hydration heat development process. The measurement proper consisted in monitoring and recording the temperature versus time plot for the specimen under test. The released heat amount was determined by calculation from the temperature gradient, the ambience specific thermal losses, the material thermal capacity and the test specimen mass.
Abstract: The use of rapidly renewable raw materials in the building industry is seen as very promising with regard not only to the environmental issues but also to its economic aspects. A number of producers, not only in this country, have been trying to replace fine construction materials with secondary raw materials or rapidly renewable ones. As an example, technical hemp is a very promising material due to its good mechanical and thermal insulation characteristics. One of the possibilities is its use as filling component for non-constructional filling materials.
Combining binders on the basis of non-hydraulic lime with hemp chaff yields a range of new construction materials. These products offer excellent work characteristics for permanent, environmentally sustainable buildings. These products as a whole form a natural composite construction material that can be used to build insulation walls, floor and roof insulation layers, and to obtain excellent heat and acoustic characteristics of buildings.
Abstract: In the last years we have to think about the question of emission reduction. One of the biggest producer of these emission is industry, where the cement industry comes under it. The effort of cement-workers and other manufacturers of building materials is the reduction of harmful oxides in our air, including CO2, which is one of a group of unfavourable oxides.This paper deals with the study possibility of partial compensation limestone by FBC-ash. The expected effect is the reduction of CO2 emissions and saving limestone. Following the previous stage of the research a recipes were designed for Portland clinker burning limestone-based and FBC ash, it was carried out laboratory burning and on produced cements were made basic technological tests.
Abstract: The characterization of historic lime mortars is crucial for many cultural heritage conservation issues. In this work, the characterization of a historical lime mortar is described. Samples for chemical analysis were obtained after different milling times and using the RILEM acid digestion method on several replicates. Qualitative and quantitative determination of phases in the mortar and in the residues after acid attack and the potential presence of CaCO3 polymorphs, were accomplished with X-ray powder diffraction. Results suggest that representativeness of the sample and the homogenisation, although not always achievable in conservation practice, are strongly affecting results.
Abstract: Non-destructive acoustic analysis method Impact-echo method as a traditional for civil engineering was used for experiment. This paper reports the experiment during hardening and drying of specimens of alkali activated slag mortars. Alkali activated slag is a material having a great potential to be used in practice. The main drawback of this material is a high level of autogenous and especially drying shrinkage, which causes a deterioration of the mechanical properties. The aim of this paper is introduce the effect of method curing of mortars and time curing on the microstructure of alkali activated slag mortars. An understanding of microstructure performance relationships is the key to true understanding of material behaviours.
Abstract: Alkali-activated slag (AAS) is a material which has great potential for use in building industry. However, its major disadvantage is an increased shrinkage followed by formation of microcracks. The aim of this work was to investigate the influence of carbon nanotubes and hydroxypropyl methylcellulose on the mechanical properties and cracking tendency of alkali-activated slag material. The results showed that both admixtures have a positive effect on compressive as well as flexural strength. Impact-echo measurement revealed that both admixtures reduce cracking tendency and can retain water in the binder.
Abstract: Increasing energy prices, along with escalating demands for thermal insulation properties of enclosure structures, force the owners of buildings to reduce the operating costs of heating. That is why the question of reducing the energy consumption of buildings, also including the category of historical buildings , has been gaining ground. The reduction of energy consumption of these buildings is often accompanied by the requirement to eliminate moisture problems of base structures caused by leaking or broken waterproofing of the bottom part of the object. The subsequent increase of the thermal resistance of the building envelope must be performed by means of special insulation materials allowing the drainage of liquid water from the structure. The paper presents the properties and the influence of the developed materials on the course of built-in moisture in the base structure affected by this phenomenon using Delphin simulation software, based on the measured thermal and technical parameters. The developed material is a composition of pozzolan binder, foaming agent and waste resulting from the production of cellular concrete blocks. According to tests carried out in , it is possible to produce concretes with sufficient strengths for rehabilitation boards when you substitute natural aggregates with waste aluminosilicate and, according to [2, 3, 4, 5, 6], you will achieve better rehabilitation and thermal insulation properties by using porous filler. The developed material is intended for the so-called soft rehabilitation, and its function is specifically presented on a structure built from sandstone blocks. This type of structures can be found in north Bohemia and the application of rehabilitation work must be very carefully considered, because quick drying of built-in moisture in masonry, for instance by means of cutting the lower part of the structure and by inserting waterproofing, will cause shape changes of the structure accompanied by the formation of cracks.
Abstract: Hybrid alkali activated cements based on fly ashes because of their structure and characteristics of phase composition are able to be used in different materials with the unique service properties. The paper is enclosing some specific features of hybrid fly ash alkali activated cement mix design and structure formation in order to achieve materials for different applications.
Abstract: The paper discusses approaches to compositional build-up of high strength alkali activated cements made using water glass as alkaline activator represented by commercial products in a form of powder and liquid. The purpose was to study the influence of fineness of ground granulated blast-furnace slags, admixtures and additives, compatible with alkali activated cements, water glass and mode of manufacturing technology in order to reach high compressive strength (≥ 80 MPa at standard age (28 days)) and early strength (≥ 20 MPa after 3 h of hardening in normal conditions).