Martin Keppert

Properties of municipal solid waste incineration ashes with respect to their separation temperature

Fly ashes generated by power and heating plants are commonly used in the production of building materials in some countries, mainly as partial replacement of cement or aggregates in concrete. The ashes from municipal solid waste incinerators can be applied in a similar way. However, their chemical and mineralogical composition, granulometry and toxic constituents have to be taken into account. In this paper, four types of municipal solid waste incinerator (MSWI) ashes produced by the modern MSWI facility in Liberec, Czech Republic, were investigated. The relationship between the particular ash properties (morphology, chemical composition) and its separation temperature in the incinerator line is discussed. A coal fly ash (class F) is characterized as well, for a comparison because its utilization in building industry is more developed. The studied MSWI ashes exhibit high concentration of chlorides and sulfates which is an unfavourable feature for a potential concrete admixture. On the other hand, three of four ashes are found to be pozzolanic active and certain hydration reactions are indicated.

Time Progress of Compressive Strength of High Performance Concrete

Development in the field of concrete engineering is increasingly focused on the practical application of high performance concrete (HPC) or ultra-high performance concrete (UHPC) in construction practise. Newly developed kings of concrete are newly using in transport and building structures. The process of hydration of hydraulic binders based on Portland cement doesn ́t stop after 28 days, when the test of compressive strength take place, but it ́s a long time process that takes for many months. For design we use the values of strength of 28 days. This paper explorers how does the long-term development of compressive strength of HPC runs. The composition of HPC is significantly different from the common concrete lower strength classes. The question of the influence of additives, filler on microsilica based, silica flour to the time development of compressive strength is being explored in this paper. There is also recorded the influence of curing condition of the test specimens to the compressive strength. The age of testing samples starts at a very early ages 1, 3, 7, 21, 28, 45, 90 and 180 days. The strength in uniaxial compression was measured on cubes with dimension 100 mm.

Water transport parameters of autoclaved aerated concrete: Experimental assessment of different modeling approaches:

The water-permeability, moisture-diffusivity, and sorptivity concepts of modeling liquid water transport in porous building materials are analyzed. An overall assessment of the particular models is performed using the moisture profiles measured for two types of autoclaved aerated concrete. The water-permeability and moisture-diffusivity modeling approaches are found suitable from a point of view of accuracy of moisture-transport simulation but they have certain limitations. While the water-permeability concept is advisable for compact materials, the moisture-diffusivity concept should be preferred for materials with a high water penetration rate. Therefore, a combination of both these approaches in a single laboratory is beneficial. The sorptivity concept, on the other hand, can be recommended for a basic assessment of water transport capabilities of building materials only.

Characterization of Building Stones Involved in Historical Masonry

Basic physical properties, pore size distribution and hygric properties of several types of stones which are used in reconstructions of historical buildings on the territory of the Czech Republic, namely several types of sandstone and argillite, are investigated. Basic physical characteristics are measured using the water vacuum saturation method, pore distribution by mercury porosimetry. Values of water absorption coefficient and apparent moisture diffusivity are determined by methods utilizing the results of water sorptivity measurements. Water vapor transport properties are accessed by the cup method. The obtained data represents valuable information for the application of studied materials in reconstructions and renewal of historical buildings.

Identification of Water Diffusivity of Inorganic Porous Materials Using Evolutionary Algorithms

Two evolutionary algorithms are introduced as universal approaches for the identification of water transport characteristics of inorganic porous materials in both absorption and desorption phases. At first, genetic algorithm and genetic programming are applied for the inverse analysis of water content profiles measured in an absorption experiment. A comparison of results with the output of the commonly used Boltzmann–Matano approach shows that the calculated diffusivities can reproduce experimental data with a similarly good or even slightly better accuracy. In the second part of investigations, a water desorption experiment is realized for autoclaved aerated concrete, a typical representative of inorganic porous materials used in the construction sector. The genetic algorithm and genetic programming exhibit an excellent performance also in this case. Both approaches can thus be considered as viable, more universal alternatives to the traditional methods.

Wet-Treated MSWI Fly Ash Used as Supplementary Cementitious Material

Municipal solid waste incineration (MSWI) is a common technique in treatment of domestic waste. This technique annually produces approximately 25 Mt solid residues (i.e., bottom and fly ash) worldwide which is also a major issue in current research. In this research we are concerned with reusing the fly ash (FA) as supplementary cementitious material (SCM) in concrete. Such application solves the problem with heavy metal immobilization as well. To remove the high content of undesired soluble salts, number of washing treatments has been applied. Chemical composition of FA has been examined before and after treatments. The impact of cement substitution by FA in concrete was evaluated by measurement of its compressive strength and durability.

Mechanical, hygric and thermal properties of building stones

Basic physical properties, pore distribution, mechanical, hygric, and thermal properties of several types of building stones which were used in historical buildings on the Czech territory in medieval times, namely several types of sandstone and argillite, are investigated. Bulk density, matrix density and open porosity are measured using the water vacuum saturation method, pore distribution by mercury porosimetry, compressive and bending strength by a hydraulic testing device. Apparent moisture diffusivity is determined by utilizing the results of water sorptivity measurements, the dependence of moisture diffusivity on moisture content is obtained by measuring moisture profiles using a capacitance technique and subsequent solution of the inverse problem of moisture diffusion. Water vapor diffusion permeability is measured by the cup method, sorption isotherms are determined by the desiccator method. Thermal conductivity and specific heat capacity are measured by an impulse technique in the moisture range from the dry state to full water saturation.

The properties of innovated mortars utilizing secondary raw material

This paper studied lime mortars containing waste brick powder. The powder originates from grinding of thermal insulating bricks. The aim of the study is to find out appropriate application of this secondary raw material. For this purpose we tried to replace silica sand by the brick powder in different quantities (10%, 30% and 50% of weight). An influence of the brick powder replacement is determined through the properties of special mortars, which were compared with a pure lime mortar (with no powder replacement). Specifically in this article experimental methods and results of basic physical properties, pore structure characterization, mechanical properties and hydric transport abilities (water vapour as well as liquid water transport) are described.

Basic Physical and Mechanical Properties of Composites Based on Three Different Cements

This article is focused on cement based composites. Two cements differing in mineralogical composition are utilised as main binder in composites mixtures. Results of measured physical parameters of studied materials are presented. For the sake of comparison, a reference material with Portland cement was also prepared. Basic physical properties (measured by water vacuum saturation method and by helium pycnometry), characterizations of pore system (determined by mercury porosimetry) and mechanical properties are the matter of this study. Composites show various open porosity; the results of open porosity of materials containing special cements show higher values, in comparison with composite based on Portland cement. This fact of course influences other material characteristics - mainly mechanical properties.

Monitoring of Kinetics of Pozzolanic Reaction

The pozzolanic additions are widely used as concrete component for numerous technical, economic and environmental reasons. Obviously the hydration process in a pozzolana containing system differs from hydration of Ordinary Portland Cement (OPC) what is indicated macroscopically by slower increase of strength and lower hydration heat. This paper aims to study pozzolanic reaction from perspective of chemical kinetics. From this point of view pozzolanic reaction and carbonation are two parallel reactions which are competing for portlandite (Ca (OH)2). The rate of each of these two reactions is characterized by rate constant and order of reaction. The system under study was 1:1 mixture lime – ceramic powder. The course of reaction was primarily studied by thermogravimetry which results were further subjected to kinetic analysis. MAS NMR spectroscopy was used for study of structural changes taking place in material in the course of pozzolanic reaction.