Mineral Building Materials Research Articles

Differences between <i>A</i><i>. t</i><i>hiooxidans</i> and <i>A</i><i>. </i><i>ferrooxidans</i> Biofilms Formed on Concrete and Stoneware

Sulfur-oxidizing bacteria (SOB) of Acidithiobacillus genus, especially of A. thiooxidans and A.ferrooxidans species are considered as very aggressive biological factors that influences deterioration of many materials, including mineral building materials like concrete and stoneware. Biofilms formed by these bacteria play a significant role in microbiologically influenced corrosion (MIC) of various materials in conditions that ensure sufficient moisture. The aim of this work was to assess differences between A. thiooxidans and A. ferrooxidans biofilms formed on concrete and stoneware. Both strains were prone to form biofilms on concrete and stoneware. However, the type of mineral materials strongly influenced metabolic activities of the tested strains, thus providing to formation of biofilms displaying different features. The higher activities of cells were observed in biofilms of A.ferrooxidans bacteria. The higher total biomass attached to the material surface as well as concentration of proteins in liquid culture medium were observed in biofilms grown on concrete samples. The optimal time of biofilm growth on tested materials was 48 hours on concrete, and 72 hours on stoneware. Amongst materials tested, concrete samples were more susceptible to corrosion in the presence of A. thiooxidans and A. ferrooxidans bacteria.

Laboratory study of fungal bioreceptivity of different fractions of composite flooring tiles showing efflorescence

Fungi can grow in extreme habitats, such as natural stone and mineral building materials, sometimes causing deterioration. Efflorescence-concentrated salt deposits-results from water movement through building material; it can damage masonry materials and other bricks. Fungal isolate KUR1, capable of growth on, and dissolution of stone chips composing terrazzo-type floor tiles, was isolated from such tiles showing fiber-like crystalline efflorescence. The isolate's ribosomal DNA sequences were 100% identical to those of Nigrospora sphaerica. The ability of KUR1 to colonize and degrade the different stone chips composing the tiles was studied in axenic culture experiments. When exposed to each of the different mineral chip types composed of dolomite, calcite, or calcite-apatite mineral in low-nutrition medium, the fungus showed selective nutrient consumption, and different growth and stone mineral dissolution rates. Micromorphological examination of the fungus-colonized chips by electron microscopy showed the production of a fungal biofilm with thin films around the hyphae on the surface of the examined chips and disintegration of the calcite-apatite fraction. More than 70% dissolution of the introduced powdered (<1mm particle size) mineral was obtained within 10days of incubation for the soft calcite-apatite fraction.

Simulation of transport processes and chemical reactions in building materials

Usually the prediction of the lifetime of building materials is based on costly and time-consuming laboratory experiments. Numerical simulation of transport processes and the resulting chemical reactions in building materials is a versatile tool to estimate durability and corrosion processes of structures. Several studies exist on the characterization of reactions in porous building materials and the resulting deterioration [1]. Chemical reactions between corrosive media and mineral building materials take place on the material surface as well as in the pore volume. Thus the program TransReac combines two main modules: chemical reaction involving thermodynamics and kinetics and the transport of species into pores [1,2]. Using thermodynamic parameters of involved species and experimental determinated transport characteristics of the examined building materials, reactions depending on time and position were simulated. Gibbs energy, density and other thermodynamic parameters, e.g. heat capacity can be found in [3,4]. This database is proved successful in building material research. Different kind of chemical attack to mineral building material were simulated and verified by experimental data, e.g. corrosion caused by sulphate or ammonium solutions, acid and debonding of gypsum plaster [1,2]. The paper is concentrated on the dissolution of silica from aggregates in alkaline concrete pore solution at various temperatures, in regard to the simulation of the initial phase of alkali-silica-reaction of concrete.

Leaching standards for mineral recycling materials – A harmonized regulatory concept for the upcoming German Recycling Decree

In this contribution we give a first general overview of results of recent studies in Germany which focused on contaminant leaching from various materials and reactive solute transport in the unsaturated soil zone to identify the key factors for groundwater risk assessment. Based on these results we developed new and improved existing methods for groundwater risk assessment which are used to derive a new regulatory concept for the upcoming “Decree for the Requirements of the Use of Alternative Mineral Building Materials in Technical Constructions and for the Amendment of the Federal Soil Protection and Contaminated Sites Ordinance” of the German Federal Ministry of Environment. The new concept aims at a holistic and scientifically sound assessment of the use of mineral recycling materials (e.g., mineral waste, excavated soils, slag and ashes, recycling products, etc.) in technical constructions (e.g., road dams) and permanent applications (e.g., backfilling and landscaping) which is based on a mechanistic understanding of leaching and transport processes. Fundamental for risk assessment are leaching standards for the mineral recycling materials. For each application of mineral recycling materials specific maximum concentrations of a substance in the seepage water at the bottom of an application were calculated. Technical boundary conditions and policy conventions derived from the “German precautionary groundwater and soil protection policy” were accounted to prevent adverse environmental effects on the media soil and groundwater. This includes the concentration decline of highly soluble substances (e.g., chloride and sulphate), retardation or attenuation of solutes, accumulation of contaminants in sub-soils and the hydraulic properties of recycling materials used for specific applications. To decide whether the use of a mineral recycling material is possible in a specific application, the leaching qualities were evaluated based on column percolation tests with various samples and compared with application-specific maximum concentrations. In the upcoming federal decree this simplified concept is realized using detailed tables which classify the leaching quality of mineral recycling materials and demonstrate potential application. A quality assurance system will be mandatory which defines specific testing programs (material properties and limit concentrations to be tested, number and schedule of testing) for the different mineral recycling materials using standardized methods (column percolation test).

Variation in spectral shape of urban materials

Airborne Hyperspectral Scanner System (HSS) images of 2.7 m spatial resolution and laboratory/field spectroradiometric data were used for reflectance characterization of synthetic and mineral building materials in southeastern Brazil. An impervious surface image was generated from a five-endmember mixture model with the 37 reflective HSS bands to select sampling sites for creation of a spectral library. Principal component analysis was applied to this library and to the pixels identified as impervious surfaces in the HSS image to identify patterns of spectral response and potential discrimination of urban materials. For both aerial and laboratory/field data sets, PC1 showed high within-class brightness variation due to surface aging, degradation and painting as well as illumination-viewing effects. PC2 indicated an important spectral shape contrast between the near-infrared and the shortwave infrared, which has the potential for discriminating urban materials. When tested with the spectral angle mapper, which reduced the brightness influence on classification and allowed spectral shape comparison, near-infrared and shortwave infrared bands differentiated most of the impervious surfaces studied. Synthetic materials with spectra that declined in magnitude at longer wavelengths (e.g. polyvinyl chloride and painted surfaces) were discriminated from mineral materials with spectra that were flat (e.g. asphalt) or ascending (red tile). Despite having brightness that is distinct from steel and red tile roofs, aluminium was misclassified by spectral angle mapper into the two classes with ascending slope curves. The overall classification accuracy was 74%.

Investigations on the leaching behaviour of irrigated construction elements

In this paper, results regarding the leaching of trace elements out of mineral building materials under irrigation are presented. The leaching in the irrigation test is compared with the leaching under constant water exposure to determine the relevance of the irrigation scenario for the assessment of the environmental compatibility of mineral building materials.

A frost decay exposure index for porous, mineral building materials

The disintegrative process of freezing and thawing of porous, mineral materials represents a significant challenge in the design and construction of building enclosures. In this paper, we present a simple method for assessing the relative potential of a climate to accelerate frost decay based on multi-year records of daily air temperatures and rainfall, with special emphasis on masonry. Distributions of 4-day rainfall prior to days with freezing events provide quantitative information on the geographically dependant frost decay risk in porous, mineral building materials in a given climate. Data from 168 weather stations in Norway are analysed, using weather data from the reference 30-year period 1961–1990.

Characterization of Mineral Building Materials by Mercury‐Intrusion Porosimetry

AbstractMineral building materials are generally heterogeneous and porous solids. Their engineering properties are closely associated with their porosity and pore‐size distribution, which can be studied by mercury intrusion. The entire pore‐size distribution curves are used to determine changes in the pore structure of a material class in a qualitative way. Certain parameters derived from pore‐size distributions can be correlated to engineering properties. These key values are applied as criteria to evaluate the quality and durability of a building material. However, because of the heterogeneity of natural and artificial building materials and the influence of moisture content on their pore structure the results are strongly affected by preparation conditions such as sampling and drying. A correct analysis requires a knowledge of these effects. The paper describes the use of mercury porosimetry to study mineral building materials such as cementitious materials, bricks, and renderings. Furthermore, the influence of preparation effects on the precision of measurements is discussed.

High-performance weather-protective flashings

High-performance weather-protective flashings

Transreac: a model for the calculation of combined chemical reactions and transport processes and its extension to a probabilistic model

Transreac is a computer model for the simulation of the chemical attack to which mineral building materials are exposed. For reliability analysis, Transreac is used in conjunction with the Monte Carlo simulation method. The probabilistic model was evaluated for cement mortar corroded as a result of sulfate attack. The experimentally derived corrosion effects and their scatter are in good agreement with simulation results. In addition, the probability of failure was predicted and a sensitivity analysis was performed.

Einfluss der elektrochemischen Doppelschicht auf die Sorption und den Transport von Chlorionen im Zementstein / Influence of the electrochemical double layer on sorption and transport of chlorides in hardened cement paste

Abstract Besides the formation of Friedel salt the transport and binding of chlorides in concrete is mainly defined by the electrochemical double layer at the interface between cement matrix and pore solution. Due to the alkaline pore solution the surface of hardened cement paste is negatively charged which may change to positive values by the potential regulating calcium ions. Inverting of the surface charge leads to an attraction of anions and therefore, to an adsorption of chloride ions in the diffuse part of the electrochemical double layer. Influence from outside like sulphates and carbon dioxide may lead to a decomposition of Friedel salt. Apart from these effect temperature, pH-value and certain environmental conditions affects the electrochemical double layer as well. The chloride equilibrium is mainly controlled by adsorbed ions in the electrochemical double layer. The model presented here is relevant for the assessment of ion transport processes in mineral building materials. Continuing investigations may lead to optimize transport models and a better evaluation of the critical chloride threshold value in reinforced concrete.

A model for the calculation of combined chemical reactions and transport processes and its application to the corrosion of mineral-building materials Part II. Experimental verification

A model for the simulation of corrosion processes of mineral building materials is provided. The model combines the calculation of several transport processes with the quantitative simulation of the chemical reactions. The model was verified by experiments on the corrosion of cement mortar by sulfate solutions and acid, the corrosion of cement mortar and concrete in a seepage water treatment plant (ammonium attack), and the corrosion of a sandstone with calcitic binder by acidic solutions with and without sulfate content. The corresponding simulations were calculated using solely the properties of the uncorroded materials (experimentally determined or estimated by the literature). The comparison of the measured and calculated corrosion behaviour lead to the conclusion that the algorithm is able to simulate very different corrosion processes without any change of the model, despite some difficulty in detail.

A model for the calculation of combined chemical reactions and transport processes and its application to the corrosion of mineral-building materials: Part I. Simulation model

The numerical simulation of corrosion processes can be a valuable tool for the planning of durable structures exposed to chemical attack and for planning of their maintenance and repair. In this paper, a simulation model—incremental in time and space—of corrosion of mineral-building materials is described. The model combines the calculation of transport processes with the quantitative simulation of chemical reactions. The following transport processes are incorporated: capillary suction, diffusion of solved species (including the influence of the diffusion potential), water vapor diffusion, and diffusion of solved species through the inner surface of cracks. The reactions are simulated by the repeated calculation of the thermodynamic and kinetic stable phase assemblage. Due to the thermodynamic module, the simulation does not depend on the specific reaction. Additional modules are incorporated for the actualization of transport parameters and material strength as well as for the expansion in the case of sulphate attack.

Evaluation of mineral building materials: Problems related to resistivity methods

A study of the influence of fracture initiation on the resistivity of mineral building materials was preceded by an investigation into the electrical and electrochemical processes that could interfere with geo-electrical D/C measurements. The phenomena being discussed are the self potentials, the contact potentials, the polarization, diffusion and capillarity effects, the transition problems, and finally the leakage currents. Practical solutions developed for problems related to these phenomena are discussed in this paper.

Silicon-Microemulsions-Konzentrate / Silicone Microemulsion Concentrates

The technology of silicone microemulsion concentrates eliminates for the first time the use of organic solvents in the hydrophobic impregnation of mineral building materials and coatings, in coating-priming and in wall-drying by drill hole injection. Water-based silicone microemulsions meet the requirements such as effectiveness, durability, aplication, toxicity and ecology. The use of water instead of organic solvents and the modern concentrate technique make an effective contribution to environmental protection.

Recycling of demolition waste and its influence on the market of natural mineral building materials

Recycling of demolition waste and its influence on the market of natural mineral building materials