Table of contents

All the world as well as our conference faced to the pandemic in 2020. Therefore, the 23^rd International Conference on Building Materials, Products and Technologies (ICBMPT 2020) had to be postponed from the usual date in June to the new date 22^nd to 24^th September 2020.

The participants appreciated our choice to organize the conference again in the beautiful town of Telč in the Czech Republic, which is popular with many tourists, because it belongs to the cultural heritage under protection of UNECSCO.

List of Scientific committee, Editors are availble in this pdf.

All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

• Type of peer review: Single-blind

Single-anonymous: authors' identities are known to the reviewers, reviewers' identities are hidden from authors

Double-anonymous: author and reviewer identities are hidden to each other

Triple-blind: author and reviewer identities are hidden to each other, and from the Editor(s)

Open: author and reviewer identities are known to each other

• Describe criteria used by Reviewers when accepting/declining papers. Was there the opportunity to resubmit articles after revisions?

• scientific quality

• style and organization

• appropriate level of English

• good level of figures and tables

• adequate references and discussion to related work

There was the opportunity to resubmit an article after minor as well as major revisions.

• Conference submission management system:

Each article undergoes assessment by the given editor and then it is sent to 2 or 3 reviewers. According their reviews and recommendations the paper is sent back to the author for revisions. The final approvement of the paper is done by the editor.

• Number of submissions received: 30

• Number of submissions sent for review: 26

• Number of submissions accepted: 26

• Acceptance Rate (Number of Submissions Accepted / Number of Submissions Received X 100): 26/30*100=86,67

• Average number of reviews per paper: 2,8

• Total number of reviewers involved: 58

• Any additional info on review process (ie plagiarism check system):

Each article is checked by a plagiarism detection software (PlagScan).

• Contact person for queries:

Martin Nejedlík, Research Institute for Building Materials, e-mail: conference@vustah.cz

The role of various SCM's on rheology of fresh sprayed mortar was studied. The mix design was inspired by recent trends in SCM's with use of ground limestone, calcined clays and natural pozzolanas. New formulations were correlated to commonly used SCM's like blastfurnace slag and fly ash. Sprayed mortar designed mostly for thin profile coatings is demanding material in terms of rheology requiring good adhesion, pumpability, shootability, stability after spraying, low segregation and minimum rebound. Particle packing model was used for sprayed mortar mix design. Time and shear rate dependent rheological parameters were calculated using conventional models to describe the properties of fresh sprayed mortars. A procedure for determining the segregation of the mortar using a rheometer was proposed.

The objective of this work is the optimization of the synthesis of β-belite cement. Belite cement (dicalcium silicate) is a promising material due to a lower CO₂ emission and lower energy consumption during its production. Cement with a high content of β-belite was prepared from ground limestone, amorphous silica and alkaline silicate solution. The raw materials were mixed, the mixtures were compacted and then burnt in an electric furnace. Different CaO/SiO₂ ratios, firing temperatures, raw materials and firing time were tested. The samples were characterized by XRD, SEM and free lime content. Differences between the cements with high content of β-belite prepared on a laboratory scale (tens of grams) and on a larger scale (tens of kilograms) were studied. Belite cement prepared on a larger scale had better properties compared to a laboratory scale. Optimal synthesis of β-belite cement consisted of mixing ground limestone, silica fume and liquid potassium silicate and burning at temperature 1100°C for more than 2 hours.

The interfacial transition zone in concrete with ordinary Portland cement (OPC) and concrete containing OPC and doped with 20% of limestone powder and 30% of metakaolin was studied by Raman spectroscopy - optical profilometry and cluster analysis. Mechanical properties, including strength characteristics and absorbability were tested after 28 days of curing. Concrete with ordinary Portland cement has lower density and absorbability and higher compressive and tensile strength than concrete with limestone powder and metakaolin. It has been found that a large amount of portlandite is formed in the interfacial transition zone in concrete with ordinary Portland cement. In concrete with the addition of metakaolin and limestone powder, the thickness of the interfacial transition zone is reduced, less portlandite is produced, but a thin layer of calcite is formed around quartz grains. This results in lower concrete strength in the area of the interfacial transition zone.

Metals and metal containing compounds have significant effect on cement hydration mechanism and kinetics. The recycling of waste materials leads to increase of content of metals in various industrial products and visibly affects properties of the Portland cement. One of the metals that has been known to drastically increase the setting time is zinc. Zinc forms various hydroxyl species with calcium cations. Pore solution thus has lowered concentration of calcium which suppresses formation of portlandite. Due to insufficient concentration of calcium the formation of CSH gel and further hydration of clinker grains is inhibited The aim of this study is to quantify the negative effects of zinc at different concentrations at ambient temperature at 20°C. Isoperibolic calorimetry was used to measure the negative effects of zinc on hydration kinetics of ordinary Portland cement. Zinc was added to the cement in the form of two soluble salts Zn(NO₃)₂ hydrate, ZnCl₂ and a poorly soluble compound ZnO. The concentration of zinc added was chosen between 0.1 and 1 wt. % of clinker. Significant retardation of cement hydration with increasing zinc content was proven.

The work deals with the impact of crushed brick on properties of Portland cement binder. The source of brick recycled materials is not only the demolition waste, but also the waste from brick production. One way to reduce the amount of this recyclate is to use it in cement-based composite. The advantages of using bricks as aggregate are their lower bulk density compared to conventional aggregates. Economic and ecological benefits are also important, because less natural sources need to be mined. First, the phase composition of used brick aggregate, its particle size and morphology were analysed. Test specimens with different content of brick recyclate were prepared and tested for the mechanical properties. Subsequently, the microstructure of prepared samples was examined using a scanning electron microscope. The phase composition of samples was analysed by X-ray diffraction analysis.

External renders are an essential part of the architecture of the first half of the 20th century. The aesthetic effect of such plasterwork was achieved by surface treatment, colouring or by using various filler components that acted with their colour or structure. The binder of the plasters was most often Portland cement which played an important role in the processing of plasters or surface finishes, and in addition, formed the functional properties of the plasters (hardness, durability, resistance to external conditions).

This paper summarizes the results of a survey focused on the characterization of components used for the creation of external rendering taken from several architecturally significant buildings in the city of Brno dating back to the first half of the 20th century (villas, apartment buildings, public apartment houses). The survey into the collected samples performed by means of petrographic (light polarizing microscopy) and phase (powder X-ray diffraction) analysis revealed interesting information concerning the wide range of materials (components) used and the craftsmanship involved in their processing, all of which fundamentally influence the art-craft and utility properties of the buildings. The information gathered can serve as an important source of information for the renovation of early 20th century architecture.

The article deals with the classification of fillers according to the type and method of rock processing and their use as a partial cement replacement in the concrete mixture. The aim is to better classify fillers by their origin, maximise their usability and design a concrete mixture with effective use of filler as a cement replacement.

The article compares the fillers that originated from natural stone. The research is focused primarily on the granite filler, as it is not currently explored in detail. As the results of existing research differ, tests of the filler and its effect on the compressive strength of cement composites were performed, for better characterization of the effect of filler pozzolanic activity. The results of the tests are compared with each other, and the probable causes of differences in the individual research results are described.

Fiber reinforced polymer (FRP) rebars have increasing popularity in the construction industry all around the world although steel rebars are widely used for reinforcing of the concrete so far. FRP bars, which have higher tensile strength compared to steel rebars with the same nominal diameter under normal conditions, are composed of resin matrix and fibers. In this paper, the load-bearing capacity of FRP reinforced concrete after elevated temperature exposition are present. The results are compared with concrete sample with steel reinforcement. Commercially produced glass FRP (GFRP) and carbon FRP (CFRP) rebars with sand coatings surface treatments were implemented in concrete beam and subjected to four-point bending load. The residual flexural strength of reinforced concrete after heating to 1000°C was obtained and evaluated and compared to results of non-heated elements. The results indicate that fire resistance of FRP reinforced beams can reach at least 60 minutes according the standard ČSN EN 13501-2.

Gypsum is one of the most environmentally friendly building materials and therefore its importance increases nowadays. Since the gypsum is mostly used in the form of the paste, the influence of aggregates on properties of gypsum mortars is not investigated very often. The article deals with the structure and properties of gypsum mortars with two different aggregates (silica sand and basalt). It was found, that even if the chemical composition and shape of particles of both aggregates differs significantly, the structure and properties of gypsum mortars with both types of aggregates are similar and the properties of the gypsum composite depends more on the aggregate granulometry and the quality of its surface. The aggregate with rougher surface of particles has more distinct interfacial transition zone, higher porosity and higher compressive strength.

This article deals with HPC (High Performance composite) materials whose main advantages are increased mechanical properties, durability and stability. The limiting parameter for such materials is the presence of air bubbles that cannot be removed just by the compacting. Mixing of cement mixtures under reduced pressure can be used to reduce porosity and eliminate the presence of air bubbles. Moreover, it is associated by the improvement of the mechanical properties. The influence of preparation of HPC by mixing under the atmospheric pressure and by mixing under reduced pressure to parameters like mechanical properties, porosity, microstructure was studied in this paper. The porosity of the samples was analysed in a cross-section using an optical method. The effect of the reduced pressure on the resulting strength of the samples was observed.

Foam glass is currently a material produced from waste glass that cannot be used in the glass industry. Therefore, it is currently made from secondary raw materials obtained by recycling unusable waste glass. Due to the large proportion of closed pores in the material structure, the foam glass achieves excellent thermal insulation properties and limited water absorption. The porous structure of the glass is relatively regular, and the pores predominantly have a round character; therefore, the foam glass exhibits very good mechanical properties at a low density. Foam glass in the form of aggregate represents an interesting raw material from which it is possible to produce various types of light composites with a very good ratio of thermal insulation and mechanical properties. The contribution describes the results of research in the field of the development of ultra-lightweight aggregate concretes with subsequent use for producing prefabricated thermal insulating masonry elements for the construction of energy efficient buildings.

The aim of the presented work was evaluation of an effect of various conditions on the performance of two developed concretes based on alkali-activated slag and cement kiln by-pass dust (BD). BD was used as a partial replacement of natural aggregates while slag as an aluminosilicate precursor activated by a combination of waterglass and sodium hydroxide solution (resulting silicate modulus of 0.5). The concretes differed only in an activator dose which was 4 and 6% of Na₂O with respect to the slag weight. The prepared specimens were sealed-cured for the first 28 days and then their resistance to freeze-thaw cycles and aggressive solutions (ammonium nitrate, acetic acid and sulphates) was tested. Evolution of dynamic modulus showed that both concretes resisted well to freeze-thaw cycles as well as to most solutions, where their dynamic modulus tended to increase in most cases or did not change significantly. Only the concrete with 4% Na₂O showed poor resistance to acetic acid solution as the specimens completely disintegrated until 50 days.

In this work the influence of alkaline activator on immobilization of lead and copper in alkali-activated blast furnace slag was investigated. A total of five alkali activators were used; sodium waterglass, potassium waterglass, sodium hydroxide, potassium hydroxide and sodium carbonate. The leaching test according to ČSN EN 12457°-4 was used to evaluate the level of immobilization of heavy metals, the leached solutions were analyzed by ICP-OES. For a better understanding of immobilization process, the selected samples were characterized by analytical methods (SEM, XPS). It was found that the degree of immobilization of Pb²⁺ and Cu²⁺ in AAS was very high regardless of the type of alkaline activator used. The high degree of immobilization is caused by formation of insoluble or poorly soluble lead and copper compounds in an alkaline environment while the insoluble compounds have been confirmed by SEM and XPS.

The term calcium-silicate composite can be recalled several basic building materials. The most common representatives are lime-silicate bricks and autoclaved aerated concrete. It is any material based on the reaction of lime and siliceous raw material. In this paper, attention is paid to composites based on autoclaved aerated concrete production technology. Possibilities of lightening the composite utilizing waste expanded perlite as a secondary raw material were investigated without the use of aluminium powder, which is commonly used in aerated concrete technology. Replacements of 10%, 30%, 50%, and 100% waste expanded perlite for sand were used. Based on physico-mechanical properties, and with the assessment of the microstructure, it has been found that up to 50% of the replacement of waste expanded perlite results in a lightening of the composite while increasing the compressive strength.

This paper assesses the feasibility of using flue dust, which is a residue from metakaolin manufacturing in a rotary kiln as a raw material for production of alkali-activated materials. This material contains besides metakaolin also residues of clays, and mullite. Metakaolin and blast furnace slag were used as initial materials. Flue dust was used for the replacement of initial materials up to 100%. Mortars were prepared for the determination of compressive strength by adding sand at the weight ratio of 1:1. As an alkaline activator was used potassium water glass and s/w ratio was 1.25. The prepared samples were tested for physical-mechanical properties after 28, 56, 90 and 180 days. Setting time and leaching characteristic were also evaluated.

The application of renewable and waste materials for the production of building materials is currently one of the main trends, especially with regard to environmental aspects. This is a reduction in the volume of materials that could be a waste and at the same time a reduction in the cost (including carbon footprint) for special wood treatment products that would have to be produced. One example given in this article is the possible application of a mineralization of wood matrix by kiln dust produced in a cement plant. This treatment can be primarily used in the production of wood-based panels bonded with cement, whose main purpose is to limit the leaching of soluble components, which affect the setting of the cement. If the cement kiln dust is applied for the mineralization of wooden elements, the flammability of wood can be positively influenced. Bypass cement kiln dusts contain significant amount of chloride, which in this case function as a reducing agent. In this article, the effect of the wood mineralization by the cement kiln dust from CEMMAC a.s. Horné Srnie was investigated on thermal degradation of wood by a simultaneous thermal analysis TG / DSC.

The aim of the research is a development of a new energy effective roof system, fulfilling a function of a roof covering as well as solar active element, reducing energy performance of buildings. There were designed and tested energy active roof elements, consisted of glass-fibre-reinforced-concrete carrier with integrated photovoltaic and heat-exchange layer, which ensures cooling of photovoltaic elements as well as enables a transfer of excessive thermal energy into a storage tank for a later use. The effort of project solvers is to achieve entirely new economic efficient using solar energy by means of energy active roof covering. Current research and tests proved, that there is a possibility to create such a system using present materials and technological solutions. However, for the successful realization it is necessary to solve further technological aspects, namely mutual connection of the roof elements and prove load-bearing capacity and fire resistance of the designed system.

Monolithic as well as precast Portland Cement Concrete pavement have shown a gradual increase in quantity and severity of defects and failures in recent years. Especially, the radical increase in the auto-destructive deterioration of the concrete structure, which is most often described as the expansion reaction, is alarming. The consequences may lead to extreme reduction of the lifetime of concrete on loaded or unloaded surface courses. The main causes are due to the combined effect of environmental effects (climate, chemical pollution), drainage of roads and the behaviour of the existing cement binders, provided that we do not reflect the modification of pavement structure layers. Only the impact of climate effects can be effectively reduced on the existing roads. The paper presents a summary of results obtained from the current portfolio of secondary concrete protection products. The testing was performed in terms of resistance to water infiltration and durability against the common effects of freeze/thaw and salt. The results show a dependence or independence according to the material basis when exposed to secondary protection products. Oils, silicate emulsions and a group with other material bases, so called other products, behave quite differently.

This paper deals with the problematics of utilization of continuous hydrostatic weighing to monitor the volume changes in research of new building materials. The aim of this paper is to describe the abilities of continuous hydrostatic weighing and to present the capabilities and results of measurements made using this method. The volume changes in this paper were measured using the laboratory scales connected to computer. The volume changes were studied on the cement-based composites containing up to 40 wt.% of cement substitution by secondary raw material. The high temperature fly ash, packing glass, foundry sand and slag were used as the cement substitution. This research shows that the continuous hydrostatic weighing produces results comparable to other methods for volume change measuring. Therefore, this method can be used for volume change monitoring without using any economically demanding laboratory equipment.

Cement-containing as well as cement-free building materials are regarded as dielectrics. Therefore, electrically conducting admixtures are to be added to them in order to increase their electrical conductivity. Steel or carbon fibres, metal powder, graphite, carbon soot or carbon nanotubes are commonly used for this purpose. The conductivity increase offers new application options, such as sensor property materials, self-heated materials, or electromagnetic smog shielding materials. The specimens of the mixes to be studied were subjected to an electrical analysis carried out within the frequency range from 100 MHz to 3 GHz by means of an ZNC vector analyser and an SPEAG-made DAK-12 coaxial probe and, furthermore, a dedicated automatically measuring device operating within the frequency range from 40 Hz to 1 MHz. The frequency spectra of interest were measured on various copolymer specimens differing from each other by the content of graphite and carbon nanotubes. Higher content of these admixtures increases the electrical conductivity and the building materials thus become easier to measure by means of electromagnetic measuring methods.

Our entire planet is filled by communication routes, and as a result of the evolving information technologies, their numbers will continue to grow in the future. Demand for their reliability and hence the importance of protecting related technologies from all kinds of interference is increasing as well. Therefore, it is necessary to develop new materials in order to protect these routes against negative influences of the environment such as the atmospheric discharge. The main aim of the research is to develop and verify the properties of the cement composite that can be applied in systems of protection of building structures against lightning strike and overvoltage. The first step in the development of this material was the selection of suitable feedstocks, which by their presence in the newly developed material will increase its electrical conductivity respectively reduce its electrical impedance. For this purpose, a spectrum of potential raw materials with a high content of metals and organic carbon was chosen. By means of a suitably selected set of laboratory methods which consisted of determination of specific surface, impedance and total organic carbon content (TOC), materials with the most suitable properties were selected and their parameters determined also in a cement matrix. In order to realize this goal specimens with each conducive material as filler were created with incorporated copper electrodes. Impedance has been significantly reduced compared to the reference samples. The lowest values in the tens of ohms were obtained from samples containing carbon grit 0.5–4.0. This fact proves that the tested fillers can be used in order to produce electrically conductive cement composites.

For more accurate determination of specific activities of radionuclides by gamma spectrometry in materials, it is necessary to take into account two important factors. These are the effect of true coincidences and self-absorption of gamma radiation directly in the measured sample. The corrections for these factors are determined for the specific measurement geometry defined by the detector, the measuring vessel and their relative positions. Corrections are calculated by Monte Carlo simulation. The results show a significant effect of material bulk density on the correction values.

In some specific cases, the building structures can be exposed to extreme dynamic loads. Namely, it can be car crash, earthquake or the effect of explosion. For these cases, it is useful to know the dynamic mechanical properties of building materials. The paper presents two unique procedures for instrumented impact testing of building materials (concrete and sandstone). These tests may help in practice with selection of suitable materials for buildings and structures which may be threatened by dynamic effects of mechanical stresses. The method how to achieve a higher dynamic material stability is also presented.

Newly developed tile grouts are intended mainly for environment with strong chemical loading. For this reason, chemical resistance was one of the key parameters observed. The grout for cast basalt tile was polymer based, in particular with epoxide binder and it utilized solidified hazardous wastes as fillers. It is well-known that epoxide binder has high resistance to solutions of inorganic substances. However, it is easily degraded by organic compounds. This was taken into consideration when assessed aggressive environments and their concentrations were selected. Examined substances were 60% solution of sulfuric acid, vapors of this acid (at concentration 96%) and 10% solution of acetic acid. After exposition to action of these aggressive substances, first of all the visual changes were assessed, i.e. change of color, formation of blisters, cracks, flaking or change of sheen. Then influence on microstructure, changes of bulk density and strengths of materials were observed.