Table of contents

PREFACE

The 24th conference Construmat 2018, was held in Herlany, Slovakia on 13th – 15th of June 2018. The traditional meeting of academic departments working in the field of building material engineering, technology, and testing, was organised, this year, by the Department of Material Engineering, Institute of Environmental Engineering at the Faculty of Civil Engineering of the Technical University of Košice, Slovakia.

The Construmat 2018 offered an international platform for the dissemination of original research results, new ideas and discovered advances in the field of material engineering and related interdisciplinary topics. In addition, the valuable professional programme was extended by a social program including the interesting technical excursions.

List of Sponsors, Editors, Scientific Committee, Organising Committee and List of Reviewers are available in this Pdf.

List of Delegate list are available 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 proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

During restoration and maintenance of historical buildings, statues and sculptures are often neglected elements in the pre-construction condition surveys, especially in case they are not part of the supporting structure but only an ornamental and aesthetic complement of the architectural whole. The condition of a number of such artworks requires restoration or static assessment from the viewpoint of safety and durability. In the case of statues made of stone, artificial stone or concrete, an inseparable part of the pre-construction condition survey is determining the method of their reinforcement with steel elements, which is, considering the often complex spatial aspects of their surface, relatively complicated. The paper offers some possibilities of its solution on three examples. The diagnostic methods were proposed based on the authors' workplace's long-term experience with the diagnostics of reinforced concrete structures. During the past 10 years, about 1,000 such diagnostics have been performed. These experiences were subsequently experimentally applied to several historical sculptures with great success.

Many research teams currently deal with the issue of determining the distribution of steel fibres in the hardened steel fibre reinforced concrete, both in terms of fibre concentration, and in terms of homogeneity of fibre distribution in the concrete. The basic element in the development of new non-destructive methods is the development of new principles and devices on adequate test specimens, in which precise spacial distribution of fibres, including the orientation of individual fibres, would be quite evident. The paper presents two technologically completely different possibilitites of dealing with this issue. X-ray radiography is a traditional and long-established method, but in the field of construction, the authors' workplace is one of the few in the Czech Republic able to use it. The method of creating transparent specimens is completely unique, as it has been developed and is used only at the authors' workplace.

The requirement to reduce the nitrogen oxide emissions in the production of electricity and heat by combustion of mainly brown coal leads to the installation of NO_x reduction technologies. The presented paper focuses on a partial replacement of Portland cement with siliceous fly ash after denitrification by a selective non-catalytic reduction method (SNCR) where urgent urea or ammonia water solution is injected into the combustion chamber. As the third component of the ternary binder the limestone and/or recycled concrete powder was used. The activity index of compressive strengths and the workability of mortars were tested in accordance with EN 196-1.

The properties of alkaline activated brick dust mixed with different amounts of water glass with a silicate modulus (M) of 1.0 were studied in connection with the temperature of curing. The influence of the amount of alkaline solution and the temperature of curing on the microstructure and mechanical properties of hardened materials was studied. The flexural and compressive strengths of the hardened products, as well as their microstructure, were determined. Part of the samples was stored under laboratory conditions (20 °C) for 7 and 28 days, other set of samples was stored at 60 °C for 7 and 28 days. One set of samples was treated for 7 days at 60 °C and 21 days at 20 °C. The microstructure of the hardened products was studied by means of porosimetry and scanning electron microscopy.

The paper deals with process of manufacturing the fibre-cement materials and methods of testing their climatic performance. Basic raw materials for production fibre-cement sheets are cement, cellulose fibers, reinforcing fibers - polyvinyl alcohol (PVA) fibers, filler, additives and water. Production follows the modified Hatschek's technology. The paper described the most important tests for climatic performance: Freeze-thaw test and Heat rain test. The fibre-cement profiled sheets were tested. The Freeze-thaw test includes assessment of frost resistance, precipitated salts efflorescence on the face-side surface, peeling of the coating on the edges, peeling of the coating on the face-side surface, longitudinal cracks in the various locations on the face-side, transverse cracks in the various locations on the face-side, shape deformation, swelling water between the layers of coating and material delamination on the edges. The frost resistance RL for fibre-cement profiled sheets after 100 freeze-thaw cycles was 0.95, when min. RL = 0.70. The fibre-cement profiled sheets were tested to 50 heat-rain cycles. After 50 cycles, the samples were checked for cracking (longitudinal, transverse and at the fixing points), delamination and other visible defects (especially the presence of formed drops on the underside of corrugated sheets). The tested modified recipe of fibre-cement profiled sheet met the Heat rain test requirements.

Carbon nanoparticles, whether in the form of nanotubes, fibers or graphenoids, can under suitable application improve mechanical as well as durability properties of cement composites. The use of carbon nanoparticles in concrete is limited by their relatively high cost but also by the difficulty of their dispersion in concrete. The experimental research was focused on the issue of dispersion of carbon nanotubes (CNT) and the effect of CNT in concrete. Concrete with different doses of multi-walled CNT (0.0015 % and 0.012 % from the weight of cement) was prepared. The dispersion of CNT, superplasticizing admixture based on polycarboxylate ether, and water was carried out using ultrasonic cavitator. The impact of various doses of CNT on the strength of concrete after 7 and 28 days and frost resistance of concrete after 100 cycles was observed. The best results were achieved with the addition of 0.012 % CNT of cement weight, representing a dose of 43.2 g per 1 m³ of concrete. The increase in compressive strength was 11.9 %, 17.3 % in flexural strength, 15.2 % in the tensile splitting strength and 26.9 % is the tensile strength of concrete surface layers after 28 days compared to the reference samples without CNT. Changes in properties of concrete with the addition of CNT were observed also in the case of frost resistance of concrete (8 % increase in the coefficient of frost resistance of concrete with the addition of 0.012 % CNT of cement weight).

New road segmental bridge have been built near the city of Žilina, aligned on European highway corridor. The use of segmental concrete box girder was chosen as the flexible system and appropriate method in a municipal zone. The same parallel precast post-tensioned box girder structures were used with main spans of 60.5 m for total length of 1042m. The balanced cantilever method, with the self-launching gantry was used for erection. The shorter end spans, adjacent to the abutment, had to be built by employing falsework. Generally, the early segmental bridges have not been realized without problems following to the structure collapse. In order to assure the safety under construction stage of bridges and subsequently in service, the data was collected during casting and erection of the bridges since August 2016 to November 2017. The experimental research was divided into the laboratory testing and continuous in-situ strain and temperature monitoring of the bridge superstructure. The paper illustrates fabrication and erection process of the bridge and some results of superstructure testing.

This paper deals with rebound hammer testing of concrete in the early stage of ageing. Six types of concrete were produced for the purpose of the presented experiment and differed in the water/cement ratio and were otherwise identical as to the input components. SilverSchmidt PC L test hammer was used to determine the rebound coefficient Q and compressive strength of cube test specimens. The aim of the experiment was to verify the possibility of creating a conversion relationship between the determined parameter of the used non-destructive method and the real compressive strength of concrete in the first days of ageing of concrete. Based on the conducted experiment, it may be stated that the SilverSchmidt PC L test hammer with a mushroom plunger is a suitable instrument for determining the initial compressive strength of concrete, starting from the value of about 5 N/mm². An important conclusion is the fact that it is possible to create a regression model with relatively high accuracy, in this case approximately ± 3 N/mm².

Correct reinforcement is an essential part of constructing reinforced concrete structures. Errors in positioning, diameter, or coverage may result in defects, which is why it is necessary to make sure the reinforcement is implemented well. Even though electromagnetic detection is the most common non-destructive method for locating reinforcement in reinforced concrete, science literary sources hardly discuss it. The main reason is a lack of graphic test results – thus far the most common research outcomes have been photographs of lines drawn on the concrete surface or additions to technical drawings of the reinforcement. Only modern detectors expanded the possibilities of the method's application including graphic measurement records and a more accurate estimation of reinforcement diameter including corrections for adjacent reinforcement spacing. The paper focuses on the principle of measurement and practical examples of determining the position and coverage of reinforcement in reinforced-concrete structures using a state-of-the-art electromagnetic rebar detector – a Profometer PM-630. Aside from data recording and statistical evaluation during coverage measurement, modern instruments also allow the data to be exported and visualised.

In the experiment was monitored the influence of thermal-technical properties by binder amount. As binder was used organic based glue 4,4´MDI (Conipur 360). At the same time was verified possible dilution of binder with water. The binder was diluted in amounts of 5, 10, 15, 20, 25 and 30%. However, in the case of 25 and 30% has not been achieved complete dilution. Recycled plastic EVA (ethyl vinyl acetate) was used as filler.

The article deals with the influence of crystallisation additives on the life of self-compacting concrete (so-called SCC concrete) in case of exposure to aggressive gases. The effect of crystallization additives on the properties of such modified composites is generally tested during exposure of liquid media, in this case the attention is focused on influence of selected types of aggressive gases (CO₂ and SO₂). The impact of individual types of aggressive gases is assessed on the basis of a set of physico-mechanical and physico-chemical analyses.

Waste management and its use as a secondary raw material is a matter that is being given increasing attention. Such raw materials also include waste products from the energy industry or municipal waste disposed of from the recycling process. This study explores the use of secondary raw materials in specific cement–based cement composite as a partial binder substitute. Selected secondary raw materials were pre–treated by grinding to a specific surface of 300 and 500 m²·kg⁻¹. As a reference material, a commercially available mixture was selected to produce cement composites intended for the environment with high physical–mechanical demands. Cement was substituted by secondary raw materials at a rate of 20 and 40% in the reference recipe. Basic physical–mechanical characteristics such as compressive strength and tensile strength at bending were determined on standard 160×40×40 mm prisms. Strengths were determined after 3 and 28 days of ageing. In addition, the influence of binder substitute by the admixtures on the microstructure of cement stone was monitored by sample scanning using an RTG tomography. The positive effect of a part of the binder substitution by selected secondary raw materials on microstructure was proved in all tested samples. From the measured data, it is evident that the higher specific surface of the pre–treated admixtures did not have a significant positive effect either on strengths or the microstructure.

The article deals with the impact of samples moisture content on the results of the depth penetration of water under pressure according to EN 12390-8, considering the fact, that technical standard does not prescribe definite condition of the samples prior testing. To obtain results of the water penetration depth, samples from eight different batches (strength classes from C 12/15 to C 55/67) were prepared. The experiment simulated two boundary conditions: saturated samples were tested immediately after taking from the water. This procedure of samples treatment was marked as the reference (REF). The second one: oven dried samples were tested after cooling to room temperature. This procedure of samples treatment was marked as the comparative (COMP). The results showed an increased tendency in the penetration depth when the samples were oven dried compared to the reference method. There is also discussed the substance, aim and relevance of the technical standards in connection with practical use.

Currently ternesite, Ca₅(SiO₄)₂SO₄, is used in the cement production, is one of two key phases of calcium sulfoaluminate cement. Some investigators claim that this phase is nearly inert or very low reactive and it hydrates only after later age of hydration. In order to improve knowledge in this field, process of hydration of neat ternesite clinker under specific conditions of exposure was observed in this study. Ternesite was prepared by firing of raw meal consisting of high calcium limestone, microsilica and calcium sulfate hydrate. The resulting ternesite clinker was subsequently hydrated in four storage environments. Kinetics of hydration process was monitored in water and in environment of saturated carbonic acid, at two different temperatures of 5 and 40 °C. Mineralogical composition of hydrated samples was analyzed by X-Ray diffraction analysis (XRD) and by differential thermal analysis (DTA) in particular ages of hydration. Based on the results, it can be claimed that rate of decomposition of ternesite was related to conditions of storage. The rate of decomposition was significantly accelerated by the environment of carbonic acid and also by the elevated temperature. Presence of calcium carbonates in mineralogical forms of calcite, vaterite and aragonite, coupled with gypsum and thaumasite was identified.

Shrinkage is a due to chemical and physical processes in concrete. The results of these are volume changes that may cause cracking, deformation, decrease in strength and especially durability of a construction. The amount of water in concrete, the fine particles content, the dimension of construction, the method of curing of the fresh concrete and environmental conditions (temperature, humidity) are some factors influencing the shrinkage of concrete. This article deals with reduction the shrinkage of cement composites by addition of expansive cement Denka CSA and synthetic gypsum. The additives were used at a dosage of 10% of the original weight of cement. The obtained results showed different impact of these additives to the volume changes and the compressive strength of cement composites. The Denka CSA additive had a positive effect to monitored properties of cement mortars. It caused the lowest shrinkage; slight increasing of long-term compressive strength and decreasing of bulk densities after 2, 28 and 90 days of hardening.

The aim of experimental research was to verify the possibility of the prefabrication of the thin shielding cladding tiles from heavy weight concrete with fine. The minimal required density of the concrete was 3800 kg/m³ and the maximal particle size was 2 mm. Because of the though over technology of the complicated locks in the touch of tiles was necessary to achieve consistency around 210 mm flow with the Chryso cone test (modified slum flow test). To obtain this consistency without danger of the heavy weight aggregate segregation the superplasticizer was used. In first step was determined optimal amount of mixing water, in the second step we tested different frequency of vibration to achieve maximal consolidation and as a last step to define composition of mixture we tested 3 types of accelerators of concrete hardening to shorten time of hardening and to facilitate more effective production. As the optimal frequency of vibration for compacting process was determined 75 Hz. The best accelerator of concrete hardening for optimalized mixture was MasterSert XS100 from BASF producer.

The article deals with the optimisations of external structures and points to energy-savings and requirements of low energy construction. It defines and evaluates the problems of required thermal-technical characteristics achievement set by standard for external structures of low energy and energy passive houses. At the same time, it describes in detail different variants of their optimisation.

A typical feature of contemporary cities is the permanent shortage of land suitable for residential development inside the city. This leads to attempts in recent years to re-use the so-called Brownfields which have the appearance of the former industrial areas, the buildings of which are mostly far beyond the estimated lifetime. Apart from the standard procedure, i.e. demolition and new construction, it is possible to come across efforts, in recent years, to renovate and newly utilize the existing industrial buildings, some of which have a historical value and considerable design potential for an alternative use. The paper presents a case where an original five-story warehouse building from the mid-19th century should be prospectively used for residential purposes, while maintaining and utilizing, for aesthetic purposes, the timber ceiling structures. The paper describes the procedure of diagnosis of a timber structure and its results, suggesting potential risks of similar renovations where the object of interest has not been used and maintained for a long period of time.

For commercially produced polymer systems, only primary raw materials are used as fillers. These fillers are predominantly pure silica sand of various grading. The substitution of primary materials with secondary raw materials, and their efficient use in the manufacture of polymeric repairing substances, is an indisputable advantage of the use of secondary raw materials. There is currently no general methodology for monitoring the long-term durability and microstructure of repairing substances on a polymeric basis. In this article, long-term durability was assessed by subjecting developed substances with a high content of secondary raw materials (60% fly ash, 75% glass recyclate) to freezing cycles and subsequent cohesion testing. Additionally, through exposure of a concrete element reprofiled by the developed substance, the weather effects for approximately one year. The microstructure of polymeric repairing substances cannot be observed by the same methods used for silicate substances. With regard to the type of tested substance and the filler used, advanced CT tomography and high resolution optical microscopy were chosen for monitoring the microstructure. Based on the results of the tested substances cohesion with the underlying concrete following the freezing cycles, and the evaluation of the taken images, it can be stated that the test repairing substances have excellent long-term durability and can be used in different applications. Furthermore, it was confirmed that replacing the primary filler with the secondary raw material does not reduce the long-term durability of the polymeric repairing substances on an epoxy basis. It was confirmed that only slight degradation occurs due to the photooxidation of epoxy resin by UV radiation, but this does not have a significant effect on physical and mechanical properties.

Determination of the input material quality is crucial for calcination and for gypsum wallboard production itself. The article focused on the practical use of analytical methods in building practice. It presents procedures on how to determine the content of calcium sulphate in the raw material as well as the results from real measurements of the raw material samples, further calculation and evaluation. Together four samples from three different sources located near the potential gypsum wallboard production line were analysed using X-ray Diffraction (XRD) and Thermogravimetry (TGA).

The aim of this study is to find relation between cement properties and tendency of cement paste (concrete) to bleeding. We tested 19 cement samples collected from different batches. On cements were tested granulometry, specific surface, strengths, alkali content, content of C₃A modifications, setting times and bleeding. Tendency to bleeding of all 19 samples was tested in 3 types of cement paste mixtures. One reference mix and two mixtures with superplasticizers from different producers. Results show, that we can see partly relation between specific surface area and tendency to bleeding. With lower specific surface area, the tendency to bleeding is higher. While the content of alkali seems to have small influence. Where the higher content of alkali means higher tendency to bleeding. On the other hand, these results are not conclusive and it is required further testing on different parameters such as content of sulphur and type of gypsum added to clinker during grinding.

The amount of municipal waste produced is increasing every year. Waste preventing is the best way, but it is not always possible. There is a need to look for new ways of municipal waste management, such as material recovery of waste in the construction industry. This paper shows the possibilities of using glass waste in the production of concrete. Three fractions of glass bottle cullet - 0/4, 4/8 and 8/16mm, as a full-scale replacement of natural aggregates were used. The results of the compressive strengths of more than 50 MPa and the bending compressive strength at more than 4.4 MPa, show considerable potential in this direction of use. In addition, at half of the prepared samples, cement was replaced by fly ash from biomass combustion. The negative effect of alkali-silica reaction of glass did not appear in our experiment.

The paper presents the possibility of the Ružín (Slovakia) reservoir sediments' reuse as a 40% replacement of Portland cement in concrete. Treatment of sediments consists of sediment dry milling, adding of fly ash from local biomass incinerator plant into the dry milling process due to the low CaO sediment content and sediment's mechano-chemical activation using sodium hydroxide in the form of solid and solution as a chemical activator of pozzolanic properties. The results show the possibility of sediment reuse in building materials. However, treatment of sediments with the addition of fly ash doesn't significantly affect the development of compressive strength. Sodium hydroxide is not an effective pozzolanic activator for sediments. The absorptivity of composites increases with the fly ash and sodium hydroxide addition. Also the NaOH application form (as a solid or solution) influences the total absorption water capacity. Pouring the mixture with 5M NaOH increases the absorptivity of the hardened composites.

The increasingly stringent requirements of thermal engineering standards lead to ever greater thicknesses of thermal insulating layers in the structures, which makes the insulation of the manufacturer to improve material parameters. Thermally reflective insulation currently occupies only a small volume of products in the building industry, but their use in buildings where a large temperature gradient is created for thermal insulation offers many advantages. The pressure on the thermal insulation efficiency is increasing, so that their thickness is as small as possible.

The aim of the paper is non-destructive measurement of differently degraded specimens by high temperature intended for further testing of joints of stainless steel helical reinforcement glued into the groove and differently degraded concrete. Measurement intended for determination of possibilities of estimation of future properties of named joints is performed by the Impact-Echo method and by the ultrasonic pulse velocity method on specimens of dimensions 400 × 100 × 100 mm made of concrete of the C20/25 strength class degraded by different elevated temperature. Five sets of specimens were manufactured - four sets of specimens were heated in the furnace at temperatures of 400 °C, 600 °C, 800 °C and 1000 °C and one set was kept intact as reference. Specimens will be afterwards additionally strengthened at the tensile side of specimens and broken by four-point flexural strength test. The non-destructive measurement aims to evaluate the residual physical-mechanical properties of plain concrete in terms of resonance frequency of test specimen, and sound velocity in tested specimen before and after the temperature degradation. This assessment will serve as material information basis for interpretation of the expected behaviour of used helical reinforcement for a retrofitting process and the thermally damaged concrete reaction to such intervention.

This article presents the requirements for concrete mixing water and evaluates the possibilities of using recycled waste sludge water generated in a concrete plant from rinsing water of the concrete plant agitating centre and agitation trucks. The production of concrete mix requires large amount of water and for this reason, it is necessary to use this resource in an economic way. For further use of these waters, it is vital to know their detailed properties in order to maximize their potential in the design of concrete formulations for the purpose of replacing pure mixing water with recycled sludge water so as to preserve or improve the physical and mechanical properties of fresh concrete mix or hardened concrete. The results of the wastewater tests from the concrete plant confirm compliance with the limit concentrations according to CSN EN 1008. The attention should be paid to the limit of concentration of sulphates.

There are introduced basic information about the composition and the properties of the precast cement-based mixture in the paper. Studied multi-functional composite was developed for the easy and rapid reconstruction of the concrete structures. This composite exhibited rapid evolution of utility properties and volume stability during the process of hardening

At present, steel fibre reinforced concrete can be classified as a composite material commonly used for load-bearing building structures. Adding steel fibers to fresh mixture improves its mechanical properties in comparison to plain concrete. The problem is, however, the production technology, which has not been standardized by regulations so far, and thus, proposals for the amount of steel fibers added to the mixture are still based on the long-term experience and performed tests. The paper describes an experiment focused on the determination and assessment of mechanical properties of steel fibre reinforced concretes with high concentrations of fibres (40 kg/m³, 80 kg/m³ and 120 kg/m³). To better understand the behavior of test specimens during the three-point bending test, the acoustic emission method was used, which is able to capture active defects. The results show that the increasing amount of fibers has the influence on values of F_Rk,0.5 and F_Rk,res,1 (e.g. for concentration 40 kg/m³ is F_{Rk, 0.5} = 13.27 kN and for 120 kg/m³ is F_{Rk, 0.5} = 21.18 kN).

The principle of steel fibre reinforced concrete structures is a uniform distribution of steel fibers in the given volume (structure or structural element), which, however, is not always possible to guarantee in the production. This is closely related to a problem of performing diagnosis of the existing steel fibre reinforced concrete structures. Despite the fact that this material is not unknown, in the standards regulating quality control of the uniformity of fibre distribution, the assessment of distribution uniformity is still based on a destructive testing method. The paper describes a partial experiment which consisted in testing a proposed measuring device and in determining the depth of electromagnetic field range in the test specimens.

This paper reviews the possibilities of using alkali-activated systems in building industry. The history of research of alkali-activated systems and practical applications of these binders in building industry are summarized. This article shows where the evolution of these systems should be directed.

There is a lot of factors, which may affect the reliability of the construction, as durability, serviceability and safety of construction or its parts elements. Corrosion damage either reinforcement is one of the most important factor in reinforced concrete structures or structures made from structural steel. This corrosion damage can be determined by actual standard EN ISO 9223. This standard describe the equations, called dose-response functions, for calculation of the corrosion rate r_corr for standard materials like carbon steel, zinc and so on. These equations are determined from the corrosion rate of samples under outdoor atmospheric corrosion in cooperating with measuring of climatic data. Input parameters on calculation of the dose-response functions are sulphur dioxide, temperature, relative humidity and chloride ions. This article is focused on the calculation of the carbon steel corrosion rate according the dose-response function and its sensitive analysis for various concentration of the input parameters. This variability of the input parameters may represents the different conditions, in which the constructions may appears. In practice, this information may provide, which of the input parameter influence the most the calculated corrosion rate and if it is needed to more concentrate its measuring station network. The location of the outdoor stations with the specimens or choice of accelerated corrosion test may be also provided.

The article deals with the cement-based flooring compounds, especially with the behaviour during the early solidification process. A touch-less laser sensor and a cone-shaped mould were used for the measurement of the plastic settlement/shrinkage. The process of solidification and the strength development were determined using the ultrasonic pulse velocity measurement. Both test devices were equipped with the thermocouple to measure the real-time internal temperature evolution during solidification of the flooring compounds. The measurements presented in this paper proved to be useful for the clarification of the technological problems which arose during the manufacturing of the test specimens.

The aim of the research is to find possibilities for the re-use of environmentally eligible plastic waste as one of the options as a filler in light concretes. The plastic waste was obtained by recycling the plastics from the packaging of electrical cables, Ethylene-vinyl acetate and waste from expanded polypropylene in various proportions. All plastics are included among the medium-sized recyclable plastics according to the degree of their recycling. The experimental part of this work is devoted to verify the impact of the dose of fillers on the observed physical properties (bulk density, heat-technical parameters, sound absorption) of light concrete.

The renovation and replacement of historical plasters is still a very current topic. Today's trend is for the production of dry mortar mixtures that can be used for the renovation of historic buildings. The article therefore focuses on the preparation of gypsum-modified lime-metakaolin mortar. An experiment consisted of two stages. In the first stage of the experiment, the basic technological properties of fresh and hardened mortars were examined (bulk density of fresh and hardener mortar, compressive and flexural strength). The second stage aimed at monitoring the hydration process in different environments. Environments should simulate real factors affecting the plaster (humidity, low and higher temperatures). To determinate of the phase composition, the X-ray diffraction analysis was used. The results showed that gypsum in the lime-metakaolin plaster caused an increase in compressive and flexural strength. The presence of gypsum also conduced to the formation of ettringite and this has caused volumetric changes.

The research presented in this article was focused on proving the effect of wood chips parameters on the hardening process of silicate matrix in cement-bonded particleboard. Namely content of humidity in the chips (in range 30 to 90%) was significant. This amount of humidity was chosen with respect to real conditions of cement-bonded particleboards production. Influence of humidity could be reflected in the content of sugar (cellulose etc.) in wooden chips. The sugars affect the hardening of matrix negatively. Thus, phase composition and microstructure of matrix of cement-bonded particle boards were analysed during 2 to 28 days. Investigation of physico-chemical parameters and microstructure was also supplemented by verification of the basic material characteristics of cement-bonded particleboards (strength and modulus of elasticity in bending, transverse tensile strength perpendicular to the plane of the board, etc.). Slightly negative effect of increasing chip humidity content on the mineralogical composition and microstructure including physical parameters was shown in scope of the experiments. Therefore attention during cement-bonded particleboards production has to be paid even to moisture of the chips.

Nowadays effort is made to study what effects may impact the environment and to address the issue of waste management. The majority of all waste produced is construction waste and demolition debris (approx. 65%). This category includes soil excavated during the construction of e.g. foundations or utility infrastructure. In most cases, this soil finds no use at the original construction site and is landfilled. The challenge is to find a useful purpose for this soil. In order to re-use soils in construction, they must be modified. Currently, there are several techniques of soil modification, most notably compaction and stabilisation. Stabilisation is usually achieved by the addition of binders (lime, cement). A lesser known technology of soil modification is fluidification by means of fluidifiers, plasticisers, or other admixtures. In the Czech Republic, this technology is currently not being used. Within the following contribution is described the testing of two types of soil in which was verify the possibility of liquefaction by using binders and additives. As optimal was appeared the use of 1.5% lime, 4% cement and 1% plasticiser SVC-1062. The binders soil effectively stabilized and the plasticiser positively influenced the rheological properties of the mixture.

In this work the effect of two types of polyethylene glycol on the rheological properties of alkali activated slag pastes have been investigated. Polyethylene glycols were incorporated in the alkali activated slag pastes in quantities ranging between 0.5 and 5% by mass of slag. All rheological measurements were performed on all pastes with water-to-slag ratio of 0.4. Rheological parameters (shear stress and viscosity) of obtained fresh pastes were studied. Rheological behaviour of pastes modified with polyethylene glycols fits the Newtonian model. In this study also isothermal calorimerty test were performed with different amount of polyethylene glycols concerning time. Results showed that the heat flow generally decreases with increasing polymer dosage.

The starting raw materials for aluminosilicate grog manufacturing are fissile claystones and shales. These raw materials are available in the Czech Republic and grogs with up to 45 % aluminium oxide content are manufactured. However, refractory production cannot do without higher-Al₂O₃ -content grogs. This group includes grogs with alumina content of 45 % to 70 %, which constitute a transition between fire clay and mullite grogs. Because of the high market price of these grogs, however, there is an effort to seek ways to manufacture these in the Czech Republic. The primary condition for manufacturing is the correct choice of raw material, a suitable treatment facility, and a kiln capable of firing at temperatures above 1400 °C. This paper assesses some local raw materials for grog manufacturing and compares the results with a mullite grog of similar properties that is available on the European market.

Forsterite ceramics is a part of the refractory magnesium ceramics. The aim of this paper is to characterize the properties of forsterite ceramics in dependence on different compositions of the raw material mixture. Forsterite ceramics is not currently produced in the Czech Republic. Forsterite ceramics is used in industry for its high refractoriness and also for its coefficient of linear thermal expansion which is close to metals. The primary objective of this article is to synthesize forsterite ceramics via solid state reaction. Different raw materials were used for materials mixtures and properties of fired samples were investigated, considering the influence of the raw materials mixtures. Specifically the apparent porosity, water absorption, mineralogical composition, coefficient of linear thermal expansion and refractoriness were investigated.

One of the possible methods to reduce degradation effects due to the influence of moisture on building structures and materials is the use of hydrophobic agents - hydrophobization. The article deals with the influence of the hydrophobic preparations use on the change of mortar mixtures properties, where not only the impact on capillary absorption, but also other key properties which can be influenced by the application of the hydrophobic agent, are monitored. By realizing a wide range of measurements, optimal concentrations were determined to achieve properties comparable with the rehabilitation materials without negative effect on other key properties of mortar mixtures, when is mainly a significant reduction of the capillary absorption factor of mortar mixtures only at tiny changing the thermal conductivity factor of the mortar mixtures and without proved changing the other monitored properties.

Cement-based composites change their properties in dependence on added materials. Scientific papers display results on changes in various mechanical and thermophysical properties. In this paper, the effect of different amount of plastic in two shapes (granules and fibers) and horse manure on thermophysical and mechanical properties of cement-based composites are tested. To understand the structural changes 1-D process of water uptake and porosity measurements were done. The economic growth brings new possibilities for industry development but also increasing problem with waste disposal. Our tests were aimed at finding the optimal balance between plastic disposal in cement based materials and changes in some important properties. The best results of thermophysical properties were for plastic and natural fibers, where horse manure samples had even better mechanical properties than plastic ones.

Pozzolanic behaviour of fly ash was studied in mortars and pastes from lime-fly ash mixtures. Compressive strength increase of the mortar specimens that were cured in humid environment was a direct manifestation of a pozzolanic reaction of the fly ash with lime. Mineral composition of the reaction products was studied by X-ray diffraction analysis. Morphology of the samples was observed using SEM equipped with EDS detector. Analysis of a paste with the lime to fly ash ratio of 1:1 revealed that virtually all Ca(OH)₂ in the paste was consumed within 5 years. The crystalline products of the pozzolanic reaction included calcium hemicarboaluminate hydrate and monocarboaluminate hydrate and some ettringite.

High performance concrete (HPC) is concrete with a very high cement content and very low cement/water ratio and this leads to better properties of concrete. These concretes have a problem with traditional methods of curing because of very dense cement matrix. Water from outside cannot reach the interior of the concrete to achieve hydration and it may not have enough curing water for cement hydration. In this paper is discussed effect of internal curing of HPC. The objective of internal curing is to create water storage inside concrete. This should be achieved with hydrogel which was selected to examine influence on internal curing. Hydrogel has a high water-absorption capacity about 300% so it should create a sufficient supply of water in internal reservoir. The prediction is that the hydrogel will release water after the concrete get hardened and provide water to another cement hydration. This should lead to the concretes with better properties.

Four major clinker minerals, alite, belite, tricalcium aluminate and tetracalcium aluminate ferrite are crucial for cement properties. This work deals with alite as the most important clinker minerals. Alite is affected by the milling process technology more than other clinker minerals. It contains micro-cracks, which are formed during fast cooling, and is therefore less resistant to grinding than other clinker minerals. The paper deals with the influence of length and the technology of the milling process in 3 types of laboratory mills on the particle size and distribution, agglomeration and the change of the grain shape of the synthetically prepared triclinic alite.

This paper is introducing results of diagnostic survey of bridge reg. No. M117 in Pardubice. Which included the quality control of the concrete used in the construction after more than 40 years of operation. Compressive strength of concrete, identification of content of chlorides in concrete and identification of resistance to CH.R.L. – method C are presented in this paper. This paper come into existence with cooperation with the state-funded organization Road Administration and Maintenance of the Pardubice Region and TOP CON SERVIS s.r.o. company.

Application of various supplementary cementitious materials was adopted currently by number of research institutions worldwide. The main motivation is to find out predominantly environmental friendly technologies applicable in cement industry; however this technology is not new. Historically were various active mineral additives used in Ancient times and this technology was rediscovered at the end of 19^th century with gradual development of cement and lime industry. This paper is focused on the long-term experimental study of pozzolanic reaction monitored in terms of thermogravimetry by the determination of the consumption of lime. Various types of ceramic powder were studied during two years and their activity was estimated using predictive method. Obtained results confirmed significant impact of the finesses on the reaction kinetics and also on the total hydration potential.

This paper presents the results of an experimental study of selected characteristics of concrete following its exposure to high temperatures. The monitored parameter was the influence of high temperatures on the bond strength and tensile strength of concrete. The bond strength was tested by a pull-off test, the tensile strength was determined as the direct tensile strength. Experimental concrete panels of 2300 × 1300 × 150 mm were exposed to high temperatures (corresponding to the temperatures in a normal fire) using a fire test furnace at the AdMaS Science Centre of the Faculty of Civil Engineering, Brno University of Technology. The direct tensile strength test was performed on cylinders (diameter of 100 mm and length of 100 mm) made from core samples taken from the panel. The pull-off test was performed on the surface exposed to high temperatures. The results of the experiment show a significant influence of high temperatures on the examined characteristics, and both characteristics were found to significantly decrease with a growing thermal load.

The paper was aimed on testing the technological properties of product "Zeoslag" which consists of 10% of zeolite and 90% of ground granulated blast furnace slag. Both the Perlite and Zeolite were tested for comparison, and also cement as reference material. Mineral additives were tested according to standard for testing the slag - the binder here consists of 50% of additive to be tested and 50% of cement. Normalized sand and water according to standard recipe were used to make a testing mixtures. Following technological parameters of additives were tested: water demand for standard consistency, flexural and compressive strength development (2, 7 and 28 days) and activity index. Parameters are discussed in the terms of chemical character of additives. At the given range of modulus of hydraulicity (0.02 – 2.44), the experiment showed tight nonlinear relationship between it and strength characteristics of additive-based mortars.

Recycled concrete aggregate represents a major environmental burden in the affected area and its use as an aggregate in concrete production is widespread in many countries. However, such aggregates have worse characteristics and strength than those of natural aggregate. In particular they have a higher absorption rate than natural aggregates, need much more water for mixing, and cause a high slump loss rate depending on the elapsed time. In this context, it is possible to monitor globally extensive research aimed on the elimination of improper properties of alternative aggregates, which are an obstacle to their application in concrete. The sorptivity expressed by capillary moisture content is a characteristic of moisture transport into the material, and recently it has been recognized as an important performance characteristic of durability. The paper is focused on the specific approach to concrete mixing as a way of the improvement of recycled aggregate´s surface using 3 variations of powders as coating materials and 2 kinds of aggregate. The changes in the capillary moisture content are compared and discussed. It is clear that the kind of coating material can influence this performance parameter significantly, so the careful design of mixing process together with the selection of powdery materials is essential. The triple mixing method was found to be promising for recycled concrete aggregate concrete, when fly ash or recycled concrete powder are used in the first stage of mixing. It is a favourable result, taking into account the perspective of the application of secondary raw materials for concrete production.

Present day steelmaking slags are being successfully used as a high quality mineral aggregate for the building materials. With this, it is of vital importance to be familiar with the technical significance of the secondary application of slag, because some slag might contain increased concentration of substances harmful to human health. In terms of slag impact on the environment, radionuclides are the least researched of all pollutants emitted from the metallurgical processes. The paper presents the results of the measurement the natural radioactivity levels in concrete composites with incorporated slags in various proportions. The radionuclides´ activity index, dose rate and annual effective dose were evaluated to assess the potential radiological hazard associated with composites with slag and ferromanganese slag.

This paper studies how pozzolan materials can be mechanically activated. For this, two major grinding technologies and different types of artificial pozzolans, such as red brick dust, granulated blastfurnace slag and sheet glass, were used. Observed properties were chemical and mineral composition, amorphousness, particle size and specific surface area. Pozzolan activity of selected materials was compared by evaluation of the reaction with lime using X-Ray diffraction (XRD) analysis and differential thermal analysis (DTA).

Leaching of cement based materials and dissolution of cement hydrates under biogenic acid attack result in an increase of the porosity and changes in the pore structure of the building materials. The impact of certain physicochemical concrete/mortar parameters such as cement chemistry, water/binder (w/b) ratio, porosity and fluid permeability of cementitious materials has been recognized from a material sciences perspective. In this work the durability of cement composite made with blast furnace slag exposed to sulphur oxidizing bacteria A. thiooxidans during the period of 12 months was investigated. Leaching of calcium and silicon ions, water absorbability and porosity of the slag based composite using X-ray computed tomography was evaluated.

The properties of different Czech fluidized fly ashes FFA (class C fly ash according to ASTM C618 12a with high content of CaO in the form of anhydrite primarily) and emisions of SO₂ in flue gas during the firing of FFA are discussed. The decomposition of anhydrite CaSO4 was observed during the soaking time at 1200 °C during the firing of dry pressed bodies based on pure fluidized fly ash. The effect od fluidized fly ashes admixtures on the properties of ceramic bodies is as fluxing agent and the source of CaO for the creation of anorthite in the fired ceramic body. The properties of domestic fluidized fly ashes in connection with their utilization in ceramic technology are described.

The aim of the research program was a degradation of composites containing alkali-resistant glass fibres (ARGF) by ammonium nitrate solutions. The effect of 3 and 5% ammonium nitrate solutions and storage long time on physical properties and structure of cement composites is presented. Application of glass fibre had a positive effect on the properties of cement pastes, most notably, this was reflected on the compressive strength and transverse tensile strength. Despite the positive effects but also the application of fiberglass there was a significant loss of strength cement mortars exposed to prolonged exposure to ammonium nitrate solutions.

Mechanical and deformational properties of concrete are markedly improved by the addition of long structural fibres. This addition, however, not always improves the durability of concrete. One important factor for an estimation of concrete durability is to assess the permeation and diffusion characteristics of the surface layer. The research was performed by means of the TORRENT permeability method and the method for determination of the non-steady-state migration coefficient of chlorides in concrete – NORDTEST. The addition of long polypropylene fibres contributes to increasing the permeability of the surface layer for air and chloride solution, but no too significantly. The higher permeability was determined in concrete with concrete recyclate and polypropylene fibres. The measured results by both used methods are partially comparable and can be used for raw estimation of durability of concretes. The higher values of permeability indicate the expected lower durability of tested concretes.

The paper focuses on the experimental physical - chemical analysis of different carbonation intensity by TG/DTG and FTIR method on the selected surfaces of concretes with aggregate and with concrete recyclate, with and without polymer and steel fibres. By means of thermal analysis and infrared spectrometry, carbonation intensity from the specific amount of calcium carbonate and portlandite was tested on specimens scratched from the internal surface of cracks and on specimens from the inside of concrete. It seems that bending macrocraks do not significantly accelerate the process of carbonation in the depth of concrete. But they bring various corrosion agents to concrete. As regards the evaluation of carbonation intensity of different concrete samples, fibre concretes with concrete recyclate are more suitable for structural purposes than fibre concretes with dense aggregate.

This article describes the method of production of rubber granulate after the recycling of waste tires and the potential utilization of this material. The aim of this study was the utilization of rubber in the building industry, especially the use of granulate as rubber filler in concrete. It has been found that the use of rubber granulate as a substitute for natural aggregates in a concrete mix has a significant impact on the properties of concrete. Although studies on the utilization of rubber granulate in a concrete mix have been conducted in different sectors and in different research areas, it is clear that we do not know much about it yet. That is why it is necessary to continue and to obtain more information about the properties of concrete based on recycled rubber.

This article deals with diagnostics and current state of historical building in the grounds of the manor house Markušovce, eastern Slovakia. In the introduction, the problems of historical building, materials and structures are discussed. The next part is devoted to assessment of the selected structures, moisture survey and salinity above all. Determination of salinity shows high concentrations of chlorides, in part due to maintenance of local roads, which is in the immediate vicinity of the building.. Also, the high damp content of the masonry was confirmed due to the lack of waterproofing as well as high levels of groundwater. Near the historical building is a river Hornád that this fact suggests. The proximity of the park with trees and grassing turn causes shading of western and northern facade parts. The damp and shading of façade parts contribute to bio-corrosive manifestations, increased growth of moss and algae on the façade, and also confirm corrosion of masonry evidenced by higher sulphate content due to biogeneous sulfuric acid. The results of diagnostics tests show, that the samples from damaged parts of façade have a higher degree of salinity, this fact confirms the need for a reconstruction.

Composite materials demanded in various technical areas as well as civil engineering, have important influence on the progress in research and development of materials. Among other things, composites materials based on organic fibers, obtained from the processing of natural raw or as a product of recycling, have come to the fore in the last years. The results of the comparative study of the physical parameters (density, thermal conductivity coefficient and water absorption behaviour) of the bio-based composite are presented after 28 days of setting and hardening. The ability of the material to receive and retain water in the pore system is also very important, so parameters such as absorption and capillary absorption are also studied. Results are discussed in terms of impact of individual content of cellulosic fibers in each other properties of composite materials. Density results showed an improvement in the values with the increasing weight % fiber in composites for both types of fiber. Also, an improvement in thermal conductivity has been demonstrated, confirming the possibility of applying composites to the insulating elements. However, the results of absorption and capillary absorption imply the need to optimize the technology of preparation and surface treatment of composites.

A The article is based on the authors' many years of experience in providing laboratory proficiency testing including organization of proficiency testing by interlaboratory comparison. In the introduction are compared the basic tests in the field of aggregates, based on their coefficient of variation. Another part details the influence of each testing stage (sampling, sample preparation and the test itself) on the accuracy of the test results and proposes possible measures to reduce their variance.

Secondary casing as a part of a multi-barrier system serves to meet the safety requirements on the radioactive waste repositories. Such casing needs to be durable, radiation- and thermal resistant, with good mechanical properties; these requirements are fulfilled by concrete. However, the casing should also serve as a barrier limiting the leaching of radionuclides, in case of failure of primary package. This problem is addressed in the article by the addition of a sorption material (natural zeolite rock) in the concrete mixture. Mechanical and thermal properties of concrete containing different amount of natural zeolite rock are studied with the link to concrete porosity. The addition of natural zeolite is found to cause a decrease in thermal conductivity and specific heat capacity. Both compressive and flexural strength decrease as well when natural zeolite is added in the mixture, which correlates with the increase of open porosity of studied concrete mixtures.

Generally, the crack propagation is a problem of equilibrium and stability of silicate structures. The critical crack length depends on fracture toughness. The relationships between fracture toughness, bulk density, modulus of elasticity, and compressive strength are depicted in silicate material diagrams. Those diagrams have numerous application in engineering structural design.

The rheological behaviour and mechanical properties of lightweight lime-brick powder mortars with combined expanded clay-sand aggregates are presented in this paper. The rheological investigation included the characterization of flow properties and viscoelastic properties of the fresh mortars. Flexural and compressive strengths were determined at 7 and 28 days. These mortars are Non-Newtonian thixotropic liquids with conversion from shear-thickening to shear-thinning behaviour depending on expanded clay aggregate (ECA) content. Yield stress and consistency coefficient of mortars significantly increase with decreasing amount of ECA; the mortars become more rigid and more viscous. Some of the mortars reached higher flexural strengths than similar lime mortars with metakaolin and higher compressive strengths than pure lime mortars. The lightweight lime-brick powder mortar with the mass ratio of 1:1 between gravelous sand and ECA was identified as the best among the analyzed mortars.

The main aim of this research is to perform cultural perspectives analysis of a Life Cycle Assessment (LCA) case study to understand if the use of different Life Cycle Impact Assessment (LCIA) approaches may lead to a very different conclusions. A LCA was applied to analyse the environmental impacts of external bearing wall of two different compositions. In this study, the environmental comparison of the constructions was performed using the ReCiPe method in software SimaPro while considering three approaches of cultural theory: the hierarchist, the individualist, and the egalitarian. The results were compared using midpoint and endpoint indicators. The endpoint LCIA showed that each approach provided a different conclusion except for the hierarchist and egalitarian approach in the Resources indicator. The results for midpoint LCIA were in all impact categories the same with the exception of the terrestrial acidification and marine acidification.

The requirements placed on the thermal protection of buildings are becoming stricter worldwide, which causes an increased demand after thermal insulation materials. One of the ways of achieving sustainable development in this area is the use of secondary and renewable raw materials. This paper describes the results of research aimed at developing and studying the behaviour of thermal insulation materials made with recycled textile fibers.

The paper describes how a crystalline additive influences the properties of cement- based composites. The investigation was focused on the degradation of mortars with crystalline additive exposed to selected aggressive environments. The specimens were tested for compressive and flexural strength. The influence on the microstructure is also discussed (high pressure mercury intrusion porosimetry, SEM, DTA). The results confirmed the positive influence of a crystalline additive on the values of compressive strength after exposure to all aggressive environments.

Viscosity enhancing admixtures are widely used to improve the properties of concrete and ready-mix mortars. This study focuses on the influence of biopolymer (sodium salt of alginic acid, carrageenan, diutan gum, gellan gum, and xanthan gum) in doses of 1, 5, and 10 ‰ on the rheological properties of aerial lime-based pastes. The measurements were carried out on the Discover HR-1 hybrid rheometer with DIN concentric cylinders geometry. On the pastes the flow properties as yield stress, fluidity index and consistency coefficient as well as the viscoelastic properties (complex modulus, loss tangent, critical and flow strain) were studied. All pastes studied expressed shear-thinning behaviour and the flow curves indicated rheopectic character of samples. The significant differences in effectivity of admixtures used were observed. Xanthan and gellan gums were found less effective than the three others in influencing the rheology of aerial lime-based paste while diutan gum was so effective, that the future research with lower doses of the admixture are recommended to better explain its impact on the rheological properties.

This research deals with the possibility of using hazardous waste in epoxy resin-based polymeric substances. More specifically, it is the use of neutralising galvanic sludge (NGS), which produces as a by-product in the surface treatment of metallic elements. The objective of the research was to incorporate as much as possible of this hazardous waste into a suitable polymeric substance because the further use of this waste is very problematic and is costly to treat and dump. Experiments carried out have shown that homogenisation of this hazardous waste with a suitable epoxy resin results in the coating of all filler particles in the form of waste by the binder and there is no release of heavy metals and other undesirable contaminants. From an ecological point of view, it is, therefore, possible to use the pre-treated neutralising sludge as suitable filler in the polymer-based repairing composite. On the basis of the assessment of the mechanical properties test evaluation, it can be stated that the most suitable seems the application of 40% quantity by weight of this hazardous waste type to be used in the repairing mortar. The perfect distribution of hazardous waste particles in the epoxy matrix was confirmed by the evaluation of scanning electron microscope (SEM) images. The distribution of the individual elements found in the filler was monitored by energy dispersive X-ray analysis (EDX).