Tomáš Vlach

Textile-reinforced concrete facade panels with rigid foam core prisms

Textile-reinforced concrete (TRC) is a material that is gaining new ground in the field of construction where it not only allows for the manufacture of reduced lightweight structures but also eliminates the problem of corrosion by using alkali-resistant textile reinforcement. The aim of this paper is to investigate the bending behaviour of a newly developed TRC facade panel that incorporates polystyrene foam prisms. Numerical simulations were employed in order to choose the geometry and repartition of prisms inside the facade panel. Experimental results revealed a reduced amount of concrete by 20% via the use of rigid foam prisms with a higher failure load by 16% but a lower elasticity limit by 49% in comparison with the regular facade panels.

Thin Lightweight Panels Made of Textile Reinforced Concrete

Use of high performance concrete with reinforcement made of technical textile is increasing and new applications are being found. This paper presents new technology for the lightening of the panels made of textile reinforced concrete, which is being developed. The main focus of this research is to produce concrete elements suitable for use as facade panels with the least possible weight and environmental impact. Mechanical characteristics were measured on testing specimens with thickness of 18 mm with lightening representing 47% of their volume. Minimum thickness of concrete was 4 mm and therefore the reinforcement was covered by approximately 1.5 mm of concrete matrix. The strength of experimental test panels was measured in four-point bending stress test. Due to one-sided lightening and asymmetrical cross-section therefore, the tests were performed in both directions. For better interpretation of the results were the specimens of lightened panels tested alongside non-lightened specimens with the same thickness. Based on measured values, maximal dimensions of lightened facade panels were designed.

Nanocoating on alkali-resistant glass fibers by octadecyltrichlorosilane to improve the mechanical strength of fibers and fibers/epoxy composites

Surface defects cause the measured tensile strength of alkali glass fibers to be significantly lower than their theoretical values. Coatings can be used to “heal” surface flaws and to modify surface properties. In the present work, the nanocoating on alkali-resistant glass (ARG) fiber rovings was carried out by self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS). The ARG roving was dipped into OTS nanosol, which deposited the organic–inorganic SAMs of OTS on the ARG surface. The assessment of changes in the fiber surfaces was characterized by scanning electron microscopy (SEM) and fluorescence microscopy, while the chemical changes were characterized by X-ray photoelectron spectroscopy (XPS). Furthermore, the influence of nanocoating on the tensile properties of ARG and OTS-treated ARG with and without an epoxy matrix was also studied. The SEM analysis revealed the formation of nanoscale layers on the ARG surfaces and the XPS confirmed the deposition of organic–inorganic monolayers. The tensile strength of ARG rovings with and without the epoxy matrix was improved significantly. The OTS treatment almost created a superhydrophobic nanocoating on ARG, which was confirmed by the sessile drop water contact angle, and the water absorption by the ARG/epoxy composites reduced.

Dosage of Silica Fume in High Performance Concrete

Durability and high strength of concrete are closely associated with low porosity and generally denser material structure. This is achieved using the addition, which include also silica fume. This article deal with an effective dosage of silica fume in high performance concrete, in a proportion of 0-25 % by the weight of cement. Compressive strength, rheological behaviour and economic benefits were the main questions in this work. The expected increase in compressive strength showed itself in lower doses of silica fume, while higher doses did not produce a further increase in strength. In the case of rheological behaviour, we can confirm lower bleeding and segregation, but also faster drying of the surface layer. From the economic point of view, a small doses of silica fume are better, because then we have observed the highest increase in strength.

Cohesion of Composite Reinforcement Produced from Rovings with High Performance Concrete

The reinforcement of concrete with composite technical textile creates a tensile load-bearing capacity. It allows the elimination of steel reinforcement and minimisation of concrete cover. Based on this, the concrete cover is designed with respect to the cohesion of reinforcement with concrete. By using of textile reinforcement very thin structures could be created. The aim of this paper was to determine the interaction conditions of carbon and basalt composite reinforcement in a matrix of epoxy resin with high performance concrete (HPC). The tensile strength of used composite reinforcement and the other mechanical parameters of HPC were determined by experimental tests. Experiments copied the production method of technical textiles. These two combinations of materials present the influence on the design of the structures with textile reinforcements.

Dosage of Metakaolin in High Performance Concrete

This article deals with optimal dosage of metakaolin as addition in high performance concrete. The main criteria for assessing the optimal dosage of metakaolin was compressive strength, rheological behaviour and economic benefits. Metakaolin was added to the mixture of high performance concrete in the range from 0 to 25% weight of cement. The comparison of metakaolin and microsilica, which is often used by concrete producers due to its excellent properties, is also performed in this article. The experiments showed that using metakaolin as addition in high performance concrete affects the compressive strength and rheological behaviour positively. While the compressive strength increases especially at lower doses of metakaolin and at higher doses remained unchanged, changes in rheological behaviour were most obvious at the higher doses. From this point of view, it is possible to recommend a higher dose of metakaolin.

The Effect of Surface Treatments of Textile Reinforcement on Mechanical Parameters of HPC Facade Elements

Development of extremely thin concrete structures and demand for extremely thin elements are the reason of using composite non-traditional materials as reinforcement. Steel reinforcement is not very chemically resistant and it limits the thickness because of the required concrete cover as protection. This is the reason why textile reinforced concrete (TRC) going to be very famous and modern material. TRC in combination with fine grain high performance concrete (HPC) allows a significant saving of concrete. Due to its non-corrosive properties of composite technical textiles it is possible to design very subtle structures and elements. TRC and HPC in general are developed at the Faculty of Civil Engineering and the Klokner Institute, CTU in Prague. This present paper investigates the cohesion influence of textile reinforcement on four point bending test. All small experimental panels were reinforced with the same 3D technical textile from AR-glass roving with different type of cover layer. Different conditions of interaction between technical textiles and HPC were ensured by modified surface using silica sand and silica flour.

Comparison of Different Types of Glass Reinforcement for HPC Facade Elements from Mechanical and Economical Aspects

Concrete as the one of the most used material in civil engineering has also a very high negative environmental impact. In recent years’ environmental parameters of all building materials become the most important aspect. Especially reduction of concrete is becoming a very hot topic around the word because it can lead to the reduction of environmental impacts especially the consumption of primary energy, primary non-renewable materials and CO2 production. Textile reinforced concrete (TRC) is one of the possibilities to reduce amount of concrete in the structures. It is possible to design very thin structures because of non-corrosive properties of textile reinforcement and thus distinctly reduce the thickness. Combination with high performance concrete (HPC) allows to creating construction with mechanical properties on a required high level. This paper presents mechanical and economical comparison of different types of AR-glass reinforcement for HPC facade elements with the same amount of concrete.

Efficiency Evaluation of Concrete Surface Treatment

This paper presents the simplified method of efficiency evaluation of surface protection products for concrete elements. This evaluation method was designed to consist of as few testing procedures as possible and to use as few specimens as well. Several testing processes most of which were based on the European technical standards were used to compare five commercially available products. Those comparisons served to assess whether the chosen method has sufficient informative value and does not require a disproportionate amount of time and money. The main examined properties were impact on color and reflectivity of the original surface, durability of the coating in extreme weather conditions, wettability of the surface and amount of labor needed for its maintenance. All of these experiments were optimized so that they could be performed on one type of specimen.

The Possibilities of the Utilization of Waste Glass as Partial Replacement of Fine Aggregate for HPC

This contribution is to verify the utilization of waste glass as partial replacement of fine aggregate for high performance concrete (HPC). Test results of fresh and hardened HPC will be presented. This study has been conducted through basic experimental research in order to analyze the possibilities of recycling waste glasses (grinding glass, milled glass powder from municipal waste) as partial replacement of silica powder for HPC.