Abstract: The paper deals with the variation of resistance of selected High Performance Concrete (HPC) materials against chloride ion penetration. The resistance of chloride penetration is described by means of the diffusion coefficient and it is derived from emerging non-destructive tests. It is computed from the measurements of surface electrical resistivity (see e.g. AASTHTO TP-95 specification) data. The effect of concrete aging on the diffusion coefficient is taken into account as the concrete properties are time dependent and it is significantly important for High Performance Concrete (HPC) materials.
Abstract: Carbonation of the pore solution in alkali-activated materials (AAMs) produces alkali and/or alkali-earth carbonates. When the carbonate solubility in the water is very high (case of the most alkali carbonates), it is very hard to determine the carbonation depth in AAMs with the phenolphthalein indicator frequently used in Ordinary Portland Cement (OPC)-based materials. Carbonation gradually decreases the alkalinity of the pore solution, while the color after spraying phenolphthalein changes from colorless to pink when pH< 13 and changes back to colorless when pH< 8.2. The color change with phenolphthalein indicator may still exist in the less alkaline areas where carbonation may have already occurred. Therefore, using the indicator test is likely to underestimate the depth to which carbonation reaction has occurred in AAMs and more complete assessment is required. This study investigates the carbonation front in alkali-activated fly ash (FA) and blast furnace slag (BFS) pastes in natural laboratory conditions. Monitoring carbonation front in the samples after one year of exposure has been carried out under polarized light microscope (PLM), and environmental scanning electron microscope (ESEM). The carbonation products were sharply distinguished from the other constituents of the paste, by their crystallographic and optical characteristics under PLM, and characterized by X-Ray diffraction (XRD).
Abstract: The service life of steel reinforced concrete in aggressive marine environments could be increased substantially by embedding a self-healing mechanism that ensures autonomous healing of cracks upon their occurrence. Previous proof-of-concept experiments have shown that the incorporation of encapsulated polymer-based healing agents (HAs) counts as a very appropriate way to achieve this goal. Over the years, several polymer-precursor-capsule systems have been developed in that perspective at our laboratory. Cementitious materials containing either commercial or in-house developed encapsulated HAs have been subjected to preliminary feasibility tests (water absorption, permeability tests, etc.). However, these experiments did not yet allow for a fast and straightforward assessment of the self-healing efficiency (SHE) in relation to the expected durability and service life performance of the material. This approach would have many advantages when having to select the most suitable polymer-precursor-capsule system for a particular concrete application. In this paper, a modified chloride migration test based on the one prescribed in NT Build 492 has been proposed to support the development of self-healing concrete for marine environments. Four polymer-based HAs have been screened that way, i.e. an in-house developed high-viscosity polyurethane (PU) precursor, a commercial low-viscosity PU precursor, the same commercial PU precursor with addition of accelerator and benzoyl peroxide (BPO), and an in-house developed 2-component acrylate-endcapped precursor + cross-linker. For now, a highly repeatable SHE value of 100% could only be obtained for the second option.
Abstract: In the paper the brief introduction of soil-structure interaction research at VSB TU Ostrava is presented. Currently resistance of model foundation slabs made of steel fibre reinforced concrete exposed to vertical load is tested. Strain gauge measurement is described and particular results are presented. Strain gauge measurement efficiency is discussed.
Abstract: This work is aimed to investigate four-years impact of 5 % sodium sulphate solution on the mortar made of novel hybrid cement H-CEMENT, being prepared with maximal content of wastes and by-products and only 20 % wt. of Portland cement clinker, compared to that prepared with the reference CEM I 42.5 N (PC). H-CEMENT for its specific material composition does not meet the criteria for inclusion in the cement kinds reported in EN 197-1 but complies with all of the hygienic regulations and standards imposed on similar building materials.
Abstract: The paper is focused on the interaction of the fibre reinforced concrete slab and the subsoil using both the results of experimental measurements on the experimental stand. Performed experimental measurements include monitoring of the concentrically loaded concrete slab with the dimensions of 2 m x 2 m and thickness of 0.15 m. This slab is in the interaction with subsoil of sandy clay character. The experimental load is applied in sequential steps by using a hydraulic press. During the tests the strain gauges and hydrostatic levelling method were used for the monitoring of the settlements of the slab. The contact stresses and the stresses corresponding to a certain depth below the slab were monitored by using a flat pressure cells. In the conclusion of this paper there are formulated the basic aspects of concrete slab-subsoil interaction, the results of various performed experimental measurements and the comparison of stress below the surface resulted from interaction of soil and slab of different degree of reinforcement.
Abstract: In this work, the preliminary study about the use of secondary lead smelting slag (SLSS) as an addition to Portland cement is presented. SLSS is a waste from a Colombian secondary lead smelter. The chemical, physical and mineralogical characteristics of the raw materials were evaluated by X-ray fluorescence, particle size and X-ray diffraction. To assess the SLSS pozzolanic activity, the ASTM C618 standards were used. Additionally, cement pastes added with SLSS as Portland cement replacement in proportions of 0, 5, 10, 20 and 30% were prepared, to study the hydration process at 7, 14 and 28 of curing times. To determine the hydration products the technique of X-ray diffraction was used. Furthermore, the environmental test TCLP (Toxicity Characteristic Leaching Procedure) was performed in pastes with 28 days of curing time. Results showed that SLSS reported an index of pozzolanic activity of 87%, this value meets the standard (greater than 75%). The hydration process showed that since early curing time the waste presented a good reactivity. TCLP results satisfied the environmental standards. The outcomes showed that this waste could be used as a partial replacement of Portland cement.
Abstract: The main goal of our work is to develop an alternative building material based on “zero waste” objective, thus creating commercially valuable products from materials that are otherwise high-volume waste products. Fine dolomitic quarry dust is a waste product manufactured in several millions of cubic tons each year in the mining industry of Israel. Our study examines a sustainable and useful solution to use this quarry dust (QD) as a part of fly ash based geopolymeric systems. Mechanical, thermal and chemical properties were examined and analyzed.
Abstract: Nanostructured binder (NB) based on silicate and alumosilicate raw materials is prospective type of binders that can be applied for production of construction composites with different purpose. Production technology of nanostructured binder is characterized by using of natural raw materials only (independently of its genesis) as well as zero of chemically aggressive additives, that indicates on environmental friendliness and health safety of NB. Indicator of ecological safety of NB can be toxic effect on life activity of crop plants (phyto-effect) determined with phytoanalysis. In this paper it is determined NB to be characterized by low toxicity, so we can say about its environmental friendliness and health safety.
Abstract: The strength development of a quaternary Portland cement composite system containing blast-furnace slag, zeolitic tuff and limestone powder is presented. The composition and particle size distribution of the constituents are optimized by the incremental coefficient of the surface activity of the zeolite-containing Portland composite cements. Zeolitic tuff and limestone powder of high specific surface area lead to the increase of the surface activity of the entire system and a corresponding improvement in the performance of the cement.