Alkali reaction with reactive aggregates is an example of concrete internal corrosion. Cracks and damage to elements of a concrete structure are the result of the formation of an expansive alkali-silica gel. One of the ways to minimise the effects of this damaging reaction is to use lithium compounds as an admixture to concrete mixes. Lithium ions are believed to reduce the reaction between the alkalis and aggregate or minimise damaging expansivity by modifying chemical composition of the reaction products.This paper presents the results from the tests carried out on mortars from reactive polymineral gravel with lithium nitrate according to the modified ASTM C1260 standard and ASTM C227. The findings show that lithium ions decrease mortar expansion until it reaches the levels markedly lower than those set out in the standards. A considerable reduction in the number of microcracks may indicate either lower swelling capacity of the gels or reduced reactivity of the aggregate, leading to the reduction in the quantity of damaging expansive products

The physical, mechanical and rheological properties of self-compacting concretes enable their application in the construction of bridges which are structures particularly vulnerable to the processes of carbonation and cyclic freezing and thawing. The technology of self-compacting concrete requires an increase in high powder content in the concrete mix, which is obtained by the application of mineral additives. The paper presents test results of the physical and mechanical properties of self-compacting concrete with cement with mineral additives and of the microstructure of its surface layer. The objective of the tests was to evaluate the influence of mineral additives (limestone powder, siliceous fly ash and blast-furnace slag) on the durability of the surface layer of self-compacting concrete subjected to accelerated carbonation and the freeze-thaw process in the presence of de-icing salts. The microstructure of the surface layer of the carbonated concrete was less compact, which was confirmed by the increased surface water absorption and water penetration in the layer in comparison with the non-carbonated concrete. Moreover, carbonated concrete exhibited more significant surface scaling when compared to non-carbonated concrete.

Details var a2a_config = a2a_config || {}; a2a_config.onclick = 1; a2a_config.locale = "pl"; a2a_config.color_main = "D7E5ED"; a2a_config.color_border = "9D9D9D"; a2a_config.color_link_text = "ffffff"; a2a_config.color_link_text_hover = "ffffff"; a2a_config.color_bg = "d9d9d9"; a2a_config.icon_color = "#4e4e4e"; a2a_config.exclude_services = ["dihitt", "delicious", "whatsapp", "dzone", "sms", "stumpedia", "viber", "yahoo_messenger", "google_plus"]; Details PDF BIBTEX RIS Title Diagnosis of concrete structures distress due to alkali-aggregate reaction Journal title Bulletin of the Polish Academy of Sciences: Technical Sciences Yearbook 2015 Volume 63 Issue No 1 Authors Czapik, P. ; Owsiak, Z. ; Zapała-Sławeta, J. Divisions of PAS Nauki Techniczne Coverage 23-29 Date 2015[2015.01.01 AD - 2015.12.31 AD] Identifier DOI: 10.1515/bpasts-2015-0003 ; ISSN 2300-1917 Source Bulletin of the Polish Academy of Sciences: Technical Sciences; 2015; 63; No 1; 23-29

This study examined the physical properties of a three-component mineral binder that is typically used in deep-cold recycling. Test binders were produced using Portland cement, hydrated lime, and cement bypass dust (CBPD) as a byproduct derived from cement production. The suitability of CBPD for use in road binders was assessed. Effects of the three-component binder composition on the setting time, soundness, consistency, and tensile and compressive strengths of the cement pastes and mortars were determined. The pastes and mortars of the same consistency obtained at different w/b ratios were tested. On this basis, the mixture proportions resulting in road binders satisfying the requirements of PN-EN 13282-2:2015 were determined. By mixing cement, lime, and CBPD during the tests, binder classes N1 to N3 were obtained. The replacement of 40% of cement mass with the CBPD high in free lime produced road binders suitable for recycled base layers. The total content of CBPD and hydrated lime in the road binder should not exceed 50% by mass. The potential risk of mortar strength reduction due to KCl recrystallization was discussed.

This paper presents the results from the study of the effect of halloysite powders on the performance of the slow-setting silicate-based autoclaved aerated concrete (SW production technology). The clay mineral was used as a cement replacement. The material was tested at industrial scale. The test results indicated relationships between halloysite chemical properties and the properties of the ready-made product. The most important properties of the mineral from the kaolinite group include high specific surface area and chemical composition. Physical and mechanical properties were tested in terms of bulk density, porosity, thermal conductivity and compressive strength of the finished product. In addition, the testing programme included determining the influence of halloysite on the phase composition and microstructure of the aerated concrete, using the XRD analysis and SEM imaging