Improving of Concrete Tightness by Using Surface Blast-cleaning Waste as a Partial Replacement of Fine Aggregate

In the article the possibility of using surface blast-cleaning waste (copper slag based) as a replacement of fine aggregate in high performance concrete manufacturing was presented. Concrete with w/c ratio 0.45 and 360 kg/m3 dosage of cements: CEM I 42.5R, CEM II/B-V 42.5N and CEM III/A 42.5N was tested. The consistency measured in table flow test was assumed as 420 ± 30 mm so superplasticizer was used. The replacement rate of the fine aggregate 0–2 mm with the copper slag (CS) waste was 66 %. Concrete mixtures with sand served as reference. The performed tests focused on: compressive and tensile strength (both after 28 days), sorptivity, free water absorption capacity, Torrent air permeability, and chloride ingress depth after salt fog treatment. A freeze resistance test was also carried out according to PN-B-06265. The obtained results showed that the strength and some other tested properties of concrete mixtures with copper slag waste were similar or better than those of the mixtures with sand. The results of the tests indicate that the concrete with copper slag waste is more tight than the concrete with sand and therefore is more durable

Influence of SCM on the Permeability of Concrete with Recycled Aggregate

The article presents experimental analysis of concretes mixed by using natural and low quality recycled concrete aggregate (RCA). The resistance of concretes with both, RCA and supplementary cementitious materials (SCM) to penetration in aggressive environmental conditions was studied. The influence of fly ash, microsilica and metakaolin on the concrete permeability was investigated. Besides the fundamental mechanical properties of concrete, sorptivity, water absorption, depth of penetration of water under pressure and chloride migration coefficient were tested. The significant effect on the permeability of RCA and SCM is described and discussed. The replacement of the natural aggregate by RCA decreased the concrete resistance to penetration of aggressive media, but the application of the SCM significantly reduced this negative impact

Influence of carbonation on torrent air permeability of concrete

Air permeability testing is increasingly being used to measure the impermeability of concrete and to estimate the durability of reinforced concrete structures using this property. This paper presents the results of a preliminary study on the influence of the carbonation of concrete on its air permeability measured using the Torrent apparatus. Three batches of concrete made with CEM I cement and differing in the w/c ratio (0.45, 0.50, and 0.55) were tested. The influence of the relative humidity of concrete on the air permeability index kT was assessed using relationships available in the literature. It was shown that in carbonated concrete, these relationships need to be modified. The air permeability values obtained in tests are lower than the theoretical values calculated using the equation. The results obtained suggest that the effect of carbonation on the air permeability of concrete is significant and further research in this area is highly recommended

Review of selected aspects of shaping of physical, mechanical and thermal properties and manufacturing technology of lightweight and ultra-lightweight autoclaved aerated concrete

The paper provides an overview of selected scientific articles presenting research carried out in recent years on methods for producing autoclaved aerated concrete. Traditional technologies are briefly presented, together with innovative solutions for the production of low-density and ultra-lowdensity materials. In addition to the presentation of the manufacturing methods themselves, the results of research into the properties of the autoclaved aerated concrete obtained and their dependence on the technology used are also presented. A subjective selection and review of articles covering research into the thermal conductivity of concrete, the technological factors influencing them and the ways in which they can be shaped was also carried out. A significant number of the cited articles do not function in the world scientific circulation due to the language barrier (they are mainly in Ukrainian). In the meantime, they contain interesting research results which can inspire further research into the issues discussed concerning the production technology and the thermal and strength properties of autoclaved aerated concrete, with particular emphasis on lightweight and ultra-lightweight concrete

Zastosowanie stanowiska pomiarowego do badań przewodnictwa cieplnego materiałów budowlanych metodą „gorącego drutu”

W artykule przedstawiono wyniki badań doświadczalnych wyznaczania współczynnika przewodzenia ciepła (?) gipsu. Podczas pomiarów wykorzystano metodę „gorącej nici”, która należy do jednej z najbardziej interesujących metod z powodu swojej prostoty, łatwości realizacji oraz dokładności. W pomiarach wykorzystano platynowy czujnik Pt100, który z układem pomiarowym tworzy precyzyjny przetwornik pomiaru temperatury z wyjściem napięciowym. Pomiary rejestrowano za pomocą komputerowego systemu pomiarowego z czasem próbkowania co 0,01 s

Probabilistic analysis of the safety margin assured by shear strength models of stirrup reinforced concrete beams

The aim of this study was to assess the safety margin assured by stirrups of reinforced concrete elements subjected to shear. The safety margin was assessed by means of Monte Carlo simulation. The impact of the strength of steel and spacing of stirrups on the results was analysed as well. The used models of shear resistance were taken from the Polish standards PN-84/B-03264 and PN-EN 1992-1-1:2008. The safety margin, expressed as the logarithm of the probability of not achieving the design value of the design ultimate shear capacity was analysed as well as the impact of different assumptions on the obtained results. An attempt was made to assess the “sensitivity” of models to changes of the basic parameters of the probability distribution function of their selected variables

Transient method measured thermal properties of concrete with microspheres and latex based addition

The goal of the performed research was to determine the influence of microspheres from fly ash and the latex based addition on the thermal properties of concrete. The tested additions were used in two different proportions each and they were combined with each other. As a reference two series of concrete were used: one without any addition and another with 0.2% of air entraining agent. The thermal properties were measured using transient method with ISOMET 2114 apparatus. No clear trends were observed in case of the results of the measurements of the thermal diffusivity and the volumetric heat capacity. While the results of the thermal conductivity coefficient show that both additions has a potential of lowering the thermal conductivity but they are not so efficient as air entraining agent

Probabilistic analysis of the safety margin assured by shear strength models of stirrup reinforced concrete beams

The aim of this study was to assess the safety margin assured by stirrups of reinforced concrete elements subjected to shear. The safety margin was assessed by means of Monte Carlo simulation. The impact of the strength of steel and spacing of stirrups on the results was analysed as well. The used models of shear resistance were taken from the Polish standards PN-84/B-03264 and PN-EN 1992-1-1:2008. The safety margin, expressed as the logarithm of the probability of not achieving the design value of the design ultimate shear capacity was analysed as well as the impact of different assumptions on the obtained results. An attempt was made to assess the “sensitivity” of models to changes of the basic parameters of the probability distribution function of their selected variables