This study is focused on the experimental investigation of compressive strength and durability properties of lightweight concrete mixtures with fine expanded glass and expanded clay aggregates using different microfillers. The paper proposes the relationships between the compressive strength and density of concrete mixtures with different proportions of the lightweight aggregates mentioned above. The performed experimental studies have revealed the tendencies of possible usage of different amounts of fine lightweight aggregates and their combinations in the production of concrete mixtures depending on the demands of practical application. Following the requirements for structural concrete subjected to environmental effects, durability properties (alkaline corrosion and freeze–thaw resistance) of the selected concrete mixtures with expanded glass aggregate were studied. The results of the experimental investigations have shown that durability of tested concrete specimens was sufficient. The study has concluded that the mixtures under consideration can be applied for the production of structural elements to which durability requirements are significant.

Experimental results on cracking and deformation behavior of RC members subjected to short-term loading are frequently misinterpreted because shrinkage effect is not taken into account. Even at first loading, free shrinkage strain of concrete may well exceed the cracking strain. The shrinkage strain, restrained by reinforcement, significantly affects the cracking resistance and short-term deformations of RC members. Despite this, most known constitutive laws were derived by using the test data of shrunk RC members under the influence of tension stiffening coupled with shrinkage effect. In this paper, a numerical procedure has been proposed for eliminating shrinkage from moment-curvature and tension-stiffening relationships. The procedure is on the basis of the smeared crack approach and layer section model. It combines direct and inverse techniques of analysis of RC members. The inverse technique, earlier proposed by the first writer, aims at deriving tension-stiffening stress-strain relationships from ex...

Experimental and numerical studies have been carried out on reinforced concrete (RC) short tensile specimens. Double pull-out tests employed rectangular RC elements of a length determined not to yield any additional primary cracks. Tests were carried out with tensor strain gauges installed within a specially modified reinforcement bar and, alternatively, with fibre Bragg grating based optical sensors. The aim of this paper is to analyse the different experimental setups regarding obtaining more accurate and reliable reinforcement strain distribution data. Furthermore, reinforcement strain profiles obtained numerically using the stress transfer approach and the Model Code 2010 provided bond-slip model were compared against the experimental results. Accurate knowledge of the relation between the concrete and the embedded reinforcement is necessary and lacking to this day for less scattered and reliable prediction of cracking behaviour of RC elements. The presented experimental strain values enable future research on bond interaction. In addition, few double pull-out test results are published when compared to ordinary bond tests of single pull-out tests with embedded reinforcement. The authors summarize the comparison with observations on experimental setups and discuss the findings.

The current study proposes a simple and mechanically sound analytical approach for crack analysis of reinforced concrete (RC) flexural members at the stage of stabilized cracking. The philosophy behind the proposed methodology is to establish mean spacing between the primary cracks through the compatibility of the stress transfer and mean strain approaches. The governing parameters of crack spacing are obtained by equating mean strains of the tension reinforcement defined by these approaches. The model assumes that a single RC block of a length of mean crack spacing represents the averaged deformation behavior of the cracked member. Based on the experimental evidence, reinforcement strain within the block is characterized by a strain profile consisting of straight lines representing zones with different bond characteristics. It was shown that crack spacing is mostly governed by four geometrical parameters given in the order of significance: section height, reinforcement ratio, bar diameter, and cover. A limited comparative analysis has demonstrated that the predictions of mean crack spacing by the proposed model agree well with the tests. Considerations are given to extend the proposed methodology to the analysis of maximum crack width.