Test results concern modulus of elasticity and compressive strength of ordinary concretes made of various coarse aggregates from igneous rocks. Test results of some properties of these aggregates (3 crushed granites, 3 basalts, granodiorite, natural gravel) are also considered. The variable factor of the studies is the type of coarse aggregate. According to the analyses of regression and correlation there occurs a significant effect of the aggregate grinding ratio on the modulus of elasticity of concretes contrary to insignificant effect of the compressive strength. The modulus of elasticity of 4 concretes from Polish and Ukrainian granites and basalt aggregates is lower than respective standard values of the modulus.
The paper concerns the effect of coarse aggregate type on the strength and strain properties of concrete under instantaneous loading. The studies deal with properties of the crushed aggregates and their effect on the basic mechanical properties and instant deformability of concretes in comparison to gravel concrete. The paper presents test results of mineral composition, crushing strength, absorption by weight, content of irregular grains and mineral dust as well as bulk and specific density of the 5 coarse aggregates: basalt, granite, dolomite, quartzite and natural aggregate (gravel) derived from the Polish rock beds. Strength and strain properties of concretes under compressive instantaneous loading were analyzed. The analysis showed that strength properties and modules of elasticity of tested concretes are proportional to crushing strength of aggregates. Based on the test results of strains it was concluded that the effect of coarse aggregate type on the modulus of elasticity and the limit strain is more significant than that of concrete strength.
This paper concerns the phenomenon of cracking in reinforced concrete elements subjected to combined torsion and shear. The theoretical model developed by Rahal and Collins is described in de tail. This model is the only one which is capable of predicting the full response (e.g.: steel and concrete strains, deformations, curvatures) rectangular reinforced concrete sections subjected to combined torsion and shear throughout their post cracking loading history. The assumptions of Modified Compression Field Theory are also described because the model of Rahal and Collins is based on this theory. It also contains a concept of the new method which is capable of determining the width of cracks in reinforced concrete elements subjected to combined torque moment and shear force. The method is based on the model suggested by Rahal and Collins.
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