Compressive Properties Of Concrete Research Articles

Effects of installing concrete deck on noise radiation of steel box girders: Mechanisms, modeling, and analysis of influential factors

Steel–concrete composite box girder (SCC BG) is widely used in engineering because it can make full use of the tensile properties of steel and the compressive properties of concrete. However, research on the vibrational transmission and vibroacoustic response of the SCC BG is still relatively rare. In this study, a laboratory hammering test was performed to obtain the dynamic characteristics of a scaled specimen of an SCC BG before and after installing a concrete deck. The experimental results revealed that the vibroacoustic response was greatly reduced after the installation of concrete deck due to a reduction in the transmission of on-deck vibrations to the steel box girder. Following this, we introduce a model to predict the structural vibroacoustic response of the SCC BG based on the hybrid finite element–boundary element–statistical energy analysis method, and verify its accuracy through experiments. The accurately calibrated model is then used to study the characteristics of vibration transmission between plates of the SCC BG. The influences of the thickness of the concrete deck, concrete material, and degree of shear connection on vibroacoustic responses of the SCC BG are also discussed.

Effect of different volume fraction of steel fiber/graphite on thermal conductivity and compressive properties of concrete

The enhancement of the thermal conductivity can be utilized to reduce the temperature difference between the internal and external structural surfaces and thus the thermal induced stresses in concrete. This study investigated the compressive strength and thermal conductivity in concrete structures enhanced by the steel fiber and graphite at different volume fractions. First, the cubic and the cylinder concrete samples were fabricated by adding different volume fractions of the steel fibers, such as 0%, 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%, to the concrete mixture. The fiber enhanced samples were tested following the standard procedures, and the optimal compressive strength and thermal conductivity can be obtained in the sample with the volume fraction of steel fiber at 1.5%. Moreover, graphite powders with different volume proportions at 5%, 10%, and 15% were added to the fiber enhanced concrete samples with identical size. The compressive strength and thermal conductivity tests were also performed and the optimal content of steel fiber was 1.5%, and the graphite was 5%. These results could not only meet the design requirements of the compressive strength of the concrete, but also improve the thermal conductivity of the concrete. The research could provide some reference for the design of the high thermal conductivity concrete.

Effect of Local Binary Mixtures of Coarse Aggregates on the Compressive Properties of Concrete

Aggregates, though considered inert, are the primary components that define concrete’s thermal and elastic properties. It has been shown that factors such as maximum aggregate size, grading, shape, strength, water absorption capacity of coarse aggregates affect the properties of concrete. However, improper grading of coarse aggregate could have adverse effect on the amount of cement and water requirement for concrete production. Thus, impacting on the workability, pump-ability and durability of concrete. By maintaining a slump of 50 mm, the effect of varying sizes of coarse aggregates – 10 mm, 14 mm, 20 mm, and combination of these sizes – on the mechanical properties of concrete was obtained. Aggregates, which were used in this work, were sourced from quarries located in Auchi area of Edo State and had impact values between 16% and 28%. It was observed that the higher the coarse aggregate sizes the lower the water – cement (w/c) ratio required to obtain adequate workability. Also, the compressive strength of concrete was observed to be a function of the size of the coarse aggregates used in the concrete mix. It was observed that concrete made with equal proportions of 10 mm and 14 mm coarse aggregate had lower strengths compared to concrete made with 14 mm and 20 mm aggregates. This implies that combination of large sizes of aggregates produced stronger concrete when compared to combinations of smaller sizes of aggregates. It was also observed that density of concrete increased with increasing size of aggregates.

Experimental study on compressive properties of steel fibre concrete

The uniaxial compression tests were carry out in 5 groups steel fibre concrete specimens for 3 kinds of curing age, and the effect of steel fibre incorporation rate and curing age was studied on the compressive properties of concrete. The results show that the compressive strength of steel fibre reinforced concrete increases with the increase of the ratio of steel fibre. When the steel fibre incorporation rate is constant, the compressive strength of the steel fibre has a small increase with the growth of the curing age. The addition of steel fibre can effectively improve the crack resistance and toughness of concrete. With the addition of steel fibre, plastic deformation ability of concrete is enhanced, and the ultimate destruction form of concrete is the shear failure with obvious oblique cross section.

Influence of loading history upon the compressive properties of concrete

Synopsis The influence of sustained and cyclic load histories upon the compressive properties of concrete, mortar and paste are reported. It is shown that the effects of a sustained load produce asmall increase in strength and a relatively large increase in stifiess, whereas cyclic loading results in a small decrease in strength and a relatively large decrease in stifiess. Both load histories decrease the strain at peak stress on reloading. It is proposed that sustained loads result in redistribution of stress concentrations in the cement paste and consolidation in the gel. Cyclic loads, on the other hand, produce limited microcracking. The hypothesis is supported by the substantially greater damage observed in the specimens subjected to a cyclic load and the higher specific creep, which other researchers have shown to be largely irrecoverable.