Papers by Keyword: Strength of Concrete

Abstract: The production of lightweight concrete is mainly carried out in the traditional way using lightweight ceramic aggregates. The aim of the pilot research was to verify the possibility of producing lightweight concrete based on artificial aggregate in the form of agglomerated aggregate from high temperature fly ash. A representative of such aggregate is the artificial aggregate referred to as aploporite. This aggregate is characterised by comparable grain strength to ceramic aggregates but, on the other hand, has a relatively high absorption rate of up to 30 %. Concrete formulations with up to 50% replacement of natural aggregate by aploporite have been proposed in order to achieve the volumetric weights characteristic of lightweight concrete. The results obtained confirmed that it is possible to produce lightweight concrete with this aggregate and to achieve strengths comparable to those of ordinary concrete.

Abstract: High Strength Concretes (HSC) are concretes defined mainly by compressive strength. The strength of concrete can guarantee other excellent results of properties, namely durability. Essential for the production of HSC is a careful approach to the design of concrete composition, especially the quality of raw materials. It is primarily necessary to increase the content of the binder combined mainly with Portland cement and another admixture. Due to its excellent properties, Silica fume is largely used as an admixture, where it is necessary to consider its effective amount. It is also suitable to combine this admixture with other types of active admixtures. The question of the type of coarse aggregate fractions used is crucial. The quality and purity of aggregates is an essential part of the quality design of these concretes, influencing practically all the resulting parameters of concrete. The article presents a set of tests on designed High strength Concretes, differing in the composition of the concrete to demonstrate the variability of the design concept and its effect on the resulting values of strength and durability.

Abstract: Reinforced concrete conical structures are the basis of safety and operational reliability of railways power supply systems. The article presents optimal methods for diagnostics of reinforced concrete structures, which allow recommending the sequence and amount of repair work aimed at restoring or maintaining the required state of reinforced concrete conical section structures (contact-line supports, power transmission line supports, etc.). A design scheme is proposed for determining the residual bearing capacity of the support in the presence of cracks and corrosion of the reinforcement.

Abstract: Three bending strength computing methods of concrete filled steel tube are introduced, including empirical formula method, whole section yield method and simplify numerical method. There are some difference on their computing results. To verify their difference, single factor analysis method is used. The single factor include the thickness of steel tube, the strength of concrete and the strength of steel. The revised results of ABAQUS are used as a benchmark. The analysis include two aspects, one from the changing trends of ABAQUS’ results and the three method’ results when only one factor is increasing, the other from the magnitude of relative error between the results of ABAQUS and the results of every method. Finally, the scope of every method is obtained.

Abstract: The paper focuses on the effect which varying the type of sand used in concrete will have on the compressive strength of concrete and seeks to determine the suitability of each sand for use in concrete works. The sand samples used include Okhoro, Ikpoba, Ovia and Okhuahiaerosion sands and Ikpoba, Ovia and Okhuahia river sands. Particle size distribution of the sands was first determined and the result was used to design grades 20, 25, and 30 concretes to Department of Environment (DOE) mix design method. Twelve cubes were cast from one particular sand sample and three cubes were tested at 7, 14 and 28 days for each grade of concrete respectively .The result revealed that the sand samples that are well graded gave the highest compressive strength; while the poorly graded sands gave lower strengths. Okhuahia river sand gave the strongest concrete followed by Ikpoba, and Ovia river sands, Okhuahia, Ikpoba, Ovia and Okhoro erosion sands. Particle size distribution within a sand zone probably did not affect strength but the impurity content did. However, the inter-zonal differences in particle sizes probably did affect strength. The result also showed that only the river sands and Okhuahia erosion sand are good for concrete making.