Effect Of Aggregate Grading Research Articles

Effects of aggregate grading on the properties of steel fibre-reinforced concrete

This study investigates the effects of changing the aggregate grading and maximum aggregate size (Dmax) on the workability and mechanical properties of steel fibre-reinforced concrete (SFRC). Four different gradations and two different Dmax were used to produce SFRC mixtures with constant cement dosages and water/cement ratios. Twelve different concrete series were tested. To observe the properties of fresh concrete, slump and Ve-Be tests were performed immediately after the mixing process to investigate the effects of time on workability. The hardened properties, such as the compressive, splitting tensile and flexural strengths, were also evaluated. In addition, the toughness of the SFRC was calculated. Based on our test results, we can conclude that the grading of the aggregate and the Dmax have remarkable effects on the properties of fresh and hardened SFRC. In addition, the toughness of the SFRC was influenced by changing the grading of the aggregate and the Dmax.

English

English

RHEOLOGICAL STRAINS IN CONCRETE MODIFIED WITH STEEL FIBRE REINFORCEMENT

This paper discusses the rheological properties of normal (ordinary) strength concrete. The results of tests aimed at determining the creep strains and shrinkage strains in normal strength concretes modified with steel fibre reinforcement are presented. The tests were divided into three groups. Steel fibre reinforced concretes (SFRCs) with a different composition were studied in each of the groups. Hook steel fibres, 50-mm long and 0.8 mm in diameter, were used in the tested SFRCs. The latter had an average compressive strength of 35.17–59.18 MPa and a steel fibre content of 0, 25, 35, 50 and 65 kg per 1 m3 of the concrete mixture respectively. Functional dependences for the increase in shrinkage and creep strains over time are given. The problem of the effect of aggregate grading on creep strains is addressed. Conclusions concerning the rheological deformability of steel fibre reinforced concrete are drawn.

Effects of Aggregate Grading and Admixture/Filler on Self-Consolidating Concrete

Self-consolidating concrete (SCC) is becoming a popular choice in concrete industry due to ease of placement in congested reinforcements, reduced labor and equipment, nonsegregating character, and smooth surface. Due to its sen- sitivity to aggregate grading, proportions, admixtures, and filler contents and being a relatively new material, more infor- mation are required on the effects of aggregate grading, mineral admixture types, and fillers on fresh and strength proper- ties. In this paper a total of 10 SCC were investigated to compare the effects of aggregate size and distribution, mineral admix- ture, and filler on fresh properties through slump-flow, J-ring, L-box, column segregation, and compressive strength tests. Results show that combined aggregate distribution is critical for selecting proper SCC mixtures. Water/powder ratio and paste volume has more effects on SCC than water-cementitious material ratio. In general SCC properties can be greatly influenced by admixture types and dosage, and filler. Consistent with this trend, a study is undertaken for the development and evaluation of fresh and cracking properties of SCC using locally available crushed limestone and sand as an aggregate, fly ash and slag from local plants, commer- cial admixtures including silica fume and limestone powder. As properties of SCC vary greatly due to aggregate type, gradation; mineral and chemical admixtures types and dos- age, a total of 10 SCC mixtures were prepared using various combinations of aggregates and admixtures. This paper will evaluate and compare the fresh properties and compressive strength of various SCC mixtures developed with different combinations of aggregate, mineral admixtures, and filler. The aggregate gradations will also be compared with the developed combined aggregate gradation optimized for con- crete workability, economy and strength by Shilstone (4) for normal concrete.