Papers by Keyword: High Strength Concrete

Abstract: Concrete is a fundamental component of many structures and the backbone of the construction industry. While normal-strength concrete is typically used for smaller projects, high-strength, and even ultra-high-strength concrete are increasingly employed in large-scale construction. This type of concrete provides greater structural strength and reduces costs by minimizing the size of structural members compared to normal-strength concrete. High-strength concrete offers additional benefits such as enhanced durability, reduced permeability, and improved resistance to environmental conditions. High-strength concrete can be produced using various admixtures, including fly ash, silica fume, sugarcane bagasse, and rice husk ash. This study focuses on developing high-strength concrete suitable for high-rise buildings and infrastructure projects. This research used silica fume as a partial replacement for cement in varying proportions (5% to 15% by weight) along with highlighting the optimal percentage of silica fume replacement to achieve best performance. The mix designs utilized Sargodha and Margalla crush aggregates, with water-to-cement ratios ranging from 0.30 to 0.35. Concrete samples were cast and tested to evaluate key properties, including compressive strength, tensile strength, workability and modulus of elasticity. The study shows that incorporation of silica fume in high-strength concrete significantly enhances its mechanical properties, including workability, compressive strength, and tensile strength. The results showed marginal improvements in the modulus of elasticity as the silica fume content increased. By using high-strength concrete, designers can reduce material usage due to smaller member sizes, making it particularly valuable for high-rise buildings, long-span bridges, and offshore structures. The research concludes with recommendations for future work and further applications.

Abstract: In seismically active areas, the structural integrity of structures is significantly reliant on the efficacy of beam-to-column connections. This study investigates the potential of high-strength concrete (HSC) and engineered cementitious composites (ECC) as alternatives to conventional transverse reinforcements to alleviate joint congestion and enhance the performance of beam-column joints. Four full-scale models were tested, including progressive and cyclic load evaluations. Two models had HSC, HBCJ I (HSC in joint only), and HBCJ II (HSC in joint plus extended to members), and the other had ECC joints EBCJ I (ECC in joint only) and EBCJ II (ECC in joint plus extended to members). The evaluation encompassed load-bearing capacity, ductility, strength, and overall effectiveness. ECC exhibited superior performance to HSC in terms of ductility and load-carrying capacity. Peak displacements significantly increased with ECC by 35% from HBCJ I to EBCJ I and 19.1% from HBCJ II to EBCJ II. Furthermore, peak load-carrying capacity increased by 6% and 16%, respectively. ECC demonstrated its ability to improve seismic performance and reduce congestion, an essential issue in structural engineering, by meeting shear stress needs in joints without transverse reinforcement.

Abstract: A large quantum of vehicle waste is produced annually, of which tires pose the topmost hazard to the planet if not disposed of duly. only in Egypt, the approximately total number of tires generated annually could be about 10 million tires. Demand for tires is expected to increase each year, and in emerging economies, rising profits may increase the vehicles used and drive greater demand for tires. In 2017, approximately 287 million synthetic tires were produced in the United States and approximately 60 million tires were stored in warehouses . The disposal of those tires in landfills when they attain their end life and turn to waste is one of the essential difficult troubles inflicting numerous environmental problems . Therefore, some countries have passed laws to ban landfilling of tires and encourage the reuse of used tires for other purposes . Fiber Reinforced Concrete is a composite material composed primarily of concrete or mortar and randomly distributed with short, discontinuous, distinct fine fibers of defined geometry . The main fibers used in concrete include glass, rubber, steel, aramid and other synthetic fibers. The effectiveness of fiber-reinforced concrete depends on the nature and geometry of the fibers . One possible solution to recover waste steel fibers from the tire manufacturing process is to add them to concrete . In terms of various initiatives around the world to convert waste into new products, the purpose of this article is to quantify the steel fiber contribution of recycled tires used in the production of high-strength concrete. Steel fibers in recycled tires are extracted through mechanical recycling from used tires. In this process, rubber is crushed and granulated, iron is removed with a magnet, and cloth is removed with a vacuum. As a result, recycled tiers steel fibers are irregular in shape and come in a variety of lengths and diameters, but are highly resistant to bending because they are made of high-quality steel.. Recycled steel fibers can be used as cement reinforcing additives or reused as reclaimed steel. . However, fibers extracted from tires are contaminated with rubber particles (15-60% by weight), making them difficult to use directly for any purposeand a cleaning process is required. Also, due to its low density, it is expensive to transport. As a result, these textile fibers are often sent to landfills or incinerators. Adding steel fibers or other fibers to concrete can not only improve the toughness and ductility of concrete, but also improve the crack resistance and durability of concrete . Adding steel fibers to concrete can improve the concrete's deformation properties. Cracks in concrete develop slowly and the crack width is smaller than that of normal concrete. Concrete mixtures containing steel balls recovered from scrap tires had higher workability at less than 4%, and no significant decrease in compressive strength was observed at less than 2%. Although the effect of steel fibers on the compressive strength of concrete is negligible, the tensile and bending strengths increase significantly, but the resistance decreases when the fibers are mixed in an optimal ratio and increase slightly. There have been many studies on the use of waste tire steel fibers in conventional concrete. However, more research is needed on the effect of steel fibers from waste tires on high-strength concrete. In this study, the effect of steel fibers extracted from tires on high-strength concrete was investigated.

Abstract: The construction industry has recently focused on the use of sustainable and innovative building materials, which called for the production of many supplementary cementitious materials with concrete to make the concrete produced durable and sustainable. Since high-strength concrete has many advantages other than its high strength, it has recently been used in non-traditional applications after for a long time confined to well-known traditional applications. This study presents the effect of micro Ferrosilicon (FS) and mineral materials on high-strength concrete properties, where silica fume (SF), FS, and metakaolin (Mk) were used as additives to cement.Besides the consistency test, all-ages compressive strength, splitting tensile strength, modulus of elasticity strengthand water permeability were investigated on the produced HSC.Microstructure analyses are carried out by SEM and EDX tests. The results showed a continuous decrease in a slump with the increase in mineral material, however, 15% FS and 15% MK were determined as the optimum percentage of the desired mechanical property. HSC performs up to 88 MPa compressive strength, 7.49 MPa tensile strength, and 39.89 GPa modulus of elasticity, as well as good durability properties. Finally, the high-strength concrete under consideration is suitable for use in both conventional and non-conventional applications and supports sustainable development and infrastructure development.

Abstract: This study investigates the effect of different types of local coarse aggregate, available in Saudi Arabia, on the strength of high-strength concrete. The utilized coarse aggregates are basalt and two different aggregates of limestone, denoted as limestone 1 and limestone 2. The results of 7 and 28 days compressive strength with different percentages of Micro Silica (MS) (i.e. range from 0 to 10%) show that the compressive strength of high strength concrete (HSC) is influenced by the type of coarse aggregate. Limestone 2 reaches the highest compressive strength followed by the types limestone 1 and then basalt. Properties of coarse aggregate influence the compressive strength of HSC, such as impact value (AIV), and texture. Also, the impact value variation between saturated surface dry (SSD) and dry conditions of the coarse aggregate affect significantly the compressive strength of HSC.

Abstract: Composite admixtures which include active pozzolanic components and high-range water reducers, allows to obtain high-strength, particularly dense and durable concrete to achieve a reduction in resources and energy consumption of manufacturing.Zeolite, containing a significant amount of active silica, can serve as one of the alternative substances to resources and energy consuming mineral admixtures like metakaolin and silica fume. The deposits of zeolites are developed in Transcarpathia (Ukraine), USA, Japan, New Zealand, Iceland and other countries. It is known that zeolite tuffs exhibit pozzolanic properties and are capable to substitution reactions with calcium hydroxide.However, the high dispersion of zeolite rocks leads to a significant increase in the water consumption of concrete. Simultaneous introduction of zeolite tuffs with superplasticizers, which significantly reduce the water content, creates the preconditions for their effective use in high-strength concrete.Along with dehydrated (calcined) zeolite, natural (non-calcined) zeolite expresses itself as an effective mineral admixture of concrete. When using non-calcined zeolite, the effect of increasing in compressive strength at the age of 3 and 7 days is close to the effect obtained when using dehydrated zeolite: 8-10% and 10- 12%, respectively, and 28 days the strength growth is 13-22%. The use of non-calcined zeolite has a significant economic feasibility, so it certainly deserves attention. There were compared the effect of zeolite to metakaolinThe results of the research indicate that the use of composite admixtures, consisted of calcined (non-calcined) zeolite tuff of high dispersity and superplasticizer of naphthalene formaldehyde type, allows to obtain concretes classes C50…C65.

Abstract: In this study, an experimental investigation was done to study the behaviour of Normal Strength Concrete (NSC) and High Strength Concrete (HSC) Plain beams under torsion with the concrete mix of M40 and M100. No mineral admixtures are used to obtain the required strength of concrete. Eight NSC beams and eight HSC beams whose width was varying with 75 mm, 100 mm, and 150 mm; depth varying as 75 mm, 100 mm, 150 mm and 200 mm; and span of the beams varying 600 mm, 800 mm and 1200 mm were casted and cured to stud the effect of torsion. The principle aim of this study was to understand the torsional behaviour of the NSC and HSC beams for rotation, cracking, size effect and torsional strength. A standard torsional loading method was used for conducting the testing of beams. The results obtained were compared with different theories and code equations. It was observed that the torsional strength of the beam increases with the increase in strength of concrete. HSC beams have higher torsional strength than the NSC beams which has the same amount of reinforcement.

Abstract: Concrete filled steel tubes (CFST) represent a composite building member suitable especially for the construction of columns of a skeleton frame. Filling the steel tube with concrete allows the use of suitable properties of both materials and their interaction. This is very beneficial in a fire exposure, where a circular column has slightly better fire resistance than a square column. In case of an assessment of columns at the ultimate limit state (ULS), a buckling resistance decides. In previous research, it was found that increasing the strength of concrete increases buckling resistance only to a certain extent. The main aim of the article is to show through a theoretical study what benefit the use of ultra-high strength concrete has for buckling resistance of CFST.

Abstract: The paper deals with the experimental and theoretical results of elastic constants of polymer modified high strength concrete with high fibre volume fraction. To evaluate elastic properties of this composite system, compressive and flexural strengths were obtained experimentally. Elastic properties such as modulus of elasticity and Poisson’s ratio are first obtained based on experimental results. Simplified equations based on micromechanics, and solid mechanics theories are utilized for the evaluation of elastic properties of polymer modified randomly oriented short steel fibre reinforced high strength concrete. The micromechanics equations for the modulus of elasticity and the Poisson’s ratio are based on the fibre volume fraction and the elastic moduli of the fibre and polymer modified concrete matrix. The existing empirical equations are also used to obtain elastic constants. These equations are applied in the full range of fiber volume fraction (1% to 10%). The comparison of experimental results with theoretical values shows the good agreement with each other. The novelty of the present paper is that the modulus of elasticity of this composite system is obtained experimentally using four point bending test and the Poisson’s ratio is obtained as a function of flexural and compressive strengths with excellent accuracy for the first time.

Abstract: High strength concrete (HSC) characterized by high compressive strength but lower ductility compared to normal strength concrete. This low ductility limits the benefit of using HSC in building safe structures. Nanomaterials have gained increased attention because of their improvement of mechanical properties of concrete. In this paper we present an experimental study of the flexural behavior of reinforced beams composed of high-strength concrete and nanomaterials. Eight simply supported rectangular beams were fabricated with identical geometries and reinforcements, and then tested under two third-point loads. The study investigated the concrete compressive strength (50 and 75 N/mm²) as a function of the type of nanomaterial (nanosilica, nanotitanium and nanosilica/nanotitanium hybrid) and the nanomaterial concentration (0%, 0.5% and 1.0%). The experimental results showed that nano particles can be very effective in improving compressive and tensile strength of HSC, nanotitanium is more effective than nanosilica in compressive strength. Also, binary usage of hybrid mixture (nanosilica + nanotitanium) had a remarkable improvement appearing in compressive and tensile strength than using the same percentage of single type of nanomaterials used separately. The reduction in flexural ductility due to the use of higher strength concrete can be compensated by adding nanomaterials. The percentage of concentration, concrete grade and the type of nanomaterials, could predominantly affect the flexural behavior of HSRC beams.