Mechanical and durability properties of high-strength concrete containing steel and polypropylene fibers

Abstract not available.Vahid Afroughsabet, Togay Ozbakkalogl

The long-term compressive strength and durability properties of silica fume fiber-reinforced concrete

The long-term compressive strength and durability properties of concrete specimens produced by incorporating polypropylene fibers and silica fume were investigated. Silica fume, a cement replacement, was used at 8% (by weight of cement) and the volume fractions of the polypropylene fibers were 0%, 0.2%, 0.3% and 0.5%. Water-binder ratios were 0.46 and 0.36. The results indicate that the inclusion of fiber and particularly silica fume into the specimens led to an increased long-term compressive strength. Electrical resistance of the silica fume specimens improved remarkably, but decreased slightly due to the fiber inclusion. Water absorption of the fiber-silica fume specimens decreased exclusively compared to the reference samples. Inclusion of fiber and silica fume into the specimens had no considerable effect on the dynamic frequency results. © 2011 Elsevier B.V

Property assessment of steel-fibre reinforced concrete made with silica fume

When silica fume was used as a cement replacement, it enhanced the effectiveness of added steel fibre on the properties of concrete. Three different steel fibres were used at 0.0%, 0.5% and 1.0% by volume of concrete. Silica fume was introduced at 8% by weight of cement into the concrete mixtures that were made with water-cement ratios of 0.46 and 0.36. The early- and later-stage compressive strength, the electrical resistivity, the water absorption and the dynamic frequency of the specimens were examined. The results indicate that the inclusion of steel fibre in silica fume specimens led to the highest long-term compressive strength and the lowest resistivity. Furthermore, an improvement in the dynamic frequency and a decrease in water absorption were attained in 1% steel fibre silica fume specimens. © 2011 Elsevier Ltd. All rights reserved

Evaluation of Engineering Properties of Calcium Sulfoaluminate Cement-based Concretes Reinforced with Different Types of Fibers

Calcium sulfoaluminate (CSA) cement has recently gained increased attention due to its lower amount of CO2 emissions, as compared to that of the ordinary Portland cement (OPC). This paper evaluates the impact of different types of fibers on the engineering features of CSA-based concretes at different water-cement ratios of 0.35 and 0.28. In this study, metallic fibers including double hooked-end steel fibers and hooked-end steel fibers, and non-metallic fibers (i.e., polyvinyl alcohol (PVA) fibers) were utilized at fiber content of 1%. The mechanical properties of concretes were assessed at different curing ages. Dimensional stability of the concrete mixes was also examined. The morphology of the fractured specimens was studied by using the SEM method. The results indicate that the engineering properties of concrete were improved by introducing fibers to the concrete, irrespective of fiber type. The results show that DHE steel fiber has an important effect on the flexural performance of CSA cement-based concretes and results in deflection-hardening behavior. It was observed that fibers and particularly PVA fibers cause a decrease in shrinkage deformation. Microstructure tests demonstrate that prismatic ettringite is the main hydration product of CSA cement-based concrete. The SEM observation also confirms that the inclusion of CSA cement in concrete improves the cohesiveness between the fibers and cement matrix

High-performance fiber-reinforced concrete: a review

In recent years, an emerging technology termed, "High-Performance Fiber-Reinforced Concrete (HPFRC)" has become popular in the construction industry. The materials used in HPFRC depend on the desired characteristics and the availability of suitable local economic alternative materials. Concrete is a common building material, generally weak in tension, often ridden with cracks due to plastic and drying shrinkage. The introduction of short discrete fibers into the concrete can be used to counteract and prevent the propagation of cracks. Despite an increase in interest to use HPFRC in concrete structures, some doubts still remain regarding the effect of fibers on the properties of concrete. This paper presents the most comprehensive review to date on the mechanical, physical, and durability-related features of concrete. Specifically, this literature review aims to provide a comprehensive review of the mechanism of crack formation and propagation, compressive strength, modulus of elasticity, stress-strain behavior, tensile strength (TS), flexural strength, drying shrinkage, creep, electrical resistance, and chloride migration resistance of HPFRC. In general, the addition of fibers in high-performance concrete has been proven to improve the mechanical properties of concrete, particularly the TS, flexural strength, and ductility performance. Furthermore, incorporation of fibers in concrete results in reductions in the shrinkage and creep deformations of concrete. However, it has been shown that fibers may also have negative effects on some properties of concrete, such as the workability, which get reduced with the addition of steel fibers. The addition of fibers, particularly steel fibers, due to their conductivity leads to a significant reduction in the electrical resistivity of the concrete, and it also results in some reduction in the chloride penetration resistance of the concrete

Effect of SAPs and polypropylene fibres on the freeze-thaw resistance of low carbon roller compacted concrete pavement

Most concrete currently used in pavement is based on Portland cement (PC), being responsible for 8-10% of total CO2 emission. Moreover, external pavements are subjected to exposure classes XF4 and XD3 which are related to corrosion and freeze-thaw. Freeze-thaw resistance is an important durability property of concrete, especially for concrete pavements that are subjected to the de-icing salts. This study was designed to explore the freeze-thaw resistance and mass scaling resistance of low carbon Roller Compacted Concrete (RCC) in the presence of water and de-icing salts. Four different RCC mixes were used with a water/binder ratio of 0.45. PC was replaced with 80% ground granulated blast-furnace slag (GGBS) in all mixes to develop low carbon concrete and move towards a more sustainable cementitious composite. To assess the effectiveness of smart engineered additives, superabsorbent polymers (SAPs) were used at 0.3% by weight of total binder, and Polypropylene (PP) fibre with 12-mm length at fibre volume fractions of 0.3% for the mitigation of freeze-thaw damage. The compressive strength, freeze-thaw resistance, and mass scaling resistance of concrete specimens were evaluated. The results indicate that both additives improved the compressive strength and freeze-thaw resistance of concrete with and without de-icing salts. The inclusion of PP fibre was more effective compared to the addition of SAPs to mitigate the extent of internal structural damage and mass scaling of self-healing concrete mixes with respect to the reference concrete after 56 freeze-thaw cycles

Large-Scale Laboratory Trials of Self-Healing Technologies

Prolonging the life of the reinforced concrete structure is the most promising solution to reduce the carbon emissions from concrete. To achieve that, the structure should be protected from crack formation, which acts as an easy pathway for deleterious agents. Self-healing technologies are intended to provide long-term resilience against cracking due to various deterioration processes. Technologies that performed well in small, laboratory-scale studies are taken to the next level to assess their performance on a larger scale and monitored using various NDT equipment. A 1m long beam with a cross-section (140×120 mm) was cast with two rebars – one with a cover depth of 50 mm from the top and another with a cover depth of 20 mm from the bottom. The mix design consists of CEM IIIA (50 OPC: 50 Slag) cement and 30% lightweight aggregate as a replacement for coarse aggregate. At 28 days of curing, the concrete beams are subjected to accelerated corrosion (by applying a voltage to the bottom rebar) to induce internal cracking. Once internal cracking is induced, the beams are subjected to another 28 days under water for healing. The performance of the beams is monitored via ultrasonic pulse velocity and half-cell potential before and after voltage application. This paper shows the preliminary results and the self-healing efficiency and corrosion resistance of these beams are continuously being monitored under severe chloride conditions to predict the long-term performance

The effect of steel and polypropylene fibers on the chloride diffusivity and drying shrinkage of high-strength concrete

This paper presents an experimental study that investigates the influence of the low fiber content of polypropylene and hooked-end steel fibers on the properties of high-strength concrete. The study variables include fiber types and fiber contents. The effect of combining both fibers with a total fiber content of 1.0% was also studied in some mixtures. Silica fume, as a supplementary cementitious material, was used at 10% of the cement weight in all fiber-reinforced concrete mixtures. Compressive strength, modulus of elasticity, longitudinal resonant frequency, rapid chloride migration and free drying shrinkage tests were performed for different curing ages. The results show that replacement of the cement weight with 10% silica fume improved all of the characteristics of the concrete evaluated in this research study. It was observed that the inclusion of fibers, particularly steel fibers, enhanced the mechanical properties of concrete. It was found that the incorporation of polypropylene fibers resulted in a reduction of chloride diffusivity, while introducing steel fibers significantly increased the chloride diffusivity of concrete. Finally, the results showed that hybridization of two types of fibers was an effective way to improve the properties of concrete and specifically reduce the drying shrinkage compared with that of the plain concrete

An experimental and numerical study on how steel and polypropylene fibers affect the impact resistance in fiber-reinforced concrete

In this paper, impact loading results from numerical simulations of plain concrete (PC) and fiber-reinforced concrete (FRC) are compared with experimental testing data, which were based on a testing procedure recommended by ACI committee 544. Concrete specimens were prepared with two water-cement ratios 0.36 and 0.46. Hooked-end steel fibers with an aspect ratio equal of 80 at 0.5% and 1% volume fractions and polypropylene fibers at 0.2%, 0.3% and 0.5% volume fractions were used. Both the numerical and experimental analysis results indicated that increasing the fiber volume fraction increased the impact resistance of the concrete specimens. The impact resistance increase was greater for normal-strength than that for high-strength concrete. The results also demonstrated that steel fibers are more effective at increasing impact resistance than polypropylene fibers. © 2012 Elsevier Ltd. All rights reserved

The influence of expansive cement on the mechanical, physical, and microstructural properties of hybrid-fiber-reinforced concrete

This work reports the properties of hybrid-fiber-reinforced concrete (HyFRC) made with expansive (Type K) cement. Combinations of metallic and non-metallic fibers at total fiber volume fraction of 1% were studied. The effectiveness of double hooked-end (DHE) steel fibers in concrete containing expansive cement is investigated for the first time in this study. The mechanical, physical, and microstructural properties of concretes have been assessed. Additionally, the fiber pull-out test was also performed to investigate the effectiveness of Type K cement in improving the fiber-matrix interfacial bond. The results indicate that Type K cement has small influence on the mechanical properties of concrete fabricated at the same water-cement ratio of 0.35 with a similar consistency. However, as expected, it enhances the volume stability of concrete subjected to drying condition. The pull-out resistance of steel fibers increased by 26% as a result of full replacement of ordinary Portland cement (OPC) with Type K cement. A deflection-hardening performance is achieved by introducing of DHE steel fibers in HyFRC. The partially replacement of DHE steel fibers with other type of fibers results in a reduction in the strengths of HyFRC. The results obtained in this study proves that the bond between fiber and cement matrix is enhanced by fully replacement of OPC with expansive cement, which subsequently improves the mechanical properties of HyFRC