In this study, the synergistic effect of combining macro polypropylene (PP) fiber and rubberized concrete was evaluated based on mechanical and durability performance, as well as microstructure. The ...specimens were prepared with two different rubber volume contents at 10% and 15%, incorporating with a consistent fiber volume fraction of 0.5%. The plain concrete specimens and specimens with only PP fiber were also produced for comparison. The mechanical test results indicated that the fracture energy of plain concrete could be enhanced with both macro PP fiber and rubber aggregates. Besides, all specimens achieved compressive strength higher than 40 Mpa, and the ultrasonic pulse velocity demonstrated the good quality of concrete specimens. The fracture morphology and ESEM imaging showed the positive function of rubber aggregates and PP fibers on the post-crack propagation. The durability performance, including drying shrinkage, ASR expansion, and frost resistance were also strengthened in macro PP fiber-reinforced rubber concrete compared with plain concrete. The macro PP fiber-reinforced rubber concrete will enlarge the post-failure flexural residual load capacity and deformation and distribute stress for multiple crack propagation, thus increasing overall fracture toughness and reducing brittleness. The sustainable applications can be further explored with the combination of macro PP fiber and recycled rubber aggregate.
•Concrete with fly ash, silica-fume and coconut fibres (FA-SCFRC) is investigated.•The contents of silica-fume and coconut fibres are 15% and 2%, respectively.•Fly ash contents of 0%, 5%, 10%, and ...15% are considered.•Compression, flexure and split-tension behaviors are studied in detail.•In FA-SCFRC, 10% fly ash is optimized content with up to 95% improvement.
Concrete is one of the most widely used construction material in spite of some inherited issues (brittleness, weak in tension, etc.). A lot of effort has been made to alter concrete behavior with the help of additives e.g. cementitious material, fibres, etc. Now a days, combination of additives are gaining popularity. Researchers have studied fibre reinforced concrete, silica-fume concrete and fly ash concrete, separately; but until now, the study is not carried out on coconut fibres with addition of fly ash and silica-fume in concrete. In this work, the mechanical properties of fly ash silica-fume plain concrete (FA-SPC) and fly ash silica-fume coconut fibre reinforced concrete (FA-SCFRC) are investigated. The silica-fume content is 15%, by cement mass, with addition of 0%, 5%, 10% and 15% fly ash content, by cement mass, are added. Coconut fibres having a length of 50 mm and content of 2%, by cement mass, are added for FA-SCFRC. The stress-strain curves, load-deflection curves and load-time curves for FA-SPC and FA-SCFRC are recorded against compression, flexure and split-tension loadings, respectively. It is revealed that FA-SCFRC has generally enhanced properties than that of their respective FA-SPC. As a nutshell, FA-SCFRC with 10% fly ash content demonstrates overall best mechanical properties than that of FA-SPC.
•SFRRuC can be used as an alternative flexible pavement.•SFRRuC resist chloride permeability.•No steel fibre corrosion is found after 300 days of wet-dry chloride exposure.•Water absorption of SFRRuC ...falls within the highly durable concrete mixes range.
This study assesses the durability and transport properties of low water/binder ratio (0.35) steel fibre reinforced rubberised concrete (SFRRuC) mixes, which are proposed to be used as flexible concrete pavements. Waste tyre rubber is incorporated in concrete as fine and coarse aggregate replacement and blends of manufactured steel fibres and recycled tyre steel fibres are used as internal reinforcement. The fresh, mechanical and transport properties of plain concrete are compared with those of SFRRuC mixes having different substitutions of rubber aggregates (0, 30 and 60% by volume). The chloride corrosion effects due to exposure to a simulated accelerated marine environment (intermittent wet-dry cycles in 3% NaCl solution) is also evaluated. The results show that, although water permeability (e.g. volume of permeable voids and sorptivity) and chloride ingress increase with rubber content, this increase is minor and water and chlorides permeability are generally within the range of highly durable concrete mixes. No visual signs of deterioration or cracking (except superficial rust) were observed on the surface of the concrete specimens subjected to 150 or 300 days of accelerated chloride corrosion exposure and a slight increase in the mechanical properties is observed. This study shows that the examined low water/binder SFRRuC mixes promote good durability characteristics, making these composite materials suitable for flexible concrete pavement applications.
•Fresh and hardened properties of RCA-based mixes were evaluated.•Steel fibers effectively enhanced the hardened properties of RCA-based concrete.•Analytical regression models relating various ...hardened concrete properties were proposed.
This paper aims to develop and evaluate the performance of steel fiber-reinforced concrete made with recycled concrete aggregates (RCA) and desert dune sand. Different fresh and hardened properties of RCA concrete mixtures with and without steel fibers were evaluated and compared with those of a mixture made with natural coarse aggregates (NA). Test parameters included the RCA replacement percentage and steel fibers (SF) volume fraction (vf). Test results showed that the substitution of 30% of NA with RCA in plain concrete mixes did not reduce the design cylinder compressive strength (f′c), whereas the use of higher percentages of RCA replacement compromised the fresh and hardened properties of the concrete. The addition of SF significantly reduced the adverse effects caused by the inclusions of RCA in the mixes. RCA-based concrete mixtures having 70 and 100% RCA replacements could be produced with f′c values comparable to that of a NA-based concrete, when minimum vf values of 1, and 2% were added, respectively. The RCA replacement increased the water absorption and sorptivity but decreased the ultrasonic pulse velocity, bulk resistivity, and abrasion resistance. The addition of SF improved the hardened properties of RCA-based concrete mixes to an extent of exceeding some of those of the NA-based counterpart, as in the case of abrasion resistance. Analytical regression models were introduced to correlate different concrete properties to the 28-day cylinder compressive strength.
•The PVA-fiber was innovatively introduced to the rubberized concrete.•Fracture energy and post-failure performance were largely increased by PVA-fiber reinforcement.•Durability including ...freeze-thaw, ASR and drying shrinkage of fiber rubberized concrete were improved from control one.•Rubberized concrete could be largely applied by adding PVA-fiber as reinforcement.
In this study, the Polyvinyl Alcohol (PVA) fiber was introduced to improve the performance of the rubberized concrete. This study experimentally investigated the mechanical performance and durability of Polyvinyl Alcohol (PVA) fiber-reinforced rubber concrete. The waste rubber particles (mesh size #10–#30) were selected to partially replace fine aggregates in the plain concrete. In addition, the rubber particles were pre-treated with an alkali solution to enhance the interface bond with cement paste. The fiber-reinforced rubber concrete samples were prepared with different fine aggregate replacement ratios based on the volume of fine aggregate (15%, 20%, and 25%) and a selected fiber content (0.5% based on the total volume of the mixture). For those samples, the mechanical properties, including compressive strength, flexural behavior, and fracture energy were evaluated to compare with control samples. The results showed that fiber-reinforced samples can largely improve the post-cracking extension and fracture energy. The results of electrical resistivity test indicated the reduced permeability in the fiber-reinforced rubber concrete. The durability performance including Alkali-Silica reaction (ASR) expansion, drying shrinkage and freeze-thaw resistance were also investigated and compared with the control samples. All the durability performances were enhanced through rubber stress release and fiber crack bridging. Therefore, the PVA-fiber reinforced rubber concrete can improve durability and ductility of cementitious materials for structure construction and also can facilitate the recycling of waste rubber into cementitious materials.
•Properties of pervious concrete with recycled aggregate was studied.•Permeability, strength indices and degradation resistance were measured.•The use of recycled aggregate decreases the strength ...indices and degradation.•Polypropylene fiber, silica fume and styrene butadiene latex enhance strength indices.
Pervious concrete is considered as a type of lightweight porous concrete with no fine or with small percentage of fine aggregate. There are many advantages of this form of concrete like lower density, thermal conductivity, lower drying shrinkage and high permeability. The properties of pervious concrete with different levels of recycled concrete aggregate were presented in this research. The considered percentages of recycled aggregate replacement were 50% and 100% by weight of natural coarse aggregate. The effect of aggregate size was studied. The considered aggregate sizes were 9.5 mm and 19 mm. In addition, the effect of using either crumb or fiber rubber, polypropylene fiber, silica fume and styrene butadiene latex were investigated. The properties of pervious concrete were investigated through permeability indices (water permeability, density, voids ratio) and strength indices (compressive, flexural, splitting tensile strengths in addition to pervious concrete degradation). From the test results, the use of recycled aggregate, rubber fiber and crumb rubber slightly affected the permeability indices and negatively affected the strength indices. Based on the splitting tensile strength, the use of 50% and 100% recycled aggregate did not satisfy the typical limits of splitting tensile strength. The use of polypropylene fibers had insignificant effect on the permeability indices and compressive strength but the use of polypropylene fibers enhanced the tensile strength and degradation of pervious concrete. Also, the addition of silica fume and styrene butadiene latex increased density and enhanced the strength indices of pervious concrete. Finally, general relations between studied variables were constructed.
•Fracture behavior of fiber reinforced recycled aggregate concrete (RAC) was studied.•Macro-synthetic fibers increased the residual flexural tensile strength of RAC.•A strong influence of number of ...fibers on fracture behavior of RAC was observed.•Microstructural analysis also showed the bond between mortar paste and fibers.
In order to achieve sustainability in construction industry, recycling of construction and demolition wastes in new concrete is gaining a lot of attention. However, extensive research is needed to explore the complete behavior of resulting recycled aggregate concrete (RAC). This study aims to investigate the fracture behavior, mechanical performance and microstructure of macro-synthetic fiber reinforced RAC. For this purpose, notched beam specimens were produced using three different replacement ratios of recycled concrete aggregates (RCA) (i.e., 0, 50% and 100%) and three different dosages of macro-synthetic fibers (i.e., 0, 0.5% and 1% of volume of RAC). Three-point bending and other mechanical tests were performed to investigate the post peak behavior (residual flexural tensile strength, fracture energy and toughness) and mechanical properties (compressive strength, flexural strength and split tensile strength) of macro-synthetic fiber reinforced normal and RAC. Fracture surface analysis was also performed to develop the empirical relationships between number of fibers and post peak behavior of fiber reinforced RAC. Furthermore, microstructure characteristics of macro-synthetic fiber reinforced normal and RAC were also investigated using scanning electron microscopy (SEM). Results showed that reduction in mechanical properties of concrete was observed with the increase in RCA replacement ratio. However, increase in mechanical properties particularly split tensile strength of normal and RAC was observed with the increase in dosage of macro-synthetic fibers. Concrete specimens also showed increase in residual flexural tensile strengths with the increase in dosage of macro-synthetic fibers. RAC reinforced with 1% dosage of macro-synthetic fibers showed increase in fracture energy and toughness by 380% and 129%, respectively. A strong influence of number of fibers on residual flexural tensile strength and fracture energy of concrete mixtures was observed during the study. Microstructural analysis also showed the existence of bond between mortar paste and macro-synthetic fiber, which improved the mechanical properties and post peak behavior of macro-synthetic fiber reinforced concrete. Based on this study, it can be concluded that macro-synthetic fibers improve the fracture energy and mechanical properties of RAC leading towards higher ductility and better energy dissipation. Moreover, number of fibers strongly influences the residual flexural tensile strength and fracture energy of RAC.
Eco-efficient concrete is a comprehensive guide to the characteristics and environmental performance of key concrete types.Part one discusses the eco- efficiency and life cycle assessment of Portland ...cement concrete, before part two goes on to consider concrete with supplementary cementitious materials (SCMs). Concrete with non-reactive wastes is the focus of part three, including municipal solid waste incinerator (MSWI) concrete, and concrete with polymeric, construction and demolition wastes (CDW). An eco-efficient approach to concrete carbonation is also reviewed, followed by an investigation in part four of future alternative binders and the use of nano and biotech in concrete production.With its distinguished editors and international team of expert contributors, Eco-efficient concrete is a technical guide for all professionals, researchers and academics currently or potentially involved in the design, manufacture and use of eco-efficient concrete. * The first part of the book examines the eco-efficiency and life cycle assessment of Portland cement concrete * Chapters in the second part of the book consider concrete with supplementary cementitious materials, including properties and performance * Reviews the eco-efficient approach to concrete carbonation
Cracks in reinforced concrete structures accelerate the ingress of chlorides and therefore cause a higher risk for corrosion. In this research, autonomous healing of cracks by encapsulated ...polyurethane was investigated as a possible method to reduce reinforcement corrosion. Reinforced concrete beams were exposed weekly to a chloride solution and electrochemical parameters were measured to determine the influence of the self-healing mechanism on the corrosion process. The rebars were visually examined afterwards.
For the cracked beams an active state of corrosion was detected within an exposure period of 10 weeks and clear pitting corrosion was observed on the rebars. Autonomous crack healing with low viscosity polyurethane could significantly reduce the corrosion in the propagation stage. For these specimens no visual damage to the rebars was detected. In conclusion, the application of self-healing concrete with a low viscosity polyurethane is able to enhance the durability of reinforced concrete structures in marine environments.
Die Frage der sicheren und sinnvollen Verankerung von textiler Bewehrung im Beton beschäftigt nicht nur Anwender des innovativen Verbundwerkstoffs Carbonbeton. Auch in der Forschung sind für die ...Thematik des Verbunds und der Verankerung wesentliche Fragen nicht abschließend geklärt. Bisher existiert kein Bemessungsmodell für die Verankerung oder Übergreifung, welches bei der derzeit verfügbaren Bandbreite textiler Bewehrungen mit weicher bis steifer Tränkung gleichermaßen gültig ist. Die unterschiedlichen Versagensmechanismen des Verbunds, die aus den Charakteristika der Materialien resultieren, werden selten klar unterschieden. Dieser Artikel verdeutlicht die Auswirkungen des Formschlusses auf das Verankerungsverhalten am Beispiel einer textilen Bewehrung mit steifer Tränkung und ordnet Ergebnisse von experimentellen Untersuchungen in die bisherige Forschung ein. Hierzu wird ein Prüfaufbau für einen Auszugversuch vorgestellt, welcher auch zur Abschätzung des Verankerungsverhaltens in Praxisprojekten und zur Qualitätskontrolle in der Produktion genutzt werden kann.
Anchorage behavior of textile reinforcement in thin concrete components
The safe and reasonable anchorage of textile reinforcement in concrete is relevant for both researchers and users of the innovative composite material carbon reinforced concrete. In research, major questions of bond and anchorage remain unsolved. To date, there is no design model for anchorage or overlap which incorporates the currently available range of textile reinforcement with soft to stiff impregnation materials. The different failure mechanisms of bond, which result from the material characteristics, are rarely distinguished. This article illustrates the results of form closure on the bond behavior of textile reinforcement with stiff impregnation. Results of new experimental investigations are discussed considering previous research. A modified test setup for single fiber strand pull‐out is presented, which allows for investigation of the anchorage behavior for projects in research and practice as well as for quality control during production.
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