Over the past few decades, premature deterioration of reinforced concrete structures exposed to severe environmental actions and mechanical loading has become a serious problem. Previous studies have ...shown that the use of ultra-high performance fiber reinforced concrete (UHPFRC) improves the structural response and extends the durability of concrete structures. In this study, the flexural behavior of reinforced concrete beams retrofitted with UHPFRC is investigated and experimental results are compared with 3-D finite element analysis. The experiments were performed on reinforced concrete beams repaired in tension and compression zone, with UHPFRC of varying thicknesses. The flexural strength of repaired beams was investigated by four-point bending test and compared with that of reference beam without repair. Experimental and analytical results indicate that the ultimate flexural strength of RC beams repaired with UHPFRC in tension and compression zone is increased, with the increase of UHPFRC thickness. Thereafter, a parametric study was carried out by using MSC/Marc simulation to investigate the influence of tensile properties of UHPFRC and yield strength of tension steel on the flexural capacity of repaired beams. The investigation shows that the UHPFRC improves stiffness and delay the formation of localized cracks, thus, improving the resistance and durability of repaired beams.
Recently, addition of various natural fibers to high strength concrete has aroused great interest in the field of building materials. This is because natural fibers are much cheaper and locally ...available, as compare to synthetic fibers. Keeping in view, this current research conducted mainly focuses on the static properties of hybridized (sisal/coir), sisal and coir fiber-reinforced concrete. Two types of natural fibers sisal and coir were used in the experiment with different lengths of 10, 20 and 30 mm and various natural fiber concentrations of 0.5%, 1.0%, and 1.5% by mass of cement, to investigate the static properties of sisal fiber reinforced concrete (SFRC), coir fiber reinforced concrete (CFRC) and hybrid fiber reinforced concrete (HFRC). The results indicate that HFRC has increased the compressive strength up to 35.98% with the length of 20 mm and with 0.5% concentration, while the CFRC and SFRC with the length of 10 mm and with 1% concentration have increased the compressive strength up to 33.94% and 24.86%, respectively. On another hand, the split tensile strength was increased by HFRC with the length of 20 mm and with 1% concentration, CFRC with the length of 10 mm and with 1.5% concentration, and SFRC with the length of 30 mm and with 1% concentration have increased up to 25.48%, 24.56% and 11.80%, respectively, while the HFRC with the length of 20 mm and with 0.5% concentration has increased the compressive strength of concrete but has decreased the split tensile strength up to 2.28% compared to PC. Overall, using the HFRC with the length of 20 mm and with 1% concentration provide the maximum output in terms of split tensile strength. Graphical Abstract Experimental Investigation on the Mechanical Properties of Natural Fiber Reinforced Concrete
Steel fibre reinforced concrete (SFRC) is increasingly being used in the construction of civil infrastructure. However, there are inconsistencies among international standards and guidelines ...regarding the consideration of carbon-steel fibres for the structural verification of SFRC exposed to corrosive environments. This paper presents a review of the published research regarding carbonation- and chloride-induced corrosion of SFRC, and proposes a deterioration theory for cracked SFRC exposed to chlorides and carbonation, based on the damage at the fibre-matrix interface. The review confirms an overall agreement among academics and regulators regarding the durability of uncracked SFRC exposed to chlorides and carbonation. Contrariwise, the durability of cracked SFRC is under discussion at the technical and scientific level, as there is a large dispersion on the experimental results and some of the mechanisms governing the corrosion of carbon-steel fibres in cracks and its effects on the fracture behaviour of SFRC are not fully understood.
In order to further broaden the application scope of basalt fiber reinforced concrete (BFRC), prolong service life in complex environment, master development status and sort out development needs, ...the durability of BFRC in complex environment was systematically summarized. First of all, the reason and damage mechanism of concrete deterioration in a variety of harsh environment are analyzed and grasped. Secondly, the strengthening mechanism of basalt fiber (BF) structure in permeability, carbonization, sulfate erosion, alkali environment, freeze-thaw cycle and high temperature is reviewed in detail, and the strengthening effect and performance of BFRC are discussed from the perspective of macroscopic properties and microscopic pore structure. The addition of BF reduces the generation and development of early microcracks in concrete structures, promotes the densification of structures on a microscopic scale. What's more, the permeability, carbonation resistance, acid and alkali corrosion resistance, frost resistance and high temperature resistance of concrete structures can be significantly improved. Finally, the problems in the current research are summarized and research ideas to cope with the environmental complexity are proposed to provide a research basis for BFRC to maintain excellent performance in the actual complex application scenarios.
This paper focuses on the strengthening effect of basalt fiber on cement-based materials, and mainly introduces its strengthening effect and action mechanism from several aspects in the figure. Display omitted
Self-compacting polyolefin fibre reinforced concrete has shown high performance in both fresh and hardened state. Post-cracking behaviour provides significant residual strengths especially for large ...deformations. For small deformations, flexural residual strength could be enhanced with a small amount of steel-hooked fibres, obtaining a hybrid fibre-reinforced concrete well suited for structural use. Four types of conventional fibre-reinforced concrete with steel and polyolefin fibres were produced on the basis of the same self-compacting concrete also manufactured as reference. These concrete mixtures were manufactured separately with the same fibre contents being subsequently used for two more hybrid mixtures. Flexural and uniaxial fracture tests were performed in addition to the assessment of fresh and mechanical properties. The research showed both synergies (with the two types of fibres working together in the fracture processes) and an improvement of the orientation and distribution of the fibres on the fracture surface.
When designing fiber‐reinforced concrete (FRC) structures, one of the basic design issues is represented by the choice of a proper combination of fibers and conventional reinforcement that allows to ...obtain the best structural performance with the minimum amount of materials. The combination of rebars and fibers in the concrete matrix is generally known as Hybrid Reinforced Concrete (HRC). HRC represents a feasible solution in many structures; among these, slabs are gaining an increasing interest among practitioners. In fact, slabs are the most widespread structural elements in common practice as they are typically used to construct slabs on ground (industrial floors or foundations), slabs on piles (foundations) or elevated slabs. This paper focuses on the flexural design of FRC elevated slabs by using the most recent design provisions reported in the fib Model Code 2010. A simplified design procedure based on a consolidated design practice is proposed. Emphasis is given to the use of HRC to minimize the total reinforcement (fibers + rebars) in order to get practical and economic advantages during construction (ie, construction time and costs reduction). In more detail, a procedure for proportioning the hybrid reinforcement and then verifying the structural safety will be presented and discussed. Numerical nonlinear finite element analyses will be carried out to assess the effectiveness of the proposed design method.
•Reduction in the rate of cracking in concrete canal-lining is aimed.•Concrete reinforced with fibers (i.e. jute, nylon, and polypropylene) is examined.•Mechanical properties, water absorption, and ...linear shrinkage are investigated.•Plain concrete is taken as reference for comparison.•A significant enhancement in considered properties is noticed.
Seepage is a major water loss (20–30%) from the canal as compared to the other forms of water losses. Concrete is commonly used for canal-lining to reduce the seepage loss. Considerable seepage (15–20%) has been observed even in the cement–concrete conventional sections. The performance of canals decreases with an increase in the rate of cracking in concrete canal-lining. The rate of cracking in canal-lining can be reduced by improving the flexure, compressive, and splitting-tensile strengths of concrete. Out of these, splitting-tensile strength of concrete plays a vital role in controlling cracks. The use of fibers for characteristics improvement of concrete is very ancient. Natural fibers include many benefits, like low cost due to its abundance, least health hazards, and flexibility. The use of synthetic fibers as reinforcement in matrix has also attained intentness by reasons of its high strength, less water absorption, and low density in nature. The overall aim of the research program is to explore materials for better performance of canal-lining in terms of reduced water losses by controlling its rate of cracking due to alternate wetting and drying, and due to differential settlement, etc. The purpose of this work is to examine experimental behaviors of jute fiber reinforced concrete (JFRC), nylon fiber reinforced concrete (NFRC), and polypropylene fiber reinforced concrete (PPFRC) for controlling the rate of cracking in canal-lining. For this purpose, the mechanical properties (compressive, splitting-tensile, and flexure strengths, energies, and toughness indices), water absorption, and linear shrinkage of JFRC, NFRC, and PPFRC are determined experimentally as per ASTM standards. The properties of plain concrete (PC) are used as reference. The proportion of 1:3:1.5:0.7 (cement: sand: aggregate: water) is used for PC mix. The mixes of JFRC, NFRC, and PPFRC are manufactured by adding the jute fibers, nylon fibers, and polypropylene fibers, respectively, in the same mix design as that of PC. For production of each type of fiber reinforced composite (FRC), fibers having length of 50mm are added in concrete by an amount of 5% (by mass of cement). A reduction in compressive properties, and an improvement in splitting-tensile and flexural strengths, water absorption and linear shrinkage is exhibited by FRCs over that of PC. Among the tested FRCs, PPFRC shows better performance. This may ensure to control the rate of cracking in canal-lining, ultimately improving its performance.
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