Short term bond shear stress and cracking control of reinforced self-compacting concrete one way slabs under flexural loading

Farhad Aslani,Shami Nejadi,Bijan Samali 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.13 No.6

Fibre-reinforced self-compacting concrete (FRSCC) is a high-performance building material that combines positive aspects of fresh properties of self-compacting concrete (SCC) with improved characteristics of hardened concrete as a result of fibre addition. To produce SCC, either the constituent materials or the corresponding mix proportions may notably differ from the conventional concrete (CC). These modifications besides enhance the concrete fresh properties affect the hardened properties of the concrete. Therefore, it is vital to investigate whether all the assumed hypotheses about CC are also valid for SCC structures. In the present paper, the experimental results of short-term flexural load tests on eight reinforced SCC and FRSCC specimens slabs are presented. For this purpose, four SCC mixes – two plain SCC, two steel, two polypropylene, and two hybrid FRSCC slab specimens – are considered in the test program. The tests are conducted to study the development of SCC and FRSCC flexural cracking under increasing short-term loads from first cracking through to flexural failure. The achieved experimental results give the SCC and FRSCC slabs bond shear stresses for short-term crack width calculation. Therefore, the adopted bond shear stress for each mix slab is presented in this study. Crack width, crack patterns, deflections at mid-span, steel strains and concrete surface strains at the steel levels were recorded at each load increment in the post-cracking range.

The torsional behavior of reinforced self-compacting concrete beams

Aydin, Abdulkadir C.,Bayrak, Baris Techno-Press 2019 Advances in concrete construction Vol.8 No.3

Torsional behaviors of beams are investigated for the web reinforcement and the concrete type. Eight beams with self-compacting concrete (SCC) and twelve beams with conventional concrete (CC) were manufactured and tested. All the models manufactured as the $250{\times}300{\times}1500mm$ were tested according to relevant standards. Two concrete types, CC and SCC were designed for 20 and 40 MPa compressive strength. From the point of web reinforcement, the web spacing was chosen as 80 and 100 mm. The rotation angles of the concrete beams subjected to pure torsional moment as well as the cracks occurring in the beams, the ultimate and critical torsional moments were observed. Moreover, the ultimate torsional moments obtained experimentally were compared with the values evaluated theoretically according to some relevant standards and theories. The closest estimations were observed for the skew-bending theory and the Australian Standard.

Influence of coarse aggregate properties on specific fracture energy of steel fiber reinforced self compacting concrete

Raja Rajeshwari, B.,Sivakumar, M.V.N. Techno-Press 2020 Advances in concrete construction Vol.9 No.2

Fracture properties of concrete depend on the mix proportions of the ingredients, specimen shape and size, type of testing method used for the evaluation of fracture properties. Aggregates play a key role for changes in the fracture behaviour of concrete as they constitute about 60-75 % of the total volume of the concrete. The present study deals with the effect of size and quantity of coarse aggregate on the fracture behaviour of steel fibre reinforced self compacting concrete (SFRSCC). Lower coarse aggregate and higher fine aggregate content in SCC results in the stronger interfacial transition zone and a weaker stiffness of concrete compared to vibrated concrete. As the fracture properties depend on the aggregates quantity and size particularly in SCC, three nominal sizes (20 mm, 16 mm and 12.5 mm) and three coarse to fine aggregate proportions (50-50, 45-55, 40-60) were chosen as parameters. Wedge Split Test (WST), a stable test method was adopted to arrive the requisite properties. Specimens without and with guide notch were investigated. The results are indicative of increase in fracture energy with increase in coarse aggregate size and quantity. The splitting force was maximum for specimens with 12.5 mm size which is associated with a brittle failure in the pre-ultimate stage followed by a ductile failure due to the presence of steel fibres in the post-peak stage.

Cracking of Fiber-Reinforced Self-Compacting Concrete due to Restrained Shrinkage

Kwon, Seung-Hee,Ferron, Raissa P.,Akkaya, Yilmaz,Shah, Surendra P. Korea Concrete Institute 2007 International Journal of Concrete Structures and M Vol.1 No.1

Fiber-reinforced self-compacting concrete (FRSCC) is a new type of concrete mix that can mitigate two opposing weaknesses: poor workability in fiber-reinforced concrete and cracking resistance in plain SCC concrete. This study focused on early-age cracking of FRSCC due to restrained drying shrinkage, one of the most common causes of cracking. In order to investigate the effect of fiber on shrinkage cracking of FRSCC, ring shrinkage tests were performed for polypropylene and steel fiber-reinforced SCC. In addition, finite element analyses for those specimens were carried out considering drying shrinkage based on moisture diffusion, creep, cracking resistance of concrete, and the effect of fiber. The analysis results were verified via a comparison between the measured and calculated crack width. From the test and analysis results, the effectiveness of fiber with respect to reducing cracking was confirmed and some salient features on the shrinkage cracking of FRSCC were obtained.

Steel Fiber Reinforced Self-Compacting Concrete: A Comprehensive Review

Jawad Ahmad,Zhiguang Zhou,Ahmed Farouk Deifalla 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.6

Self-compacting concrete (SCC), which flows under its own weight without being compacted or vibrating, requires no outside mechanical force to move. But like normal concrete, SCC has a brittle character (weak in tension) that causes sudden collapse with no advance notification. The tensile capacity of SCC has increased owing to the addition of steel fiber (SF). Various research concentrates on increasing the tensile strength (TS) of SCC by incorporating SF. To collect information on past research, present research developments, and future research directions on SF-reinforced SCC, however, a detailed review of the study is necessary. The main aspects of this review are the general introduction of SCC, fresh properties namely slump flow, slump T50, L box, and V funnel, and strength properties such as compressive, tensile, flexure, and elastic modulus. Furthermore, failure modes of steel fiber-reinforced SCC are also reviewed. Results suggest that the SF decreased the filling and passing ability. Furthermore, improvement in strength properties was also observed. However, some studies reported that SF had no effect or even decreased compressive capacity. Additionally, SF improved the tensile capacity of SCC and avoid undesirable brittle failure. Finally, the review recommends the substitution of secondary cementitious materials in SF-reinforced SCC to improve its compressive capacity.

Long-term flexural cracking control of reinforced self- compacting concrete one way slabs with and without fibres

Farhad Aslani,Shami Nejadi,Bijan Samali 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.4

In this study experimental result of a total of eight SCC and FRSCC slabs with the same cross-section were monitored for up to 240 days to measure the time-dependent development of cracking and deformations under service loads are presented. For this purpose, four SCC mixes are considered in the test program. This study aimed to compare SCC and FRSCC experimental results with conventional concrete experimental results. The steel strains within the high moment regions, the concrete surface strains at thetensile steel level, deflection at the mid-span, crack widths and crack spacing were recorded throughout the testing period. Experimental results show that hybrid fibre reinforced SCC slabs demonstrated minimum instantaneous and time-dependent crack widths and steel fibre reinforced SCC slabs presented minimum final deflection.

Effect of Shrinkage Restraint on Deflections of Reinforced Self-compacting Concrete Beams

Ilker Kalkan,이종한 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.7

This paper presents the results of a study aimed at investigating the effects of restrained shrinkage on the in-plane deflection behavior of reinforced beams cast with self-compacting concrete. The load-deflection data from the tests on two sets of heavilyreinforced concrete beams were analyzed. The first set of beams was made with self-compacting concrete while conventionally vibrated concrete with shrinkage reducing admixture was used in the second set. It was found out that the first set underwent shrinkage cracking at early ages and this cracking caused the member responses of the beams to be closer to the fully-cracked response at the initial stages of loading. The second set of beams was found to have initial responses approximate to the uncracked response and the maximum shrinkage restraint stresses were calculated to be in the order of 20-40% of the modulus of rupture of concrete. The maximum shrinkage-induced restraint stress expressions of the AS 3600-2001, AS 3600-2009, EC2, and CSA A23.3-04 codes were found to underestimate the restraint stresses developed in the first set, yet the estimates from code solutions were in closer agreement with the experimental values in the second set.

Flexural and Shear Behavior of Steel Fiber Reinforced SCC Beams

Youcef Fritih,Thierry Vidal,Anaclet Turatsinze,Gérard Pons 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.6

This paper deals with the effect of steel fiber reinforcement on the behavior of Self-Compacting Concrete (SCC) beams. Bending tests were carried out to examine the effect of low fiber content (0.25% by volume) on the flexural behavior of beams with different amounts of steel rebar reinforcement. The study compares the behavior of reinforced concrete beams cast either with control SCC and the one of Fiber-Reinforced Self-Compacting Concrete (FRSCC). Fibers used were made of stainless amorphous metal. Their influence was studied through the global and local mechanical responses of the beams. The results show that fiber reinforcement allows the control of cracking to be improved. Yielding, ductility and load bearing capacity are not modified by the fiber reinforcement; its effects are limited to the kinetics and distribution of cracks. If it was observed that the used fiber content reduced stresses in the stirrups, they could not be considered as a solution to replace stirrups. However, their ability to transfer tensile stress through a crack provided greater beam stiffness, notably with a low steel bar reinforcement ratio. It was concluded that stainless steel fiber reinforcement is a suitable solution to control crack width in reinforced concrete elements in aggressive environments with respect to the limitations imposed by design codes such as the European code Eurocode 2.

Studying the effects of CFRP and GFRP sheets on the strengthening of self-compacting RC girders

Mazloom, Moosa,Mehrvand, Morteza,Pourhaji, Pardis,Savaripour, Azim Techno-Press 2019 Structural monitoring and maintenance Vol.6 No.1

One method of retrofitting concrete structures is to use fiber reinforced polymers (FRP). In this research, the shear, torsional and flexural strengthening of self-compacting reinforced concrete (RC) girders are fulfilled with glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) materials. At first, for verification, the experimental results were compared with numerical modeling results obtained from ABAQUS software version 6.10. Then the reinforcing sheets were attached to concrete girders in one and two layers. Studying numerical results obtained from ABAQUS software showed that the girders stiffness decreased with the propagations of cracks in them, and then the extra stresses were tolerated by adhesive layers and GFRP and CFRP sheets, which resulted in increasing the bearing capacity of the studied girders. In fact, shear, torsion and bending strengths of the girders increased by reinforcing girders with adding GFRP and CFRP sheets. The samples including two layers of CFRP had the maximum efficiencies that were 90, 76 and 60 percent of improvement in shear, torsion and bending strengths, respectively. It is worth noting that the bearing capacity of concrete girders with adding one layer of CFRP was slightly higher than the ones having two layers of GFRP in all circumstances; therefore, despite the lower initial cost of GFRP, using CFRP can be more economical in some conditions.

Stress-strain relationships for steel fiber reinforced self-compacting concrete

Aslani, Farhad,Natoori, Mehrnaz Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.2

Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, toughness, energy absorption capacity and fracture toughness. Modification in the mix design of SCC may have a significant influence on the SFRSCC mechanical properties. Therefore, it is vital to investigate whether all of the assumed hypotheses for steel fiber reinforced concrete (SFRC) are also valid for SFRSCC structures. Although available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates material's mechanical properties. The present study includes: a) evaluation and comparison of the current analytical models used for estimating the mechanical properties of SFRSCC and SFRC, b) proposing new relationships for SFRSCC mixtures mechanical properties. The investigated mechanical properties are based on the available experimental results and include: compressive strength, modulus of elasticity, strain at peak compressive strength, tensile strength, and compressive and tensile stress-strain curves.