Self-compacting Concrete Beams Research Articles

Effect of Coarse Aggregate Size on Shear Behavior of Self-Compacting Concrete and Conventional Concrete Beams

This research presents an experimental study to investigate the effect of coarse aggregate maximum size on the shear behavior of self-compacting concrete (SCC) and conventional concrete (CC) slender beams having the same compressive strength and make a comparison between the shear behavior of concrete beams. The experimental program included casting and testing eight beams with a constant size of 150mm height ×125mm width×1000mm length. Two coarse aggregate maximum sizes were used (10mm and 20mm) with SCC and CC in normal and high strength concrete. The results showed that increasing the coarse aggregate maximum size from 10mm to 20mm results in a slight increase in the diagonal cracking load and ultimate shear strength of SCC beams, while for CC beams the result was more significant. Also, it was found that the effect of increasing the coarse aggregate maximum size was more significant for normal strength as compared with high strength beams for both concrete types. Furthermore, the comparison between the shear behavior of SCC and CC beams having the same compressive strength and a concrete with the same coarse aggregate maximum size revealed that the SCC exhibited less diagonal cracking load and less ultimate strength compared with CC.

Torsional Strength Enhancement of Reinforced SCC Box Beams Using Internal Transverse Steel Bracing Technique

An experimental investigation was conducted, in this paper, to evaluate the torsional strength enhancement of reinforced self-compacting concrete box beams using internal transverse steel bracing technique. Seven beam specimens have dimensions of (2100x300x300mm) for length; width and depth respectively, were poured and tested under pure torsion. Three variables were adopted in the present study; presence or absence of steel bracings, type of steel bracing (X-Type and XW-Type) and a number of steel bracing (1,3 and 5). Accordingly, the tested beams are divided into three groups (based on steel bracing type), the first group consists of one non-strengthened beam specimen (reference), the second group consists of three beams strengthened by X-Type steel bracing; while, the third group consists of three beams strengthened by XW-Type steel bracing. It was found that the ultimate torque moment increased by about (14.4%, 34.3% and 59.2%) for beam specimens containing one, three and five X-Type steel bracing, respectively, in comparison with the reference beam. While, the ultimate torque moment increased by about (21.9%, 41.8% and 71.6%), for beam specimens containing one, three and five XW-Type steel bracing, respectively, in comparison with the reference beam. The paper concludes that the contribution was enhanced using the adopted technique.

Shear strength of self-compacting concrete and recycled aggregate concrete beams: an appraisal of design codes

Provisions are given in design codes for the calculation of shear strength of conventional concrete (CC) beams. In this paper, a database is generated for self-compacting concrete (SCC) and recycled aggregate concrete (RAC) slender beams with and without shear reinforcement which were investigated for shear strength. Shear capacities of 103 SCC beams and 109 RAC beams with and without shear reinforcement are calculated using the provisions of ACI 318-14, JSCE-2007, NZS 3101-2006 and AS 3600-2009. Calculated nominal shear strengths (Vn) are compared with the experimental shear strengths (Vexp) and statistical parameters are obtained for each code. It was found that all the four codes yielded unconservative estimates of the shear capacities for SCC and RAC beams without shear reinforcement having longitudinal reinforcement less than 1% and depth greater than 450 mm. All the four codes produced reasonable and conservative estimates of the shear capacities of SCC and RAC beams with shear reinforcement. AS 3600-2009 produced minimum average of Vexp/Vn with least scatter but at the same time it yielded maximum unconservative results. A modification in the depth factor of AS 3600-2009 reduced the percentage of unconservative results from 18.67 to 7.8% for SCC beams and 24.67 to 8% for RAC beams without any increase in coefficient of variation (COV).

Bond Behavior of Tension Bar at Lap Splice of SCC Beam

This paper investigates the bond strength of tension lap splice in the ordinary concrete (OC)beam and self-compacted concrete (SCC) beam. A total of six beam specimens were cast for thebending test. Results indicate that the SCC beam and OC beam present similar bond strength at thelap splice of tension bar. Current code for the tension lap splice is available for the SCC beam. Bothof the SCC and OC beams with transverse stirrups could have ductile flexural behavior in the regionof tension lap splicer. Only minor spalling between reinforcing steel and concrete was found underservice loading, such that the corrosion resistance of the tension lap splice in the SCC and OC beamscould be preserved.

Shear capacity investigation of self compacting concrete beams with rectangular spiral reinforcement

Replacing traditional closed stirrups by rectangular spiral reinforcements in concrete beams constructed using self compacting concrete (SCC) is experimentally investigated in this paper by testing twenty beams under static loading. The shear performance of SCC beams is evaluated by measuring the maximum shear load values, load-deflection curves, and crack propagation for all tested beams. Two different spirals spacing of 200 and 150 mm and five different angles of inclination for the spiral reinforcement (85°, 80°, 77.2°, 75°, and 72.5°) are adopted. The experimental shear capacity results are compared with theoretical shear strength determined by the (ACI 318) code. The results indicated that using of continuous spiral reinforcement improves the shear capacity of SCC beams up to 16.67% increase in comparison to traditional closed stirrups. Moreover, the results showed that optimum performance depends on the angles of inclination, where 85° was the optimum angle of inclination regardless of pitch spacing. It is recommended to use the continuous spiral reinforcements in SCC beams because it enhances the shear capacity, and reduces time and labor cost needed in construction.

Research on Durability of Big Recycled Aggregate Self-Compacting Concrete Beam

Deflection and crack width are the most important durability indexes, which play a pivotal role in the popularization and application of the Big Recycled Aggregate Self-Compacting Concrete technology. In this research, comparative study on the Big Recycled Aggregate Self-Compacting Concrete Beam and ordinary concrete beam were conducted by measuring the deflection and crack width index. The results show that both kind of concrete beams have almost equal mid-span deflection value and are slightly different in the maximum crack width. It indicates that the Big Recycled Aggregate Self-Compacting Concrete Beam will be a good substitute for ordinary concrete beam in some less critical structure projects.

A comparative study of the effect of adding steel fiber on the mechanical behavior of RSCC beams under displacement and force control conditions

An experimental program is carried out on 32 reinforced self-compacting concrete (RSCC) beams containing various fractions of steel fiber under different cyclic loading control conditions. For this purpose, concrete beams with 4 mix designs of (RSCC) containing fiber (0.1, 0.2 and 0.3% volume fraction) and (RSCC) without fiber as the reference concrete were subjected to harmonic cyclic loading. The results achieved from this investigation indicate that in the displacement-controlled condition, with the increase of fiber fraction, the cyclic behavior of the specimens improves and in the after-yielding region of loading, this increment results in more obvious discrepancy among loading conditions.

Flexural behavior of self-compacting concrete beams strengthened with steel fiber reinforcement

Steel fiber self-compacting concrete (SFSCC) is an innovative material that can flow underneath its own weight in the fresh state, thus eliminating any need for mechanical vibration and complexity of the formwork, and which employs the benefits of steel fiber addition in the hardened state. Hence, this study evaluated the performance of a self-compacting concrete (SCC) under the effect of filler addition and then investigated the effect of steel fiber (SF) addition on flexural behavior, splitting tensile strength, compressive strength, and modulus of elasticity. Fourteen reinforced concrete beams were tested under monotonic loads: two sets of six SCCs (with and without SFs) and two normal concretes (NCs). Ultimate capacity, deflection, crack pattern, and mode of failure were recorded. The present experimental and theoretical results were compared in accordance with ACI 318 codes to assess the applicability of the aforementioned methods to predict the flexural strength of SCC specimens. The results of the tests carried out on fresh concretes indicate excellent deformability without blocking. Moreover, the flexural strength in beams increases with increasing concrete compressive strength, longitudinal steel reinforcement ratio, and SF amount.

Strengthening of self-compacting reinforced concrete deep beams containing circular openings with CFRP

This paper shows the behavior of reinforced self-compacting concrete deep beams with circular openings strengthened in shear with various arrangements of externally bonded Carbon Fibre Reinforced Polymer (CFRP). Six simply supported deep beams were constructed and tested under two points load up to the failure for this purpose. All tested beams had same geometry, compressive strength, shear span to depth ratio, main flexural and web reinforcement. The variables considered in this study include the influence of fiber orientation, utilizing longitudinal CFRP strips with vertical strips and area of CFRP. The test results indicated that the presence of the circular openings in center of load path reduce stiffness and ultimate strength by about 50% when compared with solid one, also it was found that the externally bonded CFRP can significantly increase the ultimate load and enhance the stiffness of deep beam with openings.

Torsional strength evaluation of reinforced SCC box beams strengthened internally by opened and closed transverse concrete diaphragms

There are a few researches about box (hollow core) RC beams under the effect of torque moment; therefore, a torsional failure mechanism is not understood well. In the present paper, the concept (technique) of adding internal concrete diaphragms, in transverse direction, is adopted. Six self-compacting concrete beam specimens having a dimension of (2200x220x350mm) for length, width and height, respectively were poured and tested. Three variables are adopted in the present study, section type, number and type of the internal diaphragms. Experimental results show that the ultimate torque moment increases about (43%-61%) and (89%-94%) for beam specimens strengthened internally by two and four diaphragms respectively. Also, increasing internal diaphragms from two to four, led to increase the ultimate torque moment about (33%-46%). Furthermore, the change of section from box section with four internal diaphragms to solid section, led to increase in ultimate torque moment about (28%-33%). The paper concludes that the increase in torsional capacity is attainable for box (hollow core) beams by using the technique of strengthening by internal diaphragms; Also, the box sections can be made with internal opened diaphragms and possess same capacity or contribution of the closed ones.

Betonarme Kirişlerin Deneysel ve Teorik Burulma Momenti Değerlerinin Karşılaştırılması

The experimental investigation effect on the torsional behavior of web spacing, concrete class and concrete type of reinforcement concrete beams constitute basis of this work. The compressive strength of concrete, 20 MPa and 40 MPa, the type of concrete, conventional concrete and self-compacting concrete, web spacing of 80 mm and 100 mm, was determined the main parameters of this work. 12 unit of conventional concrete beams and 8 unit of self-compacting concrete beams of 250x300x1500 mm was manufactured. The torsional moment capacities and corresponding rotation angle values, the critical torsional moment values and corresponding critical rotation angles, torsional cracks of the beam samples that subjected to the torsion was measured experimentally. The torsional moment capacity results that were measured experimentally were compared with the elastic, plastic and skew-bending theories. The most closed results were get to the skew-bending theory. The graphic of torsional moment capacity- unit rotational angles were plotted. The low web spacing, high concrete class and self-compacting concrete type that have a positive effect on the torsional behavior was determined experimentally in this study. Experimental critical torsion values were compared with empirical values obtained from related studies.

Shear Behavior of High Strength Self Compacting Concrete Beams

This research presents an experimental study to investigate the shear behavior of high strength self-compacting concrete slender beams. The experimental program includes testing seven beams with constant size of (150mm height ×125mm width×1000mm length) to study the effect of shear span to effective depth ratio (a/d), longitudinal reinforcement ratio (ρw) and shear reinforcement ratio (ρv) on shear behavior for these beams. The experimental results showed that, increase shear span to effective depth ratio (a/d) has pronounced effect on decreasing diagonal cracking load and ultimate shear strength and increasing the ductility ratio, as (a/d) increase from 2.5 to 3.0, the decreases in diagonal cracking load and ultimate shear strength are with percentages of 17.8% , 21.6% respectively, while the ductility ratio increase with percentage of 16.7%. Also the results showed that the longitudinal reinforcement ratio (ρw) has significant effect on the gain in shear bearing capacity and ductility ratio, as increasing of longitudinal reinforcement ratio from 3.191% to 6.383% the increases in diagonal cracking load, ultimate shear strength and ductility ratio are with percentages of 43.8%, 46.6% and 37.0% respectively. Furthermore the results revealed that the vertical shear reinforcement has the major effect in improvement the shear behavior of these beams, however, using shear reinforcement (ρv) with percentage of 0.502% results in increase diagonal cracking load, ultimate shear strength and ductility ratio with percentages 50.7%, 63.6% and 48.1% respectively as compared with beam without shear reinforcement. Also presence of vertical shear reinforcement changed the mode of failure from the brittle to ductile.

Shear strength of slender SCC beams - possible differences from VC beams

ABSTRACT In comparison with vibrated concrete (VC) of the same strength class, self-compacting concrete (SCC) typically has a lower coarse aggregate content and, eventually, a smaller maximum aggregate size. This may reduce the aggregate interlock between the fracture surfaces in SCC. Since the aggregate interlock plays an important role in the shear strength of slender beams, SCC beams may have a shear strength lower than that of similar VC beams. This article summarizes experimental studies on the shear strength of reinforced SCC slender beams without and with shear reinforcement. The shear strengths of SCC beams are compared with the ones of VC beams and also to the calculated ones according to different code procedures. It is shown that powder-type SCC beams tend to have lower shear strength than similar VC beams and that the difference depends upon the concretes composition and the characteristics of the beams.

Comparative study on flexural behaviour of RCC beam and SCC ternary beams with mineral admixtures

Self compacting concrete (SCC) has an ideal fluid character at the fresh state and becomes solid once it sets/hardens completely when poured on the desired shape of the mould. The increase of workability and the control of segregation were taken care by super plasticizer (SP) and viscosity modifying agent (VMA) dosages. In this paper an attempt was made to study the flexural behaviour of ternary SCC beams. Cement was replaced with two different combinations viz metakaolin (mk)+ground granulated blast furnace slag (ggbs) and silica fume+ggbs. The experimental results of these ternary beams were compared with Conventional Vibrated Concrete (CVC) & SCC control concrete (SCC 0). Fresh properties of SCC like slump flow, spread were studied in accordance with EFNARC guidelines. Flexural strength of concrete was tested at the age of 28days. Load-deflection characteristics were studied at mid span of the beam (L/2). From the results it was observed that SCC ternary blended beams have higher flexural strength and better ductile performance compared to CVC and SCC0 beams.

Analysis of Flexural Fatigue Strength of Self Compacting Fibre Reinforced Concrete Beams

This study presents the extensive statistical investigation ofvariations in flexural fatigue life of self-compacting Fibrous Concrete (FC) beams. For this purpose, the experimental data of earlier researchers were examined by two parameter Weibull distribution.Two methods namely Graphical and moment wereused to analyse the variations in experimental data and the results have been presented in the form of probability of survival. The Weibull parameters values obtained from graphical and method of moments are precise. At 0.7 stress level, the fatigue life shows 59861 cyclesfor areliability of 90%.

Study on Flexural Behaviour of Ternary Blended Reinforced Self Compacting Concrete Beam with Conventional RCC Beam

The conventional concrete when used for structures having dense congested reinforcement, the problems such as external compaction and vibration needs special attention. In such case, the self compacting concrete (SCC) which has the properties like flow ability, passing and filling ability would be an obvious answer. All those SCC flow behavior was governed by EFNARC specifications. In present study, the combination type of SCC was prepared by replacing cement with silica fume (SF) and metakaolin (MK) along with optimum dosages of chemical admixtures. From the fresh property test, cube compressive strength and cylinder split tensile strength, optimum ternary mix was obtained. In order to study the flexural behavior, the optimum ternary mix was taken in which beam specimens of size 1200 mm x 100 mm x 200 mm was designed as singly reinforced section according to IS: 456-2000, Limit state method. Finally the comparative experimental analysis was made between conventional RCC and SCC beams of same grade in terms of flexural strength namely yield load & ultimate load, load- deflection curve, crack size and pattern respectively.

Bamboo‐reinforced self‐compacting concrete beams for sustainable construction in rural areas

The use of bamboo as longitudinal reinforcement, coupled with the application of self‐compacted concrete (SCC) in the construction industry, may be a promising solution to issues involving sustainable development in developing countries. This study seeks to investigate the flexural performance of bamboo‐reinforced SCC beams with adequate transverse reinforcement. The major design parameters were the shear span‐to‐depth ratio, the percentage of longitudinal reinforcement, and the maximum size of coarse aggregate. The load–deflection curves, serviceability and ultimate failure characteristics, cracking behavior, and ductility measures were evaluated and discussed among tested beams. Results indicated that their structural performance at service and ultimate failure would be adequate when a material reduction factor of three is used with BS 8110 design code. However, to achieve maximum ductility, the level of longitudinal reinforcement should be in range of 2.6–3.1%. Furthermore, an increase in the size of coarse aggregate will greatly impact the degree of ductility.

Flexural performance of self-compacted perforated concrete beams under repeated loading

The current paper presents an experimental study in order to verify the flexural performance of a new developed perforated beam system. This system facilitates passing the pipes of utility services through its perforations as well as it has a good-looking appearance. Three main factors were studied; namely, the percentage of mass loss (14% 19% and 26%) due to the provided perforations, the reinforcement configurations around the perforations (orthogonal reinforcement, circular stirrups, and cross-bars) and the perforations shape (circular and oval). Therefore, three perforations sizes were studied having perforation diameter to the beam total depth ratio (D/t) of 0.38, 0.50, and 0.62. Accordingly, six perforated beams along with one solid reference beam were prepared and configured then tested under repeated loading till complete collapse. It could be concluded that the perforated beams of 200mm perforations diameter (D/t=0.5) reinforced by circular stirrups and cross-bars showed approximately the same flexural capacity as that of the solid beam but cross-bars stirrups enabled the perforated beam to develop approximately the same ductility as that of the solid beam. While, the beam with circular perforations (D/t=0.5) provided by orthogonal reinforcement manifested increased flexural capacity by about 31% compared to that of the solid beam, while the developed ductility was lower than that of the solid beam by about 55%. In addition, the ductility could be outperformed by about 21% keeping the same ultimate capacity compared to those of solid beam provided that the mass loss of 14% was achieved as showed by the perforated beam with 150mm perforations diameter (D/t=0.38).

Magnetic orientation of steel fibres in self-compacting concrete beams: Effect on failure behaviour

The magnetic orientation of steel fibres in transparent silicone oil and in fresh, self-compacting concrete (SCC) beams is studied experimentally. The effect of the generated fibre locations and orientations on the failure response of the SCC beams is determined by means of three-point bend tests. A relatively small coil was designed for the magnetic orientation of single and multiple fibres in the transparent silicone oil. The time required for orienting a single fibre was measured for a range of magnetic fluxes, which showed to strongly decrease with increasing magnetic field strength. The presence of gravel on the fibre orientation behaviour was considered in order to mimic the influence by a concrete aggregate, indicating that the gravel does not prevent rotations and chain formations of fibres. A larger coil was developed for the magnetic orientation of fibres in freshly casted SCC beams. The energy absorption capacity of SCC beams subjected to three-point bending scales approximately proportionally with the number of “well-oriented fibres” bridging the catastrophic failure crack, which emphasizes the importance of adequately orienting steel fibres with the magnetic orientation technique.

Identification of mechanical and fracture properties of self-compacting concrete beams with different types of steel fibres using inverse analysis

The application of self-compacting concrete has found wide use in practice. However, its application is often limited by lack of knowledge on material parameters gained from laboratory tests, which results in difficulties in the design of progressive building structures and buildings where non-linear finite element analysis should be used. The submitted paper presents results of identification of mechanical and fracture properties of selected self-compacting concrete beams applicable for non-linear finite element analyses. A procedure dealing with the determination of mechanical and fracture properties from an extensive series of tests on notched beams is also presented. The studied material is a high-performance concrete reinforced with two types and three volume ratios of steel fibres. An inverse analysis in combination with a multi-criterial analysis is used for evaluation of fracture-mechanical characteristics.