Lightweight Self-consolidating Concrete Research Articles

Structural performance of fiber-reinforced SCC beams containing Stalite lightweight aggregates

This study intends to investigate the structural performance of large-scale fiber-reinforced lightweight self-consolidating concrete (LWSCC) as well as lightweight vibrated concrete (LWVC) beams made with Stalite aggregates under flexure loads. A total of fourteen reinforced concrete beam specimens were tested under a four-point bending configuration until failure. Two different binder contents (550–600 kg/m3), two types of lightweight aggregates (coarse and fine Stalite aggregates), two PVA fiber lengths (8–12 mm), and three fraction volumes of fibers (0.3%, 0.5%, and 1%) were considered in this study. The structural performance of the tested beam specimens was assessed in terms of load–deflection response, cracking behavior, energy absorption, displacement ductility, cracking moment, and ultimate flexural strength. This study also investigated the performance of design code provisions in predicting the cracking and ultimate moment capacities of all tested specimens. The results indicated that using shorter PVA fibers seemed to better improve the structural performance of LWSCC beams in terms of deformability, energy absorption, ductility, and ultimate flexural capacity than using longer PVA fibers. Using up to 1% PVA8 fibers in lightweight concrete beams made with Stalite aggregates proved to completely compensate for the drop in ultimate flexural strength that resulted from the use of low-density aggregates and further helped the beams to experience much higher rates of deformation. The results also showed that the model proposed by Henager and Doherty well predicted the ultimate moment capacity of LWSCC/LWVC beams reinforced with PVA fibers.

Assessment of concrete shear resistance of lightweight SCC beams containing scoria aggregates

Lightweight self-consolidating concrete (LWSCC) has become a construction material that combines the benefits of lightweight concrete (LWC) and self-consolidating concrete (SCC). However, this combination may affect the shear resistance of structural members made with such concrete. This paper evaluates the shear resistance and performance of LWSCC beams. Eight full-scale beams without stirrups were fabricated and tested to failure. Seven beams were constructed using LWSCC and one was cast using normalweight self-consolidating concrete (NWSCC). Natural lightweight coarse and fine scoria aggregates were used in preparing the concrete mix. The beams were tested over a simply supported span in a two-point loading configuration. The test parameters comprised the type of aggregates, the reinforcement ratio of longitudinal steel bars, the shear span-to-depth ratio, and the depth of the beam. The experimental results showed that employing scoria aggregates in the mix resulted in beams with a reduced self-weight, where the obtained unit weight of LWSCC was 1800 kg/m3. Compared to the beam with NWSCC, the counterpart beam with LWSCC showed 25% lower shear strength. Additionally, the LWSCC beam experienced a reduction of 20% in the flexural cracking load while the beam showed a larger number of cracks at failure. The shear strength of the beams was predicted using the relevant shear design provisions of the American Concrete Institute building code ACI 318, the Canadian standard CSA-A23.3, and Eurocode 2. The ACI 318 method provided more reliable and conservative estimates for the shear capacity of the tested beams.

Performance of Stalite lightweight SCC beam-column joints under reversed cyclic loading

This paper investigates the structural performance of Stalite lightweight self-consolidating concrete (LWSCC) beam-column joints under quasi-static reversed cyclic loading. Six beam-column joints made with different lightweight aggregate types (Stalite lightweight coarse [LC] and fine [LF] aggregates) and designed with/without joint shear reinforcement were cast and tested. The performance of tested specimens was assessed in terms of failure mode, hysteretic response, deformation, strength degradation, ductility, brittleness index, and energy dissipation capacity. The applicability and accuracy of design code provision in predicting the shear and flexural strengths of the tested joints were also investigated. The results indicated that it is possible to design Stalite LWSCC mixtures with a density ranging from 1888–1966 kg/m3, having a sufficient structural performance under cyclic loading. Properly designed LWSCC beam-column joints made with Stalite aggregates slightly reduced the load-carrying capacity by around 8.5% and ductility and dissipated energy by around 11.4% and 15.8%, respectively, compared to the normal-weight SCC (NWSCC) specimen. Despite the brittle nature of Stalite lightweight aggregates, LWSCC joints with sufficient hoops exhibited satisfactory cyclic performance and experienced ductile flexural beam failure. The results also indicated that LWSCC specimens containing Stalite fine aggregates showed better structural performance in terms of load-carrying capacity, strength degradation, ductility, brittleness index, and energy dissipation capacity compared to counterpart specimens made with Stalite coarse aggregates.

Structural Behavior of Bridge Deck Slabs Made with GFRP-Reinforced Lightweight Self-Consolidating Concrete

The use of lightweight self-consolidating concrete (LWSCC) has significantly increased due to enhanced mix designs and its projected lower overall costs than normal-weight concrete. Accelerated bridge construction (ABC) has become a common alternative to conventional construction techniques. The use of LWSCC in ABC will reduce structural loads and expedite transportation and installation of precast bridge elements. Limited research, however, has investigated LWSCC bridge elements reinforced with glass fiber–reinforced polymer (GFRP) bars. This paper reports on the performance of full-scale edge-restrained bridge deck slabs (simulating slab-on-girder bridges) fabricated with LWSCC reinforced with GFRP bars. The test specimens included three edge-restrained slabs and one unrestrained slab for comparison. The test specimens were 3,000 mm long × 2,500 mm wide × 200 mm thick and were tested up to failure under a concentrated load simulating the footprint of a standard CL-625 truck wheel load (87.5 kN) defined in current design codes. The investigated parameters were (1) reinforcement ratio; (2) top reinforcement; and (3) effect of edge-restraining. The cracking behavior, ultimate capacity, deflection, and concrete and reinforcement strains of the specimens were presented and discussed. In addition, the punching-shear capacity of the tested specimens was assessed with the currently recommended design equations. The test results indicate that the overall performance of LWSCC deck slabs reinforced with GFRP bars is similar to such structures made with normal-weight concrete.

Shear strengthening performance of GFRP reinforced lightweight SCC beams: Experimental and analytical study

Light weight construction using Glass Fibre-Reinforced Polymer (GFRP) bars and structural light weight concrete (LWC) have increased recently and offers a wide spectrum of advantages over traditional normal weight concrete (NWC) structures. However, the shear strengthening and rehabilitation performance of LWC beams reinforced with GFRP bars is very limited and currently there are no guidelines related to it. Therefore, this study presents the results of an experimental investigation on the shear strengthening behaviour of lightweight self-consolidating concrete (LWSCC) beams reinforced with GFRP bars. The test parameters studied in the experimental program were the longitudinal reinforcement ratio and strip configuration or orientation. A total of twelve shear deficient GFRP reinforced beams were prepared with a shear span to depth ratio of 3.12 and subjected to static four-point bending. Five beams in each series were externally strengthened with different configurations of Carbon Fibre-Reinforced Polymer (CFRP) strips and one beam served as a control specimen to compare the performance of the strengthened specimens. Crack patterns, load–displacement response curves, and strain in the external CFRP strips were recorded until the failure ultimate load. The results of the experimental study indicated that the external CFRP strips improved the nominal shear capacity of GFRP reinforced LWSCC beams, and the contribution of external CFRP strips was sensitive to the reinforcement ratio. The nominal shear capacity of the strengthened specimens increased from 33.3 to 168% compared to the control specimen. U-wraps with horizontal strips in the compression and tension zone were the most effective configuration, showing the highest increase in shear strength compared to other strengthened specimens. Moreover, the shear capacity was theoretically predicted using different Fiber-Reinforced Polymer (FRP) design standards and guidelines which were compared with the experimental results. All the FRP design standards have overestimated the shear capacity of LWSCC beams, and a modified equation with a set of recommendations was proposed based on the experimental study. In addition, a reduction factor of 0.75 is recommended for conservative design.

The effect of CFRP strip stirrups on the shear strength of SCC high strength lightweight concrete beams

The development and applications of structural high-strength lightweight self-consolidating concrete (HLWSCC) have increased significantly in recent years owing to its better mechanical properties and economic benefits over conventional normal weight concrete (NWC). This paper presents the results of an experimental and analytical study to evaluate the shear performance of HLWSCC beams internally reinforced with CFRP sheet stirrups. In addition to one control specimen, seven beams were cast and reinforced with CFRP sheet stirrups. The variables studied in the experimental program were the number of layers, strip spacing, strip (sheet) width, and strip configuration of CFRP stirrups. All the beams were subjected to four-point bending, and the experimental results include load–deflection response curves and strain values along with the failure modes. Experimental results showed that all the tested beams failed due to shear tension failure. However, some of the specimens also failed due to the rupture of CFRP sheet stirrups. The addition of CFRP sheet stirrups has substantially increased the shear capacity of HLWSCC beams and the increase in shear strength ranged from 64% to 140% over the control specimens. Additionally, the nominal shear strength was predicted using various Fiber Reinforced Polymer (FRP) design standards, including ACI 440.1R-15, CSA S806-12, CSA S6-14, CNR-DT (2013), JSCE, and Fib Bulletin 40. Comparing the predicted and experimental shear strength has shown that current design standards can be used safely to predict the ultimate shear strength of HLWSCC beams reinforced with newly innovative CFRP sheet stirrups.

Shear strength of steel fiber reinforced lightweight self-consolidating concrete joints under monotonic and cyclic loading

The shear behavior of precast concrete segmental bridges depends on the type of joints between the segments. However, there are few studies evaluating the shear strength of steel fiber reinforced lightweight self-consolidating concrete for application to precast concrete bridges. The purpose of this study is to compare the shear behavior of joints made of general concrete with developed concrete that includes lightweight aggregate and steel fiber under monotonic and cyclic loading. In this study, the push-off shear test was performed in accordance with experimental parameters of different concrete mixtures, key type, confining stress, and application of epoxy between the segments. The tests were carried out to assess the shear strength, shear behavior, crack propagation and failure mode of joints. The test results represented shear capacity of joints decreased 15.2% by replacing normal coarse aggregates with lightweight aggregates but could be enhanced through the incorporation of hooked-end steel fibers. The shear capacities of joints fabricated using developed mixture tended to be underestimated compared to analytically calculated strengths. Furthermore, the normalized stiffness of the joint was decreased with an increased number of load cycles under high-amplitude low-cycle load. The shear resistance through aggregate interlock may gradually decrease with increasing number of cycles resulting in failure at 85% of the failure load of the monotonically tested specimen. An appropriate level of confining stress and application of epoxy shall be considered to prevent sudden failure of joints at high amplitude cyclical loading conditions.

Bond-dependent coefficient and cracking behavior of lightweight self-consolidating concrete (LWSCC) beams reinforced with glass- and basalt-FRP bars

Crack width is one of the issues that can often control the design of flexural elements reinforced with fiber-reinforced polymer (FRP) bars due to the relatively low modulus of elasticity. This paper aims at investigating the cracking behavior of lightweight self-consolidating concrete (LWSCC) beams reinforced with glass- and basalt-FRP (GFRP and BFRP) bars and evaluating the bond-dependent coefficient (kb) values. Fifteen reinforced concrete specimens 200 mm in width, 300 mm in height, and 3100 mm in length were prepared and tested up to failure. Twelve specimens were made using LWSCC, while the other three were made with normal-weight concrete (NWC) as reference specimens. The test variables were concrete density (LWSCC and NWC); reinforcement type (GFRP and BFRP bars) with various surface conditions (sand-coated and helically grooved); and longitudinal reinforcement ratio. The experimental results show that the FRP-reinforced LWSCC (FRP-LWSCC) beams exhibited cracking behavior similar to that of the counterpart FRP-reinforced NWC (FRP-NWC) beams. The FRP-LWSCC beams had a linear crack response up to failure by concrete crushing, regardless of the amount and surface condition of the FRP reinforcement. Moreover, the recorded crack widths of the FRP-LWSCC beams are presented and compared to those predicted according to FRP design provisions. The comparisons indicate that the crack widths of the FRP-LWSCC beams can be estimated with the FRP design provisions with a variable degree of conservativeness. Furthermore, the determination of the kb factor reveals that the sand-coated GFRP and BFRP bars yielded smaller kb values than the helically grooved GFRP and BFRP bars.

Performance of lightweight SCC beams strengthened with rubberized engineered cementitious composite in shear

This study evaluated the shear behavior of lightweight self-consolidating concrete (LWSCC) beams strengthened with rubberized engineered cementitious composite (RECC). The RECC in this investigation, was developed with crumb RECC (CRECC) or powder RECC (PRECC). Four reinforced LWSCC beams layered with either CRECC or PRECC at the tension or compression zone, were constructed with no stirrups and tested in shear. Another three beams fully cast with LWSCC, CRECC, and PRECC, were tested for comparison. The performance of all tested beams was evaluated through different aspects including cracking behaviour, failure modes, ultimate shear load, post-diagonal cracking resistance, deformability, and energy absorption capacity. The experimental results indicated that strengthening LWSCC beams with either a CRECC or PRECC layer improved their ultimate shear strength, deformability, and energy absorption capacity without significant increase in their self-weight. The highest improvement in the shear behavior of the LWSCC beams was recorded when the CRECC or PRECC layer was located at the compression zone. Meanwhile, placing the RECC layer at the tension zone helped to enhance the cracking resistance, which indicates better protection for tensile reinforcing bars. The results also indicated that powder rubber seemed to be more efficient in developing RECC with higher fresh and mechanical properties compared to crumb rubber. The shear capacity of the tested composites was successfully estimated using a new model proposed based on a modification of the Eurocode’s equation.

Pull-out strength between Nano-SiO2 contained light-weightself-consolidating concrete and GFRP and steel bars

In this study, the effect of SiO2 nanoparticles on the bonding behavior of steel and glass fiber reinforced polymer (GFRP) bar embedded in contained Light-weight Self-Consolidating Concrete (LWSCC) has been studied experimentally and numerically. The measurement of the mechanical properties of LWSCC modified with SiO2 nanoparticles, including compressive and tensile strength, elastic modulus and density were also carried out. Studies are conducted on 7, and 28-day aged LWSCC samples containing 0, 2 and 5% SiO2 nanoparticles with 12 mm and 16 mm diameter GFRP and steel bars. The results show that LWSCC modified with SiO2 nanoparticles increases the bonding strength between concrete and bar. In LWSCC with 2 and 5 wt.% SiO2, the maximum pull-out force of 16 mm diameter steel bar is increased by 48.5% and 54.7%, respectively, compared to the LWSCC without nanoparticle addition. Also, bonding improvement between GFRP bars with a diameter of 16mm and LWSCC having 2 and 5 wt.% SiO2 is 32.3% and 40%, respectively.

Development of eco-efficient lightweight self-compacting concrete with high volume of recycled EPS waste materials.

Reusing the industrial waste materials is one of the main aims of sustainability and achieve the environmental protection. However, concrete is the main production for recycling waste materials and cleaning the climate. The utilization of self-consolidating lightweight concrete (SCLC) can achieve two important advantages of the structure self-weight reduction and improving workability. This paper examined the effect of waste expanded polystyrene (EPS) beads on the workability and hardened characteristics of sustainable SCLCs. Six different EPS volume fractions up to 80% replaced with normal coarse aggregate to produce SCLC mixtures with water to binder (w/b) ratio of 0.35. A total binder content of 500 kg/m3 by including 20% waste ceramic powder with 80% Portland cement and fine aggregate consist of river sand and fine ceramic with 1:1 ratio in all SCLC mixes. The workability of SCLCs was examined by slump flow time and diameter, L-box height ratio, V-funnel flow time, and segregation resistance. Moreover, the hardened properties tested at different curing periods such as compressive strength at 7, 28, and 90 days; flexural strength at 28 and 90 days; and splitting tensile strength, dry density, voids percent, water absorption, ultrasonic pulse velocity (UPV); and scanning electron microscope (SEM) at 28 days. The results verified that workability of SCLCs enhanced as EPS incorporation increased and achieved the limitations required for self-compacting concrete (SCC) while the strengths value curtailed but the compressive strength satisfied the lower value indicated by ACI for structural purposes. Depending on the water absorption and UPV, results illustrated that all produced sustainable SCLC mixtures had a good durability. Furthermore, a high linear correlation was noticed between the results.

Contribution of lightweight self-consolidated concrete (LWSCC) to shear strength of beams reinforced with basalt FRP bars

To date, the shear contribution of lightweight self-consolidating concrete (LWSCC) members reinforced with basalt fiber-reinforced polymer (BFRP) bars (LWSCC-BFRP) has not yet been investigated. Therefore, the anticorrosion properties of BFRP bars combined with the advantages of LWSCC motivated this research to assess the behavior of such members under shear. Eight beams cast using LWSCC and normal-weight concrete (NWC) reinforced with BFRP or steel bars were prepared and tested up to failure. The specimens had a total length of 3100 mm and concrete cross section of 200 mm in width and 400 mm in depth. The influence of two different types of BFRP bars of comparable quality and commercially available (sand-coated basalt and helically grooved basalt) on shear capacity was assessed. The tested beams included five beams reinforced with BFRP bars, one beam reinforced with steel bars, and two beams constructed using NWC for comparison purposes. The experimental results indicate that the adoption of LWSCC allowed for decreasing the self-weight of the reinforced concrete (RC) beams (density of 1800 kg/m3) compared to NWC. Test results show that the concrete shear capacity of the LWSCC beams increased as did the axial stiffness of the longitudinal BFRP reinforcing bars. The test results were compared with the shear capacities predicted using the provisions in several standards. Using a 0.75 concrete density reduction factor in the CSA 2012 shear equation to consider the influence of concrete density yielded a more accurate value for the concrete shear capacity. In addition, using a 0.8 concrete density reduction factor in the ACI 2015 design equation yielded an appropriate degree of conservatism compared to the NWC beams.

Behavior of Lightweight Self-Consolidating Concrete Columns Reinforced with Glass Fiber-Reinforced Polymer Bars and Spirals under Axial and Eccentric Loads

Behavior of Lightweight Self-Consolidating Concrete Columns Reinforced with Glass Fiber-Reinforced Polymer Bars and Spirals under Axial and Eccentric Loads

Shear Behavior of Lightweight Self-Consolidating Concrete Beams Containing Coarse and Fine Lightweight Aggregates

First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address

Optimal Mix Design and Quality Properties of 50 MPa Self-Consolidating Lightweight Concrete

In this study, basic data were used to quantitatively determine the initial properties of self-consolidating lightweight concrete by analyzing various characteristics, such as air content, workability, segregation resistance, filling capacity, air/dry density, and strength according to the incorporating ratio of lightweight aggregate. With the exception of Mixture (LF75-LC100) that uses 100% lightweight coarse aggregate (LC) and 75% lightweight fine aggregate (LF), all the mixtures satisfied the performance criteria for workability, segregation resistance, and filling capacity, as suggested in the JSCE, and air/dry density, as suggested in the Concrete Standard Specification. The compressive strength of all the variables, except the LF75-LC100, was measured to be at least 50 MPa, but the strength decreased in a manner similar to that depicted in previous research when LC was incorporated. The results of the above experiments indicated that 100% of the LC and 50% of the LF was the optimal mix for self-consolidating lightweight concrete.

Development length of prestressing strands cast in lightweight self-consolidating concrete

This paper investigates the development length of 0.6 in. (15.2 mm) diameter prestressing strands. Fifty flexural tests were conducted on twenty-five pretensioned concrete beam specimens, which had a cross-section of 6.75 in. by 12 in. (170 mm by 305 mm) and were 18 ft (5.5 m) long. The specimens were cast with two normal weight and four lightweight self-consolidating concrete mixtures with compressive strengths of 4000 psi (27.6 MPa) at prestress transfer and 6000 psi (41.4 MPa) at 28-day of age or 6000 psi (41.4 MPa) at prestress transfer and 7000 psi (48.3 MPa) at 28-day of age. The measured development length was approximately half the value predicted using the ACI 318 and AASHTO equations. Shear cracking leading to shear and bond failures at short embedment lengths made determination of the true development length difficult for lightweight specimens, but embedment lengths resulting in pure flexural failure were similar for all specimen types.

Performance of engineered cementitious composite covered or wrapped self-consolidating concrete beams under corrosion

In this study, effect of Engineered Cementitious Composite (ECC) covering and wrapping on corrosion resistance and structural performance of un-corroded and corroded shear beams made of self-consolidating concrete (SCC) and light weight SCC (LWSCC) has been extensively investigated. An accelerated corrosion test on beams has been performed to reach the required high degrees of corrosion (30–40% of rebar mass loss). Both corrosion and structural performance of corroded beams has been assessed and analysed. The structural performance of un-corroded and corroded beams has also been compared. The corrosion performance has been evaluated in terms of current flow, half cell potential, actual rebar mass loss, reduction in diameter etc. The structural performance has been assessed and compared in terms of load–deflection behaviour, 1st flexure/diagonal cracking load, ultimate failure load, post cracking shear resistance, ductility and energy absorption capacity, failure load and failure modes. Composite beams with ECC covering exhibited superior corrosion resistance and post-corrosion structural performance as compared to full depth SCC or LWSCC counterparts. The performance of ECC wrapped composite beams has been found to be better than those with covering. Overall, ECC can be used as covering or wrapping in conventional SCC/LWSCC beams to enhance their corrosion resistance performance significantly.

Stability of Lightweight Self-Consolidating Concrete Containing Coarse and Fine Expanded Slate Aggregates

Stability of Lightweight Self-Consolidating Concrete Containing Coarse and Fine Expanded Slate Aggregates

Durability of polymer-modified lightweight flowable concrete made using expanded polystyrene

Lightweight self-consolidating concrete (LWSCC) intended for structural and repair applications combines the advantages of improved workability and reduced dead loads resulting from the structure self-weight. This investigation evaluates the coupled effects of expanded polystyrene (EPS) and styrene-butadiene rubber (SBR) latexes on durability-related properties of LWSCC weighing between 1870 to 2360 kg/m3. The water-to-binder ratio (w/b) was regulated to ensure similar compressive strengths. Test results showed that the transport properties including sorptivity, corrosion, and chloride ion penetration were pretty similar to the control normal-weight concrete, despite the decrease in density. This was attributed to a combination of phenomena such as lower w/b that refines the concrete microstructure, EPS particles that function as internal barriers, and presence of SBR polymers that create dispersed network of impermeable films. The incorporation of SBR was beneficial to improve bonding strengths of composite slabs, especially when exposed to repeated freeze/thaw cycles. Compared to normal-weight concrete, the resistance to chemical attack improved when LWSCC is prepared with reduced w/b and/or SBR additions. Different regression models are proposed to predict the concrete durability as a function of w/b, EPS, and SBR rates.

Permeability properties of lightweight self-consolidating concrete made with coconut shell aggregate

Liquid substance intrusion into concrete is one of the issues that gradually damage its physical and structural integrity. The permeability properties of lightweight self-consolidating concrete containing coconut shell aggregate was investigated in this study. A partial replacement of crushed rock (granite) with coconut shell from 0 to 100% in step of 25% was considered for the mixtures. Rice husk ash (RHA) and Silica fume (SF) were considered for developing binary and ternary blended self-consolidating concrete with total powder content of 450 kg/m3 and 550 kg/m3. The testing of concrete involved the saturated water absorption, sorptivity and chloride ingress, which were used to examine the permeability properties of the concrete developed. The laboratory investigations showed encouraging results with better performance up to 75% replacement of crushed granite with coconut shell aggregate.