Bond of Ribbed Steel Bar in High-Performance Steel Fiber Reinforced Expanded-Shale Lightweight Concrete

For the structural application of high-performance Steel Fiber Reinforced Expanded-shale Lightweight Concrete (SFRELC), a reliable bond of ribbed steel bar should be ensured. In this paper, an experimental study was carried out on the bond properties of ribbed steel bar embedded in SFRELC by the direct pull-out test. The SFRELC was produced with a strength grade of 35 MPa and a volume fraction of steel fiber as 0%, 0.8%, 1.2%, 1.6% and 2.0%, respectively. Fifteen groups of specimens were made with a central placed steel bar with diameter of 14 mm, 20 mm and 28 mm, respectively. Complete bond stress-slip curves were determined for each group of specimens, and the characteristic values of bond-stress and slip at key points of the curves were ascertained. Results show that the bond strength, peak-slip and residual bond strength increased with the increase of the volume fraction of steel fiber. With the increase of steel bar diameter, bond strength decreased while the peak-slip increased, and the descending curves became sharp with a decreased residual bond strength. Formulas for calculating the bond strength and peak-slip were proposed. The relationships were determined for the splitting bond strength, residual bond strength with the bond strength, the splitting bond slip and residual bond slip with the peak-slip. Combined with rational fitting analyses of bond strength and slip, a constitutive model was selected for predicting the bond stress-slip of ribbed steel bar in SFRELC.

Effect of corrosion on the bond strength of self consolidated lightweight concrete

Self-consolidating lightweight concrete (SCLWC) is a concrete with excellent filling ability, good passing ability, and adequate segregation resistance. The use of SCLWC can be beneficial for structures due to significant reduction in dead loads as well as structures in seismic zone. In addition, economic impacts on construction industry by using SCLWC will be significant because of its benefits. Three SCLWC mixtures are developed by using two types of lightweight aggregates (LWA) (such as blast furnace slag and expanded shale), two supplementary cementing materials (such as fly ash and metakaolin). In addition to fresh and strength properties, the effect of different degrees of accelerated corrosion on bond characterists of deformed steel bars in SCLWC is investigated by analyzing pullout test results such as load-slip relationship, voltage versus time data, failure modes, aggregate of specimens and concrete material characteristics.

Lightweight Self-consolidating Concrete: Statistical Modelling, Mixture Design And Performance Evaluation

A response surface method based experimental study was carried out to model the influence of key parameters on properties of Lightweight Self-Consolidating Concrete (LWSCC) mixtures developed with various types of lightweight aggregates namely, furnace slag (FS), expanded clay (EC), and expanded shale (ESH). Three key parameters were selected to derive mathematical models for evaluating fresh and hardened properties. Water/binder ratio of 0.30 to 0.40, high range water reducing agent (HRWRA) of 0.3 to 1.2% (by total content of binder) and total binder content of 410 to 550 kg/m3 were used for the design of LWSCC mixtures. Slump flow diameter, V-funnel flow time, J-ring flow diameter, J-ring height difference, L-box ratio, filling capacity, bleeding, fresh air content, initial and final set times, sieve segregation, fresh/28-day air/oven dry unit weights and 7- and 28-day compressive strengths were evaluated. Utilizing the developed model, three optimum LWSCC mixes with high desirability were formulated and tested for mechanical, mass transport and durability characteristics. The optimized industrial LWSCC mixtures were produced in lab/industrial set-up with furnace slag, expanded clay, and expanded shale aggregates. The mixtures were evaluated by conducting compressive/flexural/split tensile strength, bond strength (pre/post corrosion), drying shrinkage, sorptivity, absorption, porosity, rapid chloride-ion permeability, hardened air void (%), spacing factor, corrosion resistance, resistance to elevated temperature, salt scaling, freeze-thaw iv resistance, and sulphuric acid resistance tests. It was possible to produce robust LWSCC mixtures that satisfy the European EFNARC criteria for Self-Consolidating Concrete (SCC). The proposed mix design model is proved to be a useful tool for understanding the interactions among mixture parameters that affect important characteristics of LWSCC. This understanding might simplify the mix design process and the required testing, as the model identifies the relative significance of each parameter, provides important information required to optimize mix design and consequently minimizes the effort needed to optimize LWSCC mixtures, and ensures balance among parameters affecting fresh and hardened properties. LWSCCs with FS, EC and ESH lightweight aggregates can reduce the construction pollution, increase the design solutions, extend the service life of the structure and hence, promote sustainability in construction industry.

Effect of corrosion on the bond strength of self consolidated lightweight concrete

Self-consolidating lightweight concrete (SCLWC) is a concrete with excellent filling ability, good passing ability, and adequate segregation resistance. The use of SCLWC can be beneficial for structures due to significant reduction in dead loads as well as structures in seismic zone. In addition, economic impacts on construction industry by using SCLWC will be significant because of its benefits. Three SCLWC mixtures are developed by using two types of lightweight aggregates (LWA) (such as blast furnace slag and expanded shale), two supplementary cementing materials (such as fly ash and metakaolin). In addition to fresh and strength properties, the effect of different degrees of accelerated corrosion on bond characterists of deformed steel bars in SCLWC is investigated by analyzing pullout test results such as load-slip relationship, voltage versus time data, failure modes, aggregate of specimens and concrete material characteristics.

Lightweight Self-consolidating Concrete: Statistical Modelling, Mixture Design And Performance Evaluation

A response surface method based experimental study was carried out to model the influence of key parameters on properties of Lightweight Self-Consolidating Concrete (LWSCC) mixtures developed with various types of lightweight aggregates namely, furnace slag (FS), expanded clay (EC), and expanded shale (ESH). Three key parameters were selected to derive mathematical models for evaluating fresh and hardened properties. Water/binder ratio of 0.30 to 0.40, high range water reducing agent (HRWRA) of 0.3 to 1.2% (by total content of binder) and total binder content of 410 to 550 kg/m3 were used for the design of LWSCC mixtures. Slump flow diameter, V-funnel flow time, J-ring flow diameter, J-ring height difference, L-box ratio, filling capacity, bleeding, fresh air content, initial and final set times, sieve segregation, fresh/28-day air/oven dry unit weights and 7- and 28-day compressive strengths were evaluated. Utilizing the developed model, three optimum LWSCC mixes with high desirability were formulated and tested for mechanical, mass transport and durability characteristics. The optimized industrial LWSCC mixtures were produced in lab/industrial set-up with furnace slag, expanded clay, and expanded shale aggregates. The mixtures were evaluated by conducting compressive/flexural/split tensile strength, bond strength (pre/post corrosion), drying shrinkage, sorptivity, absorption, porosity, rapid chloride-ion permeability, hardened air void (%), spacing factor, corrosion resistance, resistance to elevated temperature, salt scaling, freeze-thaw iv resistance, and sulphuric acid resistance tests. It was possible to produce robust LWSCC mixtures that satisfy the European EFNARC criteria for Self-Consolidating Concrete (SCC). The proposed mix design model is proved to be a useful tool for understanding the interactions among mixture parameters that affect important characteristics of LWSCC. This understanding might simplify the mix design process and the required testing, as the model identifies the relative significance of each parameter, provides important information required to optimize mix design and consequently minimizes the effort needed to optimize LWSCC mixtures, and ensures balance among parameters affecting fresh and hardened properties. LWSCCs with FS, EC and ESH lightweight aggregates can reduce the construction pollution, increase the design solutions, extend the service life of the structure and hence, promote sustainability in construction industry.

Evaluation of applicability of expanded shale to produce lightweight aggregate as a replacement for commercial LECA in constructions

This study examined the potential of some shales obtained from different formations in Yazd province to produce Lightweight aggregates (LWAs) as natural materials and without the application of additives. Before heating the samples, the materials' usefulness for producing lightweight aggregates was examined by detecting the elemental and mineralogical composition of the shale samples. The presence of aluminosilicates and flux content confirmed and met the required conditions discussed by Riley's theory for the bloating process. Among the studied shale samples, Kharanagh shale samples of Kh1 and Kh2 were found as the most suitable materials to produce highly porous, light and mechanically durable aggregates after heating at the optimum temperature of 1200°C for a heating duration of 10min. The produced LWAs showed low density (for sample Kh1 equal to 0.7gr/cm3 which is close to the commercial LECA), low water absorption (quick water absorption indices of 5.35% and 5.48% for samples Kh1 and Kh2, respectively, which are less than one-third of LECA water absorption), porous microstructure (porous like LECA but with smaller pore size), and good mechanical properties (with aggregate impact and aggregate crushing values less than that of LECA and in the range of values suggested for construction aims). Finally, it was revealed that the produced LWAs have suitable microstructure, physical and mechanical properties, comparable with the commercial ones, which approve their potential for use as construction materials in lightweight concrete and road surface constructions.

Effect of Steel Fiber Content on Shear Behavior of Reinforced Expanded-Shale Lightweight Concrete Beams with Stirrups

To determine the validity of steel fiber reinforced expanded-shale lightweight concrete (SFRELC) applied in structures, the shear behavior of SFRELC structural components needs to be understood. In this paper, four-point bending tests were carried out on reinforced SFRELC beams with stirrups and a varying volume fraction of steel fiber from 0.4% to 1.6%. The shear cracking force, shear crack width and distribution pattern, mid-span deflection, and failure modes of test beams were recorded. Results indicate that the shear failure modes of reinforced SFRELC beams with stirrups were modified from brittle to ductile and could be transferred to the flexure mode with the increasing volume fraction of steel fiber. The coupling of steel fibers with stirrups contributed to the shear cracking force and the shear capacity provided by the SFRELC, and it improved the distribution of shear cracks. At the limit loading level of beams in building structures at serviceability, the maximum width of shear cracks could be controlled within 0.3 mm and 0.2 mm with the volume fraction of steel fiber increased from 0.4% to 0.8%. Finally, the formulas are proposed for the prediction of shear-cracking force, shear crack width, and shear capacity of reinforced SFRELC beams with stirrups.