Self-compacting Concrete Specimens Research Articles

Effect of high temperatures on physical and compressive strength properties of self-compacting concrete incorporating palm oil fuel ash

Palm oil fuel ash (POFA) has been widely utilized to replace cement in self – compacting concrete (SCC) to reduce the cost of its production, environmental pollution and health hazard caused in the cement production. However, the effect of high temperatures on SCC incorporating POFA has not been well established. The purpose of this research is to examine effects of high temperatures on the physical and compressive strength properties of SCC incorporating POFA with replacement level of 20% by weight of cement. The compressive strengths of SCC specimens were evaluated at 28 days of curing using both cubes and cylinders. Thereafter, the SCC specimens were exposed to high temperatures of 200, 400, 600 and 800 °C using an electric furnace for a period of 2 hours after attaining the required temperatures. After exposure, mass losses together with residual compressive strength were determined. The results of the test showed that there was a continuous reduction in mass of the specimens with increase in temperature. The results also revealed that the colour of the specimens does not change at 200 °C but the colour changes started to occur between 400 °C up to 800 °C. There was an increase in the residual compressive strength for the two mixes at temperature range of 200 – 400 °C for the cubes and cylinders whereas at the temperature of 400 – 600 °C and 600 – 800 °C, there was a sharp reduction in the residual compressive strength for the two mixes for the cubes and cylinders. The SCC with and without POFA follow the same trends.

RETRACTED: The effect of polypropylene fibres on the compressive strength, impact and heat resistance of self-compacting concrete

Abstract This paper intends to study the mechanical characteristics of self-compacting concrete (SCC) containing polypropylene fibres (PPF). 99 SCC specimens containing PPF were manufactured and tested. White 12-mm long PPF were used at 0%, 0.1%, and 0.3% by volume. The slump flow and T 500 were obtained on fresh SCC, while compressive strength, splitting tensile strength, impact resistance and heat resistance tests were performed to evaluate the SCC performance in the hardened state. To determine the effect of heat on SCC with and without PPF, the compressive and splitting tensile strengths of 28-day specimens placed at 250 °C for 8 h in an oven were evaluated. For the impact test, 50 mm, 100 mm and 300 mm cubic specimens were used. Also, a correlation was determined by trial and error to relate impact resistance with compressive strength, tensile strength, concrete age, temperature and PPF content. The results showed that, by increasing the volume of fibres in SCC, dispersion decreased. It was also observed that the use of 0.1% PPF significantly enhanced the compressive strength of SCC. Furthermore, the best performance in the splitting tensile strength, impact resistance and heat resistance tests was attained at 0.3% PPF.

Experimental Study and Failure Criterion Analysis on Combined Compression-Shear Performance of Self-Compacting Concrete

To investigate the combined compression-shear performance of self-compacting concrete (SCC), eight groups of concrete specimens under different axial compression ratios were designed, and the composite performance under different axial stresses was carried out by hydraulic servo machine. The uniaxial and tensile splitting strength of SCC were also included in the study. The failure modes of SCC were presented, discussed, and compared with normal concrete (NC). The characteristic points of stress-strain curves of SCC specimens from the experiments were extracted and analyzed under different axial compression stress. Based on the experimental results, the shear strength of compression-shear load was divided into cohesive stress and residual friction stress. The variation of residual stress and cohesive stress under the combined compression-shear stress was analyzed, and the relationship was obtained by numerical regression. Research results indicated that the residual stress increases linearly with the compression stress while the cohesive stress increased at first and then decreased. The research found that the friction coefficient of SCC was much smaller than NC due to the lack of interlocking effect. Utilizing the compression-shear strength of SCC, the material failure criteria of SCC were proposed from the view of shear failure strength and octahedral stress space, which could fit the experimental results confidently following the mathematical regression analysis. The comparison with data from other literature shows favorable consistence with the obtained criteria. The results of the study could be beneficial complement in engineering practices where SCC was applicable.

Effect of binary blended pozzolanic materials on properties of self-compacting concrete

The mechanism of achieving self-compacting concrete (SCC) leads to either high shrinkage or it affects the mechanical properties of the concrete. Therefore, there is a need for blended pozzolanic materials for the production of SCC to improve its properties. The tests conducted on the fresh SCC were filling ability, passing ability, segregation resistance. While on the hardened SCC were density, compressive strength, tensile strength, water absorption, and ultrasonic pulse velocity test. At a fresh stage, the addition of the blend improved the flow and segregation resistance of the SCC produced. SCC produced with the addition of up to 20% of the blends at 7 days of curing had an 8% higher strength. At 150 days, all the SCC specimens have the same range of strength. The water absorption capacity of SCC with the addition of the blend up to 20% was found to be 12% less than that of the control specimens. Cement replaced with up to 20% blend of RHA and MK can be used to produce SCC with improved early (7 days) and later strength. It is recommended that when SCC is to be produced with a blend of RHA and MK, 20% is the optimum level of cement replacement.

Mechanical and durability properties of self-compacting concrete with marble fine aggregate

Abstract Self-compacting concrete (SCC) enhances qualities and working conditions due to the elimination of compaction during construction. The usage of river sand in concrete affects natural resources and groundwater. This the paper deals the different testing methods to test high-flow ability, resistance against segregation, and passing ability of self- compacting concrete for M60 grade of concrete with a partial replacement of marble waste as a fine aggregate. Slump flow, V-funnel, L-box and U-box tests were carried out to examine the performance of fresh state SCC. In hardened state, the tests were conducted and cured at different periods to find compressive strength, tensile strength and flexure strength test with the replacement of marble fine aggregate percentage of 0%, 25%, 50% and 100% in SCC for 14, 28 and 56 curing days. The chemical admixture super plasticizer master Glenium sky 8233 and the viscosity modifying agent are used. The specimens are cast with 0.28 water-powder ratio. And also durability of SCC is tested by RCPT, WPT, chemical attack tests like acid and sulphate attack are conducted at the age of 28 and 56 days in SCC specimens. The results are compared with the conventional SCC and found satisfied up to 25% of partial replacement of fine aggregate as a marble aggregate for 28 and 56 curing days.

Evaluation of Self-Compacting Concrete Strength with Non-Destructive Tests for Concrete Structures

Self-compacting concrete (SCC) shows to have some specificities when compared to normal vibrated concrete (NVC), namely higher cement paste dosage and smaller volume of coarse aggregates. In addition, the maximum size of coarse aggregates is also reduced in SCC to prevent blocking effect. Such specificities are likely to affect the results of non-destructive tests when compared to those obtained in NVC with similar compressive strength and materials. This study evaluates the applicability of some non-destructive tests to estimate the compressive strength of SCC. Selected tests included the ultrasonic pulse velocity test (PUNDIT), the surface hardness test (Schmidt rebound hammer type N), the pull-out test (Lok-test), and the concrete maturity test (COMA-meter). Seven sets of SCC specimens were produced in the laboratory from a single mixture and subjected to standard curing. The tests were applied at different ages, namely: 1, 2, 3, 7, 14, 28, and 94 days. The concrete compressive strength ranged from 45 MPa (at 24 h) to 97 MPa (at 94 days). Correlations were established between the non-destructive test results and the concrete compressive strength. A test variability analysis was performed and the 95% confidence limits for the obtained correlations were computed. The obtained results for SCC showed good correlations between the concrete compressive strength and the non-destructive tests results, although some differences exist when compared to the correlations obtained for NVC.

Quality of the surface finish of self-compacting concrete

In this work, surface damage due to the presence of pores in self-compacting concrete specimens is studied and cataloged with the QSI method which simplifies the inspection of concrete samples with optimal results, even in curved areas. 48 test tubes distributed in a total of 12 mixtures were analyzed. The rheology of the concretes was analyzed and controlled. In concretes that obtain viscosities higher than 42 Pa s, a large number of large pores are detected on its surface, compared to concretes with lower viscosity and/or shear stress. The specimen with the worst surface finish that was manufactured (mixture nº. 11) had a viscosity of 58 Pa s and a shear stress of 26 Pa (QSI = 5.9%), compared to 14 Pa s and 15 Pa, respectively, of the concrete element that less surface area affected (QSI = 0.6%). The mixes H-2, H-3 and H-12 have the combination of lower values of viscosity and shear stress. This allows obtaining the best surface finishes, with average QSI values, respectively of 1.3% 1.6% and 1.6%. By increasing the flowability of the SCC, the number of pores and their size decrease. The values of viscosity and shear stress must be balanced to ensure an adequate flowability of the SCC.

Performance enhancement of self-compacting concrete in saline environment by hydrophobic surface protection

The purpose of this research is to enhance the performance of self-compacting concrete (SCC) to make it a more sustainable alternative to traditional concrete. SCC serves the purpose in harsh environments, therefore, requires protection against de-icing agents and harmful saline environments. This paper reports the results from a laboratory study evaluating the efficacy of two impregnants; pure-silane and water-based silane. Both materials were applied on dry and wet SCC specimens manufactured with high and medium doses of superplasticizer. When treatment is applied on dry samples, a significant reduction in chloride penetration was noticed. However, the impregnants were less effective when applied on specimens subjected to intermediate and long-term exposure to water. In dry conditions, pure-silane performed better than the water-based silane, although they had a similar performance when applied on wet specimens. In addition, increasing the internal moisture content has shown an adverse effect on the efficacy of both materials.

Effect of Recycled Plastic Granules as a Partial Substitute for Natural Resource Sand on the Durability of SCC

This investigation is focused on durability studies of binary blended self-compacting concrete (SCC) with the replacement effect of electronic plastic waste, namely high-impact polystyrene (HIPS) granules as partial sand. In the current investigation, for all the SCC mixes, cement is replaced with pozzolanic material fly ash in the binder content of 497 kg/m3 and an adopted water-to-binder ratio of 0.36. Durability properties such as porosity, water absorption, and sorptivity are assessed for the curing periods of 28 and 90 days on SCC specimens produced with HIPS (0%–40% replacement by volume of sand). Both surface and internal water absorption rates were found to be minimal for SCC with HIPS. Replacement of HIPS up to 30% in SCC exhibited improved trends for all tests results. Reported durability parameter values were within permissible limits and revealed the excellent performance of HIPS in SCC. The optimum durability values can be attributed to the dense microstructure of SCC obtained with the combined effect of HIPS and fly ash. The continuous gradation of aggregates in the matrix reduced porosity due to the spherical shape of HIPS; additionally, the hydrophobicity of HIPS inhibits moisture migration in SCC. The additional benefits of fly ash, such as pozzolanic action and the filler effect at the interfacial transition zone (ITZ) are also major contributions to the long-term performance of durability. Electronic plastic waste replacement for fine aggregates in concrete compensates for the disposal problem and conserves natural sand.

Properties of self compacting concrete exposed to wetting and drying cycles in oil products

Although the early deterioration of concrete exposed to petroleum products has being observed yet, the behavior of Self Compacting Concrete (SCC) being exposure to oil products is still unknown. In the present investigation, the mechanical and physical properties of hardened SCC cyclically being exposed to oil products (crude oil, gas oil, motor oil and fuel oil) have tested and discussed. The numbers of exposure cycles are 2, 3, 4, 5 and 6. Each exposure cycle consists of twenty days immersion in water or different oil products followed by air drying at ambient temperature for a period of ten days. The results have been compared to other specimens cured in water or continuously exposed to oil products for the same period. The results show that the effect of continuous exposure to oil products on the mechanical properties is more severe than that of cyclic exposure of SCC specimens. The compressive strength, splitting tensile strength, modulus of rupture, and static modulus of elasticity of SCC specimens have slightly deteriorated until the fifth cycle of exposure for all types of oil products comparing to reference specimens (cured in water). Eventually at the sixth cycle all properties have decreased.

Experimental investigation of reinforced SCC beam-column joint with rectangular spiral reinforcement under cyclic loading

This paper presents an experimental study on continuous rectangular spiral reinforced self-compacting concrete (SCC) beam-column subassemblies subjected to cyclic loading. Total three sets of exterior beam-column joint for different flexural strength ratio, with continuous rectangular spiral reinforcement and individual closed stirrups as reference specimen, are considered in the investigation and the flexural strength ratio adopted for three-set were 1.3, 1.5, 2.0. In this work, self-compacting concrete specimens with three different inclinations of stirrups angles (75°, 80°, 85°) are considered for the spiral reinforcement. For better understanding and analysis, all the (twelve) specimens are shrinked to one-third scale. The reinforced beam column sub assemblage has been subjected to cyclic tests to understand its crack propagation and resistive capacity during the seismic excitations. The primary objective of this study is focused on the seismic behaviour of the joint, in terms of load displacement pattern, hysteresis behaviour, failure pattern and energy dissipation. Further more studies are carried out to distinguish and analyse the performances with conventionally closed stirrups. The observed findings are motivating as continuous spiral stirrups outperformed the conventional stirrups in terms of ultimate strength, stiffness degradation, ductility factor and cumulative energy dissipation. These findings would be beneficial to the engineers to build, feasible, suitable and efficient upgrading technique for structural joints in seismic zones.

Influence of time-dependent rheological properties on distinct-layer casting of self-compacting concrete

The construction quality of self-compacting concrete (SCC) is possibly degraded by the distinct-layer casting in real structures due to the time-variable rheology of cement paste. This paper aims to investigate the influence of fly ash, water to binder ratio (w/b) and retarder dosage on distinct-layer casting of self-compacting concrete (SCC). Cubic specimens were cast in two layers with different delay durations of 20, 40 min and 60 min and the interface bond strength was tested using a self-designed method. On the other hand, yield stress and viscosity of cement mortars formulated from SCC mixtures were evaluated and the flocculation states of cement pastes were observed using an opto-digital microscope. Experimental results show that a weak interface is induced by the distinct-layer casting for SCC and the interface bond strength decreases with the longer delay for casting the second layer. The addition of fly ash, higher w/b ratio or higher dosage of retarder behave favorable effects on alleviating the distinct-layer casting induced degradation of interface bond strength for SCC specimens. This is attributed to the decreasing formation of floc particles in cement paste and lower time-dependent increase of static yield stress of cement mortar matrix. Relationships between the relative interface bond strength and static yield stress or static yield stress and average floc size can be expressed by exponential equations. Therefore, the negative effect of distinct-layer casting on SCC structures can be improved by controlling the flocculation process of cement paste.

Effects of sulfate rich solid waste activator on engineering properties and durability of modified high volume fly ash cement based SCC

The engineering properties and durability of high volume low calcium fly ash (HVFA) cement based self-compacting concrete (SCC) modified with addition of circulating fluidized bed combustion (CFBC) fly ash were explored. Experimental results showed that an addition of CFBC fly ash did not influence the stability and passing and filling abilities of modified HVFA cement based SCCs. But its presence significantly improved the compressive strength, bonding behavior, and durability of the hardened SCC specimens. The added small amount of CFBC fly ash was found to increase the earlier compressive strength of hardened SCC specimen at one day of curing up to 43.8% higher than that of the control SCC specimen, which indicates a remarkable contribution of CFBC fly ash addition to shortening the time of construction. At ages of 3, 7, and 28 days, such increases were up to 30.2%, 22.3%, and 17.8%, respectively.

Size effect on strength of Fiber-Reinforced Self-Compacting Concrete (SCC) after exposure to high temperatures

This pioneer study investigates the size effect on the compressive and tensile strengths of fiber-reinforced selfcompacting concrete (FR-SCC) with different specimens, before and after exposure to elevated temperatures. 432 selfcompacting concrete (SCC) specimens with two concrete grades (50 and 80MPa) and three steel fiber ratios (0%, 0.5% and 1%) were prepared and tested. Moreover, based on the experimental results, new formulations were proposed to predict the residual strengths for different specimens. A parametric study was also carried out to investigate the accuracy of proposed formulations. Residual strength results showed that the cylinder specimen with dimensions of 100x200 mm was the most affected, while the cube with a size of 100 mm maintained a constant difference with the standard cylinder (150x300 mm). Temperature effect on the cube specimen (150 mm) was the least in comparison to other specimen sizes and types. In general, provision of steel fibers in SCC mixtures resulted in a reduction in temperature effect on the variance of a conversion factor. Parametric study results confirm that the proposed numerical models are safe to be used for all types of SCC specimens.

The effects of shrinkage-reducing admixtures used in self-compacting concrete on its strength and durability

This study explores the effects of shrinkage-reducing admixtures (SRA) used in self-compacting concrete (SCC), a specific type of concrete which is gradually receiving widespread use, yet to be improved to the desired properties and expected to replace traditional concrete in the future, on its strength and durability.In this study, SCC mixtures with and without (reference) different SRA dosages were produced to define the optimum SRA utilization rate in SCC mixtures. After deciding the SRA dosage to be used in mixtures, properties of reference and SRA-added SCC mixtures were evaluated by focusing mainly on the workability, strength and durability properties after subjected to either direct water submersion or cyclic Na2SO4 solution.As a result of the experimental program, it was concluded that the presence of SRA has adverse effects on the mechanical properties of SCC specimens although these effects are not dramatic regardless of the harshness of environmental exposure. The influence of SRA addition on fresh-state properties was also minimal so that the workability of reference and SRA-added SCC mixtures were found to be similar. Occurrence and further development of both drying and restrained shrinkage were substantially restricted with varying rates when SRA was incorporated in SCC mixtures. Overall, this study concludes that with a proper selection of SRA dosage, SCC mixtures performing well even under very hazardous environments can successfully be produced and be taken advantage of without sacrificing much of workability and/or mechanical properties and risking the occurrence and further development of shrinkage-originated cracking.

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.

Combined Use of Shrinkage Reducing Admixture and CaO in Cement Based Materials

The combined addition of a Shrinkage-Reducing Admixture (SRA) with a CaO-based expansive agent (CaO) has been found to have a synergistic effect to improve the dimensional stability of cement based materials. In this work, aimed to further investigate the effect, mortar and self-compacting concrete specimens were prepared either without admixtures, as reference, or with SRA alone and/or CaO. Their performance was compared in terms of compressive strength and free shrinkage measurements. Results showed that the synergistic effect in reducing shrinkage is confirmed in the specimens manufactured with SRA and CaO. In order to clarify this phenomenon, the effect of SRA on the hydration of CaO as well as cement was evaluated through different techniques. The obtained results show that SRA induces a finer microstructure of the CaO hydration products and a retarding effect on the microstructure development of cement based materials. A more deformable mortar or concrete, due to the delay in microstructure development by SRA, coupled with a finer microstructure of CaO hydration products could allow higher early expansion, which might contribute in contrasting better the successive drying shrinkage.

Performance analysis of self compacting concrete without super plasticizer

The use of self compacting concrete (SCC) in civil engineering works has become an attractive option which produces confident cohesive concrete. This paper reviewed the feasibility of preparing a SCC without using super-plasticizer but with only mineral admixtures that are available locally, with the coarse aggregate size of with 20 mm well graded aggregates which is entirely a different way of preparation of SCC. The enhancement aspects were tested and ascertained with the EFNARC guidelines. The hardened properties of SCC were tested and compared with control concrete of M25 grade. In the preliminary investigation, mechanical properties of the SCC which have been prepared by the above said method were tested by its unique testing methodologies. Based on the test results, in the second phase, the flexural behavior of the SCC specimens, using beam specimens were tested for its load carrying capacity by loading frame. In both the phases of investigation, the results revealed that this type of SCC will be promising and effective combination to that of the traditional type of SCC prepared by Glenium product and also cost effective.

Experimental study of the mechanical behavior of self-compacting concrete based on fracture mechanics

ABSTRACT Considering the physical nonlinearity of concrete and the fundamentals of fracture mechanics for quasi-brittle materials, the objective of this study was to determine the fracture energy and the length of the fracture process zone (FPZ) as well as the modulus of elasticity, the tensile strength and the compressive strength of self-compacting concrete (SCC) to characterize its mechanical behavior. A series of tests, including a three-point bending test of SCC and conventional vibrated concrete (CVC) specimens, with a notch at mid-span, and tensile and compressive tests were performed. The mechanical parameters obtained from the CVC specimens were considered as a comparative reference. The effect of the following variables was evaluated and considered at two levels: compressive strength (30 and 50 MPa), granular composition (fine and coarse particle size) and maximum diameter of the aggregate (12 and 20 mm). The effect of these variables on the mechanical behaviors of the SCC specimens was evaluated based on the test results of specimens of four types of concrete, which were obtained from the combination of the variables. The bending tests were performed according to the RILEM TC 89-FMT recommendations, which are based on the size-effect method.

Behavior of Self-Compacting Concrete Columns Reinforced Longitudinally with Steel Tubes

This study investigates the behavior of self-compacting concrete (SCC) specimens reinforced with small-diameter steel tubes in lieu of reinforcing bars. Twenty specimens were cast and tested. Four specimens were reinforced with normal steel bars (reference specimens) and the remaining 16 with steel tubes. All specimens contained steel helices with a pitch of either 50 mm or 75 mm. Deformed steel bars of 16-mm diameter were used in the four reference specimens as longitudinal reinforcement. Steel tubes of 33.7-mm outside diameter with 2-mm wall thickness (ST33.7) and steel tubes of 26.9-mm outside diameter with 2.6-mm wall thickness (ST26.9) were used as longitudinal reinforcement in the remaining 16 specimens. The specimens were divided into five groups with four specimens in each group. From each group, one specimen was tested under concentric load, one under 25-mm eccentric load, one under 50-mm eccentric load, and one under flexural load. Although the nominal yield tensile strength of the steel bars was 150 and 250 MPa greater than the nominal yield tensile strength of steel tubes ST33.7 and ST26.9, respectively, the results revealed that steel tube reinforced self-compacting concrete (STR SCC) specimens have ultimate load similar to reference specimens. Ductility of concentrically loaded STR SCC specimens was higher than that of the reference specimens. This study also reveals the challenges associated with using steel tubes as longitudinal reinforcement in STR SCC column specimens due to slip of steel tubes in concrete and explores remedial measures for the slip of steel tubes.