High-performance Concrete Specimens Research Articles

Effects of acidic environments and sorptivity on high-performance concrete containing natural pozzolan and limestone filler

Even though high-performance concrete (HPC) is a more robust type of concrete, acidic environments can still have a negative impact on it. Acids can dissolve other components in the concrete as well, leading to a loss of material and increased porosity. This makes the concrete even more susceptible to further degradation. Acidic environments attack the calcium hydroxide (CH), a key component of the cement paste that binds the aggregate in concrete. This reaction weakens the structure and reduces the overall strength of the concrete. The purpose of this study is to assess how HPC containing natural pozzolan (NP) and limestone filler (LF) responds to acidic environments and sorptivity. The cement (PC) was replaced by NP and LF in different mass proportions. The mixtures HPCC (100% PC), HPC18 (10%LF + 90%PC), HPC7 (20%NP + 80%PC), and HPC14 (5%LF + 10%NP + 85%PC) were prepared. The sorptivity was evaluated by measuring the sorptivity coefficient (S, cm*s-0.5) after 28 days of submersion in distilled water. HPC specimens were submersed in distilled water, 5% sulfuric acid (H2SO4), and 5% hydrochloric acid (HCl) for up to 180 days in order to test their acid resistance. Visual inspection and changes in mass were used to evaluate the specimens' resistance to acid attack. The results showed that replacing PC with LF and NP reduced the sorptivity of HPC. Substituting 10% of PC mass with LF increased the HPC's resistance to sulfuric acid. However, substituting the PC with NP and/or LF reduced the HPC's resistance to hydrochloric acid. According to visual inspection and mass losses, the sulfuric acid was more aggressive than hydrochloric acid.

Improving Corrosion Resistance and Prolonging the Service Life of High-performance Concrete Structures Using Fly Ash and Ground Granulated Blast-furnace Slag

This study investigates the impact of ground granulate blast-furnace slag (GGBFS) and fly ash (FA) on both the corrosion resistance of steel reinforcement, assessed through the accelerated macrocell corrosion test (AMCT), and the durability characteristics of high-performance concrete (HPC). Additionally, the study encompasses an analysis of various concrete properties, including the pH of fresh concrete mixtures as well as water absorption, chloride permeability, and surface resistivity (SR) in hardened concrete specimens. Microstructure analysis on HPC specimens as well as the service life prediction of RCS were also performed in this study. Test results show that the HPC incorporating 35% GGBFS or 35% GGBFS + 20% FA as cement replacement resulted in a lowered pH of fresh mixtures while water absorption and chloride permeability of these specimens increased significantly. In addition, the incorporation of 35% GGBFS or 35% GGBFS + 20% FA concurrently enhanced the SR of HPC specimens. Moreover, these HPC specimens exhibited better corrosion resistance ability as their respective AMCT values were about 1.54 and 1.45 times higher than that of the control specimen. Further, the research highlighted a substantial extension in the corrosion initiation time of concrete structures employing 35% GGBFS or 35% GGBFS + 20% FA, about 3 and 6 times longer than the HPC without GGBFA and FA, respectively. The experimental results, confirmed by the substantial microstructural enhancement in the HPC containing GGBFS and FA, also demonstrated a close interplay between durability and other concrete properties such as water absorption, chloride permeability, and SR.

Hybrid and ensemble models by coupled with automated meta-heuristic algorithms for compressive and flexural strength and slump of high-performance concrete

High-performance concrete (HPC) is a specialized type of concrete designed to meet stringent performance and uniformity standards that are difficult to achieve with conventional materials and standard mixing, placing, and curing methods. The testing process to determine the mechanical properties of HPC specimens is complex and time-consuming, and making improvements can be difficult after the test result does not meet the required properties. Anticipating concrete characteristics is a pivotal facet in the realm of High-Performance Concrete (HPC) manufacturing. Machine learning (ML)-driven models emerge as a promising avenue to tackle this formidable task within this context. This research endeavors to employ a synergy of ML hybrid and ensemble frameworks for the prognostication of the mechanical attributes within HPC, encompassing compressive strength (CS), slump (SL), and flexural strength (FS). The formulation of these hybrid and ensemble constructs was executed through the integration of Support Vector Regression (SVR) with three distinct meta-heuristic algorithms: Prairie Dog Optimization (PDO), Pelican Optimization Algorithm (POA), and Mountain Gazelle Optimizer (MGO). Some criteria evaluators were used in the training, validation, and testing phases to assess the robustness of the established models, and the best model was proposed for practical applications through comparative analysis of the results. As a result, the hybrid and ensemble models were the potential methods to predict concrete properties accurately and efficiently, thereby reducing the need for expensive and time-consuming testing procedures. In general, the ensemble model, i.e., SVPPM, had a more suitable performance with high values of R2 equal to 0.989 (MPa), 0.984 (mm), and 0.992 (MPa) and RMSE = 3.82 (MPa), 9.5 (mm), and 0.30 (MPa) for CS, SL, FS compared to other models, respectively.

Enhancing Mechanical Behaviour and Durability of High Performance Concrete with Silica Fume, Ground Blast Furnace Slag, and Marble Powder

Abstract This study investigates the impact of waste additives on the behaviour of high-performance concrete and its environmental implications, with a specific focus on resource conservation. The research objectives were realised through the preparation of high-performance concrete specimens incorporating industrial waste materials and marble powder as partial replacements for cement and fine aggregates, respectively. Silica fume and ground blast furnace slag were introduced as substitutes for 8% of the cement’s weight. Powdered marble was volumetrically substituted at levels of 5%, 10%, and 15% of the fine aggregates. The physical and mechanical properties of both fresh and cured concrete specimens were evaluated at different ages, encompassing parameters such as density, compressive strength, impulse velocity, water absorption, and durability. The findings demonstrated that high-performance concrete formulated with silica fume and ground blast furnace slag exhibited superior properties compared to compositions relying exclusively on Portland cement. Furthermore, the inclusion of marble powder as an alternative building material constituent in high-performance concrete resulted in increased efficiency and improved resistance against chemical acid attacks. Significantly, this approach contributes to reduce aggregate demands, environmental preservation, and the production of environmentally sustainable concrete.

Experimental study of interfacial bonding performance between section steel and ultra high-performance concrete

The key to fully exploiting the benefits of section steel and ultra high-performance concrete (UHPC) is to improve their bonding. The primary goal of this study was to investigate the interfacial bonding performance between these two materials. Section steel - reinforced ultra high-performance concrete (SSRUHPC) and section steel-reinforced concrete (SSRC) specimens were subjected to push-out tests. Failure modes, load-slip (PS) curves, and strain distributions were studied, and the experimental results showed that the PS curves of all specimens have a similar trend: a no-slip stage followed by a slip stage, a failure stage, and a residual stage. By increasing the cover thickness and stirrup ratio and lowering the embedded length, the bond strength between the section steel and UHPC may markedly increase. The results of this study show that the bonding between section steel and UHPC is superior to that between section steel and ordinary concrete. Finally, after carefully considering the experimental results, regression formulae for the SSRUHPC bond strength were developed, and the computed results were found to be accurate. Unlike other bond strength formulae, the formulae in this study consider the influence of the stirrup ratio on the bond strength, and the R2 values range from 0.763 to 0.961.

Assessment of Water Transport and Chemical Attack of Meta-Illite Calcined Clay Blended Cement in High-Performance Concrete.

Rapid urbanisation causes a rise in the need for infrastructure, which in turn fuels the creation of additional concrete and further increases cement supplies. Activation of illite-based clay mineral and usage in concrete production is one of the sustainable ways to address the cement industry anthropogenic issues. This study evaluates the durability properties of water transport (water absorption, and capillary water absorption), and resistance to aggressive environments (5% solutions of hydrochloric acid, HCl; sodium sulphate, Na2SO4; and calcium chloride, CaCl2) of meta-illite calcined clay (MCC)-based high-performance concrete (HPC). For this purpose, concrete was produced with 5, 10, 15, 20, 25 and 30% MCC content in partial substitution of CEM II. Results from the water absorption tests indicate an average percentage value of 3.57%, 3.35% and 2.52% for all the observed mixes at 28, 56 and 90 days, respectively, with MCCC-10 HPC having an average best value of 2.23% across the curing ages. On all observed days, the 5 to 15% cement replacements had very close average water sorptivity value of 0.125 ± 0.001 mm/min0.5 with the control mix (0.113 ± 0.011 mm/min0.5). The aggressive environments exposure findings of the hardened MCC-based HPC specimens of 10 to 20% recorded an approximately 15% compressive strength loss in HCl, Na2SO4 and CaCl2 solutions over the 90 days of curing. In all, the HPC mixes of 5 to 15% MCC content obtained an average durability performance factor of 89%. As a result, these findings imply that MCC can replace cement in up to 15% of HPC production.

Attack resistance mechanism, uniaxial compressive mechanical properties and meso-simulation of high-performance concrete exposed to brine in salt lake for 10 years

The study investigated the corrosion resistance, corrosion micro-mechanisms, and the uniaxial compression stress–strain constitutive relationship of high-performance concrete (HPC) specimens subjected to long-term brine corrosion in an underground salt lake environment (Xining, China), which possesses a salt content of 180894.5mg/L. A three-dimensional random aggregate concrete meso-model was established considering the mesostructural characteristics of concrete. The mechanical behavior of HPC was assessed using the LS-DYNA software platform. The findings indicated that both the compressive strength and the dynamic elastic modulus of HPC demonstrated a pattern of initial increase, followed by a decrease, with extended brine exposure. Nevertheless, after 10 years of exposure to salt lake brine, the compressive strength of the HPC samples was still considerably greater than their original strength, with minimal evident corrosion damage to the concrete. Physical and chemical corrosion products formed exclusively in the spherical pores created by the air-entraining agent within the shallow layer of HPC, without notable micro-cracks or spalling. The HPC specimens exposed to brine for ten years under uniaxial compression load exhibited typical characteristics of splitting failure. In addition, the results from the mesoscopic numerical simulations aligned well with the experimental findings. The study shows that the three-dimensional random aggregate concrete mesoscopic model can simulate the uniaxial compressive mechanical behavior of HPC specimens under long-term corrosion conditions.

Strength recovery of thermally damaged high-performance concrete subjected to post-fire carbonation curing

This study investigates the efficacy of post-fire curing using carbonation with a 20% carbon dioxide concentration and a relative humidity cycle set between 40% and 90% for restoring the mechanical properties of thermally damaged high-performance concrete (HPC) specimens containing 0%–40% silica fume. The HPC specimens were exposed to temperatures of 600, 800, and 1000 °C for 1 h, and the compressive strength recovery was measured. The microstructure, porosity, pore size distribution, and chemical composition of the HPC specimens were analyzed to explore the strength recovery mechanism. After exposure to elevated temperatures, the average compressive strength of samples without silica fume decreased by 49.2 MPa. Subsequent carbonation recuring resulted in a significant recovery of 73.9 MPa in the average compressive strength. This recovery surpassed the original strength for the samples heated to 600 and 800 °C, attributable to the filling and coalescing effects of calcium carbonate polymorphs formed through the carbonation of residual cement particles and β-C2S. The samples containing 20% silica fume exhibited the second highest average strength recovery of 34.1 MPa. However, the strength recovery for the samples with 40% silica fume exposed to 800 and 1000 °C was negligible, as the microcracks exceeding 1 μm in width had barely been restored by the carbonation of the low-calcium calcium silicates with low reactivity. Overall, this study presents an exciting future prospect for the labor and cost-effective restoration of thermally damaged concrete structures through the use of carbonation curing.

Self-healing capability of conventional, high-performance, and Ultra High-Performance Concrete with commercial bacteria characterized by means of water and chloride penetration

This study analyzes the self-healing capability of conventional, High-Performance, and Ultra High-Performance Concrete specimens, incorporating commercial bacteria products that are easily accessible, marketed, and affordable from different sectors. Bacteria were incorporated into different mediums: immobilized in diatomaceous earth and liquid. Specimens were pre-cracked to a range of 50–450 μm cracks and were left to heal for 28 days in 3 different conditions (1) water immersion, 2) one week of water immersion followed by three weeks in a humidity chamber, and 3) humidity chamber. To evaluate the self-healing enhancements of specimens using a bacteria-based healing agent, self-healing efficiency was quantified by optical assessment of crack closure, recovery of water tightness via water permeability testing, and chloride permeability via cracks and matrix. The results show that bacterial agents increased the protection against chloride penetration in cracked and healed specimens of conventional concrete, especially when the specimens were healed in water immersion. Owing to the dense matrix of HPC and UHPC, the chloride penetration in the presence of cracks up to 400 μm can be kept below 10 mm. Crack closure greater than 50% is required in UHPC samples to get a significant healing ratio. The penetration through the cracks is approximately twice that of the matrix penetration in conditions when healing is not enhanced.

Analysis of High Performance Concrete Mixed with Nano-Silica in Front of Sulfate Attack.

Nano-silica (NS) is an effective material to improve the strength and durability of high-performance concrete (HPC), but little information is available regarding its role in HPC response to long-term sulfate attack. In this study, six different dosages of NS (0%, 1%, 2%, 3%, 4%, and 5%) as cement partial replacement were mixed into HPC and the casted specimens were soaked in sulfate solution for different periods (0, 100, 200, and 300 days). The mass change, dynamic elastic modulus, compressive and splitting strength, microstructure morphology, and porosity characteristics of HPC specimens were measured by mass tests, mechanical properties tests, scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) tests. The results showed that the incorporation of NS decreased the mass loss, elevated the compressive and splitting strength, and reduced the porosity formation of HPC in front of sulfate attack. The percentage of 1% NS was among the most effective dosages as, after soaking for 300 days, it decreased the mass loss by 13.5%, elevated the elastic modulus as well as compressive and splitting strength by 50.4%, 31.7%, and 69.8% in comparison of unmodified HPC, respectively. The sulfate attack resistance was delayed in a higher (2-5%) mixed dosage, mainly due to the agglomeration of nano particles, especially after long-term reactions. This study can provide experimental references regarding the performance of HPC mixed with NS in front of sulfate attack.

Behavior of high-performance concrete beams having tension lap spliced anchor-ended bars under repeated loading

In the current paper, a newly developed technique in tension lap splices of steel bars is presented and investigated to verify its efficiency. Consequently, an experimental and numerical study on sixteen high-performance concrete (HPC) specimens containing lap splices without confining reinforcement were performed. The experimental program comprised two phases; the first one was a preliminary study that involved concrete prisms containing the developed splices and tested under axial tension, while the second phase was four-point flexural testing of RC beams having the adopted tension splices and subjected to repeated loading. Both phases included two sub-groups; a reference sub-group having conventional straight-ended splices and the other sub-group implicated in the newly developed technique based on anchor-ended splices. Experimental tests showed that by applying the developed technique, not only higher tensile stress at failure was achieved but also a bond-induced failure was switched to a flexural failure. Furthermore, a splice length of five times bar diameter was found to be sufficient to achieve the full tensile strength of the reinforcing steel bars in the case of the anchor-ended technique. Finally, numerical modeling was employed to study further parameters about the anchor-ended splices. As a result, a proposed equation was obtained based on statistical analysis to predict the ultimate strength of the anchor-ended splice.

Mechanical properties of high-performance concrete under triaxial compression

It is well known that the mechanical properties of a material are related to lateral confinement. In this paper, 60 cylindrical high-performance concrete (HPC) specimens with different concrete strength grades were cast and subjected to a conventional triaxial experiment to study the mechanical properties of the material. The experimental results indicated that the specimens exhibited longitudinal splitting failure patterns under uniaxial compression and inclined plane shear failure patterns under triaxial compression. The stress–strain curves were divided into three stages: an elastic rising stage, a plastic rising stage and a softening descending stage. The application of lateral confining pressure effectively increased the triaxial compressive strength. As the concrete strength increased, the descending stage of the stress–strain curves became steeper, indicating an increase in brittleness. Based on the experimental results, the failure criterion of the HPC was analysed using the Drucker–Prager yield criterion and Kotsovos failure theory. The parameters of the Drucker–Prager yield criterion were determined, and the applicable range of the Kotsovos failure theory was also obtained.

Experimental and Numerical Investigations on High Performance SFRC: Cyclic Tensile Loading and Fatigue.

In the present study, the capability of high-strength short steel fibers to control the degradation in high-performance concrete was experimentally examined and numerically simulated. To this end, notched prismatic high-performance concrete specimens with (HPSFRC) and without (HPC) short steel fibers were subjected to static and cyclic tensile tests up to 100,000 cycles. The cyclic tests showed that the rate of strain increase was lower for HPSFRC specimens and that the strain stagnated after around 10,000 cycles, which was not the case with HPC specimens. The microscopic examinations showed that in HPSFRC, a larger number of microcracks developed, but they had a smaller total surface area than the microcracks in the HPC. To further investigate the influence of fibers on the behavior of HPSFRC in the cracked state, displacement-controlled crack opening tests, as well as numerical simulations thereof, were carried out. Experiments have shown, and the numerical simulations have confirmed, that the inclusion of short steel fibers did not significantly affect the ultimate strength; however, it notably increased the post-cracking ductility of the material. Finally, the unloading/reloading behavior was examined, and it was observed that the unloading stiffness was stable even for significant crack openings; however, the hysteresis loops due to unloading/reloading were very small.

Investigation of Mechanical Properties, Durability and Microstructure of Low-Clinker High-Performance Concretes Incorporating Ground Granulated Blast Furnace Slag, Siliceous Fly Ash and Silica Fume

The main assumption of eco-efficient High-Performance Concrete (HPC) design is the reduction of Portland cement clinker content without negatively affecting the composite’s mechanical and durability properties. In this paper, three low-clinker HPC mixtures incorporating slag cement (CEM III/B as per EN 197-1) and Supplementary Cementitious Materials (SCMs)—Ground Granulated Blast Furnace Slag (GGBFS), Siliceous Fly Ash (SFA) and Silica Fume (SF)—were designed. The maximum amount of Portland cement clinker from CEM III/B varied from 64 to 116 kg in 1 m3 of concrete mix. The compressive strength of HPC at 2, 7, 14, 28, 56, 90 days, and 2 years after casting, as well as the modulus of elasticity on 2-year-old specimens, was tested. The depth of water penetration under pressure and internal frost resistance in freeze–thaw tests were evaluated after 56 days of curing. Additionally, the concrete pH value tests were performed. The microstructure of 2-year-old HPC specimens was analyzed using Scanning Electron Microscopy (SEM). The research proved that it is possible to obtain low-clinker High-Performance Concretes that reach compressive strength of 76–92 MPa after 28 days of curing, show high values of modulus of elasticity (49–52 GPa) as well as increased resistance to frost and water penetration under pressure.

Synergic Effect of Sugarcane Bagasse Ash Based Cement on High Performance Concrete Properties

High performance concrete (HPC) is produced in this study by utilizing the agriculture industry by-product. The usage of by-product helps to condense the disposal issues, ecological degradation and also makes the production of concrete economical. The raw sugarcane bagasse ash from sugarcane industry is processed to ensure the suitability with the properties of cement to be used in HPC. Sugarcane bagasse ash (SCBA) is used as binder in HPC as an alternative of ordinary Portland cement. The properties of the SCBA have been studied. Investigation were carried out experimentally on M 60 grade of high performance concrete blended with SCBA to assess the workability, strength and durability properties at different ages of curing. Three SCBA blended HPC specimens were tested for each trial and test. Test results indicate improved performance in strength and durability properties up to 15% substitution level of SCBA with ordinary Portland cement.

Effect of Fly Ash and Reactive MgO on the Engineering Properties and Durability of High-Performance Concrete Produced with Alkali-Activated Slag and Recycled Aggregate

AbstractThis study investigated the engineering properties and durability of high-performance recycled aggregate concrete (HPRAC) specimens. The specimens were prepared using alkali-activated slag ...

Development of an experimental apparatus aimed at performing thermal-induced spalling tests based on a propane gas burner through tests on ultra-high performance concrete

The modelling of thermal spalling of concrete structures is a challenging subject that requires relevant and reliable experimental data concerning temperature distribution and material degradations. For this purpose, a new device dedicated to the study of concrete thermal-induced spalling was designed and manufactured and is now under development. The experimental apparatus consists of a propane supplied burner surmounted by a furnace that can heat uniformly a concrete specimen surface according to ISO 834 standard fire curve. Temperature-time curves on the heated face and at different points of high performance concrete specimens that underwent spalling are reported and commented. The thermal conditions for which spalling and explosive spalling occurred are also examined and analyzed. An indicative thermal gradient value of about 14 °C/mm was found to be critical for the spalling occurrence. The analysis of the debris mass and dimensions distributions highlighted their usefulness in numerical modelling purpose. Lastly, the paper analyses how the undertaken tests results can ease the finite element modelling of spalling of concrete structures.

Suggested modified testing techniques to the ACI 544-R repeated drop-weight impact test

Experimental tests were conducted in this study to introduce two simplified modifications to the setup of the ACI 544-2R repeated impact test aiming to reduce the results scattering of this test. The first modification is the using of sand bedding as a replacement to the steel baseplate, while the second is the using of notched specimens that are either centrally line notched or cross notched and loaded through a line or cross knife-like load transferring steel plate. Hence, the drop impact load is distributed along the specimen’s notch using the topping knife-like plate. To evaluate the proposed modification techniques, 90 cylindrical high performance concrete specimens were tested in six groups. The test results showed that, in notched specimens, the cracks were formed along the projections of notches, while several random cracks were formed in those without notches. The results also showed that the effect of fine sand bedding depends on the loading pattern, and that the dispersion of results can be reduced by using notched specimens with the load distributed along these notches. Using line notched specimens with sand bedding was found to exhibit the lowest results dispersion among the six investigated loading cases. The COV reduced by more than 60% compared to the current ACI 544-2R testing technique. At 90% level of confidence with a maximum error of 10%, the minimum required number of specimens is 55 for the ACI 544-2R test procedure, while only 7 specimens are required if sand bedding with line notch specimens are used.

Damage Assessment using Acoustic Emission on Concrete Beam

The selection of reliable technique for damage assessment is important in civil engineering structure. The present study proposed Acoustic emission (AE) technique by using the fundamental AE parameter to evaluate damage accumulated on Ultra High-Performance Concrete (UHPC) specimens. The UHPC beam with dimension of 515 mm x 98 mm x 98 mm was tested under three-point bending test with stepwise flexural load. In order to detect and to collect the AE data, Micro-SAMOS (μ-SAMOS) digital AE system and R6I sensors type were used while data analyses were carried out using AEwin software. The damage level that take place during increasing static loading on tested concrete beams and the mechanism was successfully evaluated using the AE technique.

Flexural toughness evaluation of basalt fibre reinforced HPC beams with and without initial notch

Chopped basalt fibre can be very beneficial to reinforce high performance concrete (HPC) and reduce its high brittleness. High performance fibre reinforced concrete (HPFRC) is an advance concrete composite with an extensive variety of structural applications. The main assets is its post-peak ductile behaviour in tension. This study aims to investigate the flexural toughness behaviour of notched and unnotched high performance basalt fibre reinforced concrete (HPBFRC) and HPC specimens in terms of load–deflection curves. Nine HPC mixtures were made with a fibre content of 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, and 2%. Fifty four specimens with/without notch were tested under three-point bending experiments. The toughness indices and fracture energy of specimens were compared based on investigational observations. Results revealed that the fracture energy and toughness of unnotched HPBFRC specimens under three-point loading is greater than that of specimens with notch. Furthermore, an improvement of the splitting tensile strength, flexural strength, fracture energy and toughness of HPBFRC specimens is observed makes them as an appropriate choice for numerous civil engineering applications.