This study was carried out in order to study the flexural behavior of fiber-reinforced ultra-high... more This study was carried out in order to study the flexural behavior of fiber-reinforced ultra-high-performance concrete (UHPC) containing hybrid microsteel straight fibers and natural fine aggregates under four-point flexural loading. The experimental results revealed that the fiber pullout mechanism had a progressive pullout (collapse) mode. A highly flexural crack developed when the fiber pulling mechanism was explicitly triggered, leading to the failure of most beams. The maximum load in beams reinforced by 1.2, 1.6, and 2.0% exceeded that in beams without longitudinal reinforcement by 56, 73, and 94%, respectively. Further, bar reinforcements at 125, 115, 95, 85, and 75 mm depths led to increases of 56, 55, 73, 96, and 94% in beam load capacity, respectively. In addition, bar reinforcement at 115, 95, 85, and 75 mm depths reduced the beams’ ductility by 40, 23, 35, and 39% compared to those with 125 mm depth. All studied UHPC beams had an uncracked phase that extended to a curvat...
The design of moored semi submersible systems constitutes a challenging engineering problem in wh... more The design of moored semi submersible systems constitutes a challenging engineering problem in which, the platform offset, stability, payload and system-optimized cost requirements are to be met simultaneously. This problem is complicated by the incomplete understanding of the nonlinearities associated with the multiple interactions such as wave to wave, wave to platform, platform to mooring, fluid to mooring and mooring to seabed. In this study, an attempt has been made to probe into these nonlinearities through numerical, experimental, and parametric studies. In the numerical study, moored semi submersibles were analyzed in the time domain. The dynamic equilibrium conditions were satisfied through a set of coupled nonlinear differential equations for the six DOF motions. For representing the platform to mooring nonlinear interactions, the 6x6 mooring stiffness matrix was derived based on the mooring stiffness and on the fairlead coordinates relative to the structure CG. For the ev...
In current practice, the performance-based concrete mix (PBCM) approach has become quite popular ... more In current practice, the performance-based concrete mix (PBCM) approach has become quite popular because it enhances the quality of materials that are fundamentally necessary for a particular situation. In the present study, experimental analysis is performed to determine the optimal mechanical properties and microstructural characteristics of concrete for sustainable development and cost effectiveness. Specifically, a mixture of high-volume fly ash (FA) and ultrafine calcium carbonate (UFCC) is investigated as a partial substitution of cement. For optimizing the concrete’s performance, various curing regimes are applied to evaluate the best conditions for obtaining ideal mechanical and microstructural properties. The results show that concrete containing 10% UFCC with a mean particle size of 3.5 µm blended with 40% FA yielded the best performance, with an enhancement of 25% in the compressive strength in the early age. Moreover, the UFCC improved the compactness and refined the int...
The entire mechanical properties of steel fiber-reinforced concrete (SFRC) are significantly depe... more The entire mechanical properties of steel fiber-reinforced concrete (SFRC) are significantly dependent on the fiber–matrix interactions. In the current study, a finite element (FE) model was developed to simulate the pullout response of hooked-end SFRC employing cohesive–frictional interactions. Plain stress elements were adapted in the model to exemplify the fiber process constituents, taking into consideration the material nonlinearity of the hooked-end fiber. Additionally, a surface-to-surface contact model was used to simulate the fiber’s behavior in the pullout mechanism. The model was calibrated against experimental observations, and a modification factor model was proposed to account for the 3D phenomenalistic behavior of the pullout behavior. Realistic predictions were obtained by using this factor to predict the entire pullout-slip curves and independent results for the peak pullout load. The numerical results indicated that the increased fiber diameter would alter the mode...
In this study, the optimum dosages of silica fume (SF) and natural pozzolan (NP) were experimenta... more In this study, the optimum dosages of silica fume (SF) and natural pozzolan (NP) were experimentally and statistically assessed for the best strength and durability properties of high-performance concrete (HPC). SF and NP were used as partial replacement Portland cement (PC) by up to 12 and 25 wt.%, respectively. Additionally, the prediction models based on second-level factorial (SLF) and response surface design (RSD) were formulated to estimate the HPC properties and their validation. The SLF-based model was further employed to investigate the significance and interactions of the PC, SF, and NP blends. The 28-day strength of the blended-cement HPC with a water-to-binder ratio of 0.25 was generally higher than that of the control concrete. The positive synergy of PC–NP–SF was also observed in the HPC permeability. The paired - test of the mean square error (MSE) of the SLF- and RSD-based models revealed that the MSE of the former was notably less than that of the latter. These resu...
In this study, we investigate the potential use of the material excavated by tunnel boring machin... more In this study, we investigate the potential use of the material excavated by tunnel boring machines (TBMs) as structural concrete aggregate. Accordingly, several experimental and statistical investigations on the mechanically and thermally processed material were carried out. The raw TBM excavated material contained a considerable amount of macro–micro quartz sand. Additionally, the poor-grain size distribution of the TBM material and its weak interface bonding demonstrated the impracticality of using it as a sand filler. Microstructural investigations of the crushed limestone material revealed that around 20% of it was composed of calcium carbonate, whereas no pozzolanic compounds were observed. The results indicate that the TBM excavated material can be used as a structural concrete aggregate. The properties of the fresh TBM-aggregate-based concrete were well within the acceptable range. The porosity and chloride diffusivity of the TBM-aggregate-based concrete mixtures were slight...
In the present work, the structural responses of 12 UHPC beams to four-point loading conditions w... more In the present work, the structural responses of 12 UHPC beams to four-point loading conditions were experimentally and analytically studied. The inclusion of a fibrous system in the UHPC material increased its compressive and flexural strengths by 31.5% and 237.8%, respectively. Improved safety could be obtained by optimizing the tensile reinforcement ratio (ρ) for a UHPC beam. The slope of the moment–curvature before and after steel yielding was almost typical for all beams due to the inclusion of a hybrid fibrous system in the UHPC. Moreover, we concluded that as ρ increases, the deflection ductility exponentially increases. The cracking response of the UHPC beams demonstrated that increasing ρ notably decreases the crack opening width of the UHPC beams at the same service loading. The cracking pattern the beams showed that increasing the bar reinforcement percentages notably enhanced their initial stiffness and deformability. Moreover, the flexural cracks were the main cause of ...
Prediction, Deep beams, Steel fibers, Concrete, Shear capacity. The design of many structural ele... more Prediction, Deep beams, Steel fibers, Concrete, Shear capacity. The design of many structural elements requires the use of deep concrete beams. However, their geometrical proportions make these beams viable to total shear failure without ample warning. Available researches have shown that the employment of steel fibers in concrete improves the structural performance of deep beams. However, validated capacity prediction models that facilitate the design for these beams are scarce in the approachable references. Several investigators have been suggesting predictive formulae for the evaluation of the shear strength of steel fiber reinforced concrete (SFRC) beams. In the current study, an equation that can predict the shear capacity of SFRC deep beams was derived in terms of compressive strength of concrete, shear span, beam sectional dimensions, and fiber factor. The derived equation compares fairly well with the authors’ experimental data and the data available in the literature.
In this paper, the influence of aggregate size on the mechanical behavior of steel fiber reinforc... more In this paper, the influence of aggregate size on the mechanical behavior of steel fiber reinforced concrete (SFRC) deep beams is reported. Two full-scale SFRC deep beams were developed with conventional concrete and tested under four-point conditions at 2 mm/min loading rate. The first beam was prepared with normal concrete of maximum aggregate size of 10 mm (CA10), whereas, the second beam was developed by 20 mm and 10 mm mixed coarse aggregate (CA20-10). Because of the improved fiber distribution, the ductility of SFRC deep beams with CA10 was marginally higher and had notably higher load capacity with respect to CA20-10. The SFRC deep beam with 10 mm CA compared to that of CA2010. Moreover, mutually SFRC deep beams with CA10 and CA20-10 concrete exhibited complete asymmetric displacement response to incremental loading. Naturally, the nonuniform fiber dispersion and aggregate interlock produced the different shear resistance on both sides of the beam. The failure pattern of SFRC...
The influence of different kinds of dynamic forces on multistory structures is notable. This pape... more The influence of different kinds of dynamic forces on multistory structures is notable. This paper studies the effect of harmonic and impulsive loading and free-vibration on a threestory shear frame structure. A persistent pulse loading was considered at the upper level of the structure, and the resulted mathematical model of the time-dependent multi-level displacements were derived. For harmonic force, normalized response amplitudes under the applied harmonic loading is plotted against the frequency ratio ω/ω1. These frequencyresponse curves show three resonance conditions at ω=ω1, ω=ω2 and ω=ω3; at these exciting frequencies, the steady-state response is unbounded. At other exciting frequencies, the vibration is finite and could be calculated from the derived equations. When the structure is excited with harmonic loading over a range of frequencies, the structure experiences resonance at some frequency. Resonance occurs when the frequency of the excitation is equal to the natural ...
Efficient load transmission between concrete and steel reinforcement by bonding action is a key f... more Efficient load transmission between concrete and steel reinforcement by bonding action is a key factor in the process of the design procedure of bar-reinforced concrete structures. To enhance the bond strength of steel/concrete composites, the impact of graphene nanoplatelets (GnP) on the bond stress and bond stress–slip response of deformed reinforcement bars, embedded in high-performance concrete (HPC), was investigated using bar pullout tests. In the current study, 36 samples were produced and examined. The main variables were the percentages of GnP, the steel reinforcement bar diameter, and embedded length. Bond behavior, failure mode, and bond stress-slip response were studied. Based on the experimental findings, the inclusion of GnP had a significant favorable influence on the bar-matrix interactions due to the bridging action of GnP as a nano reinforcement. For 0.02 wt.% of GnP, the bond strength was enhanced by more than 41.28% and 53.90% for steel bar diameters of 10 and 16...
In this investigation, the age-dependent hydration development of blended pastes containing Portl... more In this investigation, the age-dependent hydration development of blended pastes containing Portland cement (PC), pulverized fuel ash (PFA) and silica fume (SF) was assessed by quantifying the amount of CH and non-evaporable water using thermo-gravimetric analysis (TGA). Microstructure was investigated using scanning electron microscope (SEM). It was observed that the amount of liberated CH increases up to three-days in PC-PFA binary blended pastes, after which it progressively decreases and this reduction was proportional to the PFA dosage. The introduction of SF to PC-PFA binary mixtures to form ternary blended pastes has caused an early reduction of CH at one day where the majority of SF has been consumed during the first seven-days. The incorporation of 10% SF to PC-PFA pastes altered the low rate of hydration at early age. In addition, the presence of PFA showed insignificant influence on the non-evaporable water content until three-days then its effect became significant after...
The development of self-compacting alkali-activated concrete (SCAAC) has become a hot topic in th... more The development of self-compacting alkali-activated concrete (SCAAC) has become a hot topic in the scientific community; however, most of the existing literature focuses on the utilization of fly ash (FA), ground blast furnace slag (GBFS), silica fume (SF), and rice husk ash (RHA) as the binder. In this study, both the experimental and theoretical assessments using response surface methodology (RSM) were taken into account to optimize and predict the optimal content of ceramic waste powder (CWP) in GBFS-based self-compacting alkali-activated concrete, thus promoting the utilization of ceramic waste in construction engineering. Based on the suggested design array from the RSM model, experimental tests were first carried out to determine the optimum CWP content to achieve reasonable compressive, tensile, and flexural strengths in the SCAAC when exposed to ambient conditions, as well as to minimize its strength loss, weight loss, and UPVL upon exposure to acid attack. Based on the resu...
Abstract In this paper, 24 high performance concrete (HPC) mixtures with 0.25 and 0.40 water-to-b... more Abstract In this paper, 24 high performance concrete (HPC) mixtures with 0.25 and 0.40 water-to-binder ratios (w/b) were designed and cast with binary and ternary blends of Portland cement (PC), silica fume (SF) and natural pozzolan (NP). The effect of using NP and SF on the strength and the chloride permeability of the concrete was investigated. The experimental results and simplex-lattice theory were used to develop the quadratic and third order analytical models for predicting the strength and the permeability of HPC. ANOVA confirms the accuracy of the quadratic model and therefore its efficiency requires relatively less experimental data. Two different numerical methods have been used to optimize the cementitious components of HPC using the quadratic model and lower and upper bounds of the experimental test results. Firstly, the “solver” tool of MS office provides unique optimum components of PC, SF and NP. The corresponding optimum percentages (by weight) of PC, SF and NP for HPC with 0.25 and 0.40 w/b are 86.04%, 8.16% and 5.80% and 88.78%, 5.85% and 5.37%, respectively. Secondly, the ternary plots produced by MATLAB establishes a single area for manufacturing HPC with w/b of 0.40 (the optimized PC-SP-NP component ranges are 0.875–0.925, 0.10–0.15 and 0.000–0.075, respectively) and two candidate superior strength zones for developing HPC with w/b of 0.25 (the optimum PC-SP-NP components are 0.875–0.950, 0.050–0.075, and 0.00–0.08 or 0.875–0.900, 0.08–0.15, and 0.12–0.22, respectively). For better sustainable, cost-effect and eco-friendly designs, it is suggested to use the topography of the targeted response surface for optimization purposes.
Abstract This paper reports the influence of hot weather conditions and subsequent curing require... more Abstract This paper reports the influence of hot weather conditions and subsequent curing requirements on the strength and durability of multi-cementitious concrete. Five curing schemes were considered using persistent moist curing for various ages followed by exposure to natural hot weather conditions. It was observed that curing in hot weather tended to increase the initial strength of ternary blended concrete for up to 28 days; however, the development of long-term strength had insignificant effect. Binary blended concrete with silica fume (SF) exposed to hot weather have higher early age strength development compared to those under standard curing. The compressive strength and permeability of concrete was more sensitive to hot weather curing at an early age as its fly ash (FA) content increased. However, the effects of curing age diminished with high FA content and the susceptibility of long-term strength to hot weathering decreased as SF content increased. The porosity of concrete cured with continuous moistening was lower compared to those under hot weathering. The chloride permeability of binary blended concrete containing SF was less affected by hot weather curing. Using numerical models, it was found that the optimized persistent moist curing age for concrete without SF was dependent on target strength and durability requirements.
Strain-hardening cement-based composites (SHCC) have recently been developed as repair materials ... more Strain-hardening cement-based composites (SHCC) have recently been developed as repair materials for the improvement of crack control and strength of flexural members. This work focuses on strengthening and flexural enhancement using SHCC layer in tensile regions of flexural members under three different curing conditions. The curing conditions simulate the effect of different environmental conditions prevailing in the central and coastal regions of the Arabian Peninsula on the properties of SHCC as a retrofitting material. In this investigation, beams with SHCC layer were compared to control beams. The beams with SHCC layer of 50-mm thickness were cast. The results revealed that the flexural behavior and the load-carrying capacity of the normal concrete beam specimens under hot and dry environmental conditions were significantly reduced, lowering the ductility of the section. However, compressive strength is comparatively unaffected. Similarly, the hot curing conditions have also l...
This study was carried out in order to study the flexural behavior of fiber-reinforced ultra-high... more This study was carried out in order to study the flexural behavior of fiber-reinforced ultra-high-performance concrete (UHPC) containing hybrid microsteel straight fibers and natural fine aggregates under four-point flexural loading. The experimental results revealed that the fiber pullout mechanism had a progressive pullout (collapse) mode. A highly flexural crack developed when the fiber pulling mechanism was explicitly triggered, leading to the failure of most beams. The maximum load in beams reinforced by 1.2, 1.6, and 2.0% exceeded that in beams without longitudinal reinforcement by 56, 73, and 94%, respectively. Further, bar reinforcements at 125, 115, 95, 85, and 75 mm depths led to increases of 56, 55, 73, 96, and 94% in beam load capacity, respectively. In addition, bar reinforcement at 115, 95, 85, and 75 mm depths reduced the beams’ ductility by 40, 23, 35, and 39% compared to those with 125 mm depth. All studied UHPC beams had an uncracked phase that extended to a curvat...
The design of moored semi submersible systems constitutes a challenging engineering problem in wh... more The design of moored semi submersible systems constitutes a challenging engineering problem in which, the platform offset, stability, payload and system-optimized cost requirements are to be met simultaneously. This problem is complicated by the incomplete understanding of the nonlinearities associated with the multiple interactions such as wave to wave, wave to platform, platform to mooring, fluid to mooring and mooring to seabed. In this study, an attempt has been made to probe into these nonlinearities through numerical, experimental, and parametric studies. In the numerical study, moored semi submersibles were analyzed in the time domain. The dynamic equilibrium conditions were satisfied through a set of coupled nonlinear differential equations for the six DOF motions. For representing the platform to mooring nonlinear interactions, the 6x6 mooring stiffness matrix was derived based on the mooring stiffness and on the fairlead coordinates relative to the structure CG. For the ev...
In current practice, the performance-based concrete mix (PBCM) approach has become quite popular ... more In current practice, the performance-based concrete mix (PBCM) approach has become quite popular because it enhances the quality of materials that are fundamentally necessary for a particular situation. In the present study, experimental analysis is performed to determine the optimal mechanical properties and microstructural characteristics of concrete for sustainable development and cost effectiveness. Specifically, a mixture of high-volume fly ash (FA) and ultrafine calcium carbonate (UFCC) is investigated as a partial substitution of cement. For optimizing the concrete’s performance, various curing regimes are applied to evaluate the best conditions for obtaining ideal mechanical and microstructural properties. The results show that concrete containing 10% UFCC with a mean particle size of 3.5 µm blended with 40% FA yielded the best performance, with an enhancement of 25% in the compressive strength in the early age. Moreover, the UFCC improved the compactness and refined the int...
The entire mechanical properties of steel fiber-reinforced concrete (SFRC) are significantly depe... more The entire mechanical properties of steel fiber-reinforced concrete (SFRC) are significantly dependent on the fiber–matrix interactions. In the current study, a finite element (FE) model was developed to simulate the pullout response of hooked-end SFRC employing cohesive–frictional interactions. Plain stress elements were adapted in the model to exemplify the fiber process constituents, taking into consideration the material nonlinearity of the hooked-end fiber. Additionally, a surface-to-surface contact model was used to simulate the fiber’s behavior in the pullout mechanism. The model was calibrated against experimental observations, and a modification factor model was proposed to account for the 3D phenomenalistic behavior of the pullout behavior. Realistic predictions were obtained by using this factor to predict the entire pullout-slip curves and independent results for the peak pullout load. The numerical results indicated that the increased fiber diameter would alter the mode...
In this study, the optimum dosages of silica fume (SF) and natural pozzolan (NP) were experimenta... more In this study, the optimum dosages of silica fume (SF) and natural pozzolan (NP) were experimentally and statistically assessed for the best strength and durability properties of high-performance concrete (HPC). SF and NP were used as partial replacement Portland cement (PC) by up to 12 and 25 wt.%, respectively. Additionally, the prediction models based on second-level factorial (SLF) and response surface design (RSD) were formulated to estimate the HPC properties and their validation. The SLF-based model was further employed to investigate the significance and interactions of the PC, SF, and NP blends. The 28-day strength of the blended-cement HPC with a water-to-binder ratio of 0.25 was generally higher than that of the control concrete. The positive synergy of PC–NP–SF was also observed in the HPC permeability. The paired - test of the mean square error (MSE) of the SLF- and RSD-based models revealed that the MSE of the former was notably less than that of the latter. These resu...
In this study, we investigate the potential use of the material excavated by tunnel boring machin... more In this study, we investigate the potential use of the material excavated by tunnel boring machines (TBMs) as structural concrete aggregate. Accordingly, several experimental and statistical investigations on the mechanically and thermally processed material were carried out. The raw TBM excavated material contained a considerable amount of macro–micro quartz sand. Additionally, the poor-grain size distribution of the TBM material and its weak interface bonding demonstrated the impracticality of using it as a sand filler. Microstructural investigations of the crushed limestone material revealed that around 20% of it was composed of calcium carbonate, whereas no pozzolanic compounds were observed. The results indicate that the TBM excavated material can be used as a structural concrete aggregate. The properties of the fresh TBM-aggregate-based concrete were well within the acceptable range. The porosity and chloride diffusivity of the TBM-aggregate-based concrete mixtures were slight...
In the present work, the structural responses of 12 UHPC beams to four-point loading conditions w... more In the present work, the structural responses of 12 UHPC beams to four-point loading conditions were experimentally and analytically studied. The inclusion of a fibrous system in the UHPC material increased its compressive and flexural strengths by 31.5% and 237.8%, respectively. Improved safety could be obtained by optimizing the tensile reinforcement ratio (ρ) for a UHPC beam. The slope of the moment–curvature before and after steel yielding was almost typical for all beams due to the inclusion of a hybrid fibrous system in the UHPC. Moreover, we concluded that as ρ increases, the deflection ductility exponentially increases. The cracking response of the UHPC beams demonstrated that increasing ρ notably decreases the crack opening width of the UHPC beams at the same service loading. The cracking pattern the beams showed that increasing the bar reinforcement percentages notably enhanced their initial stiffness and deformability. Moreover, the flexural cracks were the main cause of ...
Prediction, Deep beams, Steel fibers, Concrete, Shear capacity. The design of many structural ele... more Prediction, Deep beams, Steel fibers, Concrete, Shear capacity. The design of many structural elements requires the use of deep concrete beams. However, their geometrical proportions make these beams viable to total shear failure without ample warning. Available researches have shown that the employment of steel fibers in concrete improves the structural performance of deep beams. However, validated capacity prediction models that facilitate the design for these beams are scarce in the approachable references. Several investigators have been suggesting predictive formulae for the evaluation of the shear strength of steel fiber reinforced concrete (SFRC) beams. In the current study, an equation that can predict the shear capacity of SFRC deep beams was derived in terms of compressive strength of concrete, shear span, beam sectional dimensions, and fiber factor. The derived equation compares fairly well with the authors’ experimental data and the data available in the literature.
In this paper, the influence of aggregate size on the mechanical behavior of steel fiber reinforc... more In this paper, the influence of aggregate size on the mechanical behavior of steel fiber reinforced concrete (SFRC) deep beams is reported. Two full-scale SFRC deep beams were developed with conventional concrete and tested under four-point conditions at 2 mm/min loading rate. The first beam was prepared with normal concrete of maximum aggregate size of 10 mm (CA10), whereas, the second beam was developed by 20 mm and 10 mm mixed coarse aggregate (CA20-10). Because of the improved fiber distribution, the ductility of SFRC deep beams with CA10 was marginally higher and had notably higher load capacity with respect to CA20-10. The SFRC deep beam with 10 mm CA compared to that of CA2010. Moreover, mutually SFRC deep beams with CA10 and CA20-10 concrete exhibited complete asymmetric displacement response to incremental loading. Naturally, the nonuniform fiber dispersion and aggregate interlock produced the different shear resistance on both sides of the beam. The failure pattern of SFRC...
The influence of different kinds of dynamic forces on multistory structures is notable. This pape... more The influence of different kinds of dynamic forces on multistory structures is notable. This paper studies the effect of harmonic and impulsive loading and free-vibration on a threestory shear frame structure. A persistent pulse loading was considered at the upper level of the structure, and the resulted mathematical model of the time-dependent multi-level displacements were derived. For harmonic force, normalized response amplitudes under the applied harmonic loading is plotted against the frequency ratio ω/ω1. These frequencyresponse curves show three resonance conditions at ω=ω1, ω=ω2 and ω=ω3; at these exciting frequencies, the steady-state response is unbounded. At other exciting frequencies, the vibration is finite and could be calculated from the derived equations. When the structure is excited with harmonic loading over a range of frequencies, the structure experiences resonance at some frequency. Resonance occurs when the frequency of the excitation is equal to the natural ...
Efficient load transmission between concrete and steel reinforcement by bonding action is a key f... more Efficient load transmission between concrete and steel reinforcement by bonding action is a key factor in the process of the design procedure of bar-reinforced concrete structures. To enhance the bond strength of steel/concrete composites, the impact of graphene nanoplatelets (GnP) on the bond stress and bond stress–slip response of deformed reinforcement bars, embedded in high-performance concrete (HPC), was investigated using bar pullout tests. In the current study, 36 samples were produced and examined. The main variables were the percentages of GnP, the steel reinforcement bar diameter, and embedded length. Bond behavior, failure mode, and bond stress-slip response were studied. Based on the experimental findings, the inclusion of GnP had a significant favorable influence on the bar-matrix interactions due to the bridging action of GnP as a nano reinforcement. For 0.02 wt.% of GnP, the bond strength was enhanced by more than 41.28% and 53.90% for steel bar diameters of 10 and 16...
In this investigation, the age-dependent hydration development of blended pastes containing Portl... more In this investigation, the age-dependent hydration development of blended pastes containing Portland cement (PC), pulverized fuel ash (PFA) and silica fume (SF) was assessed by quantifying the amount of CH and non-evaporable water using thermo-gravimetric analysis (TGA). Microstructure was investigated using scanning electron microscope (SEM). It was observed that the amount of liberated CH increases up to three-days in PC-PFA binary blended pastes, after which it progressively decreases and this reduction was proportional to the PFA dosage. The introduction of SF to PC-PFA binary mixtures to form ternary blended pastes has caused an early reduction of CH at one day where the majority of SF has been consumed during the first seven-days. The incorporation of 10% SF to PC-PFA pastes altered the low rate of hydration at early age. In addition, the presence of PFA showed insignificant influence on the non-evaporable water content until three-days then its effect became significant after...
The development of self-compacting alkali-activated concrete (SCAAC) has become a hot topic in th... more The development of self-compacting alkali-activated concrete (SCAAC) has become a hot topic in the scientific community; however, most of the existing literature focuses on the utilization of fly ash (FA), ground blast furnace slag (GBFS), silica fume (SF), and rice husk ash (RHA) as the binder. In this study, both the experimental and theoretical assessments using response surface methodology (RSM) were taken into account to optimize and predict the optimal content of ceramic waste powder (CWP) in GBFS-based self-compacting alkali-activated concrete, thus promoting the utilization of ceramic waste in construction engineering. Based on the suggested design array from the RSM model, experimental tests were first carried out to determine the optimum CWP content to achieve reasonable compressive, tensile, and flexural strengths in the SCAAC when exposed to ambient conditions, as well as to minimize its strength loss, weight loss, and UPVL upon exposure to acid attack. Based on the resu...
Abstract In this paper, 24 high performance concrete (HPC) mixtures with 0.25 and 0.40 water-to-b... more Abstract In this paper, 24 high performance concrete (HPC) mixtures with 0.25 and 0.40 water-to-binder ratios (w/b) were designed and cast with binary and ternary blends of Portland cement (PC), silica fume (SF) and natural pozzolan (NP). The effect of using NP and SF on the strength and the chloride permeability of the concrete was investigated. The experimental results and simplex-lattice theory were used to develop the quadratic and third order analytical models for predicting the strength and the permeability of HPC. ANOVA confirms the accuracy of the quadratic model and therefore its efficiency requires relatively less experimental data. Two different numerical methods have been used to optimize the cementitious components of HPC using the quadratic model and lower and upper bounds of the experimental test results. Firstly, the “solver” tool of MS office provides unique optimum components of PC, SF and NP. The corresponding optimum percentages (by weight) of PC, SF and NP for HPC with 0.25 and 0.40 w/b are 86.04%, 8.16% and 5.80% and 88.78%, 5.85% and 5.37%, respectively. Secondly, the ternary plots produced by MATLAB establishes a single area for manufacturing HPC with w/b of 0.40 (the optimized PC-SP-NP component ranges are 0.875–0.925, 0.10–0.15 and 0.000–0.075, respectively) and two candidate superior strength zones for developing HPC with w/b of 0.25 (the optimum PC-SP-NP components are 0.875–0.950, 0.050–0.075, and 0.00–0.08 or 0.875–0.900, 0.08–0.15, and 0.12–0.22, respectively). For better sustainable, cost-effect and eco-friendly designs, it is suggested to use the topography of the targeted response surface for optimization purposes.
Abstract This paper reports the influence of hot weather conditions and subsequent curing require... more Abstract This paper reports the influence of hot weather conditions and subsequent curing requirements on the strength and durability of multi-cementitious concrete. Five curing schemes were considered using persistent moist curing for various ages followed by exposure to natural hot weather conditions. It was observed that curing in hot weather tended to increase the initial strength of ternary blended concrete for up to 28 days; however, the development of long-term strength had insignificant effect. Binary blended concrete with silica fume (SF) exposed to hot weather have higher early age strength development compared to those under standard curing. The compressive strength and permeability of concrete was more sensitive to hot weather curing at an early age as its fly ash (FA) content increased. However, the effects of curing age diminished with high FA content and the susceptibility of long-term strength to hot weathering decreased as SF content increased. The porosity of concrete cured with continuous moistening was lower compared to those under hot weathering. The chloride permeability of binary blended concrete containing SF was less affected by hot weather curing. Using numerical models, it was found that the optimized persistent moist curing age for concrete without SF was dependent on target strength and durability requirements.
Strain-hardening cement-based composites (SHCC) have recently been developed as repair materials ... more Strain-hardening cement-based composites (SHCC) have recently been developed as repair materials for the improvement of crack control and strength of flexural members. This work focuses on strengthening and flexural enhancement using SHCC layer in tensile regions of flexural members under three different curing conditions. The curing conditions simulate the effect of different environmental conditions prevailing in the central and coastal regions of the Arabian Peninsula on the properties of SHCC as a retrofitting material. In this investigation, beams with SHCC layer were compared to control beams. The beams with SHCC layer of 50-mm thickness were cast. The results revealed that the flexural behavior and the load-carrying capacity of the normal concrete beam specimens under hot and dry environmental conditions were significantly reduced, lowering the ductility of the section. However, compressive strength is comparatively unaffected. Similarly, the hot curing conditions have also l...
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Papers by Yassir Abbas