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![Schematic diagram of ITZ in concrete [1].](profile/Ameer-Hilal/publication/308968131/figure/fig10/AS:416798840246273@1476383995229/Schematic-diagram-of-ITZ-in-concrete-1.png)
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![Figure 2. Deterioration of normal concrete [7].](profile/Ameer-Hilal/publication/308968131/figure/fig1/AS:416798836051968@1476383994420/Deterioration-of-normal-concrete-7_Q320.jpg)
Concrete is a composite material that consists of a binding medium and aggregate
particles and can be formed in several types. It may be considered to consist of three
phases: a cement paste, the aggregate, and the interfacial transition zone (ITZ) between
them. In addition to ordinary Portland cement, the essential components of the base of
concre...
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This experimental study evaluated the performance of normal ordinary Portland cement (OPC) concrete and high-performance concrete (HPC) that were designed by the conventional method (ACI) and densified mixture design algorithm (DMDA) method, respectively. Engineering properties and durability performance of both the OPC and HPC samples were studied...
Environmental friendly and high performance concrete is very import for the applications in sewage and water treatment industry. Using mineral additives such as fly ash and silica fume has been proven an effective approach to improve concrete properties. This paper reports a study of the effect of using both polymer and metakaolin additives togethe...
Self Compacting Concrete (SCC) is the new category of High Performance Concrete (HPC) characterized by its ability to spread and self consolidate in the form work exhibiting any significant separation of constituents. In this study, the benefits of Fly Ash (FA) & Marble stone powder (MP) and Rice husk ash (RHA) as partial replacement of Portland ce...
Citations
... The formed hydration products are found to be lower, and this may be the cause of a reduction in compressive strength. The nonuniform and porous nature of the microstructure may be the reason for the increased permeability to the chloride ions [64]. ...
The prevalence of catastrophic structural member failure caused by steel corrosion in civil infrastructure underscores the importance of reducing reinforcement corrosion to enhance overall infrastructure costs, reliability, and sustainable development. This study examines the use of corrosion inhibitors to improve the durability and strength of concrete structures, with a focus on their long-term effectiveness in resisting corrosion in reinforced concrete structures. Multiple approaches such as inhibitors, repairing processes, and coatings have been explored to prevent concrete corrosion damage, with an emphasis on concrete corrosion performance in coastal and corrosive situations. This study investigates the effect of six different corrosion inhibitors (zinc oxide, magnesium oxide, urea, sodium nitrate, sodium molybdate, and diethyl ether) on the compressive strength, durability, and microstructural properties of concrete samples. The compressive strength is assessed using both destructive (28 days cube compressive strength) and non-destructive (Ultrasonic Pulse Velocity) test methods, while concrete durability is evaluated using the rapid chloride permeability test . SEM imaging is also conducted to analyze the microstructure of each mix. The findings of this study highlight the importance of inhibitors in enhancing the durability of reinforced concrete structures.
... Changed samples had more evenly distributed cracks and less cracking when compared to the control sample, which spalled between 600 and 800 C (Effect of Temperature on Pore Structure and Strength of Concrete, n.d). No significant cracking was observed between 23 C and 200 C, which may be attributed to less disintegration of the aggregate-paste bond and a milder thermal gradient between the specimen's core (Hilal, 2016). Surface cracking was detected in control HSC at temperatures over 200 C, attributed to the thick microstructure (Wang et al., 2021), which prevents simple pore pressure release and is prone to cracking. ...
In this article, CNTs have been used in concrete, and the resulting properties are evaluated. Also, the CNT-reinforced concrete was exposed to elevated temperature, and the corresponding change in mechanical performance was investigated. Mechanical properties were studied, such as compressive and flexural strengths, stress-strain response, elastic modulus, compressive toughness, mass loss, and deterioration caused by exposure to elevated temperatures. Concrete specimens were heated to 200, 400, 600, and 800 °C at a heating rate of 5 °C/min and then tested for residual properties. CNT-reinforced concrete showed a higher compressive strength, elastic modulus, flexural strength, and compressive toughness than the control specimens. 0.15-CNT reinforced samples showed an increase of nearly 33% in Compressive strength and 50% in flexural strength. From the visual inspection, CNT-reinforced specimens showed less cracking at higher temperatures. Moreover, the effect of plastering concrete with CNTs was studied, which depicted better strength retention on exposure to fire. At 600 °C, 0.3 P-CNT plaster samples retained up to 43% of compressive strength and 46% of flexural strength, whereas control samples only retained up to 29% and 34% of their original strengths, respectively. Thus, it can be concluded that CNTs utilization in concrete is efficient for improved concrete fire resistance.
... With a rise in design complexity, the cost of building supplies, the use of new building methods and sensitivity to local and environmental concerns, there is a growing need for modifications to certain qualities of construction materials [57]. Certain qualities of concrete mixtures can occasionally be changed by adding additives, such as increased flow for the same water-cement ratio, greater strength, and durability resulting from the cement paste's reduced porosity [58,59]. Natural materials as admixtures to improve the quality of concrete have become necessary and reduce reliance on chemical admixtures [60]. ...
Due to its higher porosity, the interfacial transition zone (ITZ), that is, the zone between the hardened cement paste (HCP) and the aggregate, is the weakest point in concrete. It is less resistant to cracking than both HCP and aggregate, and microcracks begin in this zone when the load is applied and propagates into the mass of concrete. The goal of this research is to investigate how various dosages of cassava flour (CF) addition affect the ITZ and how this is related to the mechanical properties of concrete, including its resistance to sulfuric acid. CF is added as a percentage of Portland pozzolanic cement (PPC) used as a binder, with dosages of 1, 2, 3, 4, and 5%. The morphology of CF and PPC was studied using x-ray diffraction (XRD) and x-ray fluorescent (XRF) techniques. Changes in the thickness of the ITZ were observed using a scanning electron microscope (SEM). The effect of sulfuric acid was observed by immersing samples of concrete in a 2% sulfuric acid solution. The results show that adding CF up to 3% progressively reduced the thickness of ITZ and improved the densification of concrete. As more CF was added, the ITZ began to widen again, but even at 5% CF addition, the thickness of the ITZ remained well below that of the control. The workability of fresh concrete decreased with an increase in CF dosage, but CF addition increased the compressive, tensile, and flexural strengths of hardened concrete. The greatest compression resistance was achieved at a 3% cassava flour addition level, which was 83.8 MPa after 180 days of curing and 8.9 MPa, 4.7 MPa for flexural and splitting strengths, respectively, after 90 days of curing. All the concrete samples containing CF had lower strengths than the control after immersion in sulfuric acid, with the concrete with 3% CF performing better than the others. The research concludes that CF used as an additive to concrete in dosages up to 5% improves the ITZ zone, leading to improved mechanical properties. However, resistance to sulfuric acid attacks is reduced. In all tests, it has been shown that a CF dosage of 3% gives the best results.
... In addition, due to their finer size, they are capable of accommodating extremely [78]. According to Hilal, the inclusion of nano-additives not only reduces the porosity but also improves the physical and mechanical interaction with the surrounding matrix [79]. ...
Agricultural wastes are environmental hazards, as these wastes can catch fire, resulting in the loss of human and animal lives and properties. Alternatively, the wastes are dumped in large spaces, which are already limited. Cementitious composites are quasi-brittle and develop cracks at the micro and nano level, which affect their strength, durability, and esthetics. Transforming agricultural wastes to biochar and using it as fibers in cementitious materials for crack arresting and enhancing fracture toughness is an environment-friendly approach. In this research, nano to microscale carbonaceous inert fibers (biochar) of millet and maize were prepared through pyrolysis followed by ball milling. The X-ray spectroscopy (EDX) revealed that 82.08% and 86.89% of the carbon content was retained in millet and maize, respectively. The scanning electron microscope (SEM) confirmed the presence of angular, flaky, and needle-like particles in the carbonaceous inerts, which may enhance the strength and the fracture response of the cementitious materials. These inerts were added individually to mortar specimens at dosage levels of 0, 0.025%, 0.05%, 0.08%, 0.2% and 1% by mass of cement. The dispersion of the synthesized nano inerts was ensured by UV-VIS spectroscopy. The compressive strength, flexural strength, porosity, and fracture toughness of cement mortar were evaluated. The carbonized nano intrusions reduced the porosity and density of the mortar specimens. The minimum porosity was noted with 1% and 0.08% dosages of millet and maize, respectively, whereas the minimum density was observed at 1% dosage for both. An increase in compressive and flexural strengths was also noticed. The compressive strength increased by 32% and 28% with 0.2% and 0.5% millet and maize, respectively. An increase of 168% and 114% in fracture toughness was noticed at optimized dosages of 0.5% and 1% of maize and millet, respectively. It is concluded that the addition of carbonaceous inert fibers of millet and maize resulted in lightweight porous mortars with enhanced strength and fracture toughness. The fracture toughness increases with dosage as the nanoparticles enhance the tortuosity.
... In addition, due to their finer size, they are capable of accommodating extremely [78]. According to Hilal, the inclusion of nano-additives not only reduces the porosity but also improves the physical and mechanical interaction with the surrounding matrix [79]. ...
Agricultural wastes are environmental hazards, as these wastes can catch fire, resulting in the loss of human and animal lives and properties. Alternatively, the wastes are dumped in large spaces, which are already limited. Cementitious composites are quasi-brittle and develop cracks at the micro and nano level, which affect their strength, durability, and esthetics. Transforming agricultural wastes to biochar and using it as fibers in cementitious materials for crack arresting and enhancing fracture toughness is an environment-friendly approach. In this research, nano to microscale carbonaceous inert fibers (biochar) of millet and maize were prepared through pyrolysis followed by ball milling. The X-ray spectroscopy (EDX) revealed that 82.08% and 86.89% of the carbon content was retained in millet and maize, respectively. The scanning electron microscope (SEM) confirmed the presence of angular, flaky, and needle-like particles in the carbonaceous inerts, which may enhance the strength and the fracture response of the cementitious materials. These inerts were added individually to mortar specimens at dosage levels of 0, 0.025%, 0.05%, 0.08%, 0.2% and 1% by mass of cement. The dispersion of the synthesized nano inerts was ensured by UV–VIS spectroscopy. The compressive strength, flexural strength, porosity, and fracture toughness of cement mortar were evaluated. The carbonized nano intrusions reduced the porosity and density of the mortar specimens. The minimum porosity was noted with 1% and 0.08% dosages of millet and maize, respectively, whereas the minimum density was observed at 1% dosage for both. An increase in compressive and flexural strengths was also noticed. The compressive strength increased by 32% and 28% with 0.2% and 0.5% millet and maize, respectively. An increase of 168% and 114% in fracture toughness was noticed at optimized dosages of 0.5% and 1% of maize and millet, respectively. It is concluded that the addition of carbonaceous inert fibers of millet and maize resulted in light-weight porous mortars with enhanced strength and fracture toughness. The fracture toughness increases with dosage as the nanoparticles enhance the tortuosity.
... With a rise in design complexity, the cost of building supplies, the use of new building methods and sensitivity to local and environmental concerns, there is a growing need for modifications to certain qualities of construction materials [57]. Certain qualities of concrete mixtures can occasionally be changed by adding additives, such as increased flow for the same water-cement ratio, greater strength, and durability resulting from the cement paste's reduced porosity [58,59]. Natural materials as admixtures to improve the quality of concrete have become necessary and reduce reliance on chemical admixtures [60]. ...
... portlandite, calcium silicate hydrate gel, ettringite), which is the main contributor to the mechanical resistances [5]. Aside from the intrinsic properties of the matrix, the porosity created at the cement-aggregate interface and at the C-S-H gel itself-both of them factors that can be altered by hydrophobic admixtures-can have a high impact on durability and mechanical performance [20,21]. In terms of chemical interactions, siloxanes, silanes and related compounds hydrolyze forming reactive silanols that can form covalent Si-O-Si or Si-O-Al bonds [3] with the siliceous aggregates and silicate/aluminosilicate phases present in the hydrated cement paste. ...
In this work, hydrophobic mortars are produced by combining a silane-based admixture with the pre-treatment of the aggregates with an alkoxysilane-ended fluoropolymer. A comparative study is presented to determine the effect of the components, under different curing conditions, on the hydrophobicity, mechanical performance, composition and micro-structure. The combination of both strategies allows obtaining hydrophobic properties at different curing conditions, whereas the silane loses effectiveness at high humidity and the modified aggregate at low humidity. The silane hinders cement hydration and promotes gaps in the aggregate-matrix interfacial transition zone, decreasing mechanical resistance, whereas the modified aggregate changes the interfacial transition zone morphology without significant effects on resistance. The combination of both strategies partially compensates the negative impact of the silane admixture, especially when the mortars are cured at high humidity. Thus, this combination increases versatility of the mortars and poses as a potential route to address the limitations of silane admixtures.
... Until now, there has been no clear explanation of the reasons for the porosity of concrete and other materials in materials science. Therefore, researchers often used such a term as "voids" when describing pores in the structure of concrete and in other materials [45,46,47]. At the same time, it has long been observed that the porosity of concrete increases with the volume of water poured into the cement for its hydration. ...
The review shows that the gas content in tablets and solutions of medicines can significantly change their physical and chemical properties, qualitative and quantitative characteristics of the mechanism of action of medicines when applied topically, and even allows you to turn “old” and known medicines into “new” medicines with completely new and previously unknown mechanisms of action. Therefore, artificial changes in the gas content in solid and liquid dosage forms were recommended as an original method of developing new drugs. It has been shown that this method is particularly promising for the development of new antiseptic, cosmetic and hygiene products. The fact is that the additional forced introduction of gas into a liquid or into solid through excessive pressure increases their volume, reduces their specific gravity and strength. Moreover, it allows you to “blow up” them by cold boiling. Conversely, the removal of gas from them due to vacuum reduces the volume, increases the specific gravity and strength. By analogy with the change in the physical and chemical properties of liquid and solid medicines, achieved by removing gases from them, it is proposed to reduce the porosity and volume of concrete and increase its specific weight and strength by degassing the water used for wetting cement in the concrete manufacturing process. Due to the fact that under normal conditions, the gas content in the water used for the manufacture of concrete directly depends on the atmospheric pressure, it is concluded that the production of concrete at different atmospheric pressure changes its quality. In particular, low atmospheric pressure can reduce the porosity and volume of concrete, as well as increase the specific gravity and strength of concrete. On the other hand, high air and/or gas pressure can increase the porosity and volume of concrete and reduce the concrete’s specific gravity and strength. Therefore, the amount of atmospheric pressure and/or air and/or gas pressure on concrete during its production should be included in the list of controlled indicators of concrete manufacturing technology.
... The performance of conventional concrete being significantly influenced by its microstructure is debatable [20]; however, researchers suggest that both mechanical testing and interfacial transition zone (ITZ) characteristics can be used to investigate concrete qualities [21]. Concrete microstructure develops over time and is the result of both concrete formulation and processes related to mixing, placement, and curing [22]. ...
... This property explains the improved durability of SCBA concrete as reported by various researchers. However, by concrete technology, there is the" wall effect" of aggregates where aggregates act as mini walls, disrupting the normal parking of the cement grains leading to accumulation of smaller grains in the zone close to the aggregates while larger grains are found further out [24]. Bagasse ash grains being smaller compared to cement grains, are expected to have parked closer to the aggregates and cement further out. ...
Background
Concrete made using sugarcane bagasse ash as a cement replacement is associated with a reduction in split tensile strength and therefore a need to establish the possible causes of tensile strength reduction and explore ways of mitigating that reduction.
Objective
The aim of this study is to establish the possible causes of tensile strength reduction in sugarcane bagasse ash concrete and determine the effect of sisal fiber addition on its mechanical properties.
Methods
Scanning Electron Microscopy was first done to analyse concrete microstructure in establishing the possible causes of tensile strength reduction in sugarcane bagasse ash concrete. Thereafter, sisal fiber addition was done by varying aspect ratios and percentages. The effect of the addition was determined on the mechanical properties of bagasse ash concrete accompanied by microstructure studies on extracted fibers and split surfaces of concrete.
Results
Concrete microstructure studies revealed that wider cracks due to drying shrinkage and poor bonding properties of sugarcane bagasse ash are the possible causes of tensile strength reduction in bagasse ash concrete. Sisal fiber addition improved the mechanical properties of bagasse ash concrete. Microstructure studies portrayed effective bridging of cracks and good adhesive properties of the fibers.
Conclusion
Sisal fibers can be used to improve on the mechanical properties of sugarcane bagasse ash concrete with 100 aspect ratio and 1.5% addition being the optimal combination.
