Search Results (14)

Grouting materials used in water-rich and chloride-exposed environments require adequate workability, mechanical performance, and durability. To optimize the formulation, a series of orthogonal tests was conducted to assess how fly ash (10–30%), rust inhibitor (1–3%), and anti-corrosion agent (2–6%) affect the fresh and hardened properties of cement grouts at a constant water-to-binder ratio of 0.5. Setting behaviour, mechanical properties, chloride ion penetration resistance, pore structure, and hydration products were investigated. Fly ash and the anti-corrosion admixture prolonged the setting time. The highest 28-day compressive and flexural strengths were obtained at 20% fly ash. At 30%, the dilution effect outweighed the later-age pozzolanic contribution and slowed strength development. Within the investigated range, 6% anti-corrosion admixture provided the greatest improvement in strength and chloride ion penetration resistance, whereas the rust inhibitor had a smaller effect on the charge passed. Mixtures containing 20% fly ash and 4–6% anti-corrosion admixture exhibited lower porosity and a refined pore-size distribution. By contrast, 30% fly ash resulted in a less favourable pore structure. SEM and XRD results indicated a denser matrix at 28 days, consistent with continued cement hydration and the later-age pozzolanic reaction of fly ash. Previous studies have mainly focused on individual mineral or chemical admixtures, whereas the combined effects of fly ash, rust inhibitors, and anti-corrosion admixtures under fixed workability conditions remain insufficiently understood. This study reveals their distinct and complementary roles, providing a basis for the multi-objective optimisation of grouting materials in chloride-rich and water-saturated environments. Overall, 20% fly ash, 4–6% anti-corrosion admixture, and 1–2% rust inhibitor provided the best performance balance under the investigated conditions. Full article

Autogenous shrinkage is a key factor contributing to early-stage cracking in high-performance concrete (HPC), which significantly affects structural durability and service life. As core components of HPC, supplementary cementitious materials (SCMs) can significantly improve concrete workability, mechanical properties, and durability, as well as reduce the risk of shrinkage cracking in HPC, by regulating hydration kinetics, pore structure, and microstructural evolution. The primary objective of this review is to elucidate the differential mechanisms by which different active pozzolanic materials regulate the autogenous shrinkage of HPC. This paper elucidates the patterns and mechanisms by which typical SCMs in HPC (such as fly ash, slag, silica fume, limestone powder, and nano-silica) affect the autogenous shrinkage of HPC. It analyzes the influence of key factors—including the type of SCMs, dosage, particle characteristics, water-to-binder (w/b) ratio, and composite blending on the autogenous shrinkage of HPC. Research indicates that highly reactive SCMs (such as silica fume and nano-silica) accelerate the self-drying process and increase autogenous shrinkage, whereas low-reactivity SCMs (such as fly ash) suppress autogenous shrinkage through dilution effects and by prolonging the hydration cycle. The combined use of multiple SCMs can achieve synergistic control of autogenous shrinkage and mechanical properties. Furthermore, this paper reviews existing autogenous shrinkage prediction models that account for the influence of SCMs and outlines future research directions. At the same time, this review identifies the limitations that currently exist in the research: there is a lack of a unified quantitative theoretical framework for the synergistic effects of multicomponent admixtures. The applicability of prediction models under multi-field coupling of temperature, humidity, and corrosive media is limited. And there is insufficient experimental data on the long-term shrinkage behavior of new low-carbon admixtures such as rice husk ash and calcined clay, which requires further dedicated research. Full article

In this study, a series of amphiphilic polyether-modified silicone oil (PMSO) polymers with hydrophilic–lipophilic balance (HLB) values ranging from 3.5 to 5 were synthesized via hydrosilylation. These polymers are self-emulsifying and can form stable micelles in water without the need for external emulsifiers, with micelle sizes ranging from 79.9 to 161.4 nm. For the first time, such amphiphilic micelles were employed as an internally incorporated hydrophobic admixture to investigate the waterproofing and corrosion resistance of cement-based materials. The results showed that PMSO micelles with an HLB value of 4 significantly reduced the water absorption of cement mortar and improved mechanical properties by enhancing the compactness and crystallinity of the cement matrix. At a dosage of 0.5 wt% PMSO in mortar, the water absorption at 48 h was reduced by 50.27% compared with the control group, and the inner and outer contact angles of the mortar specimens reached 105° and 126°, respectively. The chloride diffusion coefficient of concrete decreased by 70.8% relative to the control group. At an appropriate dosage (0.1 wt%), the flexural strength of the mortar at 28 days increased by 12.50%, and the compressive strength increased by 14.19% compared with the control group. Low-field nuclear magnetic resonance (NMR) was used to determine the changes in the pore structure of mortar specimens before and after the addition of PMSO micelles. The experimental results showed that the addition of PMSO micelles reduced the number of harmful large pores, resulting in a denser microstructure. Finally, the corrosion resistance of concrete was evaluated via electrochemical accelerated-corrosion aging tests. The cracking time of concrete containing PMSO micelles was extended from 144 h (control group) to 240 h, demonstrating improved corrosion resistance. Full article

With global sustainable construction growth, fully recycled coarse aggregate concrete (RCAC)—eco-friendly for cutting construction waste and reducing natural aggregate over-exploitation—has poor durability in seasonally freezing saline-soil regions (e.g., Tumushuke, Xinjiang): freeze-thaw and salt ions (NaCl, Na₂SO₄) cause microcracking, faster performance decline, and shorter service life, limiting its use and requiring better salt freeze resistance. To address this, a field survey of Tumushuke’s saline soil was first conducted to determine local salt type and concentration, based on which a matching 12% NaCl + 4% Na₂SO₄ mixed salt solution was prepared. RCAC specimens modified with fly ash (FA), silica fume (SF), and polypropylene fiber (PPF) were then fabricated, cured under standard conditions (20 ± 2 °C, ≥95% relative humidity), and subjected to rapid freeze-thaw cycling in the salt solution. Multiple macro-performance and microstructural indicators (appearance, mass loss, relative dynamic elastic modulus (RDEM), porosity, microcracks, and corrosion products) were measured post-cycling. Results showed the mixed salt solution significantly exacerbated RCAC’s freeze-thaw damage, with degradation severity linked to cycle count and admixture dosage. The RCAC modified with 20% FA and 0.9% PPF exhibited optimal salt freeze resistance: after 125 cycles, its RDEM retention reached 75.98% (6.60% higher than the control), mass loss was only 0.28% (67.80% lower than the control), and its durability threshold (RDEM > 60%) extended to 200 cycles. Mechanistic analysis revealed two synergistic effects for improved performance: (1) FA optimized pore structure by filling capillaries, reducing space for pore water freezing and salt penetration; (2) PPF enhanced crack resistance by bridging microcracks, suppressing crack initiation/propagation from freeze-thaw expansion and salt crystallization. A “pore optimization–ion blocking–fiber crack resistance” triple synergistic protection model was proposed, which clarifies admixture-modified RCAC’s salt freeze damage mechanism and provides theoretical/technical guidance for its application in extreme seasonally freezing saline-soil environments. Full article

Fly ash and slag are widely used as mineral admixtures to partially replace cement in low-carbon concrete. However, such composite concretes often exhibit a greater carbonation depth than plain Portland concrete with the same 28-day strength, increasing the risk of steel reinforcement corrosion. Previous mix design methods have overlooked this issue. This study proposes an optimized design method for fly ash–slag composite concrete, considering carbonation exposure classes and CO₂ concentrations. Four exposure classes are addressed—XC1 (completely dry or permanently wet environments such as indoor floors or submerged concrete), XC2 (wet but rarely dry, e.g., inside water tanks), XC3 (moderate humidity, e.g., sheltered outdoor environments), and XC4 (cyclic wet and dry, e.g., bridge decks and exterior walls exposed to rain). Two CO₂ levels—0.04% (ambient) and 0.05% (elevated)—were also considered. In Scenario 1 (no durability constraint), the optimized designs for all exposure classes were identical, with 60% slag and 75% total fly ash–slag replacement. In Scenario 2 (0.04% CO₂ with durability), the designs for XC1 and XC2 remained the same, but for XC3 and XC4, the carbonation depth became the controlling factor, requiring a higher binder content and leading to compressive strengths exceeding the target. In Scenario 3 (0.05% CO₂), despite the increased carbonation depth, the XC1 and XC2 designs were unchanged. However, XC3 and XC4 required further increases in binder content and actual strength to meet durability limits. Overall, compressive strength governs the design for XC1 and XC2, while carbonation durability is critical for XC3 and XC4. Increasing the water-to-binder ratio reduces strength, while higher-strength mixes emit more CO₂ per cubic meter, confirming the proposed method’s engineering validity. Full article

This study investigates the root causes of substandard concrete quality in a newly constructed residential complex, addressing the critical issue of compressive strength failure in structural elements. To tackle this problem, twelve core samples were extracted from affected areas and analyzed using a combination of macro-scale techniques (high-temperature heating, acid-immersion tests) and advanced microscopic methods (SEM-EDS, XRF, XRD, FTIR, TGA). The results revealed that while material proportions generally met specifications, uneven aggregate gradation and excessive use of mineral admixtures were key factors compromising strength. Microscopic analysis further identified harmful phases and chemical corrosion products, such as sulfates, which weakened the concrete matrix. These findings underscore the necessity of stringent quality control in raw material selection, aggregate gradation, and admixture dosage. The research demonstrates that integrating macro- and microanalytical methods can significantly optimize concrete mix designs, enhance durability, and prevent premature deterioration in reinforced concrete structures. This approach has broad implications for improving construction quality and ensuring the longevity of residential and infrastructure projects. Full article

Nowadays, admixtures are used with the aim to provide strength and durability to concrete with less water use. New and low-cost admixtures gained a large amount of consideration to mitigate the problems associated with concrete’s durability and service life without upsetting its strength properties. The current work investigates the effect of three types of acetates on the workability, density, and compressive strength of concrete, which is used in structures of the Iraqi ports that suffer from corrosion damages and deterioration owing to the aggressive marine environments. Potassium acetate (KA), calcium acetate (CaA), and ethyl acetate (EA) are incorporated with different doses (1.38–5.6 wt.% of cement) in concrete mixtures using different water/cement ratios (0.48–0.54) based on an espoused central composite experimental design. The experimental results confirmed that the average workability increased with increasing the acetate dose, particularly with CaA. The density and compressive strength of 28 days of water-cured mixtures increased with increasing acetate dose following the order: Ca > K > Ethyl acetate and decreased with increasing w/c ratio. The high rise in compressive strength and workability linked to control mixtures was 30.8% and 77.3% as well as 15.7% and 64.3% for the mixtures incorporated with 5.6 wt.% CaA and KA, respectively. While it was 14.2% and 58.3% for the mixtures incorporated with 3.5 wt.% EA. RSM was employed to optimize and model the design and hardened properties of concrete mixtures. ANOVA results predicted the same trend, which was obtained from the experimental results. The mathematical models were valued with high-regression coefficients. The highest compressive strength of 42.68 MPa has been achieved for a concrete mixture of 0.48 w/c ratio by the incorporation of 5.1 wt.% CaA through a model with R² 96.97%. The relatively low-cost acetate admixtures, particularly CaA, seemed promising for the fabrication of concrete with outstanding properties. Full article

Ferrocement panels are thin-section panels that are widely used in lightweight construction. Due to lesser flexural stiffness, they are susceptible to surface cracking. Water may penetrate through these cracks and may cause corrosion of conventional thin steel wire mesh. This corrosion is one of the major factors which affect the load-carrying and durability of ferrocement panels. There is a need to improve the mechanical performance of ferrocement panels either through using some non-corrodible reinforcing mesh or through improving the cracking behavior of the mortar mix. In the present experimental work, PVC plastic wire mesh is employed to address this problem. SBR latex and polypropylene (PP) fibers are also utilized as admixtures to control the micro-cracking and improve the energy absorption capacity. The main idea is to improve the structural performance of ferrocement panels that may be utilized in lightweight, low-cost house construction and sustainable construction. The ultimate flexure strength of ferrocement panels employing PVC plastic wire mesh, welded iron mesh, SBR latex, and PP fibers is the subject of the research. Test variables are the type of mesh layer, the dosage of PP fiber, and SBR latex. Experimental tests are conducted on 16 simply supported panels of size 1000 × 450 mm and subjected to four-point bending test. Results indicate that the addition of latex and PP fibers only controls the initial stiffness and does not have any significant effect on ultimate load. Due to the increased bonding between cement paste and fine aggregates, the addition of SBR latex improves the flexural strength by 12.59% and 11.01% for iron mesh (SI) and PVC plastic mesh (SP), respectively. The results also indicate an improvement in the flexure toughness of specimens with PVC mesh as compared to specimens with iron welded mesh; however, a smaller peak load is observed (i.e., 12.21% for control specimens) compared with the specimen with welded iron mesh. The failure patterns of the specimens with PVC plastic mesh exhibit a smeared cracking pattern that shows that they are more ductile compared to samples with iron mesh. Full article

In this study, the urea-formaldehyde (UF)-tung oil solution of phenolic amide (PA) microcapsules to realize anti-fouling and anti-corrosion integration was synthesized by the in situ polymerization method. The compounds and structures were optimized by investigating six kinds of different emulsifiers. The results showed that high-core-content and narrow-particle-size-distribution microcapsules could be synthesized with sodium dodecyl benzene sulfonate (SDBS)/polyvinyl alcohol (PVA), and the core content of the microcapsules was 75 wt% at microcapsule sizes from 24.07 to 71.33 µm. The results of self-healing coatings showed that when the content of microcapsules in the coating exceeded 10 wt%, the healing agent released from the scratched surface could cover the naked metal effectively, which could pass a 7 day neutral salt spray test without rust at the scratched area. A sufficient dose anti-fouling agent can be provided to prevent diatoms and mussels from adhering. The present work shows that the complex emulsifier can better control the particle size distribution and microstructure of the microcapsules, and the admixture of the microcapsules into the resin epoxy coating can realize excellent anti-corrosion and anti-fouling functions. Full article

In this paper, the traditional, silicate-based Portland cement (PC) was employed as the control to explore the impact of adding varying amounts of metakaolin (MK) on the mechanical properties of cement mortar. In fact, as a mineral admixture, metakaolin (MK) has the ability to significantly improve the early strength and sulfate resistance of cement mortar in traditional, silicate-based Portland cement (PC). In addition to this, the performance of Portland cement mortar is greatly affected by the curing mode. The previous research mainly stays in the intermittent curing and alkaline excitation mode, and there are few studies on the influence of relatively humidity on it. Moreover, the paper investigated the impact of four different curing methods about humidity on the mechanical properties and sulfate resistance. The results show that the best content of metakaolin in Portland cement is 10% (M10), and the best curing method is 95% humidity in the first three days followed by 60% humidity in the later period (3#). Based on previous literature that suggests that adding MK thickens water film layer on the surface of mortar, the mechanism of MK increasing the early strength of cement was analyzed. The compressive strength of the Portland cement containing 10% MK (M10) after 1 day curing is 3.18 times that of pristine PC mortar, and is comparable if PC is cured for three days under the same curing conditions. The traditional PC mortar is highly dependent on the wet curing time, and normally requires a curing time of at least seven days. However, the incorporation of MK can greatly reduce the sensitivity of Portland cement to water; MK cement mortar with only three days wet curing (3#M10) can reach 49.12 MPa after 28 days, which can greatly shorten the otherwise lengthy wet curing time. Lastly, the cement specimens with MK also demonstrated excellent resistance against sulfate corrosion. The work will provide a strong theoretical basis for the early demolding of cement products in construction projects. At the same time, this study can also provide a theoretical reference for the construction of climate drought and saline land areas, which has great reference value. Full article

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered to play a significant role in its durability, Permeability Reducing Admixtures (PRA) is one of the ideal solutions for protecting structures exposed to water and waterborne chemicals. Different products have been developed to protect concrete structures against water penetration, which, based on their chemistry, performance, and functionality, have been categorized into PRA. As it has previously been tested by authors and proven to be a promising solution, a hydrophilic Crystalline Waterproofing Admixtures (CWA) has been considered for this study. This paper aims to investigate how this product affects concrete’s overall freeze–thaw resistance, self-sealing, and corrosion resistance. Various testing methods have been utilized to examine the performance of CWA mixtures, including the linear polarization resistance, resonance frequency testing, half-cell potential, and self-sealing test. The reinforcement corrosion potential and rate measurements indicated superior performance for CWA-treated samples. After being exposed to 300 freeze–thaw cycles, concrete mixes containing CWA—even non-air-entrained ones—showed a Durability Factor (DF) of more than 80% with no signs of failure, while non-air-entrained control samples indicated the lowest DF (below 60%) but the greatest mass loss. The major causes are a reduction in solution permeability and lack of water availability in the concrete matrix—due to the presence of CWA crystals. Furthermore, evidence from the self-sealing test suggests that CWA-treated specimens can seal wider cracks and at a faster rate. Full article

Novel green concrete (GC) admixtures containing 50% and 100% recycled coarse aggregate (RCA) were manufactured according to the ACI 211.1 standard. The GC samples were reinforced with AISI 1080 carbon steel and AISI 304 stainless steel. Concrete samples were exposed to 3.5 wt.% Na₂SO₄ and control (DI-water) solutions. Electrochemical testing was assessed by corrosion potential (E_corr) according to the ASTM C-876-15 standard and a linear polarization resistance (LPR) technique following ASTM G59-14. The compressive strength of the fully substituted GC decreased 51.5% compared to the control sample. Improved corrosion behavior was found for the specimens reinforced with AISI 304 SS; the corrosion current density (i_corr) values of the fully substituted GC were found to be 0.01894 µA/cm² after Day 364, a value associated with negligible corrosion. The 50% RCA specimen shows good corrosion behavior as well as a reduction in environmental impact. Although having lower mechanical properties, a less dense concrete matrix and high permeability, RCA green concrete presents an improved corrosion behavior thus being a promising approach to the higher pollutant conventional aggregates. Full article

Textile reinforced concrete (TRC) is an emerging construction material with interesting potential concerning sustainability, providing corrosion-free and lightweight solutions. Ordinarily, fiber bundles, impregnated with resin, are used. In this research the performance of reinforcement with unresin fibers is investigated. Control of cracking is considered the key performance factor and is assessed through tensile testing. However, economic and environmental aspects are addressed as well. Then, four different mixes/matrices were considered, without the addition of special/expensive admixtures. TRC ties were subject to direct tension tests, with load and deformation monitoring to assess the influence of mechanical reinforcement ratio on the cracking, failure and toughness of these composites, as well as of the matrix properties on the maximum load. It was observed that at a macro-level TRC behaves like conventional reinforced concrete, concerning crack control. Based on the maximum loads attained at the different composites, it was found that this particular TRC is economically viable. It is suggested that matrix workability may influence the maximum load. Full article

This paper investigates Phyllanthus muellerianus leaf-extract effects on steel-reinforcement corrosion in concrete immersed in 3.5% NaCl, simulating saline/marine environment. Different concentrations of the leaf-extract were admixed in steel-reinforced concrete samples, which were immersed, with normal control, in the test-environment, while positive control samples were immersed in distilled water. Electrochemical measurements of corrosion-rate (by linear-polarization-resistance instrument), corrosion-current (by zero-resistance-ammeter) and corrosion-potential (by high impedance multimeter) were obtained for assessing the reinforcing-steel corrosion. Analyzed results showed that the corrosion-rate exhibited excellent correlation (R = 98.82%, Nash-Sutcliffe Efficiency = 97.66%, ANOVA p-value = 0.0006) with function of the admixture concentration and of the corrosion noise-resistance (ratio of corrosion-potential and corrosion-current standard deviations). The 0.3333% Phyllanthus muellerianus (per weight of cement) exhibited optimal efficiency, η = 97.58% ± 1.28% (experimental) or 95.33% ± 4.25% (predicted), at inhibiting concrete steel-reinforcement corrosion in the test-environment, which compares well with the positive control performance model, η = 97.96% ± 0.03%. The experimental and predicted models followed the Langmuir adsorption isotherm, which indicated physisorption as the Phyllanthus muellerianus leaf-extract adsorption mechanism on the reinforcing-steel. These support suitability of the N-, S-, and O-containing and π-electron rich Phyllanthus muellerianus leaf-extract as an environmentally-friendly inhibitor for effective corrosion-protection of steel-reinforcement in concrete designed for the saline/marine environment. Full article