Materials

Research

13 pages, 3941 KiB

Open AccessArticle

Effects of Low Temperature, Freeze–Thaw Cycles, and Healing Conditions on Viability of Non-Ureolytic Bacteria in Biological Self-Healing Concrete

by Augusta Ivaškė, Ronaldas Jakubovskis, Renata Boris and Jaunius Urbonavičius

Materials 2024, 17(23), 5797; https://doi.org/10.3390/ma17235797 - 26 Nov 2024

Viewed by 365

Abstract

The capacity of biological self-healing concrete (BSHC) to repair cracks relies on the sustained viability and metabolic function of bacteria embedded within the concrete. BSHC structures face significant risk in cold climates due to low temperatures and freeze–thaw (FT) cycles, during which freezing [...] Read more.

The capacity of biological self-healing concrete (BSHC) to repair cracks relies on the sustained viability and metabolic function of bacteria embedded within the concrete. BSHC structures face significant risk in cold climates due to low temperatures and freeze–thaw (FT) cycles, during which freezing water can generate internal pressure that damages bacterial cells and diminishes their activity. A special feature of this study is the incorporation of bacterial spores within expanded clay aggregates, tested under varying environmental conditions. The viability of bacterial spores was measured under cold and freeze–thaw cycles by counting colony-forming units, and a specific methodology was developed to assess the efficiency of self-healing under rain-simulated conditions. It was demonstrated that bacteria embedded in concrete could endure fluctuations in low temperatures and freeze–thaw cycles, compromising approximately 50% of viable spores. Also, it was found that water immersion during concrete curing can trigger early germination, decreasing viable spore counts by nearly tenfold. Ultimately, it was demonstrated that the healing of cracks in BSHC components is influenced by the conditions under which the specimens are incubated. The results suggest that BSHC can be employed in cold climate areas, given that suitable curing conditions and adequate bacterial protection within the concrete are ensured. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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14 pages, 4640 KiB

Open AccessArticle

Effect of Amorphous Metallic Fibers on Thermal and Mechanical Properties of Lightweight Aggregate Cement Mortars Containing Carbon Nanotubes

by Se-Jin Choi, Jae-In Lee, Chae-Young Kim, Joo-Ho Yoon and Kwan-Ho Kim

Materials 2024, 17(22), 5449; https://doi.org/10.3390/ma17225449 - 8 Nov 2024

Viewed by 484

Abstract

Lightweight aggregate concrete can reduce the self-weight of a structure with a low unit weight; however, disadvantages such as reduced strength and brittleness remain. This study evaluated the thermal and mechanical properties of lightweight aggregate cement mortars containing carbon nanotubes (CNTs) and amorphous [...] Read more.

Lightweight aggregate concrete can reduce the self-weight of a structure with a low unit weight; however, disadvantages such as reduced strength and brittleness remain. This study evaluated the thermal and mechanical properties of lightweight aggregate cement mortars containing carbon nanotubes (CNTs) and amorphous metallic fibers (AMFs). A thermal property test indicated that the peak temperature of the C1A1 and C1A2 samples using AMFs was approximately 91.5–93.8 °C (approximately 57.2–61.1% higher than the C1A0 sample without AMFs). The time to reach the peak temperature was approximately 15–27 min (21.1–38.0% of that for the C1A0 sample). The 28-day split tensile strength of the sample using 20 kg/m³ of the AMFs was approximately 3.6–3.8 MPa (approximately 46.1–50.0% higher than that of CNT-only samples). The 56-day flexural strength of the C2A2 sample using 0.2% CNTs and 20 kg/m³ AMFs was the highest at approximately 11.2 MPa (approximately 24.4% higher than that of the control sample). The results of this study indicate that using CNTs and AMFs can enhance the strength and reduce the brittleness of lightweight aggregate cement mortar. Furthermore, the performance of the cement mortar is significantly improved when combined with AMFs compared to using CNTs alone. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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18 pages, 3218 KiB

Open AccessArticle

Synthesis and Characterization of Calcium Sulfoaluminate Hydrates—Ettringite (AFt) and Monosulfate (AFm)

by Wojciech Szudek, Jakub Szydłowski, Ilona Buchała and Ewa Kapeluszna

Materials 2024, 17(21), 5216; https://doi.org/10.3390/ma17215216 - 26 Oct 2024

Viewed by 649

Abstract

The goal of the presented work was to find the most favorable conditions for the synthesis and stabilization of chemically pure ettringite and monosulfate. The reaction was carried out by mixing pure tricalcium aluminate (C₃A) and gypsum (C

\bar{S}

H [...] Read more.

The goal of the presented work was to find the most favorable conditions for the synthesis and stabilization of chemically pure ettringite and monosulfate. The reaction was carried out by mixing pure tricalcium aluminate (C₃A) and gypsum (C

\bar{S}

H₂) in an excess amount of water. The impact of hydration time (2–7 days), C₃A:C

\bar{S}

molar ratio (1:1–1:3) and water vapor pressure of the selected drying agents (anhydrite-III and supersaturated CaCl₂ solution) on the phase composition of the products was evaluated. After 7 days of hydration, either ettringite or monosulfate was obtained as the main product, depending on the C₃A:C

\bar{S}

molar ratio. The synthesis carried out at a C₃A:C

\bar{S}

molar ratio of 1:3 produced pure ettringite. In the case of the sample characterized by the ratio of 1:1 (typical of monosulfate), a considerable portion of ettringite (27.9%) was present in the final products along the AFm phase. Therefore, a different synthesis method has to be selected in order to obtain pure monosulfate. The results showed that thermal analysis, X-ray diffractometry and FTIR spectroscopy can be used to distinguish the characteristic features of ettringite and monosulfate. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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23 pages, 4316 KiB

Open AccessArticle

Strength Development and Environmental Impact of Waste-Glass-Based Cements Activated with Portland Cement, NaOH, Na-Silicate or Na-Carbonates at Ambient Temperature

by Louise Lemesre, Rachida Idir and Martin Cyr

Materials 2024, 17(20), 5097; https://doi.org/10.3390/ma17205097 - 18 Oct 2024

Viewed by 510

Abstract

This paper presents an experimental approach to the study of the compressive strength, isothermal calorimetry and life cycle assessment (LCA) of alkali-activated pastes based on soda–lime–silica glass, established to investigate the effect of the nature and proportion of the activator. Four different activators [...] Read more.

This paper presents an experimental approach to the study of the compressive strength, isothermal calorimetry and life cycle assessment (LCA) of alkali-activated pastes based on soda–lime–silica glass, established to investigate the effect of the nature and proportion of the activator. Four different activators are compared: Portland cement, sodium silicate, sodium carbonate (at four percentages by weight: 5, 10, 15 and 25 wt% relative to glass) and sodium hydroxide (3.5 wt%). Portland cement and sodium carbonate were added in dry form (powder), while sodium hydroxide (pellets) and silicate were used in solution. At room temperature, glass exhibited slow reaction kinetics, with mechanical performance increasing significantly beyond 28 days of curing. The nature of the activator had a direct impact on the mechanical performance of the activated glass. Cement-activated pastes and those containing 25 wt% of sodium carbonate developed strength at an early age (0–7 days). The other activators showed lower strength development before 28 days of reaction. While a higher activator content improved short-term performance, it also increased the environmental impact, primarily due to the activator. The LCA, conducted on 11 indicators, revealed that the environmental impact was largely driven by the type and amount of activator used. A performance impact indicator (PII) related to global warming was introduced to compare pastes with different performance values. At an early age (0–28 days), the PII was lower when the activator level was high but decreased over time as the strength improved. In terms of long-term performance (360 days), hydroxide and sodium carbonate (10 wt%) achieved compressive strengths of 91 and 74 MPa, respectively. These systems offered a balance between high performance and a reduced environmental impact, making them of interest for sustainable applications. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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27 pages, 1852 KiB

Open AccessArticle

Rapid Assessment of Sulfate Resistance in Mortar and Concrete

by Seyedsaleh Mousavinezhad, William K. Toledo, Craig M. Newtson and Federico Aguayo

Materials 2024, 17(19), 4678; https://doi.org/10.3390/ma17194678 - 24 Sep 2024

Viewed by 850

Abstract

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can [...] Read more.

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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20 pages, 8079 KiB

Open AccessArticle

The Influence of Silica Fly Ash and Wood Bottom Ash on Cement Hydration and Durability of Concrete

by Jurgita Malaiškienė and Marija Vaičienė

Materials 2024, 17(16), 4031; https://doi.org/10.3390/ma17164031 - 13 Aug 2024

Cited by 1 | Viewed by 966

Abstract

This research addresses a notable gap in understanding the synergistic effects of high carbon wood bottom ash (BA) and silica fly ash (FA) on cement hydration and concrete durability by using them as a supplementary material to reduce the amount of cement in [...] Read more.

This research addresses a notable gap in understanding the synergistic effects of high carbon wood bottom ash (BA) and silica fly ash (FA) on cement hydration and concrete durability by using them as a supplementary material to reduce the amount of cement in concrete and CO₂ emissions during cement production. This study analyses the synergistic effect of FA and BA on cement hydration through X-ray diffraction (XRD), thermal analysis (TG, DTG), scanning electron microscopy (SEM), density, ultrasonic pulse velocity (UPV), compressive strength, and temperature monitoring tests. In addition, it evaluates concrete properties, including compressive strength, UPV, density, water absorption kinetics, porosity parameters, predicted resistance to freezing and thawing cycles, and results of freeze–thawing resistance. The concrete raw materials were supplemented with varying percentages of BA and FA, replacing both cement and fine aggregate at levels of 0%, 2.5%, 5%, 10% and 15%. The results indicate that a 15% substitution of BA and FA delays cement hydration by approximately 5 h and results in only a 6% reduction in compressive strength, with the hardened cement paste showing a strength similar to a 15% replacement with FA. Concrete mixtures with 2.5% BA and 2.5% FA maintained the same maximum hydration temperature and duration as the reference mix. Furthermore, the combined use of both ashes provided adequate resistance to freeze–thaw cycles, with only a 4.7% reduction in compressive strength after 150 cycles. Other properties, such as density, UPV and water absorption, exhibited minimal changes with partial cement replacement by both ashes. This study highlights the potential benefits of using BA and FA together, offering a sustainable alternative that maintains concrete performance while using waste materials. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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18 pages, 3474 KiB

Open AccessArticle

Design of Alkali-Activated Materials and Geopolymer for Deep Soilmixing: Interactions with Model Soils

by Faten Souayfan, Emmanuel Roziere, Michael Paris, Dimitri Deneele, Ahmed Loukili and Christophe Justino

Materials 2024, 17(15), 3783; https://doi.org/10.3390/ma17153783 - 1 Aug 2024

Viewed by 766

Abstract

This study focuses on the use of alkali-activated materials and geopolymer grouts in deep soilmixing. Three types of grouts, incorporating metakaolin and/or slag and activated with sodium silicate solution, were characterized at different scales to understand the development of their local structure and [...] Read more.

This study focuses on the use of alkali-activated materials and geopolymer grouts in deep soilmixing. Three types of grouts, incorporating metakaolin and/or slag and activated with sodium silicate solution, were characterized at different scales to understand the development of their local structure and macroscopic properties. The performance of the soilmix was assessed by using combinations of the grouts and model soils with different clay contents. Feret’s approach was used to understand the development of compressive strength at different water-to-solid ratios ranging from 0.65 to 1. The results suggested that incorporating calcium reduced the water sensitivity of the materials, which is crucial in soilmixing. Adding soils to grouts resulted in improved mechanical properties, due to the influence of the granular skeleton. Based on strength results, binary soilmix mixtures containing 75% of metakaolin and 25% of slag, with H₂O/Na₂O ratios ranging from 28 to 42 demonstrated potential use for soilmixing due to the synergistic reactivity of metakaolin and slag. The optimization of compositions is necessary for achieving the desired properties of soil mixtures with higher H₂O/Na₂O ratios. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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34 pages, 11583 KiB

Open AccessArticle

Strengthening Reinforced Concrete Beams through Integration of CFRP Bars, Mechanical Anchorage System, and Concrete Jacketing

by Mahmood Y. Alkhateeb and Farzad Hejazi

Materials 2024, 17(12), 2794; https://doi.org/10.3390/ma17122794 - 7 Jun 2024

Viewed by 946

Abstract

The demand for strengthening reinforced concrete (RC) structures has increased considerably. Implementing carbon-fiber-reinforced polymer (CFRP) bars and concrete jacketing are the most effective techniques for RC beam retrofitting. Using the mechanical anchorage system (MAS) to attach CFRP bars to old concrete is highly [...] Read more.

The demand for strengthening reinforced concrete (RC) structures has increased considerably. Implementing carbon-fiber-reinforced polymer (CFRP) bars and concrete jacketing are the most effective techniques for RC beam retrofitting. Using the mechanical anchorage system (MAS) to attach CFRP bars to old concrete is highly recommended to avoid any debonding when it is applied to cyclic loads. However, the design of strengthening details is the most challenging issue because it involves many effective parameters. In this study, a design process for strengthening beams using CFRP bars with new MASs and concrete jacketing is proposed, and various design schemes are studied. The number of applied MASs and the thickness and grade of the concrete jacket were investigated through experimental testing and finite element (FE) simulations to define strengthening design details, such as the number and size of employed CFRP bars. Accordingly, an analytical technique was formulated to predict the performance of the strengthened beam in terms of the nominal ultimate load. The results demonstrated the high performance of the proposed system in preventing premature debonding. The proposed system enhances the beam capacity from 44 kN to 83 kN, representing an increase of more than 90%. In contrast, the conventional near-surface mounted (NSM) system exhibits a lower percentage increase at less than 37%. Both FE simulations and analytical approaches can be effectively employed to predict the behavior and capacity of the strengthened beam while considering various design parameters. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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16 pages, 16331 KiB

Open AccessArticle

Effect of Salt Solution Erosion on Mechanical Properties and Micropore Structure of Recycled Fine Aggregate ECC

by Yuanhang Xiang, Fengxia Han and Qing Liu

Materials 2024, 17(11), 2498; https://doi.org/10.3390/ma17112498 - 22 May 2024

Cited by 2 | Viewed by 705

Abstract

This study examined the impact of sulfate and sulfate–chloride dry–wet cyclic erosion on the mechanical properties and microscopic pore structure of engineered cementitious composite (ECC) with recycled fine aggregate (RA). Uniaxial tensile tests and four-point bending tests were conducted to evaluate the mechanical [...] Read more.

This study examined the impact of sulfate and sulfate–chloride dry–wet cyclic erosion on the mechanical properties and microscopic pore structure of engineered cementitious composite (ECC) with recycled fine aggregate (RA). Uniaxial tensile tests and four-point bending tests were conducted to evaluate the mechanical properties of RAECC, while the resonance frequency ratio was used to assess the integrity of the specimens. Finally, X-ray computed tomography (X-CT) reconstruction was employed to analyze the erosion effects on the microscopic pore structure. The results showed that the uniaxial tensile strength and flexural strength of the RAECC specimens in corrosive solution first increased and then decreased, and the 5% Na₂SO₄ solution caused the most serious erosion of the specimens. The resonance frequency ratio of the specimens reached the peak value when they were subjected to dry–wet cycles 15 times in the 5% Na₂SO₄ solution. During the erosion process, the pore space of the specimen first decreased and then increased, and the number of pores increased. The erosion process is the result of the erosion products continuously filling and eventually destroying the pores, and the erosion damage produces a large number of new pores and poor sphericity, leading to a decline in mechanical properties. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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9 pages, 4748 KiB

Open AccessCommunication

Effects of Lithium Carbonate and Superplasticizer on Ultra-Early Strength of Alite-Ye’elimite-Belite-Ferrite Cement

by Peng Du, Hao Sun, Xiaolei Lu, Yongbo Huang and Xin Cheng

Materials 2024, 17(8), 1742; https://doi.org/10.3390/ma17081742 - 10 Apr 2024

Viewed by 1032

Abstract

Alite-ye’elimite-belite-ferrite cement (AYBFC) integrates the advantages of calcium sulfoaluminate cement and Portland cement, but its ultra-early strength needs to be further improved when applied to rush repair and construction works. In this study, the ultra-early strength of AYBFC was improved using lithium carbonate [...] Read more.

Alite-ye’elimite-belite-ferrite cement (AYBFC) integrates the advantages of calcium sulfoaluminate cement and Portland cement, but its ultra-early strength needs to be further improved when applied to rush repair and construction works. In this study, the ultra-early strength of AYBFC was improved using lithium carbonate (Li₂CO₃) and superplasticizer. The results showed that an appropriate amount of Li₂CO₃ could significantly improve the ultra-early strength of AYBFC, since it was capable of promoting the hydration reaction of AYBFC. After polycarboxylate superplasticizer was doped on this basis, the ultra-early compressive strength of AYBFC was further improved. This was because the superplasticizer could markedly enhance the matrix compactness despite its inhibitory effect on the hydration reaction of cement and the generation of hydration products. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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17 pages, 4054 KiB

Open AccessArticle

Experimental Investigation on the Effects of Mineral Water Composition on the Leaching of Cement-Based Materials

by Alienor Pouyanne, Sonia Boudache, Benoît Hilloulin, Ahmed Loukili and Emmanuel Roziere

Materials 2024, 17(7), 1548; https://doi.org/10.3390/ma17071548 - 28 Mar 2024

Cited by 1 | Viewed by 924

Abstract

The common phenomenon observed for concrete in aggressive water is leaching, which involves the dissolution of cement hydration products. Many studies have focused on leaching in demineralised water or acid attacks, but mineral water still deserves further investigation. In most standards, the aggressiveness [...] Read more.

The common phenomenon observed for concrete in aggressive water is leaching, which involves the dissolution of cement hydration products. Many studies have focused on leaching in demineralised water or acid attacks, but mineral water still deserves further investigation. In most standards, the aggressiveness of a given water body is determined by its pH and not its composition. The effect of the calcium content of the water on degradation is yet to be determined. In this paper, the leaching of Portland cement-based mortar was induced by two types of drinking water with different calcium contents and buffer capacity in controlled conditions. The Langelier saturation index (LSI) was used to describe water aggressiveness based on the calco-carbonic equilibrium. The studied waters had the same pH but LSIs of +0.5 and −1.0 corresponding to scaling with respect to aggressive water; demineralised water was used as a reference. Microstructural damage was checked by TGA and X-ray microtomography. Macroscopic measurements were used to monitor global degradation. The soft water caused a 53% deeper deterioration of the mortar sample than the hard water. Soft water-induced leaching was found to be similar yet slower to leaching via demineralised water (with a mass loss of −2.01% and −2.16% after 200 days, respectively). In contrast, hard water induced strongly time-dependent leaching, and the damage was located close to the surface. The roughness of leached specimens was 18% higher in hard water than in soft water. The formation of calcite on the sample surface not only affects the leaching rate by creating a protective surface layer, but it could also act as a calcium ion pump. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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26 pages, 12487 KiB

Open AccessArticle

Effect of Polymer/Nano-Clay Coatings on the Performance of Concrete with High-Content Supplementary Cementitious Materials under Harsh Exposures

by M. A. Abuzeid, M. T. Bassuoni and M. R. Sakr

Materials 2024, 17(5), 1030; https://doi.org/10.3390/ma17051030 - 23 Feb 2024

Cited by 1 | Viewed by 1311

Abstract

In recent concrete research, a novel category of coatings has emerged: polymers/nanoparticles blends. The efficacy of such coatings warrants extensive examination across various concrete mixtures, particularly those incorporating high-volume supplementary cementitious materials (SCMs) to mitigate carbon footprints, an industry imperative. This study used [...] Read more.

In recent concrete research, a novel category of coatings has emerged: polymers/nanoparticles blends. The efficacy of such coatings warrants extensive examination across various concrete mixtures, particularly those incorporating high-volume supplementary cementitious materials (SCMs) to mitigate carbon footprints, an industry imperative. This study used three vulnerable concrete mixtures to assess the effectiveness of ethyl silicate and high-molecular-weight methyl methacrylate blended with 2.5% and 5% halloysite and montmorillonite nano-clay. Findings from physical, thermal, and microstructural analyses confirmed vulnerabilities in concretes with a high water-to-binder ratio (0.6) under severe exposure conditions, notably with high SCM content (40% and 60% fly ash and slag, respectively). Neat ethyl silicate or high-molecular-weight methyl methacrylate coatings inadequately protected those concretes against physical salt attacks and salt–frost scaling exposures. However, the incorporation of halloysite nano-clay or montmorillonite nano-clay in these polymers yielded moderate-to-superior concrete protection compared to neat coatings. Ethyl silicate-based nanocomposites provided full protection, achieving up to 100% improvement (no or limited surface scaling) against both exposures, particularly when incorporating halloysite-based nano-clay at a 2.5% dosage by mass. In contrast, high-molecular-weight methyl methacrylate-based nano-clay composites effectively mitigated physical salt attacks but exhibited insufficient protection throughout the entire salt–frost scaling exposure, peeling off at 15 cycles. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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20 pages, 4162 KiB

Open AccessArticle

Assessing the Influence of Banana Leaf Ash as Pozzolanic Material for the Production of Green Concrete: A Mechanical and Microstructural Evaluation

by Md. Hamidul Islam, David William Law, Chamila Gunasekara, Md. Habibur Rahman Sobuz, Md. Nafiur Rahman, Md. Ahsan Habib and Ashanul Kabir Sabbir

Materials 2024, 17(3), 720; https://doi.org/10.3390/ma17030720 - 2 Feb 2024

Cited by 3 | Viewed by 2112

Abstract

This paper reports an investigation of the mechanical and microscopic properties of partially replaced banana leaf ash (BLA) concrete. In this research, the cement was partially replaced by BLA in two phases: Phase A (0%, 5%, 10%, 15%, 20%, 25% and 30%) and [...] Read more.

This paper reports an investigation of the mechanical and microscopic properties of partially replaced banana leaf ash (BLA) concrete. In this research, the cement was partially replaced by BLA in two phases: Phase A (0%, 5%, 10%, 15%, 20%, 25% and 30%) and Phase B (0%, 10%, 20% and 30%). The consequence of partially replacing cement with BLA in concrete was investigated by the application of a range of tests, namely X-ray fluorescence (XRF), compressive strength, splitting tensile strength, flexure strength, ultrasonic pulse velocity and scanning electron microscopy (SEM) analysis. The properties were then correlated with the properties of a standard 100% Portland cement concrete of similar strength. The XRF result of the BLA identified a composition with 48.93% SiO₂ and 3.48% Al₂O_3, which indicates that the material potentially possesses pozzolanic properties. The mechanical properties of the partially replaced BLA concrete noted minor strength loss, approximately 5% with 20% partial replacement. The nondestructive testing data showed enhanced performance up to 20% partial replacement, with ultrasonic pulse values above 3500 m/s. The scanning electron microscopy analysis illustrated that the morphology of BLA specimens contained increased microcracks compared with the control. The decrease in strength observed is attributed to the fibrous composition of the BLA. The mechanical, nondestructive testing and microscopic results highlight the potential to utilize BLA as a partial replacement for cement as a pozzolanic material in concrete at up to 20% by weight of cement. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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15 pages, 8996 KiB

Open AccessArticle

A Study on the Microstructure and Mechanical Properties of Portland Cement Incorporating Aluminosilicate Waste

by Valentin Antonovič, Donatas Sikarskas, Renata Boris, Andrius Kudžma, Jurgita Malaiškienė and Rimvydas Stonys

Materials 2024, 17(2), 354; https://doi.org/10.3390/ma17020354 - 10 Jan 2024

Cited by 3 | Viewed by 1479

Abstract

The influence of aluminosilicate pozzolanic waste, specifically spent fluid catalytic cracking waste (FCCW) and metakaolin waste (MK) from the expanded glass industry, on the properties of hardened Portland cement paste were analysed. The study involved replacing part of cement with FCCW and MK [...] Read more.

The influence of aluminosilicate pozzolanic waste, specifically spent fluid catalytic cracking waste (FCCW) and metakaolin waste (MK) from the expanded glass industry, on the properties of hardened Portland cement paste were analysed. The study involved replacing part of cement with FCCW and MK and observing their impact on the hydration, microstructure, density, and compressive strength of hardened cement paste. Various analysis methods were employed, including X-ray diffraction (XRD), thermogravimetric analysis (TG), and scanning electron microscopy (SEM), to understand the changes in the structure of the hardened cement paste during hydration. The findings revealed that FCCW tends to accelerate the cement hydration process due to its high surface area and pozzolanic activity. Notably, the formation of portlandite crystals was observed on FCCW particle surfaces in a specific direction. These crystals appeared smaller and developed in different directions in compositions containing a composite binder with mixture of FCCW and MK in a ratio 1:1. This could be influenced by pozzolanic reactions activated by fine particles of MK and the formation of calcium silicate hydrates (C-S-H) and calcium alumino silicate hydrates (C-A-S-H) in the presence of portlandite. The XRD and TG results indicated that the specimens containing a composite binder exhibited the least amount of portlandite. The compressive strength of these specimens increased compared to the control specimens, although the amount of cement was 9% lower. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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15 pages, 14013 KiB

Open AccessArticle

The Material Heterogeneity Effect on the Local Resistance of Pultruded GFRP Columns

by Yongcheng Zhu, Viktor Gribniak, Chaofeng Ding, Hua Zhu and Baiqi Chen

Materials 2024, 17(1), 153; https://doi.org/10.3390/ma17010153 - 27 Dec 2023

Cited by 1 | Viewed by 884

Abstract

Pultruded GFRP (glass fiber-reinforced polymer) materials are widely used in structural engineering because of their lightweight, corrosion immunity, and electromagnetic transparency. However, the design of load-bearing components facing substantial compressive stresses, e.g., columns, must be more stringent than steel structures due to excessive [...] Read more.

Pultruded GFRP (glass fiber-reinforced polymer) materials are widely used in structural engineering because of their lightweight, corrosion immunity, and electromagnetic transparency. However, the design of load-bearing components facing substantial compressive stresses, e.g., columns, must be more stringent than steel structures due to excessive deformability, material heterogeneity, and vulnerability to stress concentration. This manuscript investigates the failure performance of locally produced GFRP materials, focusing on the material heterogeneity effect on the mechanical resistance of a support joint of a pultruded tubular GFRP column. This experimental campaign employs relatively short rectangular profile fragments to isolate the support behavior and verify a simplified numerical finite element model, which neglects the nonlinearity of GFRP material. This work determines the material failure mechanisms behind the mechanical performance of pultruded profiles subjected to longitudinal compression for various column lengths. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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17 pages, 10633 KiB

Open AccessArticle

Mechanical Properties and Microscopic Mechanism of a Multi-Cementitious System Comprising Cement, Fly Ash, and Steel Slag Powder

by Yuzhi Zhang, Shujing Zhang, Qingke Nie, Liang Shen and Wei Wang

Materials 2023, 16(22), 7195; https://doi.org/10.3390/ma16227195 - 16 Nov 2023

Cited by 3 | Viewed by 1578

Abstract

The objective of this study was to reduce the stockpile of steel slag, which is a solid waste generated in the steelmaking process, and promote the resource utilization of steel slag powder (SSP) in construction projects. Experimental research was conducted on SSP and [...] Read more.

The objective of this study was to reduce the stockpile of steel slag, which is a solid waste generated in the steelmaking process, and promote the resource utilization of steel slag powder (SSP) in construction projects. Experimental research was conducted on SSP and fly ash (FA) as supplementary cementitious materials. Composite cement paste samples were prepared to investigate the effects of the water-to-binder ratio and cement-substitution rate on the macroscopic mechanical properties, including the setting time, fluidity, flexural strength, and compressive strength of the prepared paste. The mineral composition in the raw materials was measured using X-ray diffraction (XRD), and a micro-morphological and structural analysis of the hydrated cementitious material samples was performed using scanning electron microscopy (SEM); the SEM and Image Pro Plus (IPP) image analysis techniques were combined for a quantitative analysis of the microstructure. The results showed that the addition of FA and SSP delayed the hydration of cement, thereby improving the flowability of the composite paste. Under the same curing age and cement substitution rate, the sample strength decreased with increasing water-to-binder ratio. Under the same water-to-binder ratio and curing age, the variations in the flexural and compressive strengths of the SSP group samples were inconsistent in the early and later stages, and the sample group with 20% SSP exhibited optimal mechanical strength in the later stage. The microscopic results showed that the needle-like AFt crystals in the hydrated pores decreased in number with the increase in the SSP content. The hydration products of the FA–SSP admixture, such as C–S–H gel and RO phase, acted as pore fillers in alkaline environments. When the water-to-binder ratio was 0.4 and the FA-to-SSP ratio was 1:1 to replace 40% cement, the performance of the hardened cement paste was the best among all the test groups containing both FA and SSP. This study provides a theoretical basis for the practical application of SSP and FA as cementitious materials in construction-related fields. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (2nd Edition))

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