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13 pages, 2759 KiB

Open AccessArticle

Performance of the Cement Grouting Material and Optimization of the Mix Proportion for the Free Section of the Prestressed Anchor Bar

by Chaoguang Wu, Zhiya Chen, Xuemin Zhang, Zikun Li, Lichuan Wang, Bin Ouyang and Jin Liu

Materials 2023, 16(20), 6819; https://doi.org/10.3390/ma16206819 - 23 Oct 2023

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Abstract

Increasing the water–cement ratio and water-reducer dosage of cement slurry enhances its fluidity. However, a high water–cement ratio diminishes the beneficial effects of water reducers on fluidity. The stone content of the slurry decreases as the water-reducer dosage increases. Additionally, the water–cement ratio [...] Read more.

Increasing the water–cement ratio and water-reducer dosage of cement slurry enhances its fluidity. However, a high water–cement ratio diminishes the beneficial effects of water reducers on fluidity. The stone content of the slurry decreases as the water-reducer dosage increases. Additionally, the water–cement ratio significantly affects stone content. However, when the water–cement ratio exceeds a threshold value, stone content decreases. Furthermore, the threshold value of the water–cement ratio decreases with increasing water-reducer dosage. Without the addition of the water reducer, as the water–cement ratio increases the overall integrity of the grout stone decreases. The addition of the water reducer alters the surface pore distribution, wherein “uniform small pores” change to “localized large pores.” Based on the multi-objective optimization of Matlab, the recommended optimal mix composition for a slow-setting cement slurry is a water–cement ratio of 0.25 and water-reducer dosage of 1.5%. With the use of this optimized mix composition, the stone content and compressive strength increase by 7.8% and 145.6%, respectively, compared to those obtained using the recommended mix ratio in the specifications. Additionally, all relevant performance parameters meet the requirements specified by previous standards. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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16 pages, 4625 KiB

Open AccessArticle

Enhancement of Hydration Activity and Microstructure Analysis of γ-C₂S

by Ziyue Yan, Yaqing Jiang, Kangting Yin, Limeng Wang and Tinghong Pan

Materials 2023, 16(20), 6762; https://doi.org/10.3390/ma16206762 - 19 Oct 2023

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Abstract

This paper investigated the combined effect of chemical activators and nano-SiO₂ on the hydration reaction and the microstructure of γ-C₂S. The hydration reaction of γ-C₂S slurry activated with chemical activators (NaHCO₃, NaOH, K₂CO₃ [...] Read more.

This paper investigated the combined effect of chemical activators and nano-SiO₂ on the hydration reaction and the microstructure of γ-C₂S. The hydration reaction of γ-C₂S slurry activated with chemical activators (NaHCO₃, NaOH, K₂CO₃, and KOH at 1 mol/L) was enhanced by 1% nano-SiO₂. The hydrate reaction rate was determined by isothermal calorimetry, and the hydrated samples were characterized by XRD, TGA/DTG, SEM-EDS, and ²⁹Si MAS/NMR. The results revealed a substantial enhancement in the hydration activity of γ-C₂S due to the presence of the alkaline activator. Furthermore, nano-SiO₂ did not alter the composition of γ-C₂S hydration products, instead providing nucleation sites for the growth of hydration products. Incorporating nano-SiO₂ promoted the formation of C-(R)-S-H gel with a low calcium-to-silica ratio and increased its polymerization levels, resulting in more favorable structures. Among all the activators used in this study, potassium salts had a better activation effect than sodium salts. After 28 days of curing, the degree of hydration reaction in the KC+Si group was 48% and about 37% for the NHC+Si group. Whereas, the KH+Si and NH+Si groups only reached approximately 20% after the same hydration duration. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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11 pages, 4743 KiB

Open AccessArticle

Modelling of Chloride Transport in the Standard Migration Test including Electrode Processes

by Zine-Eddine Kribes, Rachid Cherif and Abdelkarim Aït-Mokhtar

Materials 2023, 16(18), 6200; https://doi.org/10.3390/ma16186200 - 14 Sep 2023

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Abstract

The modelling of chloride transport in concrete under an electrical field requires taking into account the electrode processes. These processes are very rarely introduced into the literature, despite their impact on chloride migration and the electroneutrality of the pore solution of the material. [...] Read more.

The modelling of chloride transport in concrete under an electrical field requires taking into account the electrode processes. These processes are very rarely introduced into the literature, despite their impact on chloride migration and the electroneutrality of the pore solution of the material. This paper aims to propose a multi-ion model for chloride migration that takes into consideration the electrode processes. The model is applied to simulate the standard chloride migration test. The generation of OH⁻ in the cathode and H⁺ in the anode allows for the monitoring of the electroneutrality. The model considers all of the ions in the pore solution. Ion fluxes are calculated using the Nernst–Planck equation. The Langmuir model is used to simulate the chloride isotherms. The thermodynamic equilibrium in the material is considered, which reflects the ion–solid interactions during the migration. Measurements of water porosity and the chemical composition of the pore solution are essential to provide input data and the initial and boundary conditions. The numerical results of the ion profiles in the material studied confirm the electroneutrality at any point within the material, in contrast with models that do not take the electrode processes into account. The proposed model allows for the more accurate simulation of the chloride migration test and electrochemical chloride extraction in reinforced concrete structures subjected to NaCl as part of maintenance and repair strategies. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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13 pages, 6034 KiB

Open AccessArticle

Enhancement of Alkali Resistance of Glass Fibers via In Situ Modification of Manganese-Based Nanomaterials

by Guangzhou Wang, Jinzhuo Zhang, Fuxin Li, Kangli Li, Minglian Xin, Jiang Zhu, Xiaolei Lu, Xin Cheng and Lina Zhang

Materials 2023, 16(16), 5663; https://doi.org/10.3390/ma16165663 - 17 Aug 2023

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Abstract

Glass fibers are widely used in cement-based precast products, given the reinforcing requirements for toughness and strength. However, inferior alkali resistance hinders the effectiveness of glass fibers in reinforcing cement-based materials. In this paper, nanoparticle coatings were applied on the surface of alkali-resistant [...] Read more.

Glass fibers are widely used in cement-based precast products, given the reinforcing requirements for toughness and strength. However, inferior alkali resistance hinders the effectiveness of glass fibers in reinforcing cement-based materials. In this paper, nanoparticle coatings were applied on the surface of alkali-resistant glass fiber (ARGF) as a protective layer via the in situ chemical reaction of oleic acid (OA) and potassium permanganate (PP). The morphology and constituents of the as-prepared ARGFs were examined using scanning electron microscopy (SEM) and obtaining X-ray photoelectron spectroscopy (XPS) measurements. Mass loss and strength retention were investigated to characterize alkali resistance of modified ARGFs. Results showed that ARGFs could be optimally coated by a layer of MnO₂-based nanoparticles consisting of approximately 70% MnO₂, 18% MnO, and 12% MnSiO₃, when modified with an optimum OA to PP ratio of 10 for 24 h. The dissolution of ARGFs matrix in 4% and 10% NaOH solutions were distinctly delayed to 28 d, as a consequence of the introduction of the MnO₂-based nanoparticle layer, compared with nontreated ARGF occurring at 3 d in 4% NaOH solution. For the optimally modified ARGFs, the mass loss was controlled to 1.76% and 2.91% after 90 d of corrosion in 4% and 10% NaOH solutions, and the retention of tensile strength was increased by approximately 25%. With respect to the increment in alkali-resistant performance, the modified ARGFs can be promising candidates for wide applications in alkaline cement-based products. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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18 pages, 6382 KiB

Open AccessArticle

Resistance of Pastes from Carbonated, Low-Lime Calcium Silica Cements to External Sulfate Attack

by Raikhan Tokpatayeva, Jan Olek and Sadananda Sahu

Materials 2023, 16(12), 4276; https://doi.org/10.3390/ma16124276 - 09 Jun 2023

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Abstract

This paper presents the results of a study on the evaluation of resistance of pastes from carbonated, low-lime calcium silica cements to external sulfate attack. The extent of chemical interaction between sulfate solutions and paste powders was assessed by quantifying the amount of [...] Read more.

This paper presents the results of a study on the evaluation of resistance of pastes from carbonated, low-lime calcium silica cements to external sulfate attack. The extent of chemical interaction between sulfate solutions and paste powders was assessed by quantifying the amount of species that leached out from carbonated pastes using ICP-OES and IC techniques. In addition, the loss of carbonates from the carbonated pastes exposed to sulfate solutions and the corresponding amounts of gypsum formed were also monitored by using the TGA and QXRD techniques. The changes in the structure of silica gels were evaluated using FTIR analysis. The results of this study revealed that the level of resistance of carbonated, low-lime calcium silicates to external sulfate attack was affected by the degree of crystallinity of calcium carbonate, the type of calcium silicate, and the type of cation present in the sulfate solution. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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13 pages, 4293 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Preconditioning Temperature on Gas Permeability of Alkali-Activated Concretes

by Patrycja Duży, Marta Choinska Colombel, Izabela Hager and Ouali Amiri

Materials 2023, 16(11), 4143; https://doi.org/10.3390/ma16114143 - 02 Jun 2023

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Abstract

Alkali-activated materials (AAM) are binders that are considered an eco-friendly alternative to conventional binders based on Portland cement. The utilization of industrial wastes such as fly ash (FA) and ground granulated blast furnace slag (GGBFS) instead of cement enables a reduction of the [...] Read more.

Alkali-activated materials (AAM) are binders that are considered an eco-friendly alternative to conventional binders based on Portland cement. The utilization of industrial wastes such as fly ash (FA) and ground granulated blast furnace slag (GGBFS) instead of cement enables a reduction of the CO₂ emissions caused by clinker production. Although researchers are highly interested in the use of alkali-activated concrete (AAC) in construction, its application remains very restricted. As many standards for hydraulic concrete’s gas permeability evaluation require a specific drying temperature, we would like to emphasize the sensitivity of AAM to such preconditioning. Therefore, this paper presents the impact of different drying temperatures on gas permeability and pore structure for AAC5, AAC20, and AAC35, which contain alkali-activated (AA) binders made from blends of FA and GGBFS in slag proportions of 5%, 20%, and 35% by the mass of FA, respectively. The preconditioning of samples was performed at 20, 40, 80, and 105 °C, up to the obtainment of constant mass, and then gas permeability was evaluated, as well as porosity and pore size distribution (mercury intrusion porosity (MIP) for 20 and 105 °C). The experimental results demonstrate up to a three-percentage-point rise in the total porosity of low-slag concrete after 105 °C in comparison to 20 °C, as well as a significant increase in gas permeability, reaching up to 30-fold amplification, contingent upon the matrix composition. Notably, the alteration in pore size distribution, influenced by the preconditioning temperature, exhibits a substantial impact. The results highlight an important sensitivity of permeability to thermal preconditioning. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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13 pages, 7514 KiB

Open AccessEditor’s ChoiceArticle

Influence of Calcination Temperature and Amount of Low-Grade Clay Replacement on Mitigation of the Alkali–Silica Reaction

by Daria Jóźwiak-Niedźwiedzka, Roman Jaskulski, Kinga Dziedzic, Aneta Antolik and Mariusz Dąbrowski

Materials 2023, 16(8), 3210; https://doi.org/10.3390/ma16083210 - 19 Apr 2023

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Abstract

Results of experimental investigation on the mitigation of alkali–silica reaction (ASR) by low-grade calcined clay are presented. Domestic clay with an Al₂O₃ content equal to 26% and SiO₂—58% was used. The calcination temperatures were as follows: 650 °C, [...] Read more.

Results of experimental investigation on the mitigation of alkali–silica reaction (ASR) by low-grade calcined clay are presented. Domestic clay with an Al₂O₃ content equal to 26% and SiO₂—58% was used. The calcination temperatures were as follows: 650 °C, 750 °C, 850 °C and 950 °C, which were chosen much more widely than presented in previous studies. Pozzolanity of the raw and calcined clay was determined with the Fratini test. The performance of calcined clay to mitigate ASR was evaluated according to ASTM C1567 using reactive aggregates. A control mortar mixture was prepared with 100% Portland cement (Na₂O_eq = 1.12%) as a binder with reactive aggregate, and test mixtures were made with 10% and 20% of calcined clay as a cement replacement. The microstructure of the specimens was observed on the polished sections using scanning electron microscope (SEM) operated in backscattered mode (BSE). The results of expansion of mortar bars with reactive aggregate showed that replacing cement with calcined clay reduced the expansion of the mortar bars. The greater the cement replacement, the better results in terms of ASR mitigation. However, the influence of the calcination temperature was not as clear. The opposite trend was found with the use of 10% or 20% calcined clay. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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Review

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16 pages, 992 KiB

Open AccessReview

Feasibility Review of Aerated Materials Application in 3D Concrete Printing

by Magdalena Rudziewicz, Marcin Maroszek, Mateusz Góra, Paweł Dziura, Katarzyna Mróz, Izabela Hager and Marek Hebda

Materials 2023, 16(17), 6032; https://doi.org/10.3390/ma16176032 - 02 Sep 2023

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Abstract

Recent years have witnessed a growing global interest in 3D concrete printing technology due to its economic and scientific advantages. The application of foamed concrete, renowned for its exceptional thermal and acoustic insulation properties, not only holds economic attractiveness but also aligns seamlessly [...] Read more.

Recent years have witnessed a growing global interest in 3D concrete printing technology due to its economic and scientific advantages. The application of foamed concrete, renowned for its exceptional thermal and acoustic insulation properties, not only holds economic attractiveness but also aligns seamlessly with the principles of sustainable development. This study explores various solutions related to 3D printing technology in construction, discussing the design, production, and properties of foamed concrete mixtures. The integration of 3D printing and the potential for automating the entire process offers opportunities to boost productivity and reduce construction costs. Furthermore, the utilization of foamed concrete with its commendable insulation properties will enable a reduction in the usage of materials other than concrete (e.g., mineral wool, facade mesh, and polystyrene), significantly facilitating the recycling process during building demolition. This, in turn, will lead to the preservation of nonrenewable natural resources and a decrease in CO₂ emissions. Despite the promising results, there have been limited studies focusing on 3D printing with foamed materials, whereas a survey of the existing body of literature indicates a notable absence of endeavors pertaining to the utilization of aerated concrete within the realm of 3D printing, especially geopolymer composites (GP) and hybrid geopolymer composites (HGP). The outcomes delineated in the ensuing discourse are demonstrative for conventionally used materials rather than the additive manufacturing variant. Hence, this work aims to systematically review existing practices and techniques related to producing foamed concrete with 3D printing technology. This analysis also contributes to the establishment of a foundational framework and furnishes a preliminary basis upon which future endeavors aimed at the 3D printing of aerated concrete can be embarked. The findings from the literature analysis justify the desirability of continuing research on this topic, particularly when considering the potential for large-scale industrial implementation. This article provides a comprehensive state of the knowledge on the development of 3D printing techniques for foamed concrete mixtures. By consolidating and analyzing findings from different studies, this article offers insights into the advancements, challenges, and potential applications of foamed concrete in additive manufacturing processes. This, in turn, contributes to the overall understanding and advancement of 3D printing technologies using foamed concrete as a versatile and sustainable construction material. The encouraging results obtained from the analysis further underscore the need for the continued exploration of 3D printing, especially with an eye towards its industrial-scale implementation. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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