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20 pages, 35686 KiB

Open AccessArticle

Exploring the Relationship between Mechanical Properties and Electrical Impedance in Cement-Based Composites Incorporating Gold Nanoparticles

by Daniel A. Triana-Camacho, David A. Miranda and Jorge H. Quintero-Orozco

Materials 2024, 17(16), 3972; https://doi.org/10.3390/ma17163972 - 9 Aug 2024

Viewed by 532

Abstract

Structural health monitoring applications have gained significant attention in recent research, particularly in the study of the mechanical–electrical properties of materials such as cement-based composites. While most researchers have focused on the piezoresistive properties of cement-based composites under compressive stress, exploring the electrical [...] Read more.

Structural health monitoring applications have gained significant attention in recent research, particularly in the study of the mechanical–electrical properties of materials such as cement-based composites. While most researchers have focused on the piezoresistive properties of cement-based composites under compressive stress, exploring the electrical impedance of such materials can provide valuable insights into the relationship between their mechanical and electrical characteristics. In this study, we investigated the connection between the mechanical properties and electrical impedance of cement-based composites modified with Au nanoparticles. Cylindrical samples with dimensions of 3 cm in diameter and 6 cm in length were prepared with a ratio of w/c = 0.47. The Au nanoparticles (Au NPs) were synthesized using pulsed laser ablation in liquids, and their size distribution was analyzed through dynamical light scattering. Mechanical properties were evaluated by analyzing the Young modulus derived from strain–stress curves obtained at various force rates. Electrical properties were measured by means of electrical impedance spectroscopy. The experimental results revealed a notable reduction of 91% in the mechanical properties of Au NPs-cement compounds, while their electrical properties demonstrated a significant improvement of 65%. Interestingly, the decrease in mechanical properties resulting from the inclusion of gold nanoparticles in cementitious materials was found to be comparable to that resulting from variations in the water/cement ratios or the hydration reaction. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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13 pages, 1729 KiB

Open AccessArticle

Prediction of Compressive Strength of Concrete Specimens Based on Interpretable Machine Learning

by Wenhu Wang, Yihui Zhong, Gang Liao, Qing Ding, Tuan Zhang and Xiangyang Li

Materials 2024, 17(15), 3661; https://doi.org/10.3390/ma17153661 - 24 Jul 2024

Viewed by 390

Abstract

The aim of this paper is to explore an effective model for predicting the compressive strength of concrete using machine learning technology, as well as to interpret the model using an interpretable method, which overcomes the limitation of the unknowable prediction processes of [...] Read more.

The aim of this paper is to explore an effective model for predicting the compressive strength of concrete using machine learning technology, as well as to interpret the model using an interpretable method, which overcomes the limitation of the unknowable prediction processes of previous machine learning models. An experimental database containing 228 samples of the compressive strength of standard cubic specimens was built in this study, and six algorithms were applied to build the predictive model. The results show that the XGBoost model has the highest prediction accuracy among all models, as the R² of the training set and testing set are 0.982 and 0.966, respectively. Further analysis was conducted on the XGBoost model to discuss its applicability. The main steps include the following: (i) obtaining key features, (ii) obtaining trends in the evolution of features, (iii) single-sample analysis, and (iv) conducting a correlation analysis to explore methods of visualizing the variations in the factors that exert influence. The interpretability analyses on the XGBoost model show that the contribution to the compressive strength by each factor is highly in line with the conventional theory. In summary, the XGBoost model proved to be effective in predicting concrete’s compressive strength. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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14 pages, 4338 KiB

Open AccessArticle

Investigation of Using Calcined Coal Gangue as the Co-Blended Precursor in the Alkali-Activated Metakaolin

by Ye Pan, Zichen Lu, Liheng Zhang, Hui Zhang, Qin Zhang and Zhenping Sun

Materials 2024, 17(14), 3610; https://doi.org/10.3390/ma17143610 - 22 Jul 2024

Viewed by 380

Abstract

The feasibility and performance of using calcined coal gangue (CCG) to substitute metakaolin (MK) as the precursor to prepare alkali-activated materials (AAMs) were thoroughly evaluated by conducting combined experiments of flowability test, mechanical measurement, calorimetry and microstructure analysis, etc. It was found that [...] Read more.

The feasibility and performance of using calcined coal gangue (CCG) to substitute metakaolin (MK) as the precursor to prepare alkali-activated materials (AAMs) were thoroughly evaluated by conducting combined experiments of flowability test, mechanical measurement, calorimetry and microstructure analysis, etc. It was found that the increased substitution ratio of CCG to MK can increase the flowability of the prepared paste by up to 28.1% and decrease its viscosity by up to 55.8%. In addition, a prolonged setting time of up to 31.8% was found with the increased substitution amount of CCG to MK, which can be attributed to the low reactivity of CCG compared to that of MK. Lastly, even though the presence of CCG can lead to a decrease in the early compressive strength of the hardened paste, a highly recovered long-term mechanical property can be found due to the continuous reaction of CCG. All of these results prove the feasibility of using CCG as one co-blended precursor with MK to prepare alkali-activated materials. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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22 pages, 10995 KiB

Open AccessArticle

Laboratory Scaled-Down Cementitious Concrete Model Used for Estimating the Bearing Capacity of a Bridge Girder Based on the Similitude Theory

by Marin Amăreanu, Ionuţ-Radu Răcănel, Ciprian Nicolae Neacşu and Daniel Dumitru Morlova

Materials 2023, 16(24), 7559; https://doi.org/10.3390/ma16247559 - 8 Dec 2023

Viewed by 1522

Abstract

Bridges are structures subjected to multiple types of loads and combinations during their service life. The uncertainties linked with the materials’ behavior and manufacturing processes often necessitate the testing of produced elements on a real scale. This is particularly true for bridge concrete [...] Read more.

Bridges are structures subjected to multiple types of loads and combinations during their service life. The uncertainties linked with the materials’ behavior and manufacturing processes often necessitate the testing of produced elements on a real scale. This is particularly true for bridge concrete precast girders, which are frequently tested to predict the ultimate carrying load. Testing procedures are time-consuming, expensive in terms of both time and money, and involve a large amount of logistics and auxiliary equipment and devices. Thus, testing scaled-down models in laboratory conditions and extrapolating the obtained results with respect to the real-scale element using similitude theory has become a very common alternative method in the last decade. In this paper, experimental data regarding the efficiency of dimensional analysis computation are discussed. The proposed method involves comparing the values at which failure in bending and shear occurs for a 1:10 cementitious concrete bridge beam model with respect to the values computed for the prototype beam. Regarding the obtained results, a very small difference between the test results and the calculated values can be noticed. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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18 pages, 9251 KiB

Open AccessArticle

Influence of Carbonation on the Properties of Steel Slag–Magnesium Silicate Hydrate (MSH) Cement

by Tian Zeng, Zhiqi Hu, Chengran Huang and Jun Chang

Materials 2023, 16(20), 6737; https://doi.org/10.3390/ma16206737 - 18 Oct 2023

Cited by 3 | Viewed by 1267

Abstract

Magnesium silicate hydrate (MSH) cement has the advantages of low energy consumption, minimal environmental pollution, carbon negativity, and reduced alkalinity, but excessive drying shrinkage inhibits its application. This paper analyzed the influence of steel slag (SS) dosage, carbon dioxide partial pressure, and carbonation [...] Read more.

Magnesium silicate hydrate (MSH) cement has the advantages of low energy consumption, minimal environmental pollution, carbon negativity, and reduced alkalinity, but excessive drying shrinkage inhibits its application. This paper analyzed the influence of steel slag (SS) dosage, carbon dioxide partial pressure, and carbonation curing time on the compressive strength, shrinkage rate, and phase composition of MSH cement. Various analysis methods, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP), were used to study the hydration products and microstructure. The results showed that under normal curing conditions, MSH cement mixed with different steel slag contents experienced a decline in strength at all ages. However, the greater the amount of SS incorporated, the lesser the degree of drying shrinkage. The compressive strength of all groups was improved, and the drying shrinkage was reduced by carbonation treatment. The samples with 5%, 10%, and 15% SS content exhibited shrinkage rates of 2.19%, 1.74%, and 1.60%, respectively, after 28 days of curing. The reason was that after carbonation treatment, hydrated magnesium carbonates (HMCs) were generated in the SS–MSH cement, and a Ca–Mg–C amorphous substance formed by hydration and carbonation of C₂S in steel slag filled in the pores, which enhanced the density of the matrix, improved the compressive strength of the specimen, and reduced the shrinkage rate. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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15 pages, 17406 KiB

Open AccessArticle

Effect of Carbonation Treatment on the Strength and CO₂ Uptake Rate of Composite Cementitious Material with a High Steel Slag Powder Content

by Zhimin He, Xuyang Shao and Xin Chen

Materials 2023, 16(18), 6204; https://doi.org/10.3390/ma16186204 - 14 Sep 2023

Viewed by 1043

Abstract

As a major steel producer, China is now eager to develop feasible solutions to recycle and reuse steel slag. However, due to the relatively poor hydration activity of steel slag, the quantity of steel slag used as a supplemental binder material is limited. [...] Read more.

As a major steel producer, China is now eager to develop feasible solutions to recycle and reuse steel slag. However, due to the relatively poor hydration activity of steel slag, the quantity of steel slag used as a supplemental binder material is limited. In order to improve the cementitious properties of steel slag, the strength and carbonation degree of the high-content steel slag powder–cement–metakaolin composite cementitious material system under CO₂ curing conditions were investigated. The compressive strengths of the mortar specimens were tested and compared. The carbonation areas were identified and evaluated. A microscopic analysis was conducted using X-ray diffraction (XRD), thermogravimetry analysis (TG), and scanning electron microscopy (SEM) to reveal the chemical mechanisms. The results showed that CO₂ curing significantly increased the early strength as the 3D compressive strength of the specimens increased by 47.2% after CO₂ curing. The strength of the specimens increased with increasing amounts of metakaolin in a low water-to-binder ratio mixture. The 3D compressive strength of the specimens prepared with 15% metakaolin at a 0.2 water-to-binder ratio achieved 44.2 MPa after CO₂ curing. Increasing the water-to-binder ratio from 0.2 to 0.5 and the metakaolin incorporation from 0% to 15% resulted in a 25.33% and 19.9% increase in the carbonation area, respectively. The calcium carbonate crystals that formed during carbonation filled the pores and reduced the porosity, thereby enhancing the strength of the mortar specimens. The soundness of the specimens after CO₂ curing was qualified. The results obtained in the present study provide new insight for the improvement of the hydration reactivity and cementitious properties of steel slag powder. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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15 pages, 10654 KiB

Open AccessArticle

Effect of Aluminium Substitution on Physical Adsorption of Chloride and Sulphate Ions in Cement-Based Materials

by Guangtai Zhang, Maoquan Li and Zheyu Zhu

Materials 2023, 16(17), 6029; https://doi.org/10.3390/ma16176029 - 1 Sep 2023

Cited by 2 | Viewed by 789

Abstract

When aluminium-rich phase minerals are added to Portland cement, Al atoms will enter the C-S-H and Al, then a substitution reaction will occur, forming a hydrated silica-calcium aluminate (C-A-S-H), which changes the molecular structure of the cement material. Due to limitations in experimental [...] Read more.

When aluminium-rich phase minerals are added to Portland cement, Al atoms will enter the C-S-H and Al, then a substitution reaction will occur, forming a hydrated silica-calcium aluminate (C-A-S-H), which changes the molecular structure of the cement material. Due to limitations in experimental methods, the research on the bonding effect between corroded ions and Al-substituted structures is still unclear. Here, the mechanism of an Al substitution reaction affecting the adsorption of chloride and sulphate ions was studied using simulation. The C-A-S-H model of aluminium random substitution was built, evaluating the binding effects among the C-A-S-H, and sulphate and chloride ions. The results demonstrated that the C-A-S-H structure generated by the Al substitution reaction increased the physical adsorption capacity of the chloride and sulphate ions. The adsorption capacity of the sulphate ions was 13.26% higher than that before the Al substitution, and the adsorption capacity of chloride ions was 21.32% higher than that before the Al substitution. The addition of high aluminium phase minerals caused the interfacial flocculants C-A-S-H and C-S-H to connect and intertwine in the the interface transition zone (ITZ) structure. The addition of high-alumina phase minerals improves the microstructure of concrete hydration products, improving the physical and mechanical properties and durability of concrete. After the addition of 20% lithium slag, the sulphate ion erosion content and the chloride ion erosion content of the concrete decreased by 13.65% and 15.72%, respectively. This paper provides a deeper understanding of the effect of high-alumina phase admixtures on concrete at the micro-scale. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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13 pages, 4181 KiB

Open AccessArticle

Effect of Synthetic Pregelatinized Starch-Modified C-S-H Particles on the Chemical Structure of C-A-S-H Generated from GGBS

by Weijie Hao and Zheyu Zhu

Materials 2023, 16(17), 5736; https://doi.org/10.3390/ma16175736 - 22 Aug 2023

Cited by 1 | Viewed by 856

Abstract

Finding new agents to enhance the strength of alkali-activated (ground granulated blast furnace slag) GGBS is beneficial for environmental protection. Here, we reveal the effect of pregelatinized starch-modifying calcium silicate hydrate (C-S-H) particles on the nanostructure tailoring of NaOH-activated GGBS hydrates. The results [...] Read more.

Finding new agents to enhance the strength of alkali-activated (ground granulated blast furnace slag) GGBS is beneficial for environmental protection. Here, we reveal the effect of pregelatinized starch-modifying calcium silicate hydrate (C-S-H) particles on the nanostructure tailoring of NaOH-activated GGBS hydrates. The results show that, for the synthetic modified C-S-H, the pregelatinized starch absorbs on the surface of C-S-H, which modifies the silicate chains and crystal structure. Adding pregelatinized starch-modified C-S-H particles can tailor the chemical structure of calcium silicaluminate hydrate (C-A-S-H) formed from GGBS hydration by increasing the mean chain length (MCL) and decreasing the Al/Si ratios. When adding C-S-H particles modified by 0.1% pregelatinized starch, the MCL of C-A-S-H is increased by 344.5% and the Al/Si ratio is decreased by 16.0%. The compressive strength of NaOH-activated GGBS samples can be enhanced by adding pregelatinized starch-modified C-S-H particles, while the addition for modified C-S-H does not significantly affect the flexural strength. The high strength of hardened blocks of hydrated GGBS is related to the long MCL silicate chains. These findings provide a potential application of pregelatinized starch-modifying C-S-H particle acting as strength-enhancing agents. Full article

(This article belongs to the Special Issue Cementitious Materials for Construction: Preparation, Characterization and Applications)

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