Materials

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14 pages, 7573 KiB

Open AccessArticle

Behavior and Performance Analysis of Fire Protection Materials Applied to Steel Structures According to Exposed Temperatures

by Hyun Kang and Oh-Sang Kweon

Materials 2025, 18(6), 1285; https://doi.org/10.3390/ma18061285 - 14 Mar 2025

Viewed by 470

Abstract

Spray-on fireproofing materials (SFRMs) and intumescent paints are commonly used to enhance the fire resistance of steel structures. Despite extensive studies on the performance of SFRMs and intumescent paints, there remains a significant lack of research on the material properties of certified products [...] Read more.

Spray-on fireproofing materials (SFRMs) and intumescent paints are commonly used to enhance the fire resistance of steel structures. Despite extensive studies on the performance of SFRMs and intumescent paints, there remains a significant lack of research on the material properties of certified products used in real-world applications, especially according to exposed temperatures. In this study, heating experiments were conducted to investigate the material properties of two widely used certified materials in Korea, focusing on their application thickness and exposure temperature. The experiments set target temperatures ranging from room temperature to 900 °C in increments of 100 °C. Additionally, various material properties, such as changes in shape and the insulation performance of the SFRM and intumescent paint, were observed at each temperature. Notably, the moisture content and discoloration depth of the SFRM displayed a consistent trend under different exposure temperatures, a material property that has not been previously reported. Furthermore, the insulation performance of the two materials differed by approximately 17% to 25% compared to an uncoated specimen exposed to the same temperature. The findings on the properties of SFRMs and intumescent paint relative to the exposure temperature presented in this study can serve as valuable data for selecting materials to improve fire resistance performance across various construction sites in the future. Additionally, they can act as key reference data in the diagnostic evaluation process for assessing the impact of fire on steel structures. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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16 pages, 2091 KiB

Open AccessArticle

Simplified Model for the Behaviour of Asphalt Mixtures Depending on the Time and the Frequency Domain

by Péter Primusz and Csaba Tóth

Materials 2025, 18(2), 466; https://doi.org/10.3390/ma18020466 - 20 Jan 2025

Viewed by 714

Abstract

Sigmoid functions are widely used for the description of viscoelastic material properties of asphalt mixtures. Unfortunately, there are still no known closed functions for describing connections among model parameters in the time and the frequency domains. In most cases, complicated interconversion methods are [...] Read more.

Sigmoid functions are widely used for the description of viscoelastic material properties of asphalt mixtures. Unfortunately, there are still no known closed functions for describing connections among model parameters in the time and the frequency domains. In most cases, complicated interconversion methods are applied for the conversion of viscoelastic material properties. To solve this problem, an empirical material model with four parameters has been developed. Parameters of the model can be quickly determined in the frequency domain and can be used in an unchanged way for the description of the material behaviour of the asphalt mixture in the time domain. The new model starts from the mathematical formula of the Ramberg–Osgood material model (short form RAMBO) and its main advantage is that its parameters are totally independent. Model calculations have been performed for the determination of factors necessary for the interconversion in the time and the frequency domains, applying the approximate procedure of Ninomiya and Ferry. The analysis of data has indicated that the interconversion factors in the time and the frequency domains depend only on the slope of the new empirical model function. Consequently, there is no need for further calculations, since the RAMBO model parameters determined in the frequency domain provide an excellent characterisation of the analysed mixture in the time domain as well. The developed new empirical material model has been verified using laboratory data and exact numerical calculations. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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13 pages, 4456 KiB

Open AccessArticle

Mechanical Properties and Microstructure of Geopolymer-Based PFSS Synthesized from Excavated Loess

by Shujie Chen, Hengchun Zhang, Zhengzhou Yang, Chao Feng, Yao Wang, Demei Yu, Tengfei Fu, Feng Zhang and Xia Huang

Materials 2025, 18(1), 30; https://doi.org/10.3390/ma18010030 - 25 Dec 2024

Viewed by 627

Abstract

Pre-mixed fluidized solidified soil (PFSS) has the advantages of pumpability, convenient construction, and a short setting time. This paper took the excavated loess in Fuzhou as the research object and used cement–fly–ash–ground granulated blast furnace slag–carbide slag as a composite geopolymer system (CFGC) [...] Read more.

Pre-mixed fluidized solidified soil (PFSS) has the advantages of pumpability, convenient construction, and a short setting time. This paper took the excavated loess in Fuzhou as the research object and used cement–fly–ash–ground granulated blast furnace slag–carbide slag as a composite geopolymer system (CFGC) to synthesize PFSS. This study investigated the fluidity and mechanical strength of PFSS under different water–solid ratios and curing agent dosages; finally, the microstructure of the composite geopolymer system–pre-mixed fluidized solidified soil (CFGC-PFSS) was characterized. The results showed that when the water–solid ratio of PFSS increased from 0.46 to 0.54, the fluidity increased by 77 mm, and the flexural strength and compressive strength at 28 d decreased to 450.8 kPa and 1236.5 kPa. When the curing agent dosage increased from 15% to 25%, the fluidity increased by 18.0 mm, and the flexural strength and compressive strength at 28 d increased by 1.7 times and 1.6 times. A large number of needle-like AFt, C-S-H gel, and C-(A)-S-H gel coagulate with soil particles to form a three-dimensional reticular structure, which is the mechanism of the strength formation of PFSS under the action of CFGC. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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19 pages, 7278 KiB

Open AccessArticle

Study on the Bending and Shear Behavior of a New Type of Wet Joint in Precast Concrete Deck for Composite Bridges

by Yan Wang, Long Hu, Wei Li, Guangshuai Zhang, Bin Han, Jin Di, Peng Fei, Xiaofeng Duan, Jinying Dong and Fengjiang Qin

Materials 2024, 17(24), 6252; https://doi.org/10.3390/ma17246252 - 21 Dec 2024

Viewed by 830

Abstract

According to the mechanical characteristics of joints in steel–concrete composite bridge decks under the combined bending and shear, improved joint details with simple structure and convenient construction were studied, including lapped U-bars, lapped headed bars, and lapped hook bars. In order to test [...] Read more.

According to the mechanical characteristics of joints in steel–concrete composite bridge decks under the combined bending and shear, improved joint details with simple structure and convenient construction were studied, including lapped U-bars, lapped headed bars, and lapped hook bars. In order to test the mechanical properties of the three joint details and compare them with the existing lapped/welded linear bars, the tests of five specimens were carried out. The cracking load, ultimate load, failure mode, crack pattern, and reinforcement strain were analyzed. The test results showed that the joint with lapped U-bars and hook bars exhibited ductile failure, while the joint with lapped headed and lapped/welded linear bars exhibited brittle failure. The cracking load of the five specimens was basically the same. The crack first occurred at the interface of pre-cast concrete and wet joints. When the ultimate bearing capacity was reached, the vertical main cracks were generated near the interface of the lapped U-bars, lapped hook bars, and welded linear bars specimens. The diagonal cracks were generated at the wet joint of the lapped headed bars specimen and lapped linear bars specimen. The lapped U-bars specimen had the highest bearing capacity, which was 22.8%, 14.2%, 50.4%, and 32.1% higher than the capacities of the lapped headed bars, lapped hook bars, lapped linear bars, and welded linear bars specimens, respectively. The load–deflection curves and crack mode obtained from the FEM of the lapped U-bars joint specimen were consistent with the test results. The bearing capacity of the FEM (351.3 KN) was 1.8% less than the test result (357.6 KN), which indicates that the bearing capacity calculated by the finite element model is reliable. There are 80 models with varying lap lengths and concrete strengths. The self-organizing migrating algorithm was used to fit the coupling effect of lap length and concrete strength. Based on doubly reinforced beam flexural capacity formulas, a bearing capacity calculation for lapped U-bars joint was proposed. The mean value of the formula calculation result and the finite element result ratio is 1.03, and the variance is 0.0004. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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11 pages, 1952 KiB

Open AccessArticle

A New Approach for Predicting Strength Based on Temperature-Time History Using Two-Parameter Maturity ANN Models

by Jerzy Wawrzeńczyk

Materials 2024, 17(24), 6157; https://doi.org/10.3390/ma17246157 - 17 Dec 2024

Viewed by 537

Abstract

One widely used method to predict concrete strength development based on temperature variations during curing is the equivalent maturity time (te) method. This method uses the activation energy (Ea) as its key parameter, which reflects the cement’s sensitivity to temperature. However, research shows [...] Read more.

One widely used method to predict concrete strength development based on temperature variations during curing is the equivalent maturity time (te) method. This method uses the activation energy (Ea) as its key parameter, which reflects the cement’s sensitivity to temperature. However, research shows that the Ea value varies depending on factors such as cement type, water/cement ratio, temperature, and additives. The permanent subject of discussion is the question of what value of the Ea parameter should be assumed. In this paper, a new approach is proposed by using a neural network analysis method to develop a strength–temperature history model. It was assumed that the ANN-fc% = f(Q, E, T, t) model would have 4 inputs: hydration heat (Q), activation energy (Ea), temperature (T), and time (t). The research was conducted on mortars using 6 cements, at curing temperatures ranging from 5 to 35 °C, assessing strength over a 90 day period. The results showed that the ANN analysis method allows for estimating the relative compressive strength with sufficient accuracy. Analysis of the input nodes indicated that Q influences early strength gain, while Ea affects later strength development. The application of the ANN model for calculating strength based on temperature changes during maturation was illustrated. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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23 pages, 36687 KiB

Open AccessArticle

The Effects of Waterborne Polyurethane-Modified Cement on the Mechanical Characterization of Grouting Concretion Stone

by Jingyu Zhang, Sili Chen, Xinchao Duan, Jinzhu Meng and Junxiang Wang

Materials 2024, 17(23), 5720; https://doi.org/10.3390/ma17235720 - 22 Nov 2024

Viewed by 840

Abstract

To improve the safety and stability of tunnel structures, developing grouting materials suitable for cold regions with excellent performance is crucial. Herein, waterborne polyurethane (WPU) was used to modify cement grouting materials. Through orthogonal testing analysis, the optimal mixing ratio of the modified [...] Read more.

To improve the safety and stability of tunnel structures, developing grouting materials suitable for cold regions with excellent performance is crucial. Herein, waterborne polyurethane (WPU) was used to modify cement grouting materials. Through orthogonal testing analysis, the optimal mixing ratio of the modified cement grouting materials was determined to be as follows: a water–cement ratio of 0.5, hydroxypropyl methyl cellulose (HPMC) content of 0.05%, WPU content of 5%, water-reducing agent (WRA) content of 0.2%. Furthermore, the dynamic mechanical properties of grouting concretion stones were studied. The influence of various external parameters on the compressive strength of the grouting concretion stones cured for different ages was evaluated. The influence degree of stone particle size on the dynamic compressive strength of the grouting stone body was d_{5–10 mm} > d_{5–20 mm} > d_{5–30 mm}. The split Hopkinson pressure bar experiment was performed to show that for the same strain rate, the absorbed energy and energy utilization rate first increase and then decrease with increasing stone particle size. When the stone particle size was 5–20 mm, the absorption energy and energy utilization rate of the grouting stone body were the highest. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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20 pages, 4721 KiB

Open AccessArticle

Study on the Effect of Hot and Humid Environmental Factors on the Mechanical Properties of Asphalt Concrete

by Xin Yan, Zhigang Zhou, Yingjia Fang, Chongsen Ma and Guangtao Yu

Materials 2024, 17(20), 4942; https://doi.org/10.3390/ma17204942 - 10 Oct 2024

Viewed by 840

Abstract

To investigate the effect of hot and humid environmental factors on the mechanical properties of asphalt mixtures research, in this paper, the dynamic modulus of asphalt mixtures under the effects of aging, dry–wet cycling, and coupled effects of aging and dry–wet cycling were [...] Read more.

To investigate the effect of hot and humid environmental factors on the mechanical properties of asphalt mixtures research, in this paper, the dynamic modulus of asphalt mixtures under the effects of aging, dry–wet cycling, and coupled effects of aging and dry–wet cycling were measured by the simple performance tester (SPT) system, and the dynamic modulus principal curves were fitted based on the sigmoidal function. The results show that under the aging effect, the dynamic modulus of asphalt mixture increases with the aging degree; the dynamic modulus of short-term aged, medium-term aged, long-term aged, and ultra-long-term aged asphalt mixtures increased by 9.3%, 26.4%, 44.8%, and 57%, respectively, compared to unaged asphalt mixtures at 20 °C and 10 Hz; the high-temperature stability performance is enhanced, and the low temperature cracking resistance performance is enhanced; under the dry–wet cycle, the aging effect of asphalt water is more obvious in the early stage, and dynamic modulus of resilience of the mixture is slightly increased. In the long-term wet–dry cycle process, water on the asphalt and aggregate erosion increased, the structural bearing capacity attenuation, and the dynamic modulus of rebound greatly reduced at 20 °C and 10 Hz. For example, the dynamic modulus of asphalt mixtures with seven wet and dry cycles increased by 3% compared to asphalt mixtures without wet and dry cycles, and the dynamic modulus of asphalt mixtures with 14 cycles of wet and dry cycles and 21 cycles of wet and dry cycles decreased by 10.8% and 16.5%, respectively, compared to asphalt mixtures without wet and dry cycles. The main curve as a whole shifted downward; the high-temperature performance decreased significantly; in the aging wet–dry cycle coupling, the aging asphalt mixture is more susceptible to water erosion, and the first wet–dry cycle after the mix by the degree of water erosion is relatively small, along with the dynamic modulus of rebound. The dynamic modulus of resilience is relatively larger, and the high-temperature performance is relatively better, while the low-temperature performance is worse. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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19 pages, 6183 KiB

Open AccessArticle

Effect of Moisture on the Fatigue and Self-Healing Properties of SiO₂/SBS Composite Modified Asphalt

by Juzhong Wang, Shangjun Yu, Yihan Wang, Linhao Sun, Ruixia Li and Jinchao Yue

Materials 2024, 17(18), 4526; https://doi.org/10.3390/ma17184526 - 14 Sep 2024

Viewed by 1172

Abstract

Moisture accelerates the degradation of asphalt properties, significantly impacting the service life of roads. Therefore, this study uses simplified viscoelastic continuous damage theory and employs frequency scanning, linear amplitude scanning, and fatigue–healing–fatigue tests with a dynamic shear rheometer. The objective is to investigate [...] Read more.

Moisture accelerates the degradation of asphalt properties, significantly impacting the service life of roads. Therefore, this study uses simplified viscoelastic continuous damage theory and employs frequency scanning, linear amplitude scanning, and fatigue–healing–fatigue tests with a dynamic shear rheometer. The objective is to investigate the effects of aging time, moisture conditions, and aging temperature on the fatigue and self-healing performance of SBS (Styrene–Butadiene–Styrene block copolymer)-modified asphalt, nano-SiO₂-modified asphalt, and nano-SiO₂/SBS composite modified asphalt in a moisture-rich environment. The results indicate that nano-SiO₂ powder enhances the low-temperature performance of modified asphalt, whereas the SBS modifier reduces temperature sensitivity and increases the recovery percentage after deformation. Compared to SBS-modified asphalt, the deformation resistance of nano-SiO₂/SBS composite modified asphalt has increased by about 30%, while nano-SiO₂-modified asphalt shows relatively poor deformation resistance. The fatigue performance of SBS-modified asphalt deteriorates under moisture, whereas the addition of nano-SiO₂ powder improves its fatigue life. Nano-SiO₂/SBS composite modified asphalt exhibits strong self-healing capabilities. Although self-healing can enhance the fatigue life of modified asphalt, moisture inhibits this improvement after self-healing. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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14 pages, 5048 KiB

Open AccessArticle

Experimental Study on the Crack Concrete Repaired via Enzyme-Induced Calcium Carbonate Precipitation (EICP)

by Gang Li, Deqiang Yan, Jia Liu, Peidong Yang and Jinli Zhang

Materials 2024, 17(13), 3205; https://doi.org/10.3390/ma17133205 - 1 Jul 2024

Cited by 4 | Viewed by 1722

Abstract

A low-carbon and environmentally friendly EICP method for repairing concrete cracks is presented to prolong the service life of concrete. In this study, we took concrete as the research object and quartz sand as the filling medium and employed the EICP injection method [...] Read more.

A low-carbon and environmentally friendly EICP method for repairing concrete cracks is presented to prolong the service life of concrete. In this study, we took concrete as the research object and quartz sand as the filling medium and employed the EICP injection method to repair concrete cracks. The internal repair effect of EICP on concrete cracks was evaluated with a combination of ultrasonic and compressive strength tests. The concrete repair mechanism of EICP was identified with a combination of EDS, XRD, and SEM tests. The results indicate that with an increase in the fracture depth, the ultrasonic sound time of the crack specimen increased gradually, and the ultrasonic wave transit time value of the crack specimen decreased significantly after EICP repair. After repair, the compressive strength rose. The highest compressive-strength recovery rate of a 0.3 mm wide specimen is 98.41%. The calcium carbonate crystal formed using EICP is vaterite. The probability density function model of the Laplace distribution was constructed, which showed good applicability and consistency in the ultrasonic sound time and compressive strength measured via experiments. The formed calcium carbonate crystals can be tightly and evenly attached to the cracks with the EICP injection repair method, resulting in a better repair effect. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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15 pages, 9928 KiB

Open AccessArticle

Study on the Mechanical Properties of Crack Mortar Repaired by Enzyme-Induced Calcium Carbonate Precipitation (EICP)

by Gang Li, Deqiang Yan, Jia Liu, Peidong Yang and Jinli Zhang

Materials 2024, 17(12), 2978; https://doi.org/10.3390/ma17122978 - 18 Jun 2024

Cited by 6 | Viewed by 1162

Abstract

As an emerging repair method, the enzyme-induced calcium carbonate precipitation (EICP) technique has the advantages of being highly economical, eco-friendly, and durable. The optimal repair conditions were obtained by taking cement mortar as the research object, adding two types of filling medium, using [...] Read more.

As an emerging repair method, the enzyme-induced calcium carbonate precipitation (EICP) technique has the advantages of being highly economical, eco-friendly, and durable. The optimal repair conditions were obtained by taking cement mortar as the research object, adding two types of filling medium, using three EICP-based repair methods to repair the cement mortar with different crack widths, and combining ultrasonic testing and strength testing to evaluate the mechanical properties and repair effects of the repair mortar. The microscopic structure of the mortar was established using mesoscopic and microscopic tests (XRD, SEM, and EDS), thereby revealing the mechanism of repair based on EICP. The test results show that, when quartz sand is used as the repair medium, more calcium carbonate adheres to the cross-section of test samples, and it has a better repair effect. Moreover, the repair effect of the injection method is significantly higher than those of the perfusion and immersion methods, and the ultrasonic wave transit time decreases by 1.22% on average. Based on the combination of quartz sand and EICP repair methods, the calcium carbonate precipitated among the sand granules contributes to a binding effect that strengthens the cohesive force among the sand granules. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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16 pages, 9379 KiB

Open AccessArticle

Steel Slag Accelerated Carbonation Curing for High-Carbonation Precast Concrete Development

by Weilong Li, Hui Wang, Zhichao Liu, Ning Li, Shaowei Zhao and Shuguang Hu

Materials 2024, 17(12), 2968; https://doi.org/10.3390/ma17122968 - 17 Jun 2024

Cited by 3 | Viewed by 1205

Abstract

Steel slag as an alkaline industrial solid waste, possesses the inherent capacity to engage in carbonation reactions with carbon dioxide (CO₂). Capitalizing on this property, the current research undertakes a systematic investigation into the fabrication of high-carbonation precast concrete (HCPC). This [...] Read more.

Steel slag as an alkaline industrial solid waste, possesses the inherent capacity to engage in carbonation reactions with carbon dioxide (CO₂). Capitalizing on this property, the current research undertakes a systematic investigation into the fabrication of high-carbonation precast concrete (HCPC). This is achieved by substituting a portion of the cementitious materials with steel slag during the carbonation curing process. The study examines the influence of varying water–binder ratios, silica fume dosages, steel slag dosages, and sand content on the compressive strength of HCPC. Findings indicate that adjusting the water–binder ratio to 0.18, adding 8% silica fume, and a sand volume ratio of 40% can significantly enhance the compressive strength of HCPC, which can reach up to 104.9 MPa. Additionally, the robust frost resistance of HCPC is substantiated by appearance damage analysis, mass loss rate, and compressive strength loss rate, after 50 freeze–thaw cycles the mass loss, and the compressive strength loss rate can meet the specification requirements. The study also corroborates the high-temperature stability of HCPC. This study optimized the preparation of HCPC and provided a feasibility for its application in precast concrete. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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18 pages, 11155 KiB

Open AccessArticle

Experimental and Numerical Study of Membrane Residual Stress in Q690 High-Strength Steel Welded Box Section Compressed Member

by Jie Wang, Aimin Xu, Jin Di, Fengjiang Qin and Pengfei Men

Materials 2024, 17(10), 2296; https://doi.org/10.3390/ma17102296 - 13 May 2024

Cited by 3 | Viewed by 1265

Abstract

High-strength steel (HSS) members with welded sections exhibit a notably lower residual compressive stress ratio compared with common mild steel (CMS) members. Despite this difference, current codes often generalize the findings from CMS members to HSS members, and the previous unified residual stress [...] Read more.

High-strength steel (HSS) members with welded sections exhibit a notably lower residual compressive stress ratio compared with common mild steel (CMS) members. Despite this difference, current codes often generalize the findings from CMS members to HSS members, and the previous unified residual stress models are generally conservative. This study focuses on the membrane residual stress distribution in Q690 steel welded box sections. By leveraging experimental results, the influence of section sizes and welding parameters on membrane residual stress was delved into. A larger plate size correlates with a decrease in the residual compressive stress across the section, with a more pronounced reduction observed in adjacent plates. Additionally, augmenting the number of welding passes tends to diminish residual stresses across the section. Results showed that membrane residual stress adhered to the section’s self-equilibrium, while the self-equilibrium in the plates was not a uniform pattern. A reliable residual stress simulation method for Q690 steel welded box sections was established using a three-dimensional thermal–elastic–plastic finite element model (3DTEFEM) grounded in experimental data. This method served as the cornerstone for parameter analysis in this study and set the stage for subsequent research. As a result, an accurate unified residual stress model for Q690 steel welded box sections was derived. Full article

(This article belongs to the Special Issue Experimental Study, Numerical Simulation & Structural Applications of Construction Materials—2nd Edition)

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