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Search Results (516)

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Keywords = super-plasticizer

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44 pages, 6212 KiB  
Article
A Hybrid Deep Reinforcement Learning Architecture for Optimizing Concrete Mix Design Through Precision Strength Prediction
by Ali Mirzaei and Amir Aghsami
Math. Comput. Appl. 2025, 30(4), 83; https://doi.org/10.3390/mca30040083 (registering DOI) - 3 Aug 2025
Viewed by 32
Abstract
Concrete mix design plays a pivotal role in ensuring the mechanical performance, durability, and sustainability of construction projects. However, the nonlinear interactions among the mix components challenge traditional approaches in predicting compressive strength and optimizing proportions. This study presents a two-stage hybrid framework [...] Read more.
Concrete mix design plays a pivotal role in ensuring the mechanical performance, durability, and sustainability of construction projects. However, the nonlinear interactions among the mix components challenge traditional approaches in predicting compressive strength and optimizing proportions. This study presents a two-stage hybrid framework that integrates deep learning with reinforcement learning to overcome these limitations. First, a Convolutional Neural Network–Long Short-Term Memory (CNN–LSTM) model was developed to capture spatial–temporal patterns from a dataset of 1030 historical concrete samples. The extracted features were enhanced using an eXtreme Gradient Boosting (XGBoost) meta-model to improve generalizability and noise resistance. Then, a Dueling Double Deep Q-Network (Dueling DDQN) agent was used to iteratively identify optimal mix ratios that maximize the predicted compressive strength. The proposed framework outperformed ten benchmark models, achieving an MAE of 2.97, RMSE of 4.08, and R2 of 0.94. Feature attribution methods—including SHapley Additive exPlanations (SHAP), Elasticity-Based Feature Importance (EFI), and Permutation Feature Importance (PFI)—highlighted the dominant influence of cement content and curing age, as well as revealing non-intuitive effects such as the compensatory role of superplasticizers in low-water mixtures. These findings demonstrate the potential of the proposed approach to support intelligent concrete mix design and real-time optimization in smart construction environments. Full article
(This article belongs to the Section Engineering)
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36 pages, 4554 KiB  
Review
Lithium Slag as a Supplementary Cementitious Material for Sustainable Concrete: A Review
by Sajad Razzazan, Nuha S. Mashaan and Themelina Paraskeva
Materials 2025, 18(15), 3641; https://doi.org/10.3390/ma18153641 - 2 Aug 2025
Viewed by 133
Abstract
The global cement industry remains a significant contributor to carbon dioxide (CO2) emissions, prompting substantial research efforts toward sustainable construction materials. Lithium slag (LS), a by-product of lithium extraction, has attracted attention as a supplementary cementitious material (SCM). This review synthesizes [...] Read more.
The global cement industry remains a significant contributor to carbon dioxide (CO2) emissions, prompting substantial research efforts toward sustainable construction materials. Lithium slag (LS), a by-product of lithium extraction, has attracted attention as a supplementary cementitious material (SCM). This review synthesizes experimental findings on LS replacement levels, fresh-state behavior, mechanical performance (compressive, tensile, and flexural strengths), time-dependent deformation (shrinkage and creep), and durability (sulfate, acid, abrasion, and thermal) of LS-modified concretes. Statistical analysis identifies an optimal LS dosage of 20–30% (average 24%) for maximizing compressive strength and long-term durability, with 40% as a practical upper limit for tensile and flexural performance. Fresh-state tests show that workability losses at high LS content can be mitigated via superplasticizers. Drying shrinkage and creep strains decrease in a dose-dependent manner with up to 30% LS. High-volume (40%) LS blends achieve up to an 18% gain in 180-day compressive strength and >30% reduction in permeability metrics. Under elevated temperatures, 20% LS mixes retain up to 50% more residual strength than controls. In advanced systems—autoclaved aerated concrete (AAC), one-part geopolymers, and recycled aggregate composites—LS further enhances both microstructural densification and durability. In particular, LS emerges as a versatile SCM that optimizes mechanical and durability performance, supports material circularity, and reduces the carbon footprint. Full article
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32 pages, 2261 KiB  
Article
Influence of Superplasticizers on the Diffusion-Controlled Synthesis of Gypsum Crystals
by F. Kakar, C. Pritzel, T. Kowald and M. S. Killian
Crystals 2025, 15(8), 709; https://doi.org/10.3390/cryst15080709 - 31 Jul 2025
Viewed by 125
Abstract
Gypsum (CaSO4·2H2O) crystallization underpins numerous industrial processes, yet its response to chemical admixtures remains incompletely understood. This study investigates diffusion-controlled crystal growth in a coaxial test tube system to evaluate how three Sika® ViscoCrete® superplasticizers—430P, 111P, and [...] Read more.
Gypsum (CaSO4·2H2O) crystallization underpins numerous industrial processes, yet its response to chemical admixtures remains incompletely understood. This study investigates diffusion-controlled crystal growth in a coaxial test tube system to evaluate how three Sika® ViscoCrete® superplasticizers—430P, 111P, and 120P—affect nucleation, growth kinetics, morphology, and thermal behavior. The superplasticizers, selected for their surface-active properties, were hypothesized to influence crystallization via interfacial interactions. Ion diffusion was maintained quasi-steadily for 12 weeks, with crystal evolution tracked weekly by macro-photography; scanning electron microscopy and thermogravimetric/differential scanning were performed at the final stage. All admixtures delayed nucleation in a concentration-dependent manner. Lower dosages (0.5–1.0 wt%) yielded platy-to-prismatic morphologies and higher dehydration enthalpies, indicating more ordered lattice formation. In contrast, higher dosages (1.5–2.0 wt%) produced denser, irregular crystals and shifted dehydration to lower temperatures, suggesting structural defects or increased hydration. Among the additives, 120P showed the strongest inhibitory effect, while 111P at 0.5 wt% resulted in the most uniform crystals. These results demonstrate that ViscoCrete® superplasticizers can modulate gypsum crystallization and thermal properties. Full article
(This article belongs to the Section Macromolecular Crystals)
15 pages, 1889 KiB  
Article
Influence of Mixing Duration and Absorption Characteristics of Superabsorbent Polymers on the Fresh and Hardened Properties of High-Performance Concrete
by Yu-Cun Gu and Kamal H. Khayat
Materials 2025, 18(15), 3609; https://doi.org/10.3390/ma18153609 - 31 Jul 2025
Viewed by 221
Abstract
This study investigates the combined influence of superabsorbent polymers (SAPs) with distinct absorption kinetics and extended mixing sequences on the rheological, mechanical, and transport properties of high-performance concrete (HPC). Two SAPs—an ionic acrylamide-co-acrylic acid copolymer (SAP-P) and a non-ionic acrylamide polymer (SAP-B)—were incorporated [...] Read more.
This study investigates the combined influence of superabsorbent polymers (SAPs) with distinct absorption kinetics and extended mixing sequences on the rheological, mechanical, and transport properties of high-performance concrete (HPC). Two SAPs—an ionic acrylamide-co-acrylic acid copolymer (SAP-P) and a non-ionic acrylamide polymer (SAP-B)—were incorporated at an internal curing level of 100%. The impact of extended mixing times (3, 5, and 7 min) following SAP addition was systematically evaluated. Results showed that longer mixing durations led to increased superplasticizer demand and higher plastic viscosity due to continued water absorption by SAPs. However, yield stress remained relatively stable owing to the dispersing effect of the added superplasticizer. Both SAPs significantly enhanced the static yield stress and improved fresh stability, as evidenced by reduced surface settlement. Despite the rheological changes, mechanical properties—including compressive and flexural strengths and modulus of elasticity—were consistently improved, regardless of mixing duration. SAP incorporation also led to notable reductions in autogenous and drying shrinkage, as well as enhanced electrical resistivity, indicating better durability performance. These findings suggest that a 3 min extended mixing time is sufficient for effective SAP dispersion without compromising performance. Full article
(This article belongs to the Special Issue Characterization and Optimization of Cement-Based Materials)
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15 pages, 2645 KiB  
Article
Carbon Footprint and Uncertainties of Geopolymer Concrete Production: A Comprehensive Life Cycle Assessment (LCA)
by Quddus Tushar, Muhammed A. Bhuiyan, Ziyad Abunada, Charles Lemckert and Filippo Giustozzi
C 2025, 11(3), 55; https://doi.org/10.3390/c11030055 - 28 Jul 2025
Viewed by 698
Abstract
This study aims to estimate the carbon footprint and relative uncertainties for design components of conventional and geopolymer concrete. All the design components of alkaline-activated geopolymer concrete, such as fly ash, ground granulated blast furnace slag, sodium hydroxide (NaOH), sodium silicate (Na2 [...] Read more.
This study aims to estimate the carbon footprint and relative uncertainties for design components of conventional and geopolymer concrete. All the design components of alkaline-activated geopolymer concrete, such as fly ash, ground granulated blast furnace slag, sodium hydroxide (NaOH), sodium silicate (Na2SiO3), superplasticizer, and others, are assessed to reflect the actual scenarios of the carbon footprint. The conjugate application of the life cycle assessment (LCA) tool SimPro 9.4 and @RISK Monte Carlo simulation justifies the variations in carbon emissions rather than a specific determined value for concrete binders, precursors, and filler materials. A reduction of 43% in carbon emissions has been observed by replacing cement with alkali-activated binders. However, the associative uncertainties of chemical admixtures reveal that even a slight increase may cause significant environmental damage rather than its benefit. Pearson correlations of carbon footprint with three admixtures, namely sodium silicate (r = 0.80), sodium hydroxide (r = 0.52), and superplasticizer (r = 0.19), indicate that the shift from cement to alkaline activation needs additional precaution for excessive use. Therefore, a suitable method of manufacturing chemical activators utilizing renewable energy sources may ensure long-term sustainability. Full article
(This article belongs to the Section Carbon Cycle, Capture and Storage)
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20 pages, 2239 KiB  
Article
Synthesis of Biomass Polycarboxylate Superplasticizer and Its Performance on Cement-Based Materials
by Zefeng Kou, Kaijian Huang, Muhua Chen, Hongyan Chu, Linye Zhou and Tianqi Yin
Materials 2025, 18(14), 3416; https://doi.org/10.3390/ma18143416 - 21 Jul 2025
Viewed by 361
Abstract
Polycarboxylate superplasticizer (PCE) is an important part of improving the overall performance of concrete. However, its synthetic raw materials are overly dependent on petrochemical products, and it also causes problems such as environmental pollution. With the development of the building material industry, the [...] Read more.
Polycarboxylate superplasticizer (PCE) is an important part of improving the overall performance of concrete. However, its synthetic raw materials are overly dependent on petrochemical products, and it also causes problems such as environmental pollution. With the development of the building material industry, the demand for petrochemical resources required for synthetic water-reducing agents will increase rapidly. Therefore, there is an urgent need to transition the synthetic raw materials of PCE from petrochemicals to biomass materials to reduce the consumption of nonrenewable resources as well as the burden on the environment. Biomass materials are inexpensive, readily available and renewable. Utilizing biomass resources to develop good-performing water-reducing agents can reduce the consumption of fossil resources. This is conducive to carbon emission reduction in the concrete material industry. In addition, it promotes the high-value utilization of biomass resources. Therefore, in this study, a biomass polyether monomer, acryloyl hydroxyethyl cellulose (AHEC), was synthesized from cellulose via the reaction route of ethylene oxide (EO) etherification and acrylic acid (AA) esterification. Biomass polycarboxylate superplasticizers (PCE-Cs) were synthesized through free radical polymerization by substituting AHEC for a portion of the frequently utilized polyether monomer isopentenyl polyoxyethylene ether (TPEG). This study primarily focused on the properties of PCE-Cs in relation to cement. The findings of this study indicated that the synthesized PCE-C5 at a dosing of 0.4% (expressed as mass fraction of cement) when the AHEC substitution ratio was 5% achieved good water reduction properties and significant delays. With the same fluidity, PCE-C5 could enhance the mechanical strength of cement mortar by 30% to 40%. This study utilized green and low-carbon biomass resources to develop synthetic raw materials for water-reducing agents, which exhibited effective water-reducing performance and enhanced the utilization rate of biomass resources, demonstrating significant application value. Full article
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17 pages, 6527 KiB  
Article
Mechanical Properties of Bio-Printed Mortars with Bio-Additives for Green and Sustainable Construction
by Sotirios Pemas, Dimitrios Baliakas, Eleftheria Maria Pechlivani and Maria Stefanidou
Materials 2025, 18(14), 3375; https://doi.org/10.3390/ma18143375 - 18 Jul 2025
Viewed by 417
Abstract
Additive manufacturing (AM) has brought significant breakthroughs to the construction sector, such as the ability to fabricate complex geometries, enhance efficiency, and reduce both material usage and construction waste. However, several challenges must still be addressed to fully transition from conventional construction practices [...] Read more.
Additive manufacturing (AM) has brought significant breakthroughs to the construction sector, such as the ability to fabricate complex geometries, enhance efficiency, and reduce both material usage and construction waste. However, several challenges must still be addressed to fully transition from conventional construction practices to innovative and sustainable green alternatives. This study investigates the use of non-cementitious traditional mixtures for green construction applications through 3D printing using Liquid Deposition Modeling (LDM) technology. To explore the development of mixtures with enhanced physical and mechanical properties, natural pine and cypress wood shavings were added in varying proportions (1%, 3%, and 5%) as sustainable additives. The aim of this study is twofold: first, to demonstrate the printability of these eco-friendly mortars that can be used for conservation purposes and overcome the challenges of incorporating bio-products in 3D printing; and second, to develop sustainable composites that align with the objectives of the European Green Deal, offering low-emission construction solutions. The proposed mortars use hydrated lime and natural pozzolan as binders, river sand as an aggregate, and a polycarboxylate superplasticizer. While most studies with bio-products focus on traditional methods, this research provides proof of concept for their use in 3D printing. The study results indicate that, at low percentages, both additives had minimal effect on the physical and mechanical properties of the tested mortars, whereas higher percentages led to progressively more significant deterioration. Additionally, compared to molded specimens, the 3D-printed mortars exhibited slightly reduced mechanical strength and increased porosity, attributable to insufficient compaction during the printing process. Full article
(This article belongs to the Special Issue Eco-Friendly Materials for Sustainable Buildings)
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27 pages, 14650 KiB  
Article
Development of High-Performance Composite Cementitious Materials for Offshore Engineering Applications
by Risheng Wang, Hongrui Wu, Zengwu Liu, Hanyu Wang and Yongzhuang Zhang
Materials 2025, 18(14), 3324; https://doi.org/10.3390/ma18143324 - 15 Jul 2025
Viewed by 205
Abstract
This study focuses on the development of high-performance composite cementitious materials for offshore engineering applications, addressing the critical challenges of durability, environmental degradation, and carbon emissions. By incorporating polycarboxylate superplasticizers (PCE) and combining fly ash (FA), ground granulated blast furnace slag (GGBS), and [...] Read more.
This study focuses on the development of high-performance composite cementitious materials for offshore engineering applications, addressing the critical challenges of durability, environmental degradation, and carbon emissions. By incorporating polycarboxylate superplasticizers (PCE) and combining fly ash (FA), ground granulated blast furnace slag (GGBS), and silica fume (SF) in various proportions, composite mortars were designed and evaluated. A series of laboratory tests were conducted to assess workability, mechanical properties, volume stability, and durability under simulated marine conditions. The results demonstrate that the optimized composite exhibits superior performance in terms of strength development, shrinkage control, and resistance to chloride penetration and freeze–thaw cycles. Microstructural analysis further reveals that the enhanced performance is attributed to the formation of additional calcium silicate hydrate (C–S–H) gel and a denser internal matrix resulting from secondary hydration. These findings suggest that the proposed material holds significant potential for enhancing the long-term durability and sustainability of marine infrastructure. Full article
(This article belongs to the Section Construction and Building Materials)
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19 pages, 3587 KiB  
Article
Relations Between the Printability Descriptors of Mortar and NMR Relaxometry Data
by Mihai M. Rusu and Ioan Ardelean
Materials 2025, 18(13), 3070; https://doi.org/10.3390/ma18133070 - 27 Jun 2025
Viewed by 299
Abstract
Concrete printing technologies play a key role in the modernization of construction practices. One factor that mitigates their progress is the development of standards and characterization tools for concrete during printing. The aim of this work is to point out correlations between some [...] Read more.
Concrete printing technologies play a key role in the modernization of construction practices. One factor that mitigates their progress is the development of standards and characterization tools for concrete during printing. The aim of this work is to point out correlations between some printability descriptors of mortars and the data obtained from low-field nuclear magnetic resonance (NMR) relaxometry techniques. In this context, the superposed effects of an acrylic-based superplasticizer and calcium nitrate accelerator were investigated. The mortars under study are based on white Portland cement, fine aggregates, and silica fume at fixed ratios. Extrusion tests and visual inspection of the filaments evaluate the extrudability and the printing window. The selected compositions were also investigated via transverse T2 and longitudinal T1 NMR relaxation times. The results indicate that both additives increase the printing window of the mortar, while the accelerator induces a faster increase in specific surface area of capillary pores S/V only after 30–60 min of hydration. Some correlations were found between the printing window and the range where the transverse relaxation rates 1/T2 and the pore surface-to-volume ratios S/V increase linearly. This suggests some promising connections between NMR techniques and the study of structural buildup of cementitious materials. Full article
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15 pages, 2464 KiB  
Article
Constitutive Modeling of Rheological Behavior of Cement Paste Based on Material Composition
by Chunming Lian, Xiong Zhang, Lu Han, Wenbiao Lin and Weijun Wen
Materials 2025, 18(13), 2983; https://doi.org/10.3390/ma18132983 - 24 Jun 2025
Viewed by 382
Abstract
The rheological behavior of cementitious paste plays a pivotal role in determining the workability, pumpability, and uniformity of fresh concrete. Classical rheological models often struggle to capture the complex flocculation and hydration effects inherent in cement-based systems, and they typically depend on parameters [...] Read more.
The rheological behavior of cementitious paste plays a pivotal role in determining the workability, pumpability, and uniformity of fresh concrete. Classical rheological models often struggle to capture the complex flocculation and hydration effects inherent in cement-based systems, and they typically depend on parameters that are difficult to measure directly, limiting their practical utility. This study presents a novel composition-based constitutive model that introduces a virtual maximum packing fraction (ϕmax) to account for interparticle flocculation and entrapped water effects. By establishing quantitative relationships between powder characteristics—such as particle size and specific surface area—and rheological parameters, the model enables physically interpretable and measurable predictions of yield stress and plastic viscosity. Our validation against 65 paste formulations with varying water-to-binder ratios, mineral admixture types and dosages, and superplasticizer contents demonstrates strong predictive accuracy (R2 > 0.98 for plain pastes and >0.85 for blended systems). The influence of superplasticizers is effectively captured through modifications to ϕmax, allowing the model to remain both robust and parameter efficient. This framework supports forward prediction of paste rheology from raw material properties, offering a valuable tool for intelligent mix design in high-performance concrete applications such as self-consolidating and 3D-printed concrete. Full article
(This article belongs to the Section Construction and Building Materials)
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16 pages, 3652 KiB  
Article
Performance and Mechanism of Polycarboxylate Superplasticizer in Red Mud Blended Cementitious Materials
by Lei Yang, Pengfei Wang, Shuqiong Luo, Yaxin Wang and Shengye Xu
Polymers 2025, 17(13), 1738; https://doi.org/10.3390/polym17131738 - 22 Jun 2025
Viewed by 542
Abstract
The utilization of red mud by blending it into cement paste is still facing poor workability issues due to the finer particle size and higher water absorption of red mud, which can be solved by the addition of polycarboxylate superplasticizer (PCE) to effectively [...] Read more.
The utilization of red mud by blending it into cement paste is still facing poor workability issues due to the finer particle size and higher water absorption of red mud, which can be solved by the addition of polycarboxylate superplasticizer (PCE) to effectively maintain the working performance. However, the specific mechanisms by which different topologies of PCEs, in terms of water-reducing (WR)- and slump-retaining (SR)-type PCEs, influence red mud blended cement paste require further clarification. This research investigates the effect of WR-PCE and SR-PCE on the rheological properties, mechanical properties, and microscopic morphology of red mud blended cement paste under different red mud contents. The results demonstrated that at saturated dosages of 0.5% WR-PCE and 0.75% SR-PCE, both types of PCEs improved paste fluidity and reduced plastic viscosity and shear stress. Moreover, the time-dependent fluidity loss rate of the SR-PCE-incorporated paste was lower to that of the WR-PCE-incorporated paste at 30 and 60 min. With 0% and 25% red mud contents, the compressive strengths at 1, 3, 7, and 28 days were higher for WR-PCE than for SR-PCE due to the enhanced hydration of C2S and C3S. Furthermore, hydration products in the WR-PCE-incorporated paste were more uniformly distributed compared to the SR-PCE-incorporated paste. However, a 50% red mud content negatively impacted paste strength, likely due to the high alkalinity destabilizing the PCE. This study aims to elucidate the mechanistic relationship between PCE topology and the improved performance of red mud blended cement paste. Full article
(This article belongs to the Special Issue Application of Polymers in Cementitious Materials)
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23 pages, 14051 KiB  
Article
A Novel Method for Water Surface Debris Detection Based on YOLOV8 with Polarization Interference Suppression
by Yi Chen, Honghui Lin, Lin Xiao, Maolin Zhang and Pingjun Zhang
Photonics 2025, 12(6), 620; https://doi.org/10.3390/photonics12060620 - 18 Jun 2025
Viewed by 325
Abstract
Aquatic floating debris detection is a key technological foundation for ecological monitoring and integrated water environment management. It holds substantial scientific and practical value in applications such as pollution source tracing, floating debris control, and maritime navigation safety. However, this field faces ongoing [...] Read more.
Aquatic floating debris detection is a key technological foundation for ecological monitoring and integrated water environment management. It holds substantial scientific and practical value in applications such as pollution source tracing, floating debris control, and maritime navigation safety. However, this field faces ongoing challenges due to water surface polarization. Reflections of polarized light produce intense glare, resulting in localized overexposure, detail loss, and geometric distortion in captured images. These optical artifacts severely impair the performance of conventional detection algorithms, increasing both false positives and missed detections. To overcome these imaging challenges in complex aquatic environments, we propose a novel YOLOv8-based detection framework with integrated polarized light suppression mechanisms. The framework consists of four key components: a fisheye distortion correction module, a polarization feature processing layer, a customized residual network with Squeeze-and-Excitation (SE) attention, and a cascaded pipeline for super-resolution reconstruction and deblurring. Additionally, we developed the PSF-IMG dataset (Polarized Surface Floats), which includes common floating debris types such as plastic bottles, bags, and foam boards. Extensive experiments demonstrate the network’s robustness in suppressing polarization artifacts and enhancing feature stability under dynamic optical conditions. Full article
(This article belongs to the Special Issue Advancements in Optical Measurement Techniques and Applications)
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20 pages, 2877 KiB  
Article
Prediction of Ultra-High-Performance Concrete (UHPC) Compressive Strength Based on Convolutional Neural Networks
by Li Xu, Xiaochun Yu, Chenhui Zhu, Ling Wang and Jie Yang
Materials 2025, 18(12), 2851; https://doi.org/10.3390/ma18122851 - 17 Jun 2025
Viewed by 417
Abstract
This paper investigates the potential of deep learning in predicting the compressive strength of ultra-high-performance concrete (UHPC) by developing a convolutional neural network (CNN) model with two convolutional layers. The proposed CNN architecture demonstrates capability in accurately predicting UHPC compressive strength from tabular [...] Read more.
This paper investigates the potential of deep learning in predicting the compressive strength of ultra-high-performance concrete (UHPC) by developing a convolutional neural network (CNN) model with two convolutional layers. The proposed CNN architecture demonstrates capability in accurately predicting UHPC compressive strength from tabular data encompassing various material compositions. Ten input variables were selected, including the cement content, water content, silica fume content, silica powder content, silica sand content, superplasticizer content, and curing parameters. The model was trained and tested on a dataset comprising 219 samples. Experimental results indicated excellent predictive performance, with the CNN achieving a coefficient of determination (R2) of 0.959 on the test set and a mean absolute percentage error (MAPE) of 5.55%, demonstrating both accuracy and stability. Comparative analysis revealed that the CNN’s performance was comparable to established machine learning methods like XGBoost (R2 = 0.961), which are typically more suited for tabular data. Furthermore, SHAP (SHapley Additive exPlanations) analysis confirmed the model’s interpretability. These findings collectively suggest that the CNN-based approach shows considerable promise for predicting compressive strength across diverse UHPC formulations. Full article
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18 pages, 5902 KiB  
Article
Effect of Combined MgO Expansive Agent and Rice Husk Ash on Deformation and Strength of Post-Cast Concrete
by Feifei Jiang, Yijiang Xing, Wencong Deng, Qi Wang, Jialei Wang and Zhongyang Mao
Materials 2025, 18(12), 2815; https://doi.org/10.3390/ma18122815 - 16 Jun 2025
Viewed by 332
Abstract
This study investigates the effects of the combined addition of MgO expansive agent (MEA) and rice husk ash (RHA) on the performance of concrete. Results show that MEA absorbs water and competes with superplasticizers for adsorption, reducing early-age fluidity. In the later stages, [...] Read more.
This study investigates the effects of the combined addition of MgO expansive agent (MEA) and rice husk ash (RHA) on the performance of concrete. Results show that MEA absorbs water and competes with superplasticizers for adsorption, reducing early-age fluidity. In the later stages, its reaction with RHA generates M-S-H gel, accelerating slump loss. At early ages (up to 7 days), due to the slow hydration of MEA and partial replacement of cement, fewer hydration products are formed. Additionally, the pozzolanic reaction of RHA has not yet developed, resulting in the low early strength of concrete. In the later stages, Mg(OH)2 fills pores and enhances compactness, while the pozzolanic reaction of RHA further optimizes the pore structure. The internal curing effect also provides the moisture needed for continued MEA hydration, significantly improving later-age strength. Moreover, in the post-cast strip of a tall building, the internal curing effect of RHA ensures the effective shrinkage compensation by MEA under low water-to-cement ratio conditions. The restraint provided by reinforcement enhances the pore-filling effect of Mg(OH)2, improving concrete compactness and crack resistance, ultimately boosting long-term strength and durability. Full article
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21 pages, 5488 KiB  
Article
Investigation into Improving the Water Resistance and Mechanical Properties of Calcined Gypsum from Phosphogypsum Composites
by Qing Wang, Yuanyuan Lou, Yanzhou Peng, Weiqi Wang, Xiaohui Luo and Abutu Simon John Smith
Materials 2025, 18(12), 2703; https://doi.org/10.3390/ma18122703 - 9 Jun 2025
Viewed by 449
Abstract
This study aimed to improve the mechanical properties and water resistance of calcined gypsum from phosphogypsum (CGP) by incorporating organic additives and inorganic admixtures. The effects of the dosage of these additives—including kaolin, nano-SiO2, polycarboxylic acid superplasticizer, and sodium methyl silicate—on [...] Read more.
This study aimed to improve the mechanical properties and water resistance of calcined gypsum from phosphogypsum (CGP) by incorporating organic additives and inorganic admixtures. The effects of the dosage of these additives—including kaolin, nano-SiO2, polycarboxylic acid superplasticizer, and sodium methyl silicate—on the properties (flexural strength, compressive strength, water absorption, and softening coefficient) of CGP composites (CGPCs) were investigated. A high water resistance of the CGPCs was achieved using nano-SiO2 and sodium methyl silicate modification, superplasticizer addition, and the partial replacement of gypsum with mineral admixtures. The results showed that the flexural and compressive strength of the composites hit 4.61 MPa and 19.54 MPa, respectively, while the softening coefficient was 0.70 and the water absorption rate was 19.85%. Microstructural investigation confirmed that the combination of nano-SiO2 and kaolin led to the formation of calcium silicate hydrate. Additionally, the superplasticizer played a crucial role in reducing the water-to-cement ratio, while unhydrated mineral particles had a filling effect, thereby enhancing the density of the hardened paste. The sodium methyl silicate formed a hydrophobic film on the surface of the hardened paste, increasing the contact angle to 109.01° and improving the water resistance of the CGPCs. Full article
(This article belongs to the Collection Concrete and Building Materials)
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