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23 pages, 3479 KiB

Open AccessArticle

Assessment of Low-Cost Sensors in Early-Age Concrete: Laboratory Testing and Industrial Applications

by Rocío Porras, Behnam Mobaraki, Zhenquan Liu, Thayré Muñoz, Fidel Lozano and José A. Lozano

Appl. Sci. 2025, 15(15), 8701; https://doi.org/10.3390/app15158701 - 6 Aug 2025

Viewed by 228

Concrete is an essential material in the construction industry due to its strength and versatility. However, its quality can be compromised by environmental factors during its fresh and early-age states. To address this vulnerability, various sensors have been implemented to monitor critical parameters. [...] Read more.

Concrete is an essential material in the construction industry due to its strength and versatility. However, its quality can be compromised by environmental factors during its fresh and early-age states. To address this vulnerability, various sensors have been implemented to monitor critical parameters. While high-precision sensors (e.g., piezoelectric and fiber optic) offer accurate measurements, their cost and fragility limit their widespread use in construction environments. In response, this study proposes a cost-effective, Arduino-based wireless monitoring system to track temperature and humidity in fresh and early-age concrete elements. The system was validated through laboratory tests on cylindrical specimens and industrial applications on self-compacting concrete New Jersey barriers. The sensors recorded temperature variations between 15 °C and 35 °C and relative humidity from 100% down to 45%, depending on environmental exposure. In situ monitoring confirmed the system’s ability to detect thermal gradients and evaporation dynamics during curing. Additionally, the presence of embedded sensors caused a tensile strength reduction of up to 37.5% in small specimens, highlighting the importance of sensor placement. The proposed solution demonstrates potential for improving quality control and curing management in precast concrete production with low-cost devices. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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21 pages, 13539 KiB

Open AccessArticle

Impact of Fiber Type on Chloride Ingress in Concrete: A MacroXRF Imaging Analysis

by Suânia Fabiele Moitinho da Silva, Wanderson Santos de Jesus, Thalles Murilo Santos de Almeida, Renato Quinto de Oliveira Novais, Laio Andrade Sacramento, Joaquim Teixeira de Assis, Marcelino José dos Anjos and José Renato de Castro Pessôa

Appl. Sci. 2025, 15(15), 8495; https://doi.org/10.3390/app15158495 - 31 Jul 2025

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Abstract

Chloride ion penetration is one of the most aggressive threats to reinforced concrete, as it triggers the electrochemical corrosion of steel reinforcement, compromising structural integrity and durability. Chloride ingress occurs through the porous structure of concrete, making permeability control crucial for enhancing structural [...] Read more.

Chloride ion penetration is one of the most aggressive threats to reinforced concrete, as it triggers the electrochemical corrosion of steel reinforcement, compromising structural integrity and durability. Chloride ingress occurs through the porous structure of concrete, making permeability control crucial for enhancing structural longevity. Fiber-reinforced concrete (FRC) is widely used to improve durability; however, the effects of different fiber types on chloride resistance remain unclear. This study examines the influence of glass and polypropylene fibers on concrete’s microstructure and chloride penetration resistance. Cylindrical specimens were prepared, including a reference mix without fibers and mixes with 0.25% and 0.50% fiber content by volume. Both fiber types were tested for chloride resistance. The accelerated non-steady-state migration method was employed to determine the resistance coefficients to chloride ion penetration, while X-ray macrofluorescence (MacroXRF) mapped the chlorine infiltration depth in the samples. Compressive strength decreased in all fiber-reinforced samples, with 0.50% glass fiber leading to a 56% reduction in strength. Nevertheless, the XRF results showed that a 0.25% fiber content significantly reduced chloride penetration, with polypropylene fibers outperforming glass fibers. These findings highlight the critical role of fiber type and volume in improving concrete durability, offering insights for designing long-lasting FRC structures in chloride-rich environments. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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20 pages, 31083 KiB

Open AccessArticle

Hybrid Mortars Activated with Alternative Steel-Compatible Salts: Impact on Chloride Diffusion and Durability

by Angily Cruz-Hernández, Francisco Velasco, Manuel Torres-Carrasco and Asunción Bautista

Appl. Sci. 2025, 15(14), 8055; https://doi.org/10.3390/app15148055 - 19 Jul 2025

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Abstract

Eco-friendly mortars have been manufactured with hybrid binders made of blast furnace slag and a reduced amount of clinker. The objective is to explore new formulations suitable for reinforced structures. Previous studies are mainly focused on activation with sulfates, a salt that is [...] Read more.

Eco-friendly mortars have been manufactured with hybrid binders made of blast furnace slag and a reduced amount of clinker. The objective is to explore new formulations suitable for reinforced structures. Previous studies are mainly focused on activation with sulfates, a salt that is corrosive to reinforcing steel. Sodium nitrate and sodium carbonate, easily implementable in construction, have been used as activators in two different concentrations that involve similar Na content. A Type II PC mortar is used as reference. The dimensional stability of the mortars during curing (at 99% RH) and subsequent drying at 40% RH, has been evaluated, as well as their porosity and mechanical properties. Böhme tests revealed that studied hybrid binders have lower wear resistance than PC mortar. Activation with Na₂CO₃ allows the obtention of mortars with reduced porosity and good compression resistance, but generates microcracking that favors chloride diffusion. Activation with nitrates favors precipitation of AFm phases identified through differential thermal analysis. Nitrates in moderate amounts (4% w/w) allow manufacturing hybrid mortars with good resistance to chloride penetration and reasonably good mechanical properties. Hence, this binder can be a promising option for reinforced structures. Higher amounts of nitrates (8%) for activation give rise to more porous mortars. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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19 pages, 2894 KiB

Open AccessArticle

Mesoscale Modelling of the Mechanical Behavior of Metaconcretes

by Antonio Martínez Raya, Gastón Sal-Anglada, María Pilar Ariza and Matías Braun

Appl. Sci. 2025, 15(12), 6543; https://doi.org/10.3390/app15126543 - 10 Jun 2025

Cited by 1 | Viewed by 535

Abstract

Metaconcrete (MC) is a class of engineered cementitious composites that integrates locally resonant inclusions to filter stress waves. While the dynamic benefits are well established, the effect of resonator content and geometry on static compressive resistance remains unclear. This study develops the first [...] Read more.

Metaconcrete (MC) is a class of engineered cementitious composites that integrates locally resonant inclusions to filter stress waves. While the dynamic benefits are well established, the effect of resonator content and geometry on static compressive resistance remains unclear. This study develops the first two-dimensional mesoscale finite-element model that explicitly represents steel cores, rubber coatings, and interfacial transition zones to predict the quasi-static behavior of MC. The model is validated against benchmark experiments, reproducing the 56% loss of compressive strength recorded for a 10.6% resonator volume fraction with an error of less than 1%. A parametric analysis covering resonator ratios from 1.5% to 31.8%, diameters from 16.8 mm to 37.4 mm, and coating thicknesses from 1.0 mm to 4.2 mm shows that (i) strength decays exponentially with volumetric content, approaching an asymptote at ≈20% of plain concrete strength; (ii) larger cores with thinner coatings minimize stiffness loss (<10%) while limiting strength reduction to 15–20%; and (iii) material properties of the resonator have a secondary influence (<6%). Two closed-form expressions for estimating MC strength and Young’s modulus (R² = 0.83 and 0.94, respectively) are proposed to assist with the preliminary design. The model and correlations lay the groundwork for optimizing MC that balances vibration mitigation with structural capacity. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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18 pages, 5475 KiB

Open AccessArticle

Heavy Equipment Detection on Construction Sites Using You Only Look Once (YOLO-Version 10) with Transformer Architectures

by Ikchul Eum, Jaejun Kim, Seunghyeon Wang and Juhyung Kim

Appl. Sci. 2025, 15(5), 2320; https://doi.org/10.3390/app15052320 - 21 Feb 2025

Cited by 14 | Viewed by 2042

Abstract

Monitoring heavy equipment in real time is crucial for ensuring safety and operational efficiency at construction sites, yet achieving both high detection accuracy and fast inference remains challenging under diverse environmental conditions. Although previous studies have attempted to improve accuracy and speed, their [...] Read more.

Monitoring heavy equipment in real time is crucial for ensuring safety and operational efficiency at construction sites, yet achieving both high detection accuracy and fast inference remains challenging under diverse environmental conditions. Although previous studies have attempted to improve accuracy and speed, their findings often lack generalizability, partly due to inconsistent datasets and the need for more advanced techniques. In response, this study proposes an enhanced object detection method that integrates transformer-based backbone networks into the You Only Look Once (YOLO-version 10) framework. Evaluations conducted on a large-scale dataset of construction-site images demonstrate notable improvements in detecting the heavy equipment of varying sizes. Comparisons with other detectors confirm that the proposed model not only achieves higher accuracy but also maintains competitive processing speed, making it suitable for real-time deployment. Additionally, the dataset is made available for broader experimentation and development. These findings underscore the method’s potential to strengthen on-site safety by providing more reliable and efficient heavy equipment detection in complex work environments, while also acknowledging areas for further refinement. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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19 pages, 3005 KiB

Open AccessArticle

A Study on Reactive Ultra-Fine Fly Ash and Sulfoaluminate Cement in Self-Leveling Mortar

by Pei-Min Chuang, Wei-Chung Yeih, Ran Huang and Jiang-Jhy Chang

Appl. Sci. 2025, 15(3), 1358; https://doi.org/10.3390/app15031358 - 28 Jan 2025

Viewed by 1073

Abstract

The purpose of this study is to find appropriate mixtures for self-leveling mortar that meet the fluidity requirements without displaying segregation by using a combination of two types of cement (Type I Portland cement and sulfoaluminate cement (SAC)) with reactive ultra-fine fly ash [...] Read more.

The purpose of this study is to find appropriate mixtures for self-leveling mortar that meet the fluidity requirements without displaying segregation by using a combination of two types of cement (Type I Portland cement and sulfoaluminate cement (SAC)) with reactive ultra-fine fly ash (RUFA). Unlike the fly ash, RUFA has a strong strength activity index and exhibits a significant pattern of amorphous phase in XRD. Appropriate mix proportions of raw materials, including the superplasticizer, require investigation in depth. A fixed water-to-binder ratio of 0.6 was selected, with varying proportions of the two cementitious materials considered (the SAC volume percentages were 0%, 10%, 20%, and 30%) and different RUFA contents (the RUFA volume percentages were 5%, 10%, and 15%). Twelve experiments were conducted to examine the properties of the self-leveling mortars. We found that a higher RUFA volume percentage results in lower porosity, higher compressive strength, and better resistance to drying shrinkage, abrasion, and restrained shrinkage cracking. Increasing the SAC volume percentage increases the porosity of self-leveling mortar and its early compressive strength but decreases late-stage strength. At a 10% volume percentage level, SAC achieves an ideal balance among drying shrinkage, brasion, and shrinkage cracking. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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17 pages, 16109 KiB

Open AccessArticle

Effect of High Percentages of Coated Recycled Aggregates on the Flexural Behavior of Reinforced Concrete Beams

by Catalina Martínez, Viviana Letelier and Bruno Wenzel

Appl. Sci. 2025, 15(2), 829; https://doi.org/10.3390/app15020829 - 16 Jan 2025

Cited by 1 | Viewed by 824

Abstract

Currently, the use of recycled aggregates (RA) in new concrete is allowed by several international regulations, although their replacement is limited to low percentages of the coarse fraction. In order to increase the percentage of RA, several authors have studied different processes to [...] Read more.

Currently, the use of recycled aggregates (RA) in new concrete is allowed by several international regulations, although their replacement is limited to low percentages of the coarse fraction. In order to increase the percentage of RA, several authors have studied different processes to improve the microstructure of its surface. Therefore, it is necessary to analyze whether the current standards simulate the structural behavior of concretes with high percentages of RA. For this purpose, beams with 0%, 50% and 100% RA replacement coated with recycled binder paste (RBP) were made and their behavior was compared with the equations of the Eurocode 2 and ACI 318-19 code. As a result, we found that when 100% coated RA was used, the reduction in compressive strength was only 12.73%, with similar cracking patterns observed in RA beams across all series. In addition, the load capacity of the beams with RA was higher than the theoretical values provided by the codes. Finally, the experimental critical deflection was higher than that calculated by the code equations. Thus, it is recommended that these higher deflections be taken into account at the time of design. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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23 pages, 6079 KiB

Open AccessArticle

Water Demand (or Specific Surface) of Aggregate as a Dominating Factor for SCC Composition Design

by Maciej Urban

Appl. Sci. 2024, 14(23), 11108; https://doi.org/10.3390/app142311108 - 28 Nov 2024

Viewed by 965

Abstract

In the modern era of superplasticizer-based concrete technology, water demand (or specific surface) of aggregate is a significantly underestimated factor influencing cement paste demand in the self-compacting concrete (SCC) design process. The presented data show that it is the key factor for optimization [...] Read more.

In the modern era of superplasticizer-based concrete technology, water demand (or specific surface) of aggregate is a significantly underestimated factor influencing cement paste demand in the self-compacting concrete (SCC) design process. The presented data show that it is the key factor for optimization criterion of SCC cement paste demand. Four models were taken into consideration (Bolomey, Stern, modified Loudon, and Relative Specific Surface), and all of them fit linearly very well (R² ≥ 0.95) to the relative thickness of coating aggregate with cement paste (t_rel). This means that all of these models may be used interchangeably in the process of SCC design without any alteration (so there is no need to develop a new model). Including the water demand of aggregate in the design procedure in its proposed version sets the bottom limit of superplasticizer dose for laboratory trials, leaving only small gap for eventual minor adjustments. Full article

(This article belongs to the Special Issue Advanced Concrete Technology and Applications in Construction Engineering, 2nd Edition)

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