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Concrete Structures: Latest Advances and Prospects for a Sustainable Future

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Civil Engineering".

Deadline for manuscript submissions: closed (29 February 2024) | Viewed by 41756

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Mariella Diaferio

E-Mail Website
Guest Editor
Department of Civil, Environmental, Territorial, Building Engineering and Chemistry (DICATECh), Polytechnic University of Bari, 70125 Bari, Italy
Interests: earthquake engineering; damage detection; experimental analysis; structural identification; rehabilitation; structural modeling
Special Issues, Collections and Topics in MDPI journals
Dr. Francisco B. Varona

E-Mail Website
Guest Editor
Civil Engineering Department, University of Alicante, Ctra. San Vicente s/n, 03690 San Vicente del Raspeig, Spain
Interests: concrete structures; high temperature exposure; steel-to-concrete bond; structural retrofitting; masonry structures; FRP strengthening; recycled concrete

Special Issue Information

Dear Colleagues,

The modern society is characterized by a widespread use of concrete as building material both in the realization of new constructions and in the existing building stock. This circumstance has pushed forward research with the challenge of developing advanced solutions that enhance the mechanical behavior and the sustainability of constructions.

In recent years, an important part of the research has been devoted to the experimental and theoretical analysis of new concrete-based construction materials, made by incorporating recycled materials, fatigue-resistant materials, nano-sized particles, etc. with the final goal of increasing the sustainability, durability, and performance of the new constructions. To investigate the use of these materials, experimental analyses, advanced simulation techniques of nonlinear response, and performance evaluation are needed.

Regarding the existing concrete building stock, the main part is reaching the end of its service life, so there is a growing attention towards safety and retrofitting interventions that will adapt the existing structures to actual performance demands. In this field, the research is mainly focused on the experimental technologies for the assessment of the safety level, modeling of the concrete structure, damage assessment, design procedures of the rehabilitation strategies, and innovative solutions for the achievement of target performances.

However, many issues in these areas yet remain. The aim of the Special Issue on “Concrete Structures: Latest Advances and Prospects for a Sustainable Future” is to contribute to the systematization and dissemination of knowledge related to recent advances in these fields of concrete structures. We would like to invite researchers to contribute original research articles as well as review articles that discuss the new trends regarding innovative concrete-based building materials, structural modeling of new and existing concrete structures, experimental investigation and diagnosis techniques, and design criteria. Experimental or numerical analyses of case studies are also welcome.

Dr. Mariella Diaferio
Dr. Francisco B. Varona
Guest Editors

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Keywords

  • damage assessment
  • performance evaluation
  • design procedures for concrete structures
  • structural modeling
  • innovative concrete-based building materials
  • diagnosis techniques
  • experimental investigation on concrete structures
  • strengthening and repair of concrete structures
  • analysis of case studies
  • life cycle assessment of structural concrete
  • sustainable concrete structures

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Published Papers (15 papers)

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Editorial

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9 pages, 203 KiB  
Editorial
Concrete Structures: Latest Advances and Prospects for a Sustainable Future
by Mariella Diaferio and Francisco B. Varona
Appl. Sci. 2024, 14(9), 3803; https://doi.org/10.3390/app14093803 - 29 Apr 2024
Cited by 1 | Viewed by 916
Abstract
Along with structural steel, structural concrete is probably one of the most widely used construction materials worldwide for building construction and civil engineering infrastructures [...] Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)

Research

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15 pages, 3904 KiB  
Article
Safety Evaluation of Existing R.C. Buildings: Uncertainties Due to the Location of In Situ Tests
by Vincenzo Sepe, Mariella Diaferio and Roberta Caraccio
Appl. Sci. 2024, 14(7), 2749; https://doi.org/10.3390/app14072749 - 25 Mar 2024
Viewed by 678
Abstract
The paper aimed to investigate the influence, on the assessment of the structural safety level of an existing r.c building, of the different choices that the technician in charge of a structural evaluation (the “analyst”) can make regarding the structural elements to be [...] Read more.
The paper aimed to investigate the influence, on the assessment of the structural safety level of an existing r.c building, of the different choices that the technician in charge of a structural evaluation (the “analyst”) can make regarding the structural elements to be tested to obtain a prescribed level of knowledge. To this end, the case study of a reinforced concrete framed structure built in the 1960s in Italy was investigated by means of numerical analyses. The probability distribution of the estimated safety levels was evaluated in the paper by means of a Monte Carlo approach, considering the alternative selections of elements done by a large number of analysts, and the probability of unsuccessful safety estimations is discussed for the knowledge levels considered in the Italian technical codes and the Eurocodes. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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13 pages, 2009 KiB  
Article
Developing a New Procedural Binary Particle Swarm Optimization Algorithm to Estimate Some Properties of Local Concrete Mixtures
by Fatima Alsaleh, Mohammad Bassam Hammami, George Wardeh and Feras Al Adday
Appl. Sci. 2023, 13(19), 10588; https://doi.org/10.3390/app131910588 - 22 Sep 2023
Cited by 1 | Viewed by 1276
Abstract
Artificial intelligence techniques have lately been used to estimate the mechanical properties of concrete to reduce time and financial expenses, but these techniques differ in their processing time and accuracy. This research aims to develop a new procedural binary particle swarm optimization algorithm [...] Read more.
Artificial intelligence techniques have lately been used to estimate the mechanical properties of concrete to reduce time and financial expenses, but these techniques differ in their processing time and accuracy. This research aims to develop a new procedural binary particle swarm optimization algorithm (NPBPSO) by making some modifications to the binary particle swarm optimization algorithm (BPSO). The new software has been created based on some fresh state properties (slump, temperature, and grade of cement) obtained from several ready-mix concrete plants located in Aleppo, Syria to predict the density and compressive strength of the regional concrete mixtures. The numerical results obtained from NPBPSO have been compared with the results from BPSO and artificial neural network ANN. It has been found that BPSO and NPBPSO are both predicting the compressive strength of concrete with less number of iterations and more accuracy than ANN (0.992 and 0.998 correlation coefficient in BPSO and NPBPSO successively and 0.875 in ANN). In addition, NPBPSO is better than BPSO as it prevents the algorithm from falling into the problem of local solutions and reaches the desired optimal solution faster than BPSO. Moreover, NPBPSO improves the accuracy of obtained compressive strength values and density by 30% and 50% successively. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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17 pages, 3176 KiB  
Article
Exploring Design Optimization of Self-Compacting Mortars with Response Surface Methodology
by Stéphanie Rocha, Guilherme Ascensão and Lino Maia
Appl. Sci. 2023, 13(18), 10428; https://doi.org/10.3390/app131810428 - 18 Sep 2023
Cited by 5 | Viewed by 1240
Abstract
The ever-evolving construction sector demands technological developments to provide consumers with products that meet stringent technical, environmental, and economic requirements. Self-compacting cementitious mixtures have garnered significance in the construction market due to their enhanced compaction, workability, fluidity, and mechanical properties. This study aimed [...] Read more.
The ever-evolving construction sector demands technological developments to provide consumers with products that meet stringent technical, environmental, and economic requirements. Self-compacting cementitious mixtures have garnered significance in the construction market due to their enhanced compaction, workability, fluidity, and mechanical properties. This study aimed to harness the potential of statistical response surface methodology (RSM) to optimize the fresh properties and strength development of self-compacting mortars. A self-compacting mortar repository was used to build meaningful and robust models describing D-Flow and T-Funnel results, as well as the compressive strength development after 24 h (CS24h) and 28 days (CS28d) of curing. The quantitative input factors considered were A (water/cement), B (superplasticizer/powder), C (water/powder), and D (sand/mortar), and the output variables were Y1 (D-Flow), Y2 (T-Funnel), Y3 (CS24h), and Y4 (CS28d). The results found adjusted response models, with significant R2 values of 87.4% for the D-Flow, 93.3% for the T-Funnel, and 79.1% for the CS24h. However, for the CS28d model, a low R2 of 39.9% was found. Variable A had the greatest influence on the response models. The best correlations found were between inputs A and C and outputs Y1 and Y2, as well as input factors A and D for responses Y3 and Y4. The resulting model was enhanced, thereby resulting in a global desirability of approximately 60%, which showcases the potential for the further refinement and optimization of RSM models applied to self-compacting mortars. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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14 pages, 7253 KiB  
Article
The Use of De-Icing Salts in Post-Tensioned Concrete Slabs and Their Effects on the Life of the Structure
by Tomás Luis Ripa Alonso, Noemí Corral Moraleda, Marcos García Alberti, Rubén Muñoz Pavón and Jaime C. Gálvez
Appl. Sci. 2023, 13(12), 6961; https://doi.org/10.3390/app13126961 - 9 Jun 2023
Viewed by 1118
Abstract
This article expounds on the problem of the use of de-icing salts in the corrosion of steel rebars in bridge decks and their effect on post-tensioning elements. In particular, this paper focuses this problem on structures affected by an aggregate–alkali reaction and without [...] Read more.
This article expounds on the problem of the use of de-icing salts in the corrosion of steel rebars in bridge decks and their effect on post-tensioning elements. In particular, this paper focuses this problem on structures affected by an aggregate–alkali reaction and without any waterproof treatment using the example of one structure whose repair was carried out in 2020. In this structure, the internal stresses due to the aggregate–alkali reaction caused longitudinal cracks in the upper face of the deck, through which the penetration of chloride ions was concentrated, causing, finally, the brittle fracture of the steel bars and the corrosion of the prestressing elements. This article also explains some conclusions about the most probable mechanisms that resulted in the brittle fracture of the steel bars due to the extraordinary and unexpected nature of this phenomenon. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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15 pages, 4344 KiB  
Article
Cow Dung Ash in Mortar: An Experimental Study
by Muluken Alebachew Worku, Woubishet Zewdu Taffese, Behailu Zerihun Hailemariam and Mitiku Damtie Yehualaw
Appl. Sci. 2023, 13(10), 6218; https://doi.org/10.3390/app13106218 - 19 May 2023
Cited by 9 | Viewed by 4352
Abstract
This study investigated the impact of using cow dung ash (CDA) as a partial replacement for ordinary Portland cement (OPC) in mortar. Mortar mixes are prepared by replacing OPC with CDA at varying levels: 5%, 10%, 15%, 20%, 25%, and 30%. The chemical [...] Read more.
This study investigated the impact of using cow dung ash (CDA) as a partial replacement for ordinary Portland cement (OPC) in mortar. Mortar mixes are prepared by replacing OPC with CDA at varying levels: 5%, 10%, 15%, 20%, 25%, and 30%. The chemical composition of CDA shows that it is composed primarily of SiO2, Al2O3, and Fe2O3, with a significant amount of loss of ignition. The workability, hardened properties, and microstructure of CDA-containing mortars are also analyzed. The increasing CDA content in mortar reduces workability and, beyond 5%, it causes high water absorption due to CDA’s porous nature and unremoved organic compounds. This impacts the density and compressive strength of the hardened mortar as well as compromising its homogeneous characteristics. When using 5% CDA, the bulk density and compressive strength of the mortar are comparable to those of the control mixes. Nonetheless, as the proportion of CDA increases, both the bulk density and compressive strength of the mortar diminish. The thermal stability of mortar mixes with 10%, 20%, and 30% CDA is unaffected at temperatures between 500 °C and 600 °C. The Fourier-transform infrared spectroscopy (FTIR) analysis reveals the presence of unreacted particles and wide stretched C–S–H gels in the mortar samples. In general, the results suggest that CDA can be utilized as a substitute for OPC at a ratio of up to 10% in the manufacturing of mortar and can serve as a feasible alternative cementitious material. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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13 pages, 3002 KiB  
Article
Comparison of the Effectiveness of Reducing the Leaching of Formaldehyde from Immobilized Wool in Geopolymer and Cement Mortar
by Beata Łaźniewska-Piekarczyk, Dominik Smyczek and Monika Czop
Appl. Sci. 2023, 13(8), 4895; https://doi.org/10.3390/app13084895 - 13 Apr 2023
Cited by 1 | Viewed by 1223
Abstract
Innovative building materials should also be pro-environmental. This article discusses the environmental footprint of geopolymer and cement-based mortars. It describes the methodology for preparing geopolymer and cement mortars using mineral wool waste. The phenol–formaldehyde resin used in mineral wool is a source of [...] Read more.
Innovative building materials should also be pro-environmental. This article discusses the environmental footprint of geopolymer and cement-based mortars. It describes the methodology for preparing geopolymer and cement mortars using mineral wool waste. The phenol–formaldehyde resin used in mineral wool is a source of phenol and formaldehyde emissions to the environment. The prepared mortar samples were subjected to durability tests to assess the correlation between the amount of mineral wool and the flexural and compressive strength of the samples. The key element of the paper is to test whether immobilisation of mineral wool in the geopolymer will reduce leaching of phenol and formaldehyde into the environment. The results revealed that cements prepared with mineral wool showed higher compressive strength, whereas geopolymer samples had better flexural strength. The study also proved that immobilisation of the wool in the geopolymer reduces phenol and formaldehyde leaching significantly. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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22 pages, 7520 KiB  
Article
Comparative Analyses of Selected Neural Networks for Prediction of Sustainable Cementitious Composite Subsurface Tensile Strength
by Slawomir Czarnecki and Mateusz Moj
Appl. Sci. 2023, 13(8), 4817; https://doi.org/10.3390/app13084817 - 11 Apr 2023
Cited by 3 | Viewed by 1422
Abstract
The article assesses comparative analyses of some selected machine-learning algorithms for the estimation of the subsurface tensile strength of cementitious composites containing waste granite powder. Any addition of material to cementitious composites causes their properties to differ; therefore, there is always a need [...] Read more.
The article assesses comparative analyses of some selected machine-learning algorithms for the estimation of the subsurface tensile strength of cementitious composites containing waste granite powder. Any addition of material to cementitious composites causes their properties to differ; therefore, there is always a need to prepare a precise model for estimating these properties’ values. In this research, such a model of prediction of the subsurface tensile strength has been carried out by using a hybrid approach of using a nondestructive method and neural networks. Moreover, various topologies of neural networks have been evaluated with different learning algorithms and number of hidden layers. It has been proven by the very satisfactory results of the performance parameters that such an approach might be used in practice. The errors values (MAPE, NRMSE, and MAE) of this model range from 10 to 12%, which, in the case of civil engineering practice, proves that this model is sufficient for being used. This novel approach can be a reasonable alternative for evaluating the properties of spacious cementitious composite elements where there is a need to analyse not only the compressive strength but also its subsurface tensile strength. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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15 pages, 5555 KiB  
Article
A Calculation Model for Determining the Bearing Capacity of Strengthened Reinforced Concrete Beams on the Shear
by Zeljko Kos, Zinovii Blikharskyi, Pavlo Vegera and Iryna Grynyova
Appl. Sci. 2023, 13(8), 4658; https://doi.org/10.3390/app13084658 - 7 Apr 2023
Cited by 1 | Viewed by 2056
Abstract
This article presents research on the bearing capacity and methods of calculating reinforced concrete beams on the shear without internal shear reinforcement, which are strengthened with a composite FRCM system. The test samples were divided into two series: the first series—control, in which [...] Read more.
This article presents research on the bearing capacity and methods of calculating reinforced concrete beams on the shear without internal shear reinforcement, which are strengthened with a composite FRCM system. The test samples were divided into two series: the first series—control, in which the variable parameter was the shear span (a/d = 2, a/d = 1.5, and a/d = 1); and the second series—reinforced by the FRCM system, without load, and strengthened at different load levels. The method of calculating experimental beams was tested according to the current code and data from the fib report. In this article, recommendations for determining the angle of inclined struts θ, the coefficient of the concrete shear strength CRd,c, and the coefficient of the load level at which strengthening is performed are proposed. The calculation with the these recommendations showed a good convergence of experimental and theoretical data in the 16–29% range, which is a much higher convergence than the calculation without these recommendations. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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22 pages, 10018 KiB  
Article
Accounting for Resilience in the Selection of R Factors for a RC Unsymmetrical Building
by S. Prasanth, Goutam Ghosh, Praveen Kumar Gupta, Claudia Casapulla and Linda Giresini
Appl. Sci. 2023, 13(3), 1316; https://doi.org/10.3390/app13031316 - 18 Jan 2023
Cited by 15 | Viewed by 1914
Abstract
Several design codes consider the non-linear response of a building by using one of the most important seismic parameters, called the response reduction factor (R). The lack of a detailed description of the R factor selection creates the need for a deeper study. [...] Read more.
Several design codes consider the non-linear response of a building by using one of the most important seismic parameters, called the response reduction factor (R). The lack of a detailed description of the R factor selection creates the need for a deeper study. This paper emphasises a methodology for the selection of a proper R factor based on resilience aspects. Unsymmetrical/irregular buildings have become the most common in recent times due to aesthetic purposes. However, because of the complexity due to the torsional effect, the selection of the R factor is even more difficult for this type of building. Therefore, a high-rise G+10-storey L-shaped building is herein considered. The building has re-entrant corners based on the structural/plan arrangement. Different R factors were used in the building design, considering buildings subjected to both unidirectional and bidirectional seismic loading scenarios. The building response with respect to various R factors (R equal to 3, 4, 5 and 6) in terms of its performance level, functionality, damage ratio and resilience was assessed at two design levels, i.e., design basic earthquake (DBE) and maximum considered earthquake (MCE). The study concludes that, considering the above criteria along with the resilience aspect, a maximum R factor up to 4 can be recommended for unidirectional loading, whereas for bidirectional loading, the maximum recommended R factor is 3. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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30 pages, 10631 KiB  
Article
Earthquake Retrofitting of “Soft-Story” RC Frame Structures with RC Infills
by George C. Manos, Konstantinos Katakalos, Vassilios Soulis and Lazaros Melidis
Appl. Sci. 2022, 12(22), 11597; https://doi.org/10.3390/app122211597 - 15 Nov 2022
Cited by 3 | Viewed by 2791
Abstract
Multi-story, old reinforced concrete (RC) structures with a “soft-story” on the ground floor, sustain considerable damage to the soft story during earthquakes due to the presence of masonry infills in the upper stories. Aspects of such masonry infill–RC frame interaction are briefly discussed [...] Read more.
Multi-story, old reinforced concrete (RC) structures with a “soft-story” on the ground floor, sustain considerable damage to the soft story during earthquakes due to the presence of masonry infills in the upper stories. Aspects of such masonry infill–RC frame interaction are briefly discussed and a particular retrofitting scheme for the soft story is studied. It consists of RC infills, added within the bays of the ground floor frames and combined with RC jacketing of the surrounding frame, aiming to avert such soft-story deficiency. The impact of such a retrofit is studied through the measured response of 1/3 scaled single-story, one-bay frames subjected to cyclic seismic-type horizontal loads. It is shown that this retrofit results in a considerable beneficial increase in stiffness, strength, and plastic energy consumption. The importance of the presence of effective steel ties connecting this RC infill with the surrounding frame is also demonstrated. In order to achieve these desired beneficial effects to such vulnerable buildings, additional design objectives are established with the aim of avoiding premature failure of the RC infill panel and/or fracture of the steel ties and to protect the surrounding RC frame from undesired local damage. A numerical methodology, which is validated by using the obtained experimental results, is shown to be capable of predicting reasonably well these important response mechanisms and can therefore be utilized for design purposes. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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15 pages, 3865 KiB  
Article
Impact Resistance and Flexural Performance Properties of Hybrid Fiber-Reinforced Cement Mortar Containing Steel and Carbon Fibers
by Jong-Gun Park, Dong-Ju Seo and Gwang-Hee Heo
Appl. Sci. 2022, 12(19), 9439; https://doi.org/10.3390/app12199439 - 21 Sep 2022
Cited by 4 | Viewed by 1926
Abstract
Fiber-reinforced cement mortar (FRCM) has been widely used since it has many advantages compared to plain mortar (PM), and various fibers are highly applicable as repair and reinforcement materials for concrete. In the present paper, an experimental study was planned to investigate the [...] Read more.
Fiber-reinforced cement mortar (FRCM) has been widely used since it has many advantages compared to plain mortar (PM), and various fibers are highly applicable as repair and reinforcement materials for concrete. In the present paper, an experimental study was planned to investigate the properties, such as flexural performance (flexural strength and toughness), compressive strength, and impact resistance of mono fiber-reinforced cement mortar (MFRCM) containing only steel fiber (SF) or carbon fiber (CF), as well as hybrid fiber-reinforced cement mortar (HyFRCM) containing different combinations of SF and CF. The fiber content was used in five levels (0.0, 0.25, 0.5, 0.75, and 1.0%) at a total volume fraction of 1.0% by volume. The results show that HyFRCM containing 0.75% SF and 0.25% CF improved compressive strength, flexural strength, and impact resistance compared to MFRCM and other HyFRCM, resulting in a synergistic effect of hybrid reinforced fibers. It is noted that, in the case of HyFRCM containing 0.5% SF and 0.5% CF, the flexural strength was slightly lower, but the highest flexural toughness was obtained, which led us to judge that the result shown in this investigation can be the optimal fiber combination to improve toughness and energy absorption capacity. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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12 pages, 6548 KiB  
Article
Shear Characteristics of Soil—Concrete Structure Interaction Interfaces
by Dejie Li, Chong Shi, Huaining Ruan and Bingyi Li
Appl. Sci. 2022, 12(18), 9145; https://doi.org/10.3390/app12189145 - 12 Sep 2022
Cited by 7 | Viewed by 3182
Abstract
The shear characteristics of the interfaces between soil and concrete structures are essential for the safety of the structures. In this study, a large-scale direct shear test apparatus was developed to measure the mechanical parameters of soil–concrete interfaces under conditions with different soil [...] Read more.
The shear characteristics of the interfaces between soil and concrete structures are essential for the safety of the structures. In this study, a large-scale direct shear test apparatus was developed to measure the mechanical parameters of soil–concrete interfaces under conditions with different soil types, soil moisture contents, and interfacial filling materials. The results showed that the shear stress of the soil–concrete interface increased initially and then became stable with the increase in the shear displacement. The shear displacement of the sandy soil when the shear stress became stable was smaller than that of the clayey soil. The silty sand–concrete interface had a smaller friction angle than the interface with the medium-coarse sand. Moreover, with the increase in the soil moisture content, the friction angle of the clayey soil–concrete interface decreased rapidly, whereas the cohesion first increased and then decreased, and the peak cohesion was near the plastic limit of the soil. Under the same moisture content, the friction angle and cohesion of the clay–concrete interface was reduced by filling the interface with a thin layer of sandy soil, while filling the silty sand–concrete interface with a thin layer of silt reduced the friction angle and increased the interfacial cohesion. Nonetheless, the filling had little impact on the overall shear strength of the interface. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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16 pages, 16801 KiB  
Article
The Performance of Empirical Laws for Rebound Hammer Tests on Concrete Structures
by Mariella Diaferio and Francisco B. Varona
Appl. Sci. 2022, 12(11), 5631; https://doi.org/10.3390/app12115631 - 1 Jun 2022
Cited by 2 | Viewed by 2278
Abstract
The assessment of concrete compressive strength plays a key role in the analysis of the seismic vulnerability of existing buildings. However, the adoption of classical destructive tests is usually limited by their invasiveness, cost and time needed for the execution. Thus, in order [...] Read more.
The assessment of concrete compressive strength plays a key role in the analysis of the seismic vulnerability of existing buildings. However, the adoption of classical destructive tests is usually limited by their invasiveness, cost and time needed for the execution. Thus, in order to overcome these limits and allow investigations to be extended to a large number of points, the use of the rebound hammer test is investigated here with a detailed analysis of the effects on the accuracy of the strength assessment related to the choice of the conversion model relating rebound index to compressive strength. The analysis has been performed by comparing several empirical laws calibrated with data acquired in an experimental investigation of an existing concrete building. The relationships between the coefficients of the examined conversion models are then established, with the aim of reducing the unknowns in the calibration procedure. Furthermore, the influence of the coefficients of variation of concrete strength and rebound index on the results of the calibration procedure has been analyzed, thereby supporting the assessment of the accuracy of the concrete strength. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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Review

Jump to: Editorial, Research

19 pages, 2542 KiB  
Review
An Insight into the Chemistry of Cement—A Review
by Luca Lavagna and Roberto Nisticò
Appl. Sci. 2023, 13(1), 203; https://doi.org/10.3390/app13010203 - 23 Dec 2022
Cited by 12 | Viewed by 13125
Abstract
Even if cement is a well-consolidated material, the chemistry of cement (and the chemistry inside cement) remains very complex and still non-obvious. What is sure is that the hydration mechanism plays a pivotal role in the development of cements with specific final chemical [...] Read more.
Even if cement is a well-consolidated material, the chemistry of cement (and the chemistry inside cement) remains very complex and still non-obvious. What is sure is that the hydration mechanism plays a pivotal role in the development of cements with specific final chemical compositions, mechanical properties, and porosities. This document provides a survey of the chemistry behind such inorganic material. The text has been organized into five parts describing: (i) the manufacture process of Portland cement, (ii) the chemical composition and hydration reactions involving a Portland cement, (iii) the mechanisms of setting, (iv) the classification of the different types of porosities available in a cement, with particular attention given to the role of water in driving the formation of pores, and (v) the recent findings on the use of recycled waste materials in cementitious matrices, with a particular focus on the sustainable development of cementitious formulations. From this study, the influence of water on the main relevant chemical transformations occurring in cement clearly emerged, with the formation of specific intermediates/products that might affect the final chemical composition of cements. Within the text, a clear distinction between setting and hardening has been provided. The physical/structural role of water in influencing the porosities in cements has been analyzed, making a correlation between types of bound water and porosities. Lastly, some considerations on the recent trends in the sustainable reuse of waste materials to form “green” cementitious composites has been discussed and future considerations proposed. Full article
(This article belongs to the Special Issue Concrete Structures: Latest Advances and Prospects for a Sustainable Future)
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