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15 pages, 13541 KiB

Open AccessArticle

Effectiveness of Curing Compounds for Concrete

by Filip Chyliński, Agnieszka Michalik and Mateusz Kozicki

Materials 2022, 15(7), 2699; https://doi.org/10.3390/ma15072699 - 6 Apr 2022

Cited by 8 | Viewed by 2961

Abstract

Curing compounds are widely used materials that are used in place of other methods of curing fresh concrete. The article presents an overview of the effectiveness of the concrete curing compounds widely used in Europe. Eleven different products have been tested. FTIR spectroscopy [...] Read more.

Curing compounds are widely used materials that are used in place of other methods of curing fresh concrete. The article presents an overview of the effectiveness of the concrete curing compounds widely used in Europe. Eleven different products have been tested. FTIR spectroscopy identification tests showed that all tested products might be divided into two main groups, depending on the type of their active substance. The water retention efficiency of each curing compound was examined, and the tensile strength of the cured samples was tested using the pull-off method. The dry mass content of the tested products was examined to check for a correlation between their effectiveness and active substance content. The microstructure of mortars treated with the most effective compounds and the reference mortar were examined using SEM techniques. Significant differences in microstructure were found between cured samples with different curing compounds, and also with uncured samples. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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32 pages, 12937 KiB

Open AccessArticle

Mechanical Properties, Crack Width, and Propagation of Waste Ceramic Concrete Subjected to Elevated Temperatures: A Comprehensive Study

by Hadee Mohammed Najm, Ominda Nanayakkara, Mahmood Ahmad and Mohanad Muayad Sabri Sabri

Materials 2022, 15(7), 2371; https://doi.org/10.3390/ma15072371 - 23 Mar 2022

Cited by 18 | Viewed by 2398

Abstract

Waste ceramic concrete (WOC) made from waste ceramic floor tiles has several economic and environmental benefits. Fire is one of the most common disasters in buildings, and WOC is a brittle construction material; therefore, the mechanical properties of WOC structures under high temperatures [...] Read more.

Waste ceramic concrete (WOC) made from waste ceramic floor tiles has several economic and environmental benefits. Fire is one of the most common disasters in buildings, and WOC is a brittle construction material; therefore, the mechanical properties of WOC structures under high temperatures should be considered. According to previous studies, hybrid fiber can further reduce damage to concrete under high temperatures. Meanwhile, crack width and propagation are among the key characteristics of concrete materials that need to be considered, but few studies have focused on their behavior when subjected to elevated temperatures. The new concrete materials proposed by the authors are WOC and WOC-Hybrid. WOC was prepared with Natural Coarse Aggregates (NCA), Natural Fine Aggregate (NFA), Ordinary Portland Cement (OPC 43 grade), and ceramic waste tiles with 20% replacements for coarse aggregates, 10% replacements for fine aggregates, and 10% replacement for cement. In contrast, WOC-Hybrid was prepared with the addition of hybrid fiber (1% crimped steel fiber and 1% polyvinyl alcohol fiber) in WOC. The specimens were exposed to temperatures of 100–300 °C, and then the specimens were tested for tensile and compressive strength. The present study aims to find a new method to improve concrete resistance to elevated temperatures at the lowest costs by experimental and computational analysis via machine learning models. The application of machine learning models such as artificial neural networks (ANN) and multiple linear regression (MLR) was employed in this study to predict the compressive and tensile strength of concrete. The linear coefficient correlation (R²) and mean square error (MSE) were evaluated to investigate the performance of the models. Based on the experimental analysis, the results show that the effect of hybrid fiber on the crack width and propagation is greater than that on the crack width and propagation of WOC and PC after exposure to high temperatures. However, the enhanced effect of hybrid fiber on the mechanical properties, rack width, and propagation decreases after subjecting it to a high-temperature treatment, owing to the melting and ignition of hybrid fibers at high temperatures. Regarding the computational analysis, it was found that the developed MLR model shows higher efficiency than ANN in predicting the compressive and tensile strength of PC, WOC, and WOC-Hybrid concrete. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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20 pages, 5443 KiB

Open AccessArticle

Hydration of Hybrid Cements at Low Temperatures: A Study on Portland Cement-Blast Furnace Slag—Na₂SO₄

by Shiju Joseph and Özlem Cizer

Materials 2022, 15(5), 1914; https://doi.org/10.3390/ma15051914 - 4 Mar 2022

Cited by 10 | Viewed by 2477

Abstract

Replacement of Portland cement with high volumes of blast furnace slag is known to negatively affect the early-age properties of concrete, particularly at low temperatures. In this study, the effectiveness of Na₂SO₄ on the mechanical properties, hydration kinetics and microstructure [...] Read more.

Replacement of Portland cement with high volumes of blast furnace slag is known to negatively affect the early-age properties of concrete, particularly at low temperatures. In this study, the effectiveness of Na₂SO₄ on the mechanical properties, hydration kinetics and microstructure development of a commercial CEM III/B (~69% slag) is investigated at 10 and 20 °C. Na₂SO₄ enhances compressive strength at both 10 and 20 °C, and at both early (1 and 7 days) and later ages (28 and 90 days). QXRD shows an increase in the degree of alite hydration at 1 day with Na₂SO₄ addition, while the degree of clinker and slag hydration is similar for all the systems from 7 to 90 days. An increase in ettringite content is observed at all ages in the systems with Na₂SO₄. Microstructure and pore structure shows densification of hydrates and reduction in porosity on addition of Na₂SO₄. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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12 pages, 5045 KiB

Open AccessEditor’s ChoiceArticle

Corrosion Performance of Nano-TiO₂-Modified Concrete under a Dry–Wet Sulfate Environment

by Chao Xu, Hao-Hao Liao, You-Liang Chen, Xi Du, Bin Peng and Tomas Manuel Fernandez-Steeger

Materials 2021, 14(19), 5900; https://doi.org/10.3390/ma14195900 - 8 Oct 2021

Cited by 10 | Viewed by 2044

Abstract

This study compared the effects of the sulfate dry–wet cycle on the properties of ordinary concrete and nano-TiO₂-modified concrete, including the mass loss rate, ultrasonic wave velocity, compressive strength, and XRD characteristics. In addition, a series of compression simulations carried out [...] Read more.

This study compared the effects of the sulfate dry–wet cycle on the properties of ordinary concrete and nano-TiO₂-modified concrete, including the mass loss rate, ultrasonic wave velocity, compressive strength, and XRD characteristics. In addition, a series of compression simulations carried out using the PFC2D software are also presented for comparison. The results show the following: (1) with an increase in dry–wet cycles, the damage to the concrete gradually increased, and adding nano-TiO₂ into ordinary concrete can improve the material’s sulfate resistance; (2) after 50 sulfate dry–wet cycles, the mass loss rate of ordinary concrete was –3.744%, while that of nano-TiO₂-modified concrete was −1.363%; (3) the compressive strength of ordinary concrete was reduced from 41.53 to 25.12 MPa (a reduction of 39.51%), but the compressive strength of nano-TiO₂-modified concrete was reduced from 49.91 to 32.12 MPa (a reduction of 35.64%); (4) after a sulfate dry–wet cycle, the nano-TiO₂-modified concrete surface produced white crystalline products, considered to be ettringite based on the XRD analysis; (5) when considering the peak stress and strain of the concrete samples, the numerical results agreed well with the test results, indicating the reliability of the method. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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15 pages, 3205 KiB

Open AccessArticle

Preparation and Properties of Waterborne Polypyrrole/Cement Composites

by Chao Feng, Jiaxing Huang, Peihui Yan, Fei Wan, Yunfei Zhu and Hao Cheng

Materials 2021, 14(18), 5166; https://doi.org/10.3390/ma14185166 - 9 Sep 2021

Cited by 4 | Viewed by 2017

Abstract

The electrical properties of cement are gaining importance for the application in building construction. Polypyrrole (PPy) has been widely applied in most fields because of its excellent conductivity performance, environmental friendliness, easy fabrication, and other specialties. These features made them useful for self-sensing [...] Read more.

The electrical properties of cement are gaining importance for the application in building construction. Polypyrrole (PPy) has been widely applied in most fields because of its excellent conductivity performance, environmental friendliness, easy fabrication, and other specialties. These features made them useful for self-sensing applications. In this work, waterborne polypyrrole (WPPy) was prepared via the chemical oxidative polymerization with three kinds of hydrophilic agents: sodium lignosulfonate (LGS), sodium dodecyl sulfonate (SDS), and sodium dodecyl sulfate (SLS), and then WPPy/cement composites were prepared by mixing cement with it. The contact angle, conductivity, and microstructure of WPPy were characterized by contact angle tester, four-point probes, and SEM. The composition, microstructure, and properties of WPPy/cement composites were characterized by FTIR, TGA, XRD, and SEM. The content of LGS was 40 wt%, WPPy got the optimal comprehensive performance, the conductivity was 15.06 times of the control sample and the contact angle was reduced by 69.95%. SEM analysis showed that hydrophilic agent content had great effect on the particle size of WPPy, the average diameter of WPPy particles decreased from 200 nm to 50 nm with the increase of LGS content. The results also showed that the adding of WPPy in WPPy/cement composites can significantly improve the conductivity and compactness, optimize the microstructure of cement composite. When the content of WPPy was 1.25 wt%, WPPy/cement composite showed the lowest resistivity and saturated water content of cement composite was 8 wt%. In addition, it could also inhibit the formation of Ca(OH)₂ in the early hydration process. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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20 pages, 19149 KiB

Open AccessArticle

Preparation and Mechanical-Fatigue Properties of Elastic Polyurethane Concrete Composites

by Zhen Jia, Dongzhe Jia, Quansheng Sun, Yanqi Wang and Hongjian Ding

Materials 2021, 14(14), 3839; https://doi.org/10.3390/ma14143839 - 9 Jul 2021

Cited by 19 | Viewed by 2968

Abstract

In order to solve issues related to bridge girders, expansion devices and road surfaces, as well as other structures that are prone to fatigue failure, a kind of fatigue-resistant elastic polyurethane concrete (EPUC) was obtained by adding waste rubber particles (40 mesh with [...] Read more.

In order to solve issues related to bridge girders, expansion devices and road surfaces, as well as other structures that are prone to fatigue failure, a kind of fatigue-resistant elastic polyurethane concrete (EPUC) was obtained by adding waste rubber particles (40 mesh with 10% fine aggregate volume replacement rate) to conventional engineering polyurethane concrete (PUC). Based on the preparation and properties of EPUC, its constitutive relation was proposed through compression and tensile tests; then, a scanning electron microscope (SEM), an atomic force microscope (AFM) and a 3D non-contact surface profilometer were used to study the failure morphology and micromechanisms of EPUC. On this basis, four-point bending fatigue tests of EPUC were carried out at different temperature levels (−20 °C, 0 °C, 20 °C) and different strain levels (400 με~1200 με). These were used to analyze the stiffness modulus, hysteresis angle and dissipated energy of EPUC, and our results outline the fatigue life prediction models of EPUC at different temperatures. The results show that the addition of rubber particles fills the interior of EPUC with tiny elastic structures and effectively optimizes the interface bonding between aggregate and polyurethane. In addition, EPUC has good mechanical properties and excellent fatigue resistance; the fatigue life of EPUC at a room temperature of 600 με can grow by more than two million times, and it also has a longer service life and reduced disease frequency, as well as fewer maintenance requirements. This paper will provide a theoretical and design basis for the fatigue resistance design and engineering application of building materials. Meanwhile, the new EPUC material has broad application potential in terms of roads, bridges and green buildings. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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8 pages, 1278 KiB

Open AccessArticle

Ventilation Prediction for an Industrial Cement Raw Ball Mill by BNN—A “Conscious Lab” Approach

by Rasoul Fatahi, Rasoul Khosravi, Hossein Siavoshi, Samaneh Yazdani, Esmaiel Hadavandi and Saeed Chehreh Chelgani

Materials 2021, 14(12), 3220; https://doi.org/10.3390/ma14123220 - 10 Jun 2021

Cited by 7 | Viewed by 2914

Abstract

In cement mills, ventilation is a critical key for maintaining temperature and material transportation. However, relationships between operational variables and ventilation factors for an industrial cement ball mill were not addressed until today. This investigation is going to fill this gap based on [...] Read more.

In cement mills, ventilation is a critical key for maintaining temperature and material transportation. However, relationships between operational variables and ventilation factors for an industrial cement ball mill were not addressed until today. This investigation is going to fill this gap based on a newly developed concept named “conscious laboratory (CL)”. For constructing the CL, a boosted neural network (BNN), as a recently developed comprehensive artificial intelligence model, was applied through over 35 different variables, with more than 2000 records monitored for an industrial cement ball mill. BNN could assess multivariable nonlinear relationships among this vast dataset, and indicated mill outlet pressure and the ampere of the separator fan had the highest rank for the ventilation prediction. BNN could accurately model ventilation factors based on the operational variables with a root mean square error (RMSE) of 0.6. BNN showed a lower error than other traditional machine learning models (RMSE: random forest 0.71, support vector regression: 0.76). Since improving the milling efficiency has an essential role in machine development and energy utilization, these results can open a new window to the optimal designing of comminution units for the material technologies. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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26 pages, 4943 KiB

Open AccessEditor’s ChoiceArticle

Life-Cycle Assessment of Alkali-Activated Materials Incorporating Industrial Byproducts

by Iman Faridmehr, Moncef L. Nehdi, Mehdi Nikoo, Ghasan Fahim Huseien and Togay Ozbakkaloglu

Materials 2021, 14(9), 2401; https://doi.org/10.3390/ma14092401 - 5 May 2021

Cited by 35 | Viewed by 3533

Abstract

Eco-friendly and sustainable materials that are cost-effective, while having a reduced carbon footprint and energy consumption, are in great demand by the construction industry worldwide. Accordingly, alkali-activated materials (AAM) composed primarily of industrial byproducts have emerged as more desirable alternatives to ordinary Portland [...] Read more.

Eco-friendly and sustainable materials that are cost-effective, while having a reduced carbon footprint and energy consumption, are in great demand by the construction industry worldwide. Accordingly, alkali-activated materials (AAM) composed primarily of industrial byproducts have emerged as more desirable alternatives to ordinary Portland cement (OPC)-based concrete. Hence, this study investigates the cradle-to-gate life-cycle assessment (LCA) of ternary blended alkali-activated mortars made with industrial byproducts. Moreover, the embodied energy (EE), which represents an important parameter in cradle-to-gate life-cycle analysis, was investigated for 42 AAM mixtures. The boundary of the cradle-to-gate system was extended to include the mechanical and durability properties of AAMs on the basis of performance criteria. Using the experimental test database thus developed, an optimized artificial neural network (ANN) combined with the cuckoo optimization algorithm (COA) was developed to estimate the CO₂ emissions and EE of AAMs. Considering the lack of systematic research on the cradle-to-gate LCA of AAMs in the literature, the results of this research provide new insights into the assessment of the environmental impact of AAM made with industrial byproducts. The final weight and bias values of the AAN model can be used to design AAM mixtures with targeted mechanical properties and CO₂ emission considering desired amounts of industrial byproduct utilization in the mixture. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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17 pages, 86229 KiB

Open AccessEditor’s ChoiceArticle

Use of Cement Suspension as an Alternative Matrix Material for Textile-Reinforced Concrete

by Richard Fürst, Eliška Fürst, Tomáš Vlach, Jakub Řepka, Marek Pokorný and Vladimír Mózer

Materials 2021, 14(9), 2127; https://doi.org/10.3390/ma14092127 - 22 Apr 2021

Cited by 3 | Viewed by 2605

Abstract

Textile-reinforced concrete (TRC) is a material consisting of high-performance concrete (HPC) and tensile reinforcement comprised of carbon roving with epoxy resin matrix. However, the problem of low epoxy resin resistance at higher temperatures persists. In this work, an alternative to the epoxy resin [...] Read more.

Textile-reinforced concrete (TRC) is a material consisting of high-performance concrete (HPC) and tensile reinforcement comprised of carbon roving with epoxy resin matrix. However, the problem of low epoxy resin resistance at higher temperatures persists. In this work, an alternative to the epoxy resin matrix, a non-combustible cement suspension (cement milk) which has proven stability at elevated temperatures, was evaluated. In the first part of the work, microscopic research was carried out to determine the distribution of particle sizes in the cement suspension. Subsequently, five series of plate samples differing in the type of cement and the method of textile reinforcement saturation were designed and prepared. Mechanical experiments (four-point bending tests) were carried out to verify the properties of each sample type. It was found that the highest efficiency of carbon roving saturation was achieved by using finer ground cement (CEM 52.5) and the pressure saturation method. Moreover, this solution also exhibited the best results in the four-point bending test. Finally, the use of CEM 52.5 in the cement matrix appears to be a feasible variant for TRC constructions that could overcome problems with its low temperature resistance. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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15 pages, 4671 KiB

Open AccessEditor’s ChoiceArticle

Utilizing Iron Ore Tailing as Cementitious Material for Eco-Friendly Design of Ultra-High Performance Concrete (UHPC)

by Gang Ling, Zhonghe Shui, Xu Gao, Tao Sun, Rui Yu and Xiaosheng Li

Materials 2021, 14(8), 1829; https://doi.org/10.3390/ma14081829 - 7 Apr 2021

Cited by 25 | Viewed by 3252

Abstract

In this research, iron ore tailing (IOT) is utilized as the cementitious material to develop an eco-friendly ultra-high performance concrete (UHPC). The UHPC mix is obtained according to the modified Andreasen and Andersen (MAA) packing model, and the applied dosage of IOT is [...] Read more.

In this research, iron ore tailing (IOT) is utilized as the cementitious material to develop an eco-friendly ultra-high performance concrete (UHPC). The UHPC mix is obtained according to the modified Andreasen and Andersen (MAA) packing model, and the applied dosage of IOT is 10%, 20%, and 30% (by weight), respectively. The calculated packing density of different mixtures is consistent with each other. Afterwards, the fresh and hardened performance of UHPC mixtures with IOT are evaluated. The results demonstrate that the workability of designed UHPC mixtures is increased with the incorporation of IOT. The heat flow at an early age of designed UHPC with IOT is attenuated, the compressive strength and auto shrinkage at an early age are consequently reduced. The addition of IOT promotes the development of long-term compressive strength and optimization of the pore structure, thus the durability of designed UHPC is still guaranteed. In addition, the ecological estimate results show that the utilization of IOT for the UHPC design can reduce the carbon emission significantly. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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20 pages, 3920 KiB

Open AccessEditor’s ChoiceArticle

Towards Embedded Computation with Building Materials

by Dawid Przyczyna, Maciej Suchecki, Andrew Adamatzky and Konrad Szaciłowski

Materials 2021, 14(7), 1724; https://doi.org/10.3390/ma14071724 - 31 Mar 2021

Cited by 6 | Viewed by 2475

Abstract

We present results showing the capability of concrete-based information processing substrate in the signal classification task in accordance with in materio computing paradigm. As the Reservoir Computing is a suitable model for describing embedded in materio computation, we propose that this type of [...] Read more.

We present results showing the capability of concrete-based information processing substrate in the signal classification task in accordance with in materio computing paradigm. As the Reservoir Computing is a suitable model for describing embedded in materio computation, we propose that this type of presented basic construction unit can be used as a source for “reservoir of states” necessary for simple tuning of the readout layer. We present an electrical characterization of the set of samples with different additive concentrations followed by a dynamical analysis of selected specimens showing fingerprints of memfractive properties. As part of dynamic analysis, several fractal dimensions and entropy parameters for the output signal were analyzed to explore the richness of the reservoir configuration space. In addition, to investigate the chaotic nature and self-affinity of the signal, Lyapunov exponents and Detrended Fluctuation Analysis exponents were calculated. Moreover, on the basis of obtained parameters, classification of the signal waveform shapes can be performed in scenarios explicitly tuned for a given device terminal. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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16 pages, 4171 KiB

Open AccessArticle

Static and Dynamic Performances of Chopped Carbon-Fiber-Reinforced Mortar and Concrete Incorporated with Disparate Lengths

by Yeou-Fong Li, Kun-Fang Lee, Gobinathan Kadagathur Ramanathan, Ta-Wui Cheng, Chih-Hong Huang and Ying-Kuan Tsai

Materials 2021, 14(4), 972; https://doi.org/10.3390/ma14040972 - 18 Feb 2021

Cited by 26 | Viewed by 4475

Abstract

The impact load, such as seismic and shock wave, sometimes causes severe damage to the reinforced concrete structures. This study utilized different lengths of chopped carbon fibers to develop a carbon-fiber-reinforced mortar (CFRM) and carbon-fiber-reinforced concrete (CFRC) with high impact and anti-shockwave resistance. [...] Read more.

The impact load, such as seismic and shock wave, sometimes causes severe damage to the reinforced concrete structures. This study utilized different lengths of chopped carbon fibers to develop a carbon-fiber-reinforced mortar (CFRM) and carbon-fiber-reinforced concrete (CFRC) with high impact and anti-shockwave resistance. The different lengths (6, 12, and 24 mm) of chopped carbon fibers were pneumatically dispersed and uniformly mixed into the cement with a 1% weight proportion. Then the CFRM and CFRC specimens were made for static and dynamic tests. The compressive and flexural strengths of the specimens were determined by using the standard ASTM C39/C 39M and ASTM C 293-02, respectively. Meanwhile, a free-fall impact test was done according to ACI 544.2R-89, which was used to test the impact resistances of the specimens under different impact energies. The CFRM and CFRC with a length of 6 mm exhibit maximum compressive strength. Both flexural and free-fall impact test results show that the 24 mm CFRM and CFRC enhances their maximum flexural strength and impact numbers more than the other lengths of CFRM, CFRC, and the benchmark specimens. After impact tests, the failure specimens were observed in a high-resolution optical microscope, to identify whether the failure mode is slippage or rupture of the carbon fiber. Finally, a blast wave explosion test was conducted to verify that the blast wave resistance of the 24 mm CFRC specimen was better than the 12 mm CFRC and benchmark specimens. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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17 pages, 5649 KiB

Open AccessArticle

Effect of Blast-Furnace Slag Replacement Ratio and Curing Method on Pore Structure Change after Carbonation on Cement Paste

by Junho Kim, Seunghyun Na and Yukio Hama

Materials 2020, 13(21), 4787; https://doi.org/10.3390/ma13214787 - 27 Oct 2020

Cited by 9 | Viewed by 2432

Abstract

The frost damage resistance of blast-furnace slag (BFS) cement is affected by carbonation. Hence, this study investigates the carbonation properties of pastes incorporating BFS with different replacement ratios, such as 15%, 45%, and 65% by weight, and different curing conditions, including air and [...] Read more.

The frost damage resistance of blast-furnace slag (BFS) cement is affected by carbonation. Hence, this study investigates the carbonation properties of pastes incorporating BFS with different replacement ratios, such as 15%, 45%, and 65% by weight, and different curing conditions, including air and carbonation. The BFS replacement ratio properties, determined by the Ca/Si ratio of calcium silicate hydrate in the cement paste sample, were experimentally investigated using mercury intrusion porosimetry, X-ray diffraction, and thermal analysis. The experimental investigation of the pore structure revealed that total porosity decreased after carbonation. In addition, the porosity decreased at a higher rate as the BFS replacement rate increased. Results obtained from this study show that the chemical change led to the higher replacement rate of BFS, which produced a higher amount of vaterite. In addition, the lower the Ca/Si ratio, the higher the amount of calcium carbonate originating from calcium silicate hydrate rather than from calcium hydroxide. As a result of the pore structure change, the number of ink-bottle pores was remarkably reduced by carbonation. Comparing the pore structure change in air-cured and carbonation test specimens, it was found that as the replacement rate of BFS increased, the number of pores with a diameter of 100 nm or more also increased. The higher the replacement rate of BFS, the higher the amount of calcium carbonate produced compared with the amount of calcium hydroxide produced during water curing. Due to the generation of calcium carbonate and the change in pores, the overall number of pores decreased as the amount of calcium carbonate increased. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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23 pages, 5132 KiB

Open AccessArticle

Mitigating Portland Cement CO₂ Emissions Using Alkali-Activated Materials: System Dynamics Model

by Moncef L. Nehdi and Abdallah Yassine

Materials 2020, 13(20), 4685; https://doi.org/10.3390/ma13204685 - 21 Oct 2020

Cited by 26 | Viewed by 3148

Abstract

While alkali-activated materials (AAMs) have been hailed as a very promising solution to mitigate colossal CO₂ emissions from world portland cement production, there is lack of robust models that can demonstrate this claim. This paper pioneers a novel system dynamics model that [...] Read more.

While alkali-activated materials (AAMs) have been hailed as a very promising solution to mitigate colossal CO₂ emissions from world portland cement production, there is lack of robust models that can demonstrate this claim. This paper pioneers a novel system dynamics model that captures the system complexity of this problem and addresses it in a holistic manner. This paper reports on this object-oriented modeling paradigm to develop a cogent prognostic model for predicting CO₂ emissions from cement production. The model accounts for the type of AAM precursor and activator, the service life of concrete structures, carbonation of concrete, AAM market share, and policy implementation period. Using the new model developed in this study, strategies for reducing CO₂ emissions from cement production have been identified, and future challenges facing wider AAM implementation have been outlined. The novelty of the model consists in its ability to consider the CO₂ emission problem as a system of systems, treating it in a holistic manner, and allowing the user to test diverse policy scenarios, with inherent flexibility and modular architecture. The practical relevance of the model is that it facilitates the decision-making process and policy making regarding the use of AAMs to mitigate CO₂ emissions from cement production at low computational cost. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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13 pages, 7059 KiB

Open AccessArticle

Chasing the Bubble: Ultrasonic Dispersion and Attenuation from Cement with Superabsorbent Polymers to Shampoo

by Gerlinde Lefever, Nicolas Ospitia, Dorian Serafin, Danny Van Hemelrijck and Dimitrios G. Aggelis

Materials 2020, 13(20), 4528; https://doi.org/10.3390/ma13204528 - 13 Oct 2020

Cited by 3 | Viewed by 1828

Abstract

This study aims to experimentally investigate the ultrasonic behavior of fresh cement focusing on the contribution of the entrapped air bubbles. Frequency dispersion and attenuation carry delicate information that is not possible to gather by traditional ultrasonic pulse velocity. This is measured by [...] Read more.

This study aims to experimentally investigate the ultrasonic behavior of fresh cement focusing on the contribution of the entrapped air bubbles. Frequency dispersion and attenuation carry delicate information that is not possible to gather by traditional ultrasonic pulse velocity. This is measured by simple indicators that quantify the frequency dependence of propagation velocity of longitudinal waves through fresh cementitious media. It seems that dispersion shows much stronger sensitivity to the microstructural processes, since the presence of superabsorbent polymers in mortar induces a large difference in dispersion parameters when compared to reference cement mortar, while only marginal difference in threshold-based pulse velocity. To reach this aim, references are taken from, and comparisons are made to other liquids in order first in order to validate the reliability of the methodology and to better understand the contribution of the cavities in the obtained dispersion and attenuation curves. Ultrasonic dispersion assessment of cementitious media has the potential to bring a lot of information on the microstructure of materials, as well as the ongoing processes. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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24 pages, 4853 KiB

Open AccessArticle

Mixture Optimization of Recycled Aggregate Concrete Using Hybrid Machine Learning Model

by Itzel Nunez, Afshin Marani and Moncef L. Nehdi

Materials 2020, 13(19), 4331; https://doi.org/10.3390/ma13194331 - 29 Sep 2020

Cited by 57 | Viewed by 4162

Abstract

Recycled aggregate concrete (RAC) contributes to mitigating the depletion of natural aggregates, alleviating the carbon footprint of concrete construction, and averting the landfilling of colossal amounts of construction and demolition waste. However, complexities in the mixture optimization of RAC due to the variability [...] Read more.

Recycled aggregate concrete (RAC) contributes to mitigating the depletion of natural aggregates, alleviating the carbon footprint of concrete construction, and averting the landfilling of colossal amounts of construction and demolition waste. However, complexities in the mixture optimization of RAC due to the variability of recycled aggregates and lack of accuracy in estimating its compressive strength require novel and sophisticated techniques. This paper aims at developing state-of-the-art machine learning models to predict the RAC compressive strength and optimize its mixture design. Results show that the developed models including Gaussian processes, deep learning, and gradient boosting regression achieved robust predictive performance, with the gradient boosting regression trees yielding highest prediction accuracy. Furthermore, a particle swarm optimization coupled with gradient boosting regression trees model was developed to optimize the mixture design of RAC for various compressive strength classes. The hybrid model achieved cost-saving RAC mixture designs with lower environmental footprint for different target compressive strength classes. The model could be further harvested to achieve sustainable concrete with optimal recycled aggregate content, least cost, and least environmental footprint. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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Review

Jump to: Research

41 pages, 8947 KiB

Open AccessEditor’s ChoiceReview

Fly Ash-Based Eco-Efficient Concretes: A Comprehensive Review of the Short-Term Properties

by Mugahed Amran, Roman Fediuk, Gunasekaran Murali, Siva Avudaiappan, Togay Ozbakkaloglu, Nikolai Vatin, Maria Karelina, Sergey Klyuev and Aliakbar Gholampour

Materials 2021, 14(15), 4264; https://doi.org/10.3390/ma14154264 - 30 Jul 2021

Cited by 110 | Viewed by 8450

Abstract

Development of sustainable concrete as an alternative to conventional concrete helps in reducing carbon dioxide footprint associated with the use of cement and disposal of waste materials in landfill. One way to achieve that is the use of fly ash (FA) as an [...] Read more.

Development of sustainable concrete as an alternative to conventional concrete helps in reducing carbon dioxide footprint associated with the use of cement and disposal of waste materials in landfill. One way to achieve that is the use of fly ash (FA) as an alternative to ordinary Portland cement (OPC) because FA is a pozzolanic material and has a high amount of alumina and silica content. Because of its excellent mechanical properties, several studies have been conducted to investigate the use of alkali-activated FA-based concrete as an alternative to conventional concrete. FA, as an industrial by-product, occupies land, thereby causing environmental pollution and health problems. FA-based concrete has numerous advantages, such as it has early strength gaining, it uses low natural resources, and it can be configurated into different structural elements. This study initially presents a review of the classifications, sources, chemical composition, curing regimes and clean production of FA. Then, physical, fresh, and mechanical properties of FA-based concretes are studied. This review helps in better understanding of the behavior of FA-based concrete as a sustainable and eco-friendly material used in construction and building industries. Full article

(This article belongs to the Special Issue Advanced Cement and Concrete Composites)

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