Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
5.2
3.4
Journals
Materials
Special Issues
Concrete Technology and Mechanical Properties of Concretes
materials-logo
Submit to Materials Review for Materials Propose a Special Issue

Journal Menu

► Journal Menu

Journal Browser

► Journal Browser
share announcement

Concrete Technology and Mechanical Properties of Concretes

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (10 January 2023) | Viewed by 76595

Special Issue Editor

Dr. Tomasz Ponikiewski

E-Mail Website
Guest Editor
Department of Building Processes Engineering and Building Physics, Faculty of Civil Engineering, Silesian University of Technology, Gliwice, Poland
Interests: concrete technology; special concretes; fibre-reinforced concrete; computed tomography research; SFRC; NDT; 3D concrete printing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

New trends in concrete science allow the structure of engineering objects to be shaped more quickly and safely than in the case of concrete with traditional properties and components. Technological operations of forming concrete elements are, in the case of new-generation concrete, considerably simplified and end results allow hardened concrete structures to be exposed in a more extended way. One modification of the considered concrete is to add various kinds of additives (fibres, waste, modified aggregate, etc.) to its volume as non-conventional components. This is not a new issue in the technology of concrete, however in case of concrete with modified brittle matrix composites it provides a current area of research. Technological problems in applying new-generation concrete modified with non-conventional additives and technologies is the subject of the current Special Issue.

Prof. Tomasz Ponikiewski
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • concrete technology
  • special concretes
  • self-compacting concrete
  • fibre-reinforced concrete
  • X-ray computed tomography research
  • non-destructive testing (NDT) of concrete
  • 3D-printed building materials
  • waste and recycled materials

Related Special Issue

Published Papers (28 papers)

Download All Papers
Order results
Result details
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:

Research

Jump to: Review

21 pages, 7105 KiB  
Article
Variation Pattern of the Compressive Strength of Concrete under Combined Heat and Moisture Conditions
by Ping Li, Ji Liu, Shiwei Duan and Ruiyuan Huang
Materials 2023, 16(4), 1548; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16041548 - 13 Feb 2023
Cited by 3 | Viewed by 1113
Abstract
The compressive strength of concrete is not the same in high temperature humid environments and normal temperature dry environments. In this study, quasi-static uniaxial compression experiments of concrete with different temperatures and water contents were carried out to investigate the variation pattern of [...] Read more.
The compressive strength of concrete is not the same in high temperature humid environments and normal temperature dry environments. In this study, quasi-static uniaxial compression experiments of concrete with different temperatures and water contents were carried out to investigate the variation pattern of the compressive strength of concrete under combined heat and moisture conditions. The results showed that the temperature softening effect and water softening effect of the compressive strength of concrete were coupled with each other. The compressive strength exhibited a variation trend from increase to decrease with the increase in both temperature and water content, and the relations among the heat–moisture coupling factor, temperature, and relative saturation ratio were obtained. The water absorption of concrete after immersion had a more significant effect on the compressive strength than the free water content stored inside the specimen before immersion. The “pseudo-temperature strengthening effect” distinguished the thermodynamic response of immersed concrete from that of dry concrete, and the functional relationships among the heat–moisture coupling factor, temperature, and relative water absorption ratio were established. The evolutionary mechanism of the competition between the microcrack expansion and healing of concrete under combined heat and moisture conditions was revealed. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

25 pages, 12732 KiB  
Article
An Investigation of Mechanical Properties of Recycled Carbon Fiber Reinforced Ultra-High-Performance Concrete
by Andrew Patchen, Stephen Young and Dayakar Penumadu
Materials 2023, 16(1), 314; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16010314 - 29 Dec 2022
Cited by 13 | Viewed by 2794
Abstract
Carbon fiber-reinforced concrete as a structural material is attractive for civil infrastructure because of its light weight, high strength, and resistance to corrosion. Ultra-high performance concrete, possessing excellent mechanical properties, utilizes randomly oriented one-inch long steel fibers that are 200 microns in diameter, [...] Read more.
Carbon fiber-reinforced concrete as a structural material is attractive for civil infrastructure because of its light weight, high strength, and resistance to corrosion. Ultra-high performance concrete, possessing excellent mechanical properties, utilizes randomly oriented one-inch long steel fibers that are 200 microns in diameter, increasing the concrete’s strength and durability, where steel fibers carry the tensile stress within the concrete similar to traditional rebar reinforcement and provide ductility. Virgin carbon fiber remains a market entry barrier for the high-volume production of fiber-reinforced concrete mix designs. In this research, the use of recycled carbon fiber to produce ultra-high-performance concrete is demonstrated for the first time. Recycled carbon fibers are a promising solution to mitigate costs and increase sustainability while retaining attractive mechanical properties as a reinforcement for concrete. A comprehensive study of process structure–properties relationships is conducted in this study for the use of recycled carbon fibers in ultra-high performance concrete. Factors such as pore formation and poor fiber distribution that can significantly affect its mechanical properties are evaluated. A mix design consisting of recycled carbon fiber and ultra-high-performance concrete was evaluated for mechanical properties and compared to an aerospace-grade and low-cost commercial carbon fiber with the same mix design. Additionally, the microstructure of concrete samples is evaluated non-destructively using high-resolution micro X-ray computed tomography to obtain 3D quantitative spatial pore size distribution information and fiber clumping. This study examines the compression, tension, and flexural properties of recycled carbon fibers reinforced concrete considering the microstructure of the concrete resulting from fiber dispersion. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

28 pages, 9729 KiB  
Article
Investigating the Mechanical and Durability Characteristics of Fly Ash Foam Concrete
by Sheng Li, Hongbo Li, Changyu Yan, Yongfa Ding, Xuanshuo Zhang and Jing Zhao
Materials 2022, 15(17), 6077; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15176077 - 01 Sep 2022
Cited by 4 | Viewed by 1704
Abstract
Although fly ash foam concrete (FAFC) is lightweight, heat-retaining, and insulating, its application options are constrained by its weak construction and short lifespan. The effects of various dosage ratios of the foaming agent (i.e., hydrogen peroxide), silica fume, and polypropylene fiber on the [...] Read more.
Although fly ash foam concrete (FAFC) is lightweight, heat-retaining, and insulating, its application options are constrained by its weak construction and short lifespan. The effects of various dosage ratios of the foaming agent (i.e., hydrogen peroxide), silica fume, and polypropylene fiber on the dry density, compressive strength, thermal insulation performance, pore structure parameters, and durability of FAFC were analyzed in this study, which sought to address the issues of low strength and low durability of FAFC. According to the findings, there is a negative correlation between the amount of hydrogen peroxide (as the foaming agent) and compressive strength, and, as the silica fume and polypropylene fiber (PP fiber) content rise, the strength will initially rise and then fall. The distribution of pore sizes gradually shifts from being dominated by small pores to large pores as the amount of foaming agent increases, while the porosity and average pore size gradually decrease. When the hydrogen peroxide content is 5%, the pore shape factor is at its lowest. The pore size distribution was first dominated by a small pore size and thereafter by a large pore size when the silica fume and PP fiber concentration increased. Prior to increasing, the porosity, average pore size, and pore shape factor all decreased. Additionally, the impact of PP fiber on the freeze–thaw damage to FAFC was also investigated at the same time. The findings indicate that the freeze–thaw failure of FAFC is essentially frost heave failure of the pore wall. The use of PP fiber is crucial for enhancing FAFC’s ability to withstand frost. The best frost resistance is achieved at 0.4% PP fiber content. In conclusion, the ideal ratio for overall performance was found to be 5% hydrogen peroxide content, 4% silica fume content, and 0.1% polypropylene fiber content. The results obtained could be applied in different fields, such as construction and sustainable materials, among others. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

0 pages, 5803 KiB  
Article
Recovery Behavior of the Macro-Cracks in Elevated Temperature-Damaged Concrete after Post-Fire Curing
by Lang Li, Yao Chen, Chao He, Chong Wang, Hong Zhang, Qingyuan Wang, Yongjie Liu and Guomin Zhang
Materials 2022, 15(16), 5673; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15165673 - 18 Aug 2022
Cited by 5 | Viewed by 1037 | Correction
Abstract
Studying the recovery of fire-damaged concrete is of huge economic and environmental significance. The recovery of thermal-induced cracks of fire-damaged concrete leads to the recovery of strength after post-fire curing. To identify the crack recovery behavior of fire-damaged concrete after post-fire curing and [...] Read more.
Studying the recovery of fire-damaged concrete is of huge economic and environmental significance. The recovery of thermal-induced cracks of fire-damaged concrete leads to the recovery of strength after post-fire curing. To identify the crack recovery behavior of fire-damaged concrete after post-fire curing and its relationship with the recovery of strength, in this study, concrete samples exposed to 400, 600, and 800 °C were treated with the post-fire curing process. The compressive strength recovery was investigated, as well as the crack recovery in terms of the crack length. Moreover, the recovery of the cracks was studied and divided into the categories of mortar cracks and mortar-aggregate interfacial cracks. The results indicate that, after being exposed to high temperatures, the interfacial crack was the main type of crack, and it could clearly be recovered by post-fire curing. The recovery of compressive strength mainly resulted from the recovery of interfacial cracks. The findings of this study can provide practical guidance for the application of post-fire curing to the recovery of fire-damaged concrete structures. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

16 pages, 3738 KiB  
Article
Experimental Study on the Interrelationship between the Moisture Content and Drying Shrinkage of Autoclaved Aerated Concrete Wallboard
by Jianyu Yang, Jiaming Zou, Weijun Yang, Sirong Yi and Jinzhao Liu
Materials 2022, 15(16), 5582; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15165582 - 15 Aug 2022
Cited by 1 | Viewed by 1106
Abstract
Autoclaved aerated concrete wallboard (AACW) has been widely used as a building envelope component in the infill walls of frame structures, which has broad prospects for development and utilization. However, the cracking of AACW has become a pressing problem, and this problem needs [...] Read more.
Autoclaved aerated concrete wallboard (AACW) has been widely used as a building envelope component in the infill walls of frame structures, which has broad prospects for development and utilization. However, the cracking of AACW has become a pressing problem, and this problem needs be solved or relieved effectively. We need an effective control method to reduce the cracking problem of AACW. It is necessary to study the interrelationship between the moisture content and the dry shrinkage of AACW. In this paper, a moisture content test and a drying shrinkage test of AACW were conducted, to understand the effect of the moisture content on the drying shrinkage performance of AACW. In addition, the moisture content of AACW with time was explored, and changes in the dry shrinkage value of AACW with the moisture content of AACW were obtained. According to the results and the conditions and the hypothesis of the test, the drying shrinkage value of AACW increases with time, and the drying shrinkage speed was fast in the early stage and tended to be stable in the later stage. In AACW, the drying shrinkage value and the relative humidity have a notable negative correlation. In addition, there was a positive correlation between the drying shrinkage value and the initial moisture content and the ambient temperature. When the AACW lost water from its initial moisture content to the equilibrium moisture content, the accumulated dry shrinkage value of AACW increased with the water loss. Moreover, a time-varying model of the moisture content and a prediction model of the equilibrium moisture content of AACW were established, and time-varying models of the drying shrinkage value of AACW with different initial moisture contents were proposed. The results provide a scientific basis for the reasonable maintenance and profitable control of drying shrinkage cracking of AACW. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

18 pages, 3605 KiB  
Article
Predicting the Compressive Strength of Concrete Containing Binary Supplementary Cementitious Material Using Machine Learning Approach
by Nozar Moradi, Mohammad Hadi Tavana, Mohammad Reza Habibi, Moslem Amiri, Mohammad Javad Moradi and Visar Farhangi
Materials 2022, 15(15), 5336; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15155336 - 03 Aug 2022
Cited by 30 | Viewed by 1910
Abstract
Several advantages of supplementary cementitious materials (SCMs) have led to widespread use in the concrete industry. Many various SCMs with different characteristics are used to produce sustainable concrete. Each of these materials has its specific properties and therefore plays a different role in [...] Read more.
Several advantages of supplementary cementitious materials (SCMs) have led to widespread use in the concrete industry. Many various SCMs with different characteristics are used to produce sustainable concrete. Each of these materials has its specific properties and therefore plays a different role in enhancing the mechanical properties of concrete. Multiple and often conflicting demands of concrete properties can be addressed by using combinations of two or more SCMs. Thus, understanding the effect of each SCM, as well as their combination in concrete, may pave the way for further utilization. This study aims to develop a robust and time-saving method based on Machine Learning (ML) to predict the compressive strength of concrete containing binary SCMs at various ages. To do so, a database containing a mixture of design, physical, and chemical properties of pozzolan and age of specimens have been collected from literature. A total of 21 mix design containing binary mixes of fly ash, metakaolin, and zeolite were prepared and experimentally tests to fill the possible gap in the literature and to increase the efficiency and accuracy of the ML-based model. The accuracy of the proposed model was shown to be accurate and ML-based model is able to predict the compressive strength of concrete containing any arbitrary SCMs at ay ages precisely. By using the model, the optimum replacement level of any combination of SCMs, as well as the behavior of binary cementitious systems containing two different SCMs, can be determined. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

11 pages, 922 KiB  
Article
Predictive Modeling of Compressive Strength for Concrete at Super Early Age
by Xi Peng, Zhenxin Zhuang and Qiuwei Yang
Materials 2022, 15(14), 4914; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15144914 - 14 Jul 2022
Cited by 7 | Viewed by 1227
Abstract
The compressive strength of concrete is an important parameter in construction practice. At present, there are few reports on the prediction model of the compressive strength of concrete at a super early age. For some engineering vibration analyses, it is very necessary to [...] Read more.
The compressive strength of concrete is an important parameter in construction practice. At present, there are few reports on the prediction model of the compressive strength of concrete at a super early age. For some engineering vibration analyses, it is very necessary to study the growth law of compressive strength of concrete at a super early age. To this end, a new prediction model is proposed in this work to analyze the variation of compressive strength for the concrete at a super early age. The innovations of this work mainly lie in two aspects. The first innovation is to propose a new compressive strength-age mathematical model to predict the variation of compressive strength more accurately. The second innovation is to develop a new robust regression analysis method to obtain the fitting parameters in the mathematical model more effectively. Using the experimental data of the super early age concrete, the proposed prediction model is compared with the existing power function model and the hyperbolic function model. The results of the comparative study show that the prediction model proposed in this work is more reasonable and reliable. Taking C40 under natural curing as an example, it has been shown from the comparative study that: (1) The total fitting error of the proposed model is approximately 60% of that of the power function model, and approximately 17% of that of the hyperbolic model; (2) The fitting standard deviation of the proposed model is approximately 49% of that of the power function model, and approximately 15% of that of the hyperbolic model; (3) The 28 day strength of concrete predicted by the proposed model is more in line with the actual strength growth law of concrete. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

19 pages, 7157 KiB  
Article
Simulation Analysis of Concrete Pumping Based on Smooth Particle Hydrodynamics and Discrete Elements Method Coupling
by Wang Chen, Wanrong Wu, Guoyi Lu and Guangtian Tian
Materials 2022, 15(12), 4294; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15124294 - 17 Jun 2022
Cited by 3 | Viewed by 1405
Abstract
With an increase of suction efficiency of fresh concrete pumping in confined spaces, the laminar flow state will be damaged by the return flow caused by distribution value direction changes and concrete gravity. This is a fact, but one which is rarely studied. [...] Read more.
With an increase of suction efficiency of fresh concrete pumping in confined spaces, the laminar flow state will be damaged by the return flow caused by distribution value direction changes and concrete gravity. This is a fact, but one which is rarely studied. In this work, the flow state, flow velocity, and suction efficiency of fresh concrete pumping are simulated using the coupled smooth particle hydrodynamics and Discrete Elements Method (SPH-DEM). The rheological parameters and Herschel-Bulkley-Papanastasiou (HBP) rheological model are adopted to simulate fresh concrete in the numerical simulation model. The study reveals that the error between the slump experimental result and that obtained by the HBP model is negligible. A model is therefore established for numerical simulations of the suction efficiency of fresh concrete pumping. An experimental concrete pumping platform is built, and the pressure and efficiency data during pumping are collected. A comparison of the numerical simulation with experimental results shows that the error is less than 10%. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

18 pages, 4963 KiB  
Article
Shrinkage and Durability of Waste Brick and Recycled Concrete Aggregate Stabilized by Cement and Fly Ash
by Yongfa Ding, Hongbo Li, Hubiao Zhang, Sheng Li, Xuanshuo Zhang, Shudong Hua, Jing Zhao and Yufei Tong
Materials 2022, 15(10), 3684; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15103684 - 20 May 2022
Cited by 6 | Viewed by 1445
Abstract
To study the shrinkage and freeze-thaw durability of cement-fly-ash-stabilized brick and concrete reclaimed gravel mixture (CFRBCA), recycled gravel was used to replace 100% of the natural gravel in cement-and-fly-ash-stabilized gravel (CFRCA). Five different mixture ratios of recycled brick and recycled concrete were designed. [...] Read more.
To study the shrinkage and freeze-thaw durability of cement-fly-ash-stabilized brick and concrete reclaimed gravel mixture (CFRBCA), recycled gravel was used to replace 100% of the natural gravel in cement-and-fly-ash-stabilized gravel (CFRCA). Five different mixture ratios of recycled brick and recycled concrete were designed. Dry shrinkage tests, temperature shrinkage tests, freeze-thaw cycle tests, ultrasonic tests, and microscopic analyses were then conducted. The test results showed that the water loss rate, dry shrinkage strain, and dry shrinkage coefficient of CFRBCA increased as the age and brick content increased and tended to be stable by approximately the 40th day of age. The reclaimed gravel content had a great influence on the temperature shrinkage of CFRBCA: the temperature shrinkage coefficient first increased and then decreased as the temperature decreased and reached a peak at −10 to 0 °C. The microstructure analysis showed that as the number of freeze-thaw cycles increases, cracks appear and extend in the CFRBCA, hydration products gradually change from dense to loose, and the Ca/Si ratio increases. Through these experiments, the logarithmic relationship model between ultrasonic wave velocity and CFRBCA strength damage, which can better predict the strength loss caused by CFRBCA variation with freeze-thaw cycles, was established. The brick content is the key parameter affecting the durability of the freeze-thawed CFRBCA, and thus the brick slag content should be properly controlled in engineering applications. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

14 pages, 6313 KiB  
Article
Effect of Silicon Carbide and Tungsten Carbide on Concrete Composite
by Maria Idrees, Husnain Ahmad Chaudhary, Arslan Akbar, Abdeliazim Mustafa Mohamed and Dina Fathi
Materials 2022, 15(6), 2061; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15062061 - 10 Mar 2022
Cited by 4 | Viewed by 2895
Abstract
Flexural strength of concrete is an important property, especially for pavements. Concrete with higher flexural strength has fewer cracking and durability issues. Researchers use different materials, including fibers, polymers, and admixtures, to increase the flexural strength of concrete. Silicon carbide and tungsten carbide [...] Read more.
Flexural strength of concrete is an important property, especially for pavements. Concrete with higher flexural strength has fewer cracking and durability issues. Researchers use different materials, including fibers, polymers, and admixtures, to increase the flexural strength of concrete. Silicon carbide and tungsten carbide are some of the hardest materials on earth. In this research, the mechanical properties of carbide concrete composites were investigated. The silicon carbide and tungsten carbide at different percentages (1%, 2%, 3%, and 4%) by weight of cement along with hybrid silicon carbide and tungsten carbide (2% and 4%) were used to produce eleven mixes of concrete composites. The mechanical tests, including a compressive strength test and flexural strength test, along with the rapid chloride permeability test (RCPT), were conducted. It was concluded that mechanical properties were enhanced by increasing the percentages of both individual and hybrid carbides. The compressive strength was increased by 17% using 4% tungsten carbide, while flexural strength was increased by 39% at 4% tungsten carbide. The significant effect of carbides on flexural strength was also corroborated by ANOVA analysis. The improvement in flexural strength makes both carbides desirable for use in concrete pavement. Additionally, the permeability, the leading cause of durability issues, was reduced considerably by using tungsten carbide. It was concluded that both carbides provide promising results by enhancing the mechanical properties of concrete and are compatible with concrete to produce composites. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

10 pages, 8443 KiB  
Article
A Statistical Model of Fibre Distribution in a Steel Fibre Reinforced Concrete
by Janusz Kobaka
Materials 2021, 14(23), 7297; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14237297 - 29 Nov 2021
Cited by 3 | Viewed by 1266
Abstract
The aim of the research was to create a model of steel fibre distribution in a Steel Fibre Reinforced Concrete space using statistical probability means. The model was created in order to better understand the behaviour of the composite under operating conditions. Four [...] Read more.
The aim of the research was to create a model of steel fibre distribution in a Steel Fibre Reinforced Concrete space using statistical probability means. The model was created in order to better understand the behaviour of the composite under operating conditions. Four statistical distributions (Beta, Kumaraswamy, Three Parameter Beta and Generalised Transmuted Kumaraswamy) were examined to find the distribution that best described fibre settling phenomenon caused by manufacturing process conditions. In the next stage the chosen statistical distribution was adapted to create the model of steel fibre distribution in a Steel Fibre Reinforced Concrete space. The model took into account technological conditions such as vibrating time and properties such as consistency of the tested concrete. The model showed a good agreement with the real fibre distribution. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

9 pages, 1846 KiB  
Article
Sensitivity Analysis of Stochastic Calculation of SCC Regarding Aggressive Environment
by Petr Lehner, Marie Horňáková and Kristýna Hrabová
Materials 2021, 14(22), 6838; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14226838 - 12 Nov 2021
Cited by 8 | Viewed by 1293
Abstract
Probabilistic procedures considering the durability with respect to corrosion of reinforcement caused by aggressive substances are widely applied; however, they are based on narrow assumptions. The aspects need to be evaluated both in terms of the search for suitable application of the various [...] Read more.
Probabilistic procedures considering the durability with respect to corrosion of reinforcement caused by aggressive substances are widely applied; however, they are based on narrow assumptions. The aspects need to be evaluated both in terms of the search for suitable application of the various experimental results and in terms of their impact on the result of the stochastic assessment itself. In this article, sensitivity analysis was used as an ideal tool to prove how input parameters affect the results of the evaluation, with consideration of different types of concrete (ordinary or self-compacting with and without fibres). These concretes may be used in aggressive environments, as an industrial floor or as a part of the load-bearing bridge structure. An example of a reinforced concrete bridge deck was selected as the solved structure. The results show that in the case of a classic evaluation, a larger amount of fibre reports a lower resistance of concrete, which contradicts the assumptions. The sensitivity analysis then shows that self-compacting concrete is more sensitive to the values of the diffusion coefficient, and with the consideration of fibres, the effect is even greater. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

13 pages, 4131 KiB  
Article
Strength Characteristics of Alkali-Activated Slag Mortars with the Addition of PET Flakes
by Agnieszka Kocot, Andrzej Ćwirzeń, Tomasz Ponikiewski and Jacek Katzer
Materials 2021, 14(21), 6274; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14216274 - 21 Oct 2021
Cited by 2 | Viewed by 1473
Abstract
The production of ordinary Portland cement is associated with significant CO2 emissions. To limit these emissions, new binders are needed that can be efficiently substituted for cement. Alkali-activated slag composites are one such possible binder solution. The research programme presented herein focused [...] Read more.
The production of ordinary Portland cement is associated with significant CO2 emissions. To limit these emissions, new binders are needed that can be efficiently substituted for cement. Alkali-activated slag composites are one such possible binder solution. The research programme presented herein focused on the creation of alkali-activated slag composites with the addition of PET flakes as a partial substitute (5%) for natural aggregate. Such composites have a significantly lower impact in terms of CO2 emissions in comparison to ordinary concrete. The created composites were differentiated by the amount of activator (10 and 20 wt.%) and curing temperature (from 20 to 80 °C). Their mechanical properties were tested, and a scanning electron microscope analysis was conducted. Compressive and flexural strengths ranging from 29.3 to 68.4 MPa and from 3.5 to 6.1 MPa, respectively, were achieved. The mechanical test results confirmed that a higher amount of activator improved the mechanical properties. However, the influence of the PET particles on the mechanical properties and microstructure varied with the curing temperature and amount of activator. Areas that require further research were identified. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Graphical abstract

17 pages, 5655 KiB  
Article
Influence of the Type of Cement and the Addition of an Air-Entraining Agent on the Effectiveness of Concrete Cover in the Protection of Reinforcement against Corrosion
by Wioletta Raczkiewicz, Peter Koteš and Petr Konečný
Materials 2021, 14(16), 4657; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14164657 - 18 Aug 2021
Cited by 8 | Viewed by 1633
Abstract
The concrete cover is the basic protection of the reinforcement against the influence of external factors that may lead to its corrosion. Its effectiveness depends mainly on the composition of the concrete mix, including the cement used. Depending on external environmental factors that [...] Read more.
The concrete cover is the basic protection of the reinforcement against the influence of external factors that may lead to its corrosion. Its effectiveness depends mainly on the composition of the concrete mix, including the cement used. Depending on external environmental factors that may aggressively affect the structure, various types of cements and concrete admixtures are recommended. The paper presents the results of tests that allow us to assess the effect of the type of cement used and the air-entraining agent on the effectiveness of the concrete cover as a layer protecting the reinforcement against corrosion. In order to initiate the corrosion process, the reinforced concrete specimens were subjected to cycles of freezing and thawing in a sodium chloride solution. The degree of advancement of the corrosion process was investigated using the electrochemical galvanostatic pulse technique. Additionally, the microstructure of specimens taken from the cover was observed under a scanning electron microscope. The research has shown that in the situation of simultaneous action of chloride ions and freezing cycles, in order to effectively protect the reinforcement against corrosion, the application of both blast-furnace slag cement and an air-entraining agent performed the best. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

20 pages, 4163 KiB  
Article
Optimization of Bio-Foamed Concrete Brick Strength via Bacteria Based Self-Healing and Bio-Sequestration of CO2
by Abdullah Faisal Alshalif, J. M. Irwan, Husnul Azan Tajarudin, N. Othman, A. A. Al-Gheethi, S. Shamsudin, Wahid Ali Hamood Altowayti and Saddam Abo Sabah
Materials 2021, 14(16), 4575; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14164575 - 14 Aug 2021
Cited by 9 | Viewed by 2982
Abstract
This research aimed to optimize the compressive strength of bio-foamed concrete brick (B-FCB) via a combination of the natural sequestration of CO2 and the bio-reaction of B. tequilensis enzymes. The experiments were guided by two optimization methods, namely, 2k factorial and [...] Read more.
This research aimed to optimize the compressive strength of bio-foamed concrete brick (B-FCB) via a combination of the natural sequestration of CO2 and the bio-reaction of B. tequilensis enzymes. The experiments were guided by two optimization methods, namely, 2k factorial and response surface methodology (RSM). The 2k factorial analysis was carried out to screen the important factors; then, RSM analysis was performed to optimize the compressive strength of B-FCB. Four factors, namely, density (D), B. tequilensis concentration (B), temperature (T), and CO2 concentration, were selectively varied during the study. The optimum compressive strength of B-FCB was 8.22 MPa, as deduced from the following conditions: 10% CO2, 3 × 107 cell/mL of B, 27 °C of T and 1800 kg/m3 of D after 28 days. The use of B. tequilensis in B-FCB improved the compressive strength by 35.5% compared to the foamed concrete brick (FCB) after 28 days. A microstructure analysis by scanning electronic microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction analysis (XRD) reflected the changes in chemical element levels and calcium carbonate (CaCO3) precipitation in the B-FCB pores. This was due to the B. tequilensis surface reactions of carbonic anhydrase (CA) and urease enzyme with calcium in cement and sequestered CO2 during the curing time. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Graphical abstract

19 pages, 3501 KiB  
Article
Formwork Pressure of a Heavyweight Self-Compacting Concrete Mix
by Michał A. Glinicki, Jacek Gołaszewski and Grzegorz Cygan
Materials 2021, 14(6), 1549; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14061549 - 22 Mar 2021
Cited by 10 | Viewed by 2616
Abstract
High-fluidity and self-compacting concrete (SCC) mixes were developed using special aggregates for radiation-shielding concrete. The special aggregates comprised heavyweight and hydrous aggregates (crushed magnetite, crushed serpentine, and their mixtures), which were selected to provide an enhanced attenuation of gamma and neutron radiation, respectively. [...] Read more.
High-fluidity and self-compacting concrete (SCC) mixes were developed using special aggregates for radiation-shielding concrete. The special aggregates comprised heavyweight and hydrous aggregates (crushed magnetite, crushed serpentine, and their mixtures), which were selected to provide an enhanced attenuation of gamma and neutron radiation, respectively. For the mixed concrete design with a bulk density of up to 3570 kg/m3, two cement types were used: Portland cement CEM I and slag cement CEM III/A. The basic properties of the fresh self-compacting concrete were evaluated and the lateral formwork pressure exerted by the freshly mixed self-compacting concrete was measured and analyzed. An original test setup was developed for the determination of the lateral pressure on the square column formwork with pressure measurements carried out using six strain gauge pressure transducers, which was adequate for heavyweight concrete mixture testing. Self-compacting concrete mixtures containing a magnetite aggregate or blends of serpentine and magnetite aggregates with a slump flow of at least 550 mm were developed. The lateral pressure on the formwork was directly proportional to the density of the self-compacting heavyweight concrete mixes. The maximum values of the lateral pressure recorded in the test at a casting speed of 1.5 m/h did not exceed 27 kPa and 55% of hydrostatic pressure. Concrete mixtures with basalt, magnetite, and magnetite/serpentine blended aggregates were found to develop sufficient shear strength for proper stability during casting. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

24 pages, 12311 KiB  
Article
Mesoscale Modelling of Concretes Subjected to Triaxial Loadings: Mechanical Properties and Fracture Behaviour
by Qingqing Chen, Yuhang Zhang, Tingting Zhao, Zhiyong Wang and Zhihua Wang
Materials 2021, 14(5), 1099; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14051099 - 26 Feb 2021
Cited by 5 | Viewed by 1794
Abstract
The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with [...] Read more.
The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with good robustness gave reliable and detailed damage evolution processes under different triaxial stress states. The lateral tensile stress significantly influenced the multiaxial mechanical behaviour of the concretes, accelerating the concrete failure. With low lateral pressures or tensile stress, axial cleavage was the main failure mode of the specimens. Furthermore, the concretes presented shear failures under medium lateral pressures. The concretes experienced a transition from brittle fracture to plastic failure under high lateral pressures. The Ottosen parameters were modified by the gradient descent method and then the failure criterion of the concretes in the principal stress space was given. The failure criterion could describe the strength characteristics of concrete materials well by being fitted with experimental data under different triaxial stress states. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Graphical abstract

16 pages, 39266 KiB  
Article
Combining Thermal Loading System with Acoustic Emission Technology to Acquire the Complete Stress-Deformation Response of Plain Concrete in Direct Tension
by Rui Zhang, Li Guo and Wanjin Li
Materials 2021, 14(3), 602; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14030602 - 28 Jan 2021
Cited by 9 | Viewed by 1532
Abstract
The tensile properties of plain concrete are very important for the concrete structural design, and the complete tensile stress-strain curve is essential for creating accurate and reliable designs, especially when considering special load cases such as earthquakes and impacts. To study the complete [...] Read more.
The tensile properties of plain concrete are very important for the concrete structural design, and the complete tensile stress-strain curve is essential for creating accurate and reliable designs, especially when considering special load cases such as earthquakes and impacts. To study the complete tensile stress-deformation response of plain concrete, the direct tension tests were conducted on a novel thermal tensile testing machine (TTTM), which was reformed from a hydraulic universal testing machine (UTM). Acoustic emission (AE) technology was applied to monitor the damage process of plain concrete in tests. The TTTM was powered by the thermal expansion of loading columns, and had a stiffness similar to the specimen, thus eliminating the potential AE noises in the UTM, and simulating the rapid fracture process in real concrete structures. A static-dynamic acquisition system was established to obtain the complete tensile stress-strain curves, of which the data before and at the fracture moment were respectively acquired by the static acquisition system and the dynamic acquisition system. The AE technology is a useful approach to analyze the damage process of concrete, and makes it feasible to determine the damage state and the fracture location of the specimen in real time. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

14 pages, 3445 KiB  
Article
Effect of Placement Technology on the Bond Strength Between Two Layers of Self-Compacting Concrete
by Piotr Dybeł and Milena Kucharska
Materials 2020, 13(15), 3330; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13153330 - 27 Jul 2020
Cited by 5 | Viewed by 1511
Abstract
Self-compacting concrete (SCC) should generally be placed continuously, but it is not uncommon for contractors to be forced to use interruptions in concrete works due to delivery delays. The multilayer casting of SCC can cause weak bond conditions in the contact area of [...] Read more.
Self-compacting concrete (SCC) should generally be placed continuously, but it is not uncommon for contractors to be forced to use interruptions in concrete works due to delivery delays. The multilayer casting of SCC can cause weak bond conditions in the contact area of subsequent layers. Methods of preventing cold joint or lift line formation for normal concretes are not suitable for self-compacting concretes. This article provides research on the effect of multilayer casting technology on the bond strength between two layers of SCC. Three technological variants of connecting successive layers of SCC mixture on beam elements were analyzed: The free flow of the mixture, dropping the mixture from a greater height, and mechanical disturbance of the first layer. Three delay times were applied: 30, 45, and 60 min between two layers of SCC. In general, the research revealed that, regardless of the multilayer casting variant, the bond strength between two layers decreased as the delay time was extended. The best performance and the lowest drop in bond strength were obtained for samples with a mechanically disturbed first layer, independent of the delay time. This method gave similar results to a reference element made without a break in concreting. It was also demonstrated that current recommendations and standard guidelines for multilayer casting appear to be insufficient for ensuring an adequate bond between layers. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

17 pages, 3249 KiB  
Article
Blended Cement Mixed with Basic Oxygen Steelmaking Slag (BOF) as an Alternative Green Building Material
by Assel Jexembayeva, Talal Salem, Pengcheng Jiao, Bozhi Hou and Rimma Niyazbekova
Materials 2020, 13(14), 3062; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13143062 - 09 Jul 2020
Cited by 11 | Viewed by 2671
Abstract
Portland cement tends to exhibit negative environmental impacts; thus, it is required to find measures that will improve its green credentials. In this study, we report a blended Portland slag cement as an alternative environmentally-friendly building material in order to reduce the total [...] Read more.
Portland cement tends to exhibit negative environmental impacts; thus, it is required to find measures that will improve its green credentials. In this study, we report a blended Portland slag cement as an alternative environmentally-friendly building material in order to reduce the total carbon footprint resulted from the production of the ordinary Portland cement (OPC), which may resolve the environmental issues associated with carbon dioxide emissions. The ordinary Portland cement type I enhanced by basic oxygen steelmaking slag (BOF) is produced and casted into cubic and beam-like samples for the compressive and three-point bending tests, and the compressive and flexural strengths are experimentally measured. Numerical simulations are conducted to compare with the experimental result and satisfactory agreements are obtained. X-ray diffraction (XRD) investigations and porosity tests are then carried out using the semi-adiabatic calorimetry, which indicates that 5% BOF is the optimal ratio to accelerate the hydration process while increasing the amount of hydration products, especially at the early curing age of 3 days. Scanning electron microscope (SEM) images further indicate that BOF can be used to prevent the development of microcracks while mitigating their propagation within cement mortar. Our study indicates that the compressive strength of OPC can be critically increased by BOF at the relatively low concentrations of 5%. The blended slag cement reported in this paper provides advanced understanding on the green building material that uses byproduct wastes for the mechanical and electrical performance. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

22 pages, 6684 KiB  
Article
Identification of Fracture Mechanic Properties of Concrete and Analysis of Shear Capacity of Reinforced Concrete Beams without Transverse Reinforcement
by Oldrich Sucharda
Materials 2020, 13(12), 2788; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13122788 - 20 Jun 2020
Cited by 27 | Viewed by 3711
Abstract
The study of new and innovative quasi-brittle materials offers new possibilities for use in construction, but detailed knowledge of their behavior and mechanical properties is required. The use of new materials in the design solution of a structure is usually associated with numerical [...] Read more.
The study of new and innovative quasi-brittle materials offers new possibilities for use in construction, but detailed knowledge of their behavior and mechanical properties is required. The use of new materials in the design solution of a structure is usually associated with numerical methods, which has a number of both advantages and disadvantages. Sophisticated numerical methods, without a sufficiently detailed input knowledge, can provide highly variable results with little informative value. The main goal of this article is to present the procedure for the identification of fracture mechanical parameters for a specific concrete with the use of developed inverse analysis combining multi-criteria decision analysis, stochastic modelling and nonlinear analysis. Subsequently, the identified mechanical parameters of concrete are used for the parametric study of shear resistance of structural beams without shear reinforcement, as an alternative or generalized approach to the study of damage to concrete and concrete structures. This research includes an experimental program using 24 reinforced concrete beams and a detailed determination of basic and specific mechanical properties during laboratory tests. The process of inverse analysis is illustrated in detail for the solved task. The use of nonlinear analysis for detailed failure modelling is based on a 3D computational model and a fracture plastic material model for concrete. Finally, the results of the experimental program and numerical modelling are discussed, leading to a number of conclusions. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Graphical abstract

17 pages, 5084 KiB  
Article
Effect of Placing Self-Compacting Concrete Bottom up on the Quality of Bond Conditions
by Milena Kucharska and Piotr Dybeł
Materials 2020, 13(10), 2346; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13102346 - 20 May 2020
Cited by 3 | Viewed by 1738
Abstract
A self-compacting concrete (SCC) mixture, due to its special rheological properties, may be placed differently than in traditional variants. The paper presents the results of a study on the effect of a bottom-up placing direction on the quality of bond conditions between steel [...] Read more.
A self-compacting concrete (SCC) mixture, due to its special rheological properties, may be placed differently than in traditional variants. The paper presents the results of a study on the effect of a bottom-up placing direction on the quality of bond conditions between steel and self-compacting concrete. Elements with overall dimensions of 160 × 480 × 1600 mm consisting of elementary samples with dimensions of the bond test basic modules were constructed. Ribbed steel rebars with diameters of 16 mm were used and located in formworks perpendicularly to the concrete placing direction. Bond tests were carried out according to the pull-out method. The bottom-up placing contributed to the uniformity of the bond conditions quality in the test elements and an overall improvement of the bond properties, especially in its top part. Given the increasing implementation of alternative methods of mix placing and the promising results, the topic should be further investigated. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

14 pages, 8014 KiB  
Article
Influence of Crimped Steel Fibre on Properties of Concrete Based on an Aggregate Mix of Waste and Natural Aggregates
by Jacek Katzer, Janusz Kobaka and Tomasz Ponikiewski
Materials 2020, 13(8), 1906; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13081906 - 17 Apr 2020
Cited by 12 | Viewed by 2306
Abstract
This research was inspired by the growing global shortage of natural aggregates. Different types of waste ceramics (apart from recycled concrete) are the most popular materials for the production of waste aggregates as possible substitutes for natural ones. The aim of this research [...] Read more.
This research was inspired by the growing global shortage of natural aggregates. Different types of waste ceramics (apart from recycled concrete) are the most popular materials for the production of waste aggregates as possible substitutes for natural ones. The aim of this research was to analyse the efficiency of different aggregate mixes composed of waste and natural materials focusing on two waste ceramic aggregates, which were prepared concrete mixes based on specifically composed aggregates (blend of natural aggregate, porous and iron oxide-rich (red) waste ceramic aggregate, and dense, kaolin-based (white) waste ceramic aggregate). All aggregates were thoroughly tested before utilisation for concrete mix creation. Altogether, four blends of aggregates were prepared in order to prepare concrete mixes using a simplex experiment design. The mixes were then modified by adding various amounts of crimped steel fibre. Such properties of hardened steel fibre-reinforced concrete (SFRC) such as density, compressive strength, shear strength, ultrasound propagation velocity, dynamic modulus of elasticity, and limit of proportionality during flexural testing were of special interest. Tests were conducted according to European and Japanese standards. The achieved fibre-reinforced concretes were characterised by satisfactory strength characteristics, thereby enabling the substitution of traditional reinforcement. Strength classes according to the fib Model Code 2010 were assigned. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

16 pages, 6426 KiB  
Article
Size Effect in Compressive Strength Tests of Cored Specimens of Lightweight Aggregate Concrete
by Lucyna Domagała
Materials 2020, 13(5), 1187; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13051187 - 06 Mar 2020
Cited by 20 | Viewed by 2712
Abstract
The aim of this paper is to discuss the unrecognized problem of the scale effect in compressive strength tests determined for cored specimens of lightweight aggregate concrete (LWAC) against the background of available data on the effect for normal-weight concrete (NWAC). The scale [...] Read more.
The aim of this paper is to discuss the unrecognized problem of the scale effect in compressive strength tests determined for cored specimens of lightweight aggregate concrete (LWAC) against the background of available data on the effect for normal-weight concrete (NWAC). The scale effect was analyzed taking into consideration the influence of slenderness (λ = 1.0, 1.5, 2.0) and diameter (d = 80, 100, 125, and 150 mm) of cored specimens, as well as the type of lightweight aggregate (expanded clay and sintered fly ash) and the type of cement matrix (w/c = 0.55 and 0.37). The analysis of the results for four lightweight aggregate concretes revealed no scale effect in compressive strength tests determined on cored specimens. Neither the slenderness, nor the core diameter seemed to affect the strength results. This fact should be explained by the considerably better structural homogeneity of the tested lightweight concretes in comparison to normal-weight ones. Nevertheless, there were clear differences between the results obtained on molded and cored specimens of the same shape and size. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

22 pages, 6818 KiB  
Article
Effect of Coconut Fiber Length and Content on Properties of High Strength Concrete
by Waqas Ahmad, Syed Hassan Farooq, Muhammad Usman, Mehran Khan, Ayaz Ahmad, Fahid Aslam, Rayed Al Yousef, Hisham Al Abduljabbar and Muhammad Sufian
Materials 2020, 13(5), 1075; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13051075 - 28 Feb 2020
Cited by 105 | Viewed by 11255
Abstract
Recently, the addition of natural fibers to high strength concrete (HSC) has been of great interest in the field of construction materials. Compared to artificial fibers, natural fibers are cheap and locally available. Among all natural fibers, coconut fibers have the greatest known [...] Read more.
Recently, the addition of natural fibers to high strength concrete (HSC) has been of great interest in the field of construction materials. Compared to artificial fibers, natural fibers are cheap and locally available. Among all natural fibers, coconut fibers have the greatest known toughness. In this work, the mechanical properties of coconut fiber reinforced high strength concrete (CFR-HSC) are explored. Silica fume (10% by mass) and super plasticizer (1% by mass) are also added to the CFR-HSC. The influence of 25 mm-, 50 mm-, and 75 mm-long coconut fibers and 0.5%, 1%, 1.5%, and 2% contents by mass is investigated. The microstructure of CFR-HSC is studied using scanning electron microscopy (SEM). The experimental results revealed that CFR-HSC has improved compressive, splitting-tensile, and flexural strengths, and energy absorption and toughness indices compared to HSC. The overall best results are obtained for the CFR-HSC having 50 mm long coconut fibers with 1.5% content by cement mass. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

Review

Jump to: Research

27 pages, 9654 KiB  
Review
Using Chinese Coal Gangue as an Ecological Aggregate and Its Modification: A Review
by Ying Hao, Xiaoning Guo, Xianhua Yao, Ruicong Han, Lielie Li and Min Zhang
Materials 2022, 15(13), 4495; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15134495 - 26 Jun 2022
Cited by 22 | Viewed by 2708
Abstract
Coal gangue is a kind of industrial solid waste with serious ecological and environmental implications. Producing concrete with coal gangue aggregate is one of the green sustainable development requirements. This paper reviews the properties and preparation methods of Chinese gangue aggregate, studies the [...] Read more.
Coal gangue is a kind of industrial solid waste with serious ecological and environmental implications. Producing concrete with coal gangue aggregate is one of the green sustainable development requirements. This paper reviews the properties and preparation methods of Chinese gangue aggregate, studies the influence of gangue aggregate on concrete properties and the prediction model of gangue concrete, and summarizes the influence of modified materials on gangue concrete. The studies analyzed in this review show that different treatments influence the performance of coal gangue aggregate concrete. With the increase in the replacement ratio of coal gangue aggregate in concrete, the concrete workability and mechanical performance are reduced. Furthermore, the pore structure changes lead to decreased porosity, greatly affecting the durability. Coal gangue is not recommended for producing high-grade concretes. Nevertheless, pore structure can be improved by adding mineral admixtures, fibers, and admixtures to the coal gangue concrete. Hence, the working properties, mechanical properties, and durability of the concrete can be improved effectively, ensuring that coal gangue concrete meets engineering design requirements. Adding modified materials to coal gangue concrete is a viable future development direction. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

43 pages, 8205 KiB  
Review
3D Concrete Printing: A Systematic Review of Rheology, Mix Designs, Mechanical, Microstructural, and Durability Characteristics
by Atta Ur Rehman and Jung-Hoon Kim
Materials 2021, 14(14), 3800; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14143800 - 07 Jul 2021
Cited by 84 | Viewed by 10532
Abstract
This paper provides a state-of-the-art report on the up-to-date research on the emerging 3D concrete printing technology from the concrete materials perspective. It reviews the recent research focused on understanding and characterizing the rheological necessities of the concrete printing process and discusses how [...] Read more.
This paper provides a state-of-the-art report on the up-to-date research on the emerging 3D concrete printing technology from the concrete materials perspective. It reviews the recent research focused on understanding and characterizing the rheological necessities of the concrete printing process and discusses how the researchers are tailoring compatible mix proportions for the 3D concrete printing process by using eco-friendly binders, waste aggregates, chemical admixtures, and nano-additives. This paper systematically evaluates anisotropic behavior in the mechanical properties of printed concrete and establishes an order for anisotropic behavior in the compressive, flexural, and tensile strengths along three different axes (X, Y, and Z axes) of printed concrete. It evaluates the ratio of flexural strength to the compressive strength of printed concrete along the above three axes. This article explains the influence of variation of printing process parameters on the mechanical properties and discusses reinforcement approaches used for increasing structural performance. The microstructure at the interface of adjacent layers and also at the interface of the reinforcement-cement matrix is discussed. The recent research on the durability performance of printed concrete is critically discussed and future research needs for 3D concrete printing are identified in this paper. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

40 pages, 12665 KiB  
Review
An Overview on the Rheology, Mechanical Properties, Durability, 3D Printing, and Microstructural Performance of Nanomaterials in Cementitious Composites
by Hongwei Song and Xinle Li
Materials 2021, 14(11), 2950; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14112950 - 30 May 2021
Cited by 12 | Viewed by 3347
Abstract
The most active research area is nanotechnology in cementitious composites, which has a wide range of applications and has achieved popularity over the last three decades. Nanoparticles (NPs) have emerged as possible materials to be used in the field of civil engineering. Previous [...] Read more.
The most active research area is nanotechnology in cementitious composites, which has a wide range of applications and has achieved popularity over the last three decades. Nanoparticles (NPs) have emerged as possible materials to be used in the field of civil engineering. Previous research has concentrated on evaluating the effect of different NPs in cementitious materials to alter material characteristics. In order to provide a broad understanding of how nanomaterials (NMs) can be used, this paper critically evaluates previous research on the influence of rheology, mechanical properties, durability, 3D printing, and microstructural performance on cementitious materials. The flow properties of fresh cementitious composites can be measured using rheology and slump. Mechanical properties such as compressive, flexural, and split tensile strength reveal hardened properties. The necessary tests for determining a NM’s durability in concrete are shrinkage, pore structure and porosity, and permeability. The advent of modern 3D printing technologies is suitable for structural printing, such as contour crafting and binder jetting. Three-dimensional (3D) printing has opened up new avenues for the building and construction industry to become more digital. Regardless of the material science, a range of problems must be tackled, including developing smart cementitious composites suitable for 3D structural printing. According to the scanning electron microscopy results, the addition of NMs to cementitious materials results in a denser and improved microstructure with more hydration products. This paper provides valuable information and details about the rheology, mechanical properties, durability, 3D printing, and microstructural performance of cementitious materials with NMs and encourages further research. Full article
(This article belongs to the Special Issue Concrete Technology and Mechanical Properties of Concretes)
►▼ Show Figures

Figure 1

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-28
Back to TopTop