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Testing of Cement-Based Materials

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

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 71267

Special Issue Editor

Prof. Dr. Jae Hong Kim

E-Mail Website
Guest Editor
Korea Advanced Institute of Science and Technology, Daejeon, Korea
Interests: concrete; mechanics; rheology; non-destructive testing

Special Issue Information

Dear Colleagues,

Concrete is the most consumed engineering material and has been used for more than 100 years. The construction material is used to build a structure outdoors, different from the other engineering materials produced inside manufacturing factories, which results in a unique process for its implementation. The construction material is usally produced in a local batch plant, and as a premature state it is transformed to a construction site (spatially distributed). Various producers and engineers are involved in its production, transformation, casting, and placing processes. Therefore, the application of the standard test methods is important for its quallity control and performance evaluation.

Advances in cement-based materials (e.g., high-performance concrete; high-strength concrete; self-consolidating concrete; fiber-reinforced cementitious composites; engineered cementitious composites; pervious concrete; low carbon concrete; and others) have brought the development of novel test methods to evalute their enhanced performances and material characterization. The test results and analysis for the new cement-based materials are also of interest in accompany with the test methods.

On the other hand, the technological advancement of the material characterization allows us to deeply understand the microstructure and behavior of cement-based materials. The characterization technology includes, but is not limited to, nanotechnolgy, rheological evaluation, nondstructive testing, and the multiphysics apporach. There are many other technologies related to the testing of cement-based materials. The field is rapidly advancing into new areas of discovery.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcomed.

Assoc. Prof. Jae Hong Kim
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
  • cementitious materials
  • test method
  • performance evaluation
  • material characterization

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Published Papers (20 papers)

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Research

21 pages, 8530 KiB  
Article
An Innovative Test Method for Tensile Strength of Concrete by Applying the Strut-and-Tie Methodology
by Wen-Cheng Liao, Po-Shao Chen, Chung-Wen Hung and Suyash Kishor Wagh
Materials 2020, 13(12), 2776; https://doi.org/10.3390/ma13122776 - 18 Jun 2020
Cited by 18 | Viewed by 5757
Abstract
Tensile strength is one of the important mechanical properties of concrete, but it is difficult to measure accurately due to the brittle nature of concrete in tension. The three widely used test methods for measuring the tensile strength of concrete each have their [...] Read more.
Tensile strength is one of the important mechanical properties of concrete, but it is difficult to measure accurately due to the brittle nature of concrete in tension. The three widely used test methods for measuring the tensile strength of concrete each have their shortcomings: the direct tension test equipment is not easy to set up, particularly for alignment, and there are no standard test specifications; the tensile strengths obtained from the test method of splitting tensile strength (American Society for Testing and Materials, ASTM C496) and that of flexural strength of concrete (ASTM C78) are significantly different from the actual tensile strength owing to mechanisms of methodologies and test setup. The objective of this research is to develop a new concrete tensile strength test method that is easy to conduct and the result is close to the direct tension strength. By applying the strut-and-tie concept and modifying the experimental design of the ASTM C78, a new concrete tensile strength test method is proposed. The test results show that the concrete tensile strength obtained by this proposed method is close to the value obtained from the direct tension test for concrete with compressive strengths from 25 to 55 MPa. It shows that this innovative test method, which is precise and easy to conduct, can be an effective alternative for tensile strength of concrete. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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14 pages, 4308 KiB  
Article
Alkali-Activated Slag Paste with Different Mixing Water: A Comparison Study of Early-Age Paste Using Electrical Resistivity
by Yubin Jun, Young Hwan Bae, Tae Yong Shin, Jae Hong Kim and Hong Jae Yim
Materials 2020, 13(11), 2447; https://doi.org/10.3390/ma13112447 - 27 May 2020
Cited by 10 | Viewed by 2087
Abstract
This paper reports the electrical resistivity measurements on KOH-activated ground-granulated blast-furnace slag, which was mixed with deionized water or natural seawater at three different activator-to-binder ratios (0.4, 0.45, and 0.5). Compressive strength and X-ray diffraction analyses were performed on the samples after the [...] Read more.
This paper reports the electrical resistivity measurements on KOH-activated ground-granulated blast-furnace slag, which was mixed with deionized water or natural seawater at three different activator-to-binder ratios (0.4, 0.45, and 0.5). Compressive strength and X-ray diffraction analyses were performed on the samples after the measurement. The type of mixing water did not affect the setting time of samples, whereas the setting time was delayed with an increase in activator-to-binder (a/b) ratio. Regardless of the mixing water type, the increasing ratio of electrical resistivity between a/b 0.45 and 0.5 was larger than that between a/b 0.4 and 0.45. For the same a/b ratio, the pastes mixed with seawater produced higher electrical resistivity and early strength than those with deionized water. The increase in the electrical resistivity in seawater-mixed pastes could be attributed to the formation of Cl-bearing phases such as Cl-hydrocalumite, AlOCl, and aluminum chloride hydrate. It is believed that the reaction products in seawater-mixed samples were helpful in preventing water percolation, and thus, the electrical resistivity increased compared with the deionized water-mixed sample. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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16 pages, 7962 KiB  
Article
Tensile and Fixed Elongation Properties of Polymer-Based Cement Flexible Composite under Water/Corrosive Solution Environment
by Er-Lei Bai, Gao-Jie Liu, Jin-Yu Xu and Bing-Lin Leng
Materials 2020, 13(9), 2155; https://doi.org/10.3390/ma13092155 - 07 May 2020
Cited by 7 | Viewed by 2454
Abstract
This study examined the tensile and fixed elongation properties of flexible composite made of styrene–acrylic, vinyl acetate-ethylene copolymer emulsion (VAE emulsion), and cement as cementitious material for airport pavement joint sealant. Quantitative analysis of the elastic recovery ratio and a series of specimen [...] Read more.
This study examined the tensile and fixed elongation properties of flexible composite made of styrene–acrylic, vinyl acetate-ethylene copolymer emulsion (VAE emulsion), and cement as cementitious material for airport pavement joint sealant. Quantitative analysis of the elastic recovery ratio and a series of specimen tensile indicators after water immersion, drying–wetting cycles, and corrosive solution (H2SO4, NaOH, and jet fuel) immersion were performed. Results showed excellent polymer-based cement flexible composite (PCFC) resistance against water and corrosive solution erosion, such as failure mode, elastic recovery, tensile strength, and energy absorption. When the level of water/corrosive solution erosion (immersion time, cycles) were increased, the tensile and fixed elongation properties progressively decreased. Specimens retained more than 60% elastic recovery ratio after water/corrosive solution erosion immersion for 30 days. According to erosion testing as per immersion time in corrosive solution, jet fuel had the maximum effect, NaOH solution had the least effect, and H2SO4 solution had an intermediary effect. At immersion time in the range of 1–30 days, the tensile strength does not change by more than 0.07 MPa. Within the limits of the fixed elongation tests, cohesive failure occurred after jet fuel immersion for 30 days, adhesive failure occurred after H2SO4 solution immersion for 30 days but was normal in other cases. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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20 pages, 6550 KiB  
Article
Fiber-Reinforced Cemented Paste Backfill: The Effect of Fiber on Strength Properties and Estimation of Strength Using Nonlinear Models
by Xin Chen, Xiuzhi Shi, Shu Zhang, Hui Chen, Jian Zhou, Zhi Yu and Peisheng Huang
Materials 2020, 13(3), 718; https://doi.org/10.3390/ma13030718 - 05 Feb 2020
Cited by 27 | Viewed by 2649
Abstract
This experimental investigation was conducted to research the properties of polypropylene (PP) fiber-reinforced cemented paste backfill (CPB). The unconfined compressive strength (UCS) of the fiber-reinforced CPB showed a significant improvement with average UCS increase ratios of 141.07%, 57.62% and 63.17% at 3, 7 [...] Read more.
This experimental investigation was conducted to research the properties of polypropylene (PP) fiber-reinforced cemented paste backfill (CPB). The unconfined compressive strength (UCS) of the fiber-reinforced CPB showed a significant improvement with average UCS increase ratios of 141.07%, 57.62% and 63.17% at 3, 7 and 28 days, respectively. The macroscopic failure mode and SEM analysis indicated that fibers prevented the formation of large tensile and shear cracks during the pull-out and pull-off failure modes. A linear fitting function for the UCS at a curing time of 3 days and two polynomial fitting functions for the UCS at curing times of 7 and 28 days were established to characterize the relationship between the UCS of the fiber-reinforced and unreinforced CPB. Moreover, based on composite mechanics, nonlinear models related to the UCS and fiber reinforcement index were obtained. The estimated functions containing the fiber reinforcement index λ, which consists of the fiber content and aspect ratio of fiber, could evaluate the UCS. Furthermore, the fiber reinforcement index λ quantifies the enhancement by the fibers. Both estimation results indicated that the UCS values were estimated accurately at curing times of 3, 7 and 28 days in this study. Additionally, the estimation models could be used to guide the strength design of fiber-reinforced CPB. Besides this, the results showed that fiber-reinforced CPB can be used more widely in mine backfills and meets the requirements of controlled low-strength material (CLSM) for broader applications. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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14 pages, 3517 KiB  
Article
Effects of Defects on Bond Behavior of Fiber Reinforced Cementitious Matrix Materials
by Antonio Bilotta and Gian Piero Lignola
Materials 2020, 13(1), 164; https://doi.org/10.3390/ma13010164 - 01 Jan 2020
Cited by 9 | Viewed by 2079
Abstract
High-strength fibers embedded in inorganic matrix i.e., Fiber Reinforced Cementitious Mortar materials (FRCM) are commonly used as strengthening technique for existing masonry structures, due to the low sensitivity to debonding phenomena between substrate and matrix. Nevertheless, the use of lime or cement-based matrix [...] Read more.
High-strength fibers embedded in inorganic matrix i.e., Fiber Reinforced Cementitious Mortar materials (FRCM) are commonly used as strengthening technique for existing masonry structures, due to the low sensitivity to debonding phenomena between substrate and matrix. Nevertheless, the use of lime or cement-based matrix instead of epoxy adhesive implies that attention has to be paid to the bond behavior between the fibers and the matrix, since sliding phenomena and cohesive failures in the mortar matrix can occur. The paper aims to investigate the effect of the mechanical properties of fiber and matrix on the FRCM efficiency, and potential geometrical defects, typical of real applications. The aim is to analyze the mechanical behavior of the FRCM system by simulating hypothetical bond tests, as they are usually performed in laboratories. The bond test has a significant role, as it is used for the qualification of the material, providing sometimes very scattered results. Hence, it is particularly important and greatly discussed in the scientific community and among manufactures and practitioners. The purpose is to understand where this variability could derive from and possibly how to contain it, to improve the characterization of FRCM systems. A mechanical model has been proposed to simulate the usual bond test to focus and stress the way in which each fiber slips out of the matrix as the load increases; and this has been recognized as the main reason for scattered results in bond tests. The model was then applied to the typical cases of PBO-FRCM and Glass-FRCM, hence considering different ratios for the fiber and matrix properties. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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17 pages, 5483 KiB  
Article
Influence of Granulometry on Thermal and Mechanical Properties of Cement Mortars Containing Expanded Perlite as a Lightweight Aggregate
by Matías Leyton-Vergara, Alexis Pérez-Fargallo, Jesús Pulido-Arcas, Galo Cárdenas-Triviño and Jeremy Piggot-Navarrete
Materials 2019, 12(23), 4013; https://doi.org/10.3390/ma12234013 - 03 Dec 2019
Cited by 16 | Viewed by 3183
Abstract
This research aims at clarifying the influence of the granulometry of expanded perlite, on the thermal conductivity, structural strength, density, and water absorption of lightweight mortars. Three original perlite gradations have been obtained and three pairs of twin test mortars have been tested [...] Read more.
This research aims at clarifying the influence of the granulometry of expanded perlite, on the thermal conductivity, structural strength, density, and water absorption of lightweight mortars. Three original perlite gradations have been obtained and three pairs of twin test mortars have been tested with those gradations. SEM tests have also been run to clarify the interaction, at a microscopic level, between the expanded perlite and the cement grouting. The results indicate that the mere manipulation of the granulometry may have a considerable and very beneficial effect on the mixture’s properties, such as thermal conductivity and water absorption. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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13 pages, 4646 KiB  
Article
Prediction of Electrical Conductivity of Fiber-Reinforced Cement-Based Composites by Deep Neural Networks
by Dongdong Yuan, Wei Jiang, Zheng Tong, Jie Gao, Jingjing Xiao and Wanli Ye
Materials 2019, 12(23), 3868; https://doi.org/10.3390/ma12233868 - 23 Nov 2019
Cited by 6 | Viewed by 2765
Abstract
This study presents a deep-learning method for characterizing carbon fiber (CF) distribution and predicting electrical conductivity of CF-reinforced cement-based composites (CFRCs) using scanning electron microscopy (SEM) images. First, SEM images were collected from CFRC specimens with different CF contents. Second, a fully convolutional [...] Read more.
This study presents a deep-learning method for characterizing carbon fiber (CF) distribution and predicting electrical conductivity of CF-reinforced cement-based composites (CFRCs) using scanning electron microscopy (SEM) images. First, SEM images were collected from CFRC specimens with different CF contents. Second, a fully convolutional network (FCN) was utilized to extract carbon fiber components from the SEM images. Then, DSEM and Dsample were used to evaluate the distribution of CFs. DSEM and Dsample reflected the real CF distribution in an SEM observation area and a specimen, respectively. Finally, a radial basis neural network was used to predict the electrical conductivity of the CFRC specimens, and its weights (di) were used to evaluate the effects of CF distribution on electrical conductivity. The results showed that the FCN could accurately segment CFs in SEM images with different magnifications. Dsample could accurately reflect the morphological distribution of CFs in CFRC. The electrical conductivity prediction errors were less than 6.58%. In addition, di could quantitatively evaluate the effect of CF distribution on CFRC conductivity. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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12 pages, 2660 KiB  
Article
Effects of CO2 Curing on Alkali-Activated Slag Paste Cured in Different Curing Conditions
by Yubin Jun, Seong Ho Han, Tae Yong Shin and Jae Hong Kim
Materials 2019, 12(21), 3513; https://doi.org/10.3390/ma12213513 - 26 Oct 2019
Cited by 21 | Viewed by 2832
Abstract
The effect of CO2 curing on alkali-activated slag paste activated by a mixture of sodium hydroxide and sodium silicate solutions is reported in this paper. The paste samples after demolding were cured in three different curing environments as follows: (1) environmental chamber [...] Read more.
The effect of CO2 curing on alkali-activated slag paste activated by a mixture of sodium hydroxide and sodium silicate solutions is reported in this paper. The paste samples after demolding were cured in three different curing environments as follows: (1) environmental chamber maintained at 85% relative humidity (RH) and 25 °C; (2) 3-bar CO2 pressure vessel; and (3) CO2 chamber maintained at 20% CO2 concentration, 70% RH and 25 °C. The hardened samples were then subjected to compressive strength measurement, X-ray diffraction analysis, and thermogravimetry. All curing conditions used in this study were beneficial for the strength development of the alkali-activated slag paste samples. Among the curing environments, the 20% CO2 chamber was the most effective on compressive strength development; this is attributed to the simultaneous supply of moisture and CO2 within the chamber. The results of X-ray diffraction and thermogravimetry show that the alkali-activated slag cured in the 20% CO2 chamber received a higher amount of calcium silicate hydrate (C-S-H), while calcite formed at an early age was consumed with time. C-S-H was formed by associating the calcite generated by CO2 curing with the silica gel dissolved from alkali-activated slag. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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14 pages, 5397 KiB  
Article
Comparative Analysis of Static and Dynamic Mechanical Behavior for Dry and Saturated Cement Mortar
by Ayyaz Mustafa, Mohamed A. Mahmoud, Abdulazeez Abdulraheem, Sarfaraz A. Furquan, Ayman Al-Nakhli and Mohammed BaTaweel
Materials 2019, 12(20), 3299; https://doi.org/10.3390/ma12203299 - 11 Oct 2019
Cited by 7 | Viewed by 2671
Abstract
Deformational and breakage behaviors of concrete and cement mortar greatly influence various engineering structures, such as dams, river bridges, ports, tunnels, and offshore rig platforms. The mechanical and petrophysical properties are very sensitive to water content and are controlled by the liquid part [...] Read more.
Deformational and breakage behaviors of concrete and cement mortar greatly influence various engineering structures, such as dams, river bridges, ports, tunnels, and offshore rig platforms. The mechanical and petrophysical properties are very sensitive to water content and are controlled by the liquid part in pore spaces to a large extent. The objective of this paper is to investigate the water saturation effect on the strength characteristics and deformability of cement mortar under two loading conditions, static and dynamic compression. A set of cement mortar samples was prepared and tested to study the mechanical behavior in dry and saturated states. The first part of the research incorporates the study of static mechanical properties for dry and brine-saturated cement mortar through uniaxial compressive strength tests (UCS). Second, drop-weight impact experiments were carried out to study the dynamic mechanical properties (impact resistance, deformation pattern, and fracture geometry) for dry and saturated cases. The comparative analysis revealed that water saturation caused substantial changes in compressive strength and other mechanical characteristics. Under static loading, water saturation caused a reduction in strength of 36%, and cement mortar tended to behave in a more ductile manner as compared to dry samples. On the contrary, under dynamic loading conditions, water saturation resulted in higher impact resistance and fracture toughness as compared to dry conditions. In addition, fractures could propagate to smaller depths as compared to dry case. The study will help resolve many civil, mining, and petroleum engineering problems where cement structures undergo static as well as dynamic compression, especially in a hydraulic environment where these structures interact with the water frequently. To the best of our knowledge, the effect of water saturation on the dynamic mechanical properties of cement mortar has not been well understood and reported in the literature. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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15 pages, 3016 KiB  
Article
Investigating the Effects of Polyaluminum Chloride on the Properties of Ordinary Portland Cement
by Taewan Kim, Choonghyun Kang, Sungnam Hong and Ki-Young Seo
Materials 2019, 12(20), 3290; https://doi.org/10.3390/ma12203290 - 10 Oct 2019
Cited by 5 | Viewed by 2741
Abstract
This study investigates the mechanical and microstructural properties of paste comprising ordinary Portland cement (OPC) added with polyaluminum chloride (PACl). The properties of the resulting mixture are analyzed using compressive strength, X-ray diffraction, scanning electron microscopy (SEM), mercury intrusion porosimetry, and thermogravimetric analysis. [...] Read more.
This study investigates the mechanical and microstructural properties of paste comprising ordinary Portland cement (OPC) added with polyaluminum chloride (PACl). The properties of the resulting mixture are analyzed using compressive strength, X-ray diffraction, scanning electron microscopy (SEM), mercury intrusion porosimetry, and thermogravimetric analysis. The results show that the addition of PACl improves the mechanical properties of OPC paste, that calcium-(aluminum)-silicate-hydrate (C-(A)-S-H) gel and Friedel’s salt are the major products forming from the reaction with the aluminum and chloride ions in PACl, and that the portlandite content decreases. Moreover, the size and number of micropores decrease, and compressive strength increases. All these phenomena are amplified by increasing PACl content. SEM images confirm these findings by revealing Friedel’s salt in the micropores. Thus, this work confirms that adding PACl to OPC results in a mixture with superior mechanical and microstructural properties. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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21 pages, 6383 KiB  
Article
Strength Development and Strain Localization Behavior of Cemented Paste Backfills Using Portland Cement and Fly Ash
by Yue Zhao, Abbas Taheri, Amin Soltani, Murat Karakus and An Deng
Materials 2019, 12(20), 3282; https://doi.org/10.3390/ma12203282 - 09 Oct 2019
Cited by 29 | Viewed by 3229
Abstract
This study examines the combined performance of Portland cement (PC), the binder, and fly ash (FA), the additive, towards improving the mechanical performance of the South Australian copper-gold underground mine cemented paste backfill (CPB) system. A series of unconfined compressive strength (UCS) tests [...] Read more.
This study examines the combined performance of Portland cement (PC), the binder, and fly ash (FA), the additive, towards improving the mechanical performance of the South Australian copper-gold underground mine cemented paste backfill (CPB) system. A series of unconfined compressive strength (UCS) tests were carried out on various mix designs to evaluate the effects of binder and/or additive contents, as well as curing time, on the CPB’s strength, stiffness and toughness. Moreover, the failure patterns of the tested samples were investigated by means of the three-dimensional digital image correlation (DIC) technique. Making use of several virtual extensometers, the state of axial and lateral strain localization was also investigated in the pre- and post-peak regimes. The greater the PC content and/or the longer the curing period, the higher the developed strength, stiffness and toughness. The use of FA alongside PC led to further strength and stiffness improvements by way of inducing secondary pozzolanic reactions. Common strength criteria for CPBs were considered to assess the applicability of the tested mix designs; with regards to stope stability, 4% PC + 3% FA was found to satisfy the minimum 700 kPa threshold, and thus was deemed as the optimum choice. As opposed to external measurement devices, the DIC technique was found to provide strain measurements free from bedding errors. The developed field of axial and lateral strains indicated that strain localization initiates in the pre-peak regime at around 80% of the UCS. The greater the PC (or PC + FA) content, and more importantly the longer the curing period, the closer the axial stress level required to initiate localization to the UCS, thus emulating the failure mechanism of quasi-brittle materials such as rock and concrete. Finally, with an increase in curing time, the difference between strain values at the localized and non-localized zones became less significant in the pre-peak regime and more pronounced in the post-peak regime. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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16 pages, 8624 KiB  
Article
Influence of Nanosilica on Mechanical Properties, Sorptivity, and Microstructure of Lightweight Concrete
by Mohamed Abd Elrahman, Sang-Yeop Chung, Pawel Sikora, Teresa Rucinska and Dietmar Stephan
Materials 2019, 12(19), 3078; https://doi.org/10.3390/ma12193078 - 21 Sep 2019
Cited by 69 | Viewed by 4418
Abstract
This study presents the results of an experimental investigation of the effects of nanosilica (NS) on the strength development, transport properties, thermal conductivity, air-void, and pore characteristics of lightweight aggregate concrete (LWAC), with an oven-dry density <1000 kg/m3. Four types of [...] Read more.
This study presents the results of an experimental investigation of the effects of nanosilica (NS) on the strength development, transport properties, thermal conductivity, air-void, and pore characteristics of lightweight aggregate concrete (LWAC), with an oven-dry density <1000 kg/m3. Four types of concrete mixtures, containing 0 wt.%, 1 wt.%, 2 wt.%, and 4 wt.% of NS were prepared. The development of flexural and compressive strengths was determined for up to 90 days of curing. In addition, transport properties and microstructural properties were determined, with the use of RapidAir, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) techniques. The experimental results showed that NS has remarkable effects on the mechanical and transport properties of LWACs, even in small dosages. A significant improvement in strength and a reduction of transport properties, in specimens with an increased NS content, was observed. However, the positive effects of NS were more pronounced when a higher amount was incorporated into the mixtures (>1 wt.%). NS contributed to compaction of the LWAC matrix and a modification of the air-void system, by increasing the amount of solid content and refining the fine pore structure, which translated to a noticeable improvement in mechanical and transport properties. On the other hand, NS decreased the consistency, while increasing the viscosity of the fresh mixture. An increment of superplasticizer (SP), along with a decrement of stabilizer (ST) dosages, are thus required. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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14 pages, 4371 KiB  
Article
Crack Width Estimation of Mortar Specimen Using Gas Diffusion Experiment
by Do-Keun Lee, Min-Hyuk Lim, Kyung-Joon Shin and Kwang-Myong Lee
Materials 2019, 12(18), 3003; https://doi.org/10.3390/ma12183003 - 16 Sep 2019
Cited by 6 | Viewed by 2183
Abstract
Maintenance of structures using self-healing concrete technologies has recently been actively studied. However, unlike the technological development of self-healing concrete, research focused on evaluating the self-healing performance is insufficient. Although water permeability experiments are widely used, the reliability of the test results may [...] Read more.
Maintenance of structures using self-healing concrete technologies has recently been actively studied. However, unlike the technological development of self-healing concrete, research focused on evaluating the self-healing performance is insufficient. Although water permeability experiments are widely used, the reliability of the test results may be reduced due to the viscosity of water and the possibility of elution of material inside the specimen. In this study, we propose a gas diffusion test for estimating the crack width and eventually for application to evaluation of the self-healing performance. The results verified that the proposed method can be effectively applied to the estimation of crack width. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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22 pages, 10749 KiB  
Article
Properties of Alkali-Activated Slag Paste Using New Colloidal Nano-Silica Mixing Method
by Taewan Kim, Jae Hong Kim and Yubin Jun
Materials 2019, 12(9), 1571; https://doi.org/10.3390/ma12091571 - 13 May 2019
Cited by 14 | Viewed by 3154
Abstract
Previous studies of alkali-activated slag cement (AASC) using nano-silica have mentioned mostly powdered nano-silica and binder weight replacement methods, which have a rapid decrease in fluidity, a short setting time and a low nano-silica replacement rate (< 5%). In this study, colloidal nano-silica [...] Read more.
Previous studies of alkali-activated slag cement (AASC) using nano-silica have mentioned mostly powdered nano-silica and binder weight replacement methods, which have a rapid decrease in fluidity, a short setting time and a low nano-silica replacement rate (< 5%). In this study, colloidal nano-silica (CNS) was used and the mixing-water weight substitution method was applied. The substitution method was newly applied to improve the dispersibility of nano-silica and to increase the substitution rate. In the experiment, the CNS was replaced by 0, 10, 20, 30, 40, and 50% of the mixing-water weight. As a result, as the substitution rate of CNS increased, the fluidity decreased, and the setting time decreased. High compressive strength values and increased rates were also observed, and the diameter and volume of pores decreased rapidly. In particular, the increase of CNS replacement rate had the greatest effect on decrease of medium capillary pores (50–10 nm) and increase of gel pores (< 10 nm). The new displacement method was able to replace up to 50% of the mixing water. As shown in the experimental results, despite the high substitution rate of 50%, the minimum fluidity of the mixture was secured, and a high-strength and compact matrix could be formed. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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16 pages, 3004 KiB  
Article
Mechanical Activation of Granulated Copper Slag and Its Influence on Hydration Heat and Compressive Strength of Blended Cement
by Yan Feng, Jakob Kero, Qixing Yang, Qiusong Chen, Fredrik Engström, Caisa Samuelsson and Chongchong Qi
Materials 2019, 12(5), 772; https://doi.org/10.3390/ma12050772 - 06 Mar 2019
Cited by 64 | Viewed by 3565
Abstract
Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area [...] Read more.
Mechanical activation of granulated copper slag (GCS) is carried out in the present study for the purposes of enhancing pozzolanic activity for the GCS. A vibration mill mills the GCS for 1, 2, and 3 h to produce samples with specific surface area of 0.67, 1.03 and 1.37 m2/g, respectively. The samples are used to replace 30% cement (PC) to get 3 PC-GCS binders. The hydration heat and compressive strength are measured for the binders and derivative thermogravimetric /thermogravimetric analysis (DTG/TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used to characterize the paste samples. It is shown that cumulative heat and compressive strength at different ages of hydration and curing, respectively, are higher for the binders blending the GCS milled for a longer time. The compressive strength after 90 d of curing for the binder with the longest milling time reaches 35.7 MPa, which is higher than the strength of other binders and close to the strength value of 39.3 MPa obtained by the PC pastes. The percentage of fixed lime by the binder pastes at 28 days is correlated with the degree of pozzolanic reaction and strength development. The percentage is higher for the binder blending the GCS with longer milling time and higher specific surface area. The pastes with binders blending the GCS of specific surface area of 0.67 and 1.37 m2/g fix lime of 15.20 and 21.15%, respectively. These results together with results from X-ray diffraction (XRD), FTIR, and SEM investigations demonstrate that the mechanical activation via vibratory milling is an effective method to enhance the pozzolanic activity and the extent for cement substitution by the GCS as a suitable supplementary cementitious material (SCM). Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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18 pages, 3975 KiB  
Article
Modelling the Influence of Waste Rubber on Compressive Strength of Concrete by Artificial Neural Networks
by Marijana Hadzima-Nyarko, Emmanuel Karlo Nyarko, Naida Ademović, Ivana Miličević and Tanja Kalman Šipoš
Materials 2019, 12(4), 561; https://doi.org/10.3390/ma12040561 - 13 Feb 2019
Cited by 52 | Viewed by 4470
Abstract
One of the major causes of ecological and environmental problems comes from the enormous number of discarded waste tires, which is directly connected to the exponential growth of the world’s population. In this paper, previous works carried out on the effects of partial [...] Read more.
One of the major causes of ecological and environmental problems comes from the enormous number of discarded waste tires, which is directly connected to the exponential growth of the world’s population. In this paper, previous works carried out on the effects of partial or full replacement of aggregate in concrete with waste rubber on some properties of concrete were investigated. A database containing 457 mixtures with partial or full replacement of natural aggregate with waste rubber in concrete provided by different researchers was formed. This database served as the basis for investigating the influence of partial or full replacement of natural aggregate with waste rubber in concrete on compressive strength. With the aid of the database, the possibility of achieving reliable prediction of the compressive strength of concrete with tire rubber is explored using neural network modelling. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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14 pages, 8884 KiB  
Article
A New, Carbon-Negative Precipitated Calcium Carbonate Admixture (PCC-A) for Low Carbon Portland Cements
by Lewis McDonald, Fredrik P. Glasser and Mohammed S. Imbabi
Materials 2019, 12(4), 554; https://doi.org/10.3390/ma12040554 - 13 Feb 2019
Cited by 20 | Viewed by 6850
Abstract
The production of Portland cement accounts for approximately 7% of global anthropogenic CO2 emissions. Carbon CAPture and CONversion (CAPCON) technology under development by the authors allows for new methods to be developed to offset these emissions. Carbon-negative Precipitated Calcium Carbonate (PCC), produced [...] Read more.
The production of Portland cement accounts for approximately 7% of global anthropogenic CO2 emissions. Carbon CAPture and CONversion (CAPCON) technology under development by the authors allows for new methods to be developed to offset these emissions. Carbon-negative Precipitated Calcium Carbonate (PCC), produced from CO2 emissions, can be used as a means of offsetting the carbon footprint of cement production while potentially providing benefits to cement hydration, workability, durability and strength. In this paper, we present preliminary test results obtained for the mechanical and chemical properties of a new class of PCC blended Portland cements. These initial findings have shown that these cements behave differently from commonly used Portland cement and Portland limestone cement, which have been well documented to improve workability and the rate of hydration. The strength of blended Portland cements incorporating carbon-negative PCC Admixture (PCC-A) has been found to exceed that of the reference baseline—Ordinary Portland Cement (OPC). The reduction of the cement clinker factor, when using carbon-negative PCC-A, and the observed increase in compressive strength and the associated reduction in member size can reduce the carbon footprint of blended Portland cements by more than 25%. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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13 pages, 4396 KiB  
Article
Microwave Radiation as a Pre-Treatment for Standard and Innovative Fragmentation Techniques in Concrete Recycling
by Maarten Everaert, Raphael Stein, Simon Michaux, Vincent Goovaerts, Carlo Groffils, Simon Delvoie, Zengfeng Zhao, Ruben Snellings, Peter Nielsen and Kris Broos
Materials 2019, 12(3), 488; https://doi.org/10.3390/ma12030488 - 05 Feb 2019
Cited by 21 | Viewed by 4293
Abstract
Recent advances in concrete recycling technology focus on novel fragmentation techniques to obtain aggregate fractions with low cement matrix content. This study assesses the aggregate liberation effectiveness of four different treatment processes including standard and innovative concrete fragmentation techniques. Lab-made concrete samples were [...] Read more.
Recent advances in concrete recycling technology focus on novel fragmentation techniques to obtain aggregate fractions with low cement matrix content. This study assesses the aggregate liberation effectiveness of four different treatment processes including standard and innovative concrete fragmentation techniques. Lab-made concrete samples were subjected to either standard mechanical crushing technique (SMT) or electrodynamic fragmentation (EDF). For both fragmentation processes, the influence of a microwave weakening pre-treatment technique (MWT) was investigated. A detailed analysis of the particle size distribution was carried out on samples after fragmentation. The >5.6 mm fraction was more deeply characterized for aggregate selective liberation (manual classification to separate liberated aggregates) and for cement matrix content (thermogravimetric measurements). Results highlight that EDF treatment is more effective than SMT treatment to selectively liberate aggregates and to decrease the cement matrix content of the >5.6 mm fraction. EDF fully liberates up to 37 wt.% of the >5.6 mm natural aggregates, while SMT only liberates 14–16 wt.%. MWT pre-treatment positively affects aggregate liberation and cement matrix removal only if used in combination with SMT; no significant effect in combination with EDF was recorded. These results of this study can provide insights to successfully implement innovative technology in concrete recycling plants. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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20 pages, 5285 KiB  
Article
Hydration and Microstructure of Cement Pastes with Calcined Hwangtoh Clay
by Run-Sheng Lin, Xiao-Yong Wang, Han-Seung Lee and Hyeong-Kyu Cho
Materials 2019, 12(3), 458; https://doi.org/10.3390/ma12030458 - 01 Feb 2019
Cited by 49 | Viewed by 5074
Abstract
Calcined Hwangtoh (HT) clay is a very promising supplementary cementitious material (SCM). In this work, the development of the mechanical properties and microstructures of HT-blended cement paste was studied after substituting the binder with HT powder calcined at 800 °C. The water-to-binder (w/b) [...] Read more.
Calcined Hwangtoh (HT) clay is a very promising supplementary cementitious material (SCM). In this work, the development of the mechanical properties and microstructures of HT-blended cement paste was studied after substituting the binder with HT powder calcined at 800 °C. The water-to-binder (w/b) ratios of the paste used were 0.2 and 0.5, and the quantities of HT powder added to the mixture were 0, 10, and 20%. The compressive strength test indicates that the addition of the HT powder increases the compressive strength of the paste after seven days of curing, and the highest compressive strength is obtained with the 10% HT substitution, regardless of whether the w/b ratio is 0.5 or 0.2. X-ray fluorescence (XRF), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), isothermal calorimetry, thermogravimetric analysis (TGA), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis show that the HT powder not only has a physical effect (i.e., nucleation effect and dilution effect) on cement hydration but also has a chemical effect (i.e., chemical reaction of HT). The results of scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analysis show that the paste has more ettringite during the early stage, and the microstructure is refined after the addition of the HT powder. In addition, the relationships between chemically bound water, hydration heat, and compressive strength are presented. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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11 pages, 4553 KiB  
Communication
Nonlinear Resonance Vibration Assessment to Evaluate the Freezing and Thawing Resistance of Concrete
by Jae Hong Kim, Sun-Jong Park and Hong Jae Yim
Materials 2019, 12(2), 325; https://doi.org/10.3390/ma12020325 - 21 Jan 2019
Cited by 5 | Viewed by 3546
Abstract
Under cold environments, the freezing and thawing cycles of water in concrete reduce the lifetime and durability of concrete structures. For enhanced freezing and thawing resistance, entrained air voids are generally required, but malfunctioning of air entrainment is sometimes reported in the field. [...] Read more.
Under cold environments, the freezing and thawing cycles of water in concrete reduce the lifetime and durability of concrete structures. For enhanced freezing and thawing resistance, entrained air voids are generally required, but malfunctioning of air entrainment is sometimes reported in the field. To evaluate the quality of air entrainment, this study proposes a nondestructive method that is a preceding evaluation before damage to the concrete. A nonlinear resonance vibration method is adopted in samples having an identical air void content. The durable concrete sample with resistance to freezing and thawing cycles shows higher nonlinearity in its resonance. Thus, the quality of air entrainment and, furthermore, the potential freezing and thawing resistance can possibly be evaluated by measuring the nonlinearity parameter of the concrete, which is preliminary study to attempt the preceding evaluation of freezing and thawing resistance using nondestructive method. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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