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4 pages, 183 KiB

Open AccessEditorial

Cement-Based Composites: Advancements in Development and Characterization

by Pawel Sikora and Sang-Yeop Chung

Crystals 2020, 10(9), 832; https://doi.org/10.3390/cryst10090832 - 17 Sep 2020

Cited by 5 | Viewed by 2107

Abstract

This Special Issue on “Cement-Based Composites: Advancements in Development and Characterization” presents the latest research and advances in the field of cement-based composites. This special issue covers a variety of experimental studies related to fibre-reinforced, photocatalytic, lightweight, and sustainable cement-based composites. Moreover, simulation [...] Read more.

This Special Issue on “Cement-Based Composites: Advancements in Development and Characterization” presents the latest research and advances in the field of cement-based composites. This special issue covers a variety of experimental studies related to fibre-reinforced, photocatalytic, lightweight, and sustainable cement-based composites. Moreover, simulation studies are present in this special issue to provide the fundamental knowledge on designing and optimizing the properties of cementitious composites. The presented publications in this special issue show the most recent technology in the cement-based composite field. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

Research

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21 pages, 10460 KiB

Open AccessEditor’s ChoiceArticle

Determination of Mechanical Characteristics for Fiber-Reinforced Concrete with Straight and Hooked Fibers

by Zuzana Marcalikova, Radim Cajka, Vlastimil Bilek, David Bujdos and Oldrich Sucharda

Crystals 2020, 10(6), 545; https://doi.org/10.3390/cryst10060545 - 25 Jun 2020

Cited by 43 | Viewed by 6634

Abstract

Fiber-reinforced concrete has a wide application in practice, and many fields of research are devoted to it. In most cases, this is a specific problem, i.e., the determination of the mechanical properties or the test method. However, wider knowledge of the effect of [...] Read more.

Fiber-reinforced concrete has a wide application in practice, and many fields of research are devoted to it. In most cases, this is a specific problem, i.e., the determination of the mechanical properties or the test method. However, wider knowledge of the effect of fiber in concrete is unavailable or insufficient for selected test series that cannot be compared. This article deals with the processing of a comprehensive test study and the impact of two types of fibers on the quantitative and qualitative parameters of concrete. Testing was performed for fiber dosages of 0, 40, 75, and 110 kg/m³. The fibers were hooked and straight. The influence of the fibers on the mechanical properties in fiber-reinforced concrete was analyzed by functional dependence. The selected mechanical properties were compressive strength, splitting tensile strength, bending tensile strength, and fracture energy. The results also include the resulting load–displacement diagrams and summary recommendations for the structural use and design of fiber-reinforced concrete structures. The shear resistance of reinforced concrete beams with hooked fibers was also verified by tests. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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13 pages, 17476 KiB

Open AccessArticle

Influence of the Aggregate Surface Conditions on the Strength of Quick-Converting Track Concrete

by Rahwan Hwang, Il-Wha Lee, Sukhoon Pyo and Dong Joo Kim

Crystals 2020, 10(6), 543; https://doi.org/10.3390/cryst10060543 - 24 Jun 2020

Cited by 3 | Viewed by 2014

Abstract

This experimental study investigates the effects of the aggregate surface conditions on the compressive strength of quick-converting track concrete (QTC). The compressive strength of QTC and interfacial fracture toughness (IFT) were investigated by changing the amount of fine abrasion dust particles (FADPs) on [...] Read more.

This experimental study investigates the effects of the aggregate surface conditions on the compressive strength of quick-converting track concrete (QTC). The compressive strength of QTC and interfacial fracture toughness (IFT) were investigated by changing the amount of fine abrasion dust particles (FADPs) on the aggregate surface from 0.00 to 0.15 wt% and the aggregate water saturation from 0 to 100%. The effects of aggregate water saturation on the compressive strength of the QTC and IFT were notably different, corresponding to the amount of FADPs. As the aggregate water saturation increased from 0 to 100%, in the case of 0.00 wt% FADPs, the IFT decreased from 0.91 to 0.58 MPa∙mm^1/2, and thus, the compressive strength of the QTC decreased from 34.8 to 31.4 MPa because the aggregate water saturation increased the water/cement ratio at the interface and, consequently, the interfacial porosity. However, as the aggregate water saturation increased from 0 to 100%, in the case of 0.15 wt% FADPs, the compressive strength increased from 24.6 to 28.1 MPa, while the IFT increased from 0.41 to 0.88 MPa∙mm^1/2 because the water/cement ratio at the interface was reduced as a result of the absorption by the FADPs on the surface of the aggregates and the cleaning effects of the aggregate surface. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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17 pages, 8502 KiB

Open AccessArticle

Inverse Estimation Method of Material Randomness Using Observation

by Dae-Young Kim, Pawel Sikora, Krystyna Araszkiewicz and Sang-Yeop Chung

Crystals 2020, 10(6), 512; https://doi.org/10.3390/cryst10060512 - 16 Jun 2020

Cited by 2 | Viewed by 1674

Abstract

This study proposes a method for inversely estimating the spatial distribution characteristic of a material’s elastic modulus using the measured value of the observation data and the distance between the measurement points. The structural factors in the structural system possess temporal and spatial [...] Read more.

This study proposes a method for inversely estimating the spatial distribution characteristic of a material’s elastic modulus using the measured value of the observation data and the distance between the measurement points. The structural factors in the structural system possess temporal and spatial randomness. One of the representative structural factors, the material’s elastic modulus, possesses temporal and spatial randomness in the stiffness of the plate structure. The structural factors with randomness are typically modeled as having a certain probability distribution (probability density function) and a probability characteristic (mean and standard deviation). However, this method does not consider spatial randomness. Even if considered, the existing method presents limitations because it does not know the randomness of the actual material. To overcome the limitations, we propose a method to numerically define the spatial randomness of the material’s elastic modulus and confirm factors such as response variability and response variance. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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15 pages, 10142 KiB

Open AccessArticle

Study on Visible Light Catalysis of Graphite Carbon Nitride-Silica Composite Material and Its Surface Treatment of Cement

by Weiguang Zhong, Dan Wang, Congcong Jiang, Xiaolei Lu, Lina Zhang and Xin Cheng

Crystals 2020, 10(6), 490; https://doi.org/10.3390/cryst10060490 - 07 Jun 2020

Cited by 6 | Viewed by 2330

Abstract

Cement-based composite is one of the essential building materials that has been widely used in infrastructure and facilities. During the service of cement-based materials, the performance of cement-based materials will be affected after the cement surface is exposed to pollutants. Not only can [...] Read more.

Cement-based composite is one of the essential building materials that has been widely used in infrastructure and facilities. During the service of cement-based materials, the performance of cement-based materials will be affected after the cement surface is exposed to pollutants. Not only can the surface of cement treated with a photocatalyst degrade pollutants, but it can also protect the cement-based materials from being destroyed. In this study, graphite carbon nitride-silica composite materials were synthesized by thermal polymerization using nanosilica and urea as raw materials. The effect of nanosilica content and specific surface area were investigated with the optimal condition attained to be 0.15 g and 300 m²/g, respectively. An X-ray diffractometer, thermogravimetric analyzer, scanning electron microscope, a Brunauer–Emmett–Teller (BET) specific surface area analyzer and ultraviolet-visible spectrophotometer were utilized for the characterization of as-prepared graphite carbon nitride-silica composite materials. Subsequently, the surface of cement-based materials was treated with graphite carbon nitride-silica composite materials by the one-sided immersion and brushing methods for the study of photocatalytic performance. By comparing the degradation effect of Rhodamine B, it was found that the painting method is more suitable for the surface treatment of cement. In addition, through the reaction of calcium hydroxide and graphite carbon nitride-silica composite materials, it was found that the combination of graphite carbon nitride-silica composite materials and cement is through C-S-H gel. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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14 pages, 4420 KiB

Open AccessArticle

Inhibition of the Alkali-Carbonate Reaction Using Fly Ash and the Underlying Mechanism

by Xin Ren, Wei Li, Zhongyang Mao and Min Deng

Crystals 2020, 10(6), 484; https://doi.org/10.3390/cryst10060484 - 05 Jun 2020

Cited by 2 | Viewed by 2251

Abstract

In this paper, fly ash is used to inhibit the alkali-carbonate reaction (ACR). The experimental results suggest that when the alkali equivalent (equivalent Na₂Oeq) of the cement is 1.0%, the adding of 30% fly ash can significantly inhibit the expansion in [...] Read more.

In this paper, fly ash is used to inhibit the alkali-carbonate reaction (ACR). The experimental results suggest that when the alkali equivalent (equivalent Na₂Oeq) of the cement is 1.0%, the adding of 30% fly ash can significantly inhibit the expansion in low-reactivity aggregates. For moderately reactive aggregates, the expansion rate can also be reduced by adding 30% of fly ash. According to a polarizing microscope analysis, the cracks are expansion cracks mainly due to the ACR. The main mechanisms of fly ash inhibiting the ACR are that it refines the pore structure of the cement paste, and that the alkali migration rate in the curing solution to the interior of the concrete microbars is reduced. As the content of fly ash increases, the concentrations of K⁺ and Na⁺ and the pH value in the pore solution gradually decrease. This makes the ACR in the rocks slower, such that the cracks are reduced, and the expansion due to the ACR is inhibited. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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14 pages, 1903 KiB

Open AccessArticle

Study of Bond Strength of Steel Bars in Basalt Fibre Reinforced High Performance Concrete

by Piotr Smarzewski

Crystals 2020, 10(6), 436; https://doi.org/10.3390/cryst10060436 - 29 May 2020

Cited by 11 | Viewed by 2533

Abstract

The paper presents the study on bond behaviour of steel bars. It reports the research conducted on local bond strength of short length specimens in high performance concrete (HPC) and basalt fibre reinforced high performance concrete (BFRHPC). In this study, the basalt fibre [...] Read more.

The paper presents the study on bond behaviour of steel bars. It reports the research conducted on local bond strength of short length specimens in high performance concrete (HPC) and basalt fibre reinforced high performance concrete (BFRHPC). In this study, the basalt fibre volume content, concrete cover, bar diameter and rib geometry are the main parameters. Further important factors are the directions of the casting and loading. Determining the effect of aforementioned main parameters on the bond strength in test series is required, in order to design reinforced HPC structures. The study of local bond strength in HPC and BFRHPC with five different basalt fibre fractions included tests of seventy-two short length specimens, using two concrete cover and two diameters of steel bars with different rib face angles. For different ranges of BFRHPC strength, relationships for bond strength with respect to the splitting tensile strength were obtained. The bond strength increased with the splitting tensile strength and compressive strength of BFRHPC specimens with the 12 mm and 16 mm bar respectively. The bond strength of BFRHPC was lower for the bar with the greater distances between the lugs on the bar. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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13 pages, 4130 KiB

Open AccessArticle

Influence of Combined Action of Steel Fiber and MgO on Chloride Diffusion Resistance of Concrete

by Feifei Jiang, Min Deng, Liwu Mo and Wenqing Wu

Crystals 2020, 10(4), 338; https://doi.org/10.3390/cryst10040338 - 24 Apr 2020

Cited by 2 | Viewed by 1996

Abstract

To improve the chloride diffusion resistance and durability of concrete, a new kind of steel fiber reinforced MgO concrete (SFRMC) was made by adding steel fiber and MgO to concrete simultaneously. With steel fiber for load bearing and expansion limiting, MgO as the [...] Read more.

To improve the chloride diffusion resistance and durability of concrete, a new kind of steel fiber reinforced MgO concrete (SFRMC) was made by adding steel fiber and MgO to concrete simultaneously. With steel fiber for load bearing and expansion limiting, MgO as the expander, SFRMC has both the advantages of fiber reinforced concrete and expansion concrete. The influence of steel fiber and MgO on the strength and chloride diffusion resistance of concrete was evaluated by splitting tensile test and chloride diffusion test. Mercury intrusion porosimeter (MIP) and scanning electron microscopy (SEM) were used to study the microstructure of SFRMC. The results showed that the combined action of steel fiber and MgO reduced the porosity of concrete and the chloride diffusion coefficient (CDC), which could not be achieved by steel fiber and MgO separately. In the free state, the expansion energy produced by the hydration of MgO made the concrete expand outwards. However, under the constraint of steel fiber, the expansion energy was used to tension the fiber, resulting in self-stress. In this way, compared to reference concrete RC, the tensile strength of SFRMC-1, SFRMC-2, and SFRMC-3 increased by 3.1%, 61.3%, and 64.5%, CDC decreased by 8.8%, 36.7%, and 33.1%, and the porosity decreased by 6.2%, 18.4%, and 20.6%, respectively. In addition, the SEM observations demonstrated that the interfacial transition zone (ITZ) between fiber and matrix was denser in SFRMC, which contributed to reduce the diffusion of chloride ions in the concrete. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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10 pages, 2063 KiB

Open AccessArticle

Experimental Study on Unconfined Compression Strength of Polypropylene Fiber Reinforced Composite Cemented Clay

by Qiangqiang Cheng, Jixiong Zhang, Nan Zhou, Yu Guo and Shining Pan

Crystals 2020, 10(4), 247; https://doi.org/10.3390/cryst10040247 - 26 Mar 2020

Cited by 10 | Viewed by 2402

Abstract

The effects of three main factors, including polypropylene fiber content, composite cement content and curing time on the unconfined compressive strength of fiber-reinforced cemented clay were studied through a series of unconfined compressive strength tests. The experimental results show that the incorporation of [...] Read more.

The effects of three main factors, including polypropylene fiber content, composite cement content and curing time on the unconfined compressive strength of fiber-reinforced cemented clay were studied through a series of unconfined compressive strength tests. The experimental results show that the incorporation of fibers can increase the compressive strength and residual strength of cement-reinforced clay as well as the corresponding axial strain when the stress peak is reached compared with cement-reinforced clay. The compressive strength of fiber-reinforced cement clay decreases first, then increases with small-composite cement at curing time 14 d and 28 d. However, fiber-reinforced cement clay’s strength increases with the increase of fiber content for heavy-composite cement. The compressive strength of fiber-composite cement-reinforced marine clay increases with the increase of curing time and composite cement content. The growth rate increases with the increase of curing time. The failure mode of composite cement-reinforced clay is brittle failure, while the failure mode of fiber-reinforced cemented clay is plastic failure. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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10 pages, 1895 KiB

Open AccessArticle

Comparison of Material Properties of SCC Concrete with Steel Fibres Related to Ingress of Chlorides

by Petr Lehner, Petr Konečný and Tomasz Ponikiewski

Crystals 2020, 10(3), 220; https://doi.org/10.3390/cryst10030220 - 20 Mar 2020

Cited by 25 | Viewed by 3036

Abstract

The paper focuses on the evaluation of chloride ion diffusion coefficient of self-compacting concrete with steel fibre reinforcement. The reference concrete from Ordinary Portland Cement (OPC) and Self-Compacting Concrete (SCC) with several values of added steel fibres—0%, 1% and 2% of weight—were cast [...] Read more.

The paper focuses on the evaluation of chloride ion diffusion coefficient of self-compacting concrete with steel fibre reinforcement. The reference concrete from Ordinary Portland Cement (OPC) and Self-Compacting Concrete (SCC) with several values of added steel fibres—0%, 1% and 2% of weight—were cast in order to investigate the effect of fibres. The three procedures of diffusion coefficient calculation are presented—rapid chloride penetration test, accelerated penetration tests with chloride as well as the surface measurement of electrical resistivity using Wenner probe. The resulting diffusion coefficients obtained by all methods are compared and evaluated regarding the basic mechanical properties of concrete mixtures. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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21 pages, 7557 KiB

Open AccessArticle

Experimental Investigations on the Performances of Composite Building Materials Based on Industrial Crops and Volcanic Rocks

by Raluca Iștoan, Daniela Roxana Tămaș-Gavrea and Daniela Lucia Manea

Crystals 2020, 10(2), 102; https://doi.org/10.3390/cryst10020102 - 11 Feb 2020

Cited by 5 | Viewed by 2958

Abstract

Interdisciplinary and sustainability represent the main characteristics of this paper due to the fact that this research is offering a connection between two main areas—agronomy and construction, by using hemp shiv for the design of new building materials, which can increase the sustainability [...] Read more.

Interdisciplinary and sustainability represent the main characteristics of this paper due to the fact that this research is offering a connection between two main areas—agronomy and construction, by using hemp shiv for the design of new building materials, which can increase the sustainability level of the building industry. For this reason, the main scope of this study is based on the investigation of a new category of composite building materials—lightweight mortars based on hemp shiv, volcanic rocks and white cement—which contribute to a positive environmental impact and help to increase indoor comfort. A complex report was carried out on two segments. The first one is focused upon the characteristics of the raw materials from the composition of the new materials, while the second segment presents a detailed analysis of these composites including morphological and chemical investigation, pyrolytic and fire behavior, compression and flexural strengths, and acoustic and thermal characteristics. The proposed recipes have as a variable volcanic rocks, while the hemp and the binder maintain their volumes and properties. The results were analyzed according to the influence of volcanic rocks on the new composites. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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9 pages, 5298 KiB

Open AccessArticle

Rhodamine B Removal of TiO₂@SiO₂ Core-Shell Nanocomposites Coated to Buildings

by Dan Wang, Zhi Geng, Pengkun Hou, Ping Yang, Xin Cheng and Shifeng Huang

Crystals 2020, 10(2), 80; https://doi.org/10.3390/cryst10020080 - 31 Jan 2020

Cited by 14 | Viewed by 3049

Abstract

Surface application of photocatalyst in cement-based materials could endow it with photocatalytic properties, however, the weak adhesion between photocatalyst coatings and the substrates may result in poor durability in outdoor environments. In this study, TiO₂@SiO₂ core-shell nanocomposites with different coating [...] Read more.

Surface application of photocatalyst in cement-based materials could endow it with photocatalytic properties, however, the weak adhesion between photocatalyst coatings and the substrates may result in poor durability in outdoor environments. In this study, TiO₂@SiO₂ core-shell nanocomposites with different coating thicknesses were synthesized by varying the experiment parameters. The results indicate that SiO₂ coatings accelerated the rhodamine B removal to a certain extent, owing to its high surface area; however, more SiO₂ coatings decreased its photocatalytic efficiencies. The cement matrix treated with TiO₂@SiO₂ core-shell nanocomposites showed good photocatalytic efficiency and durability after harsh weathering processing. A reaction mechanism was revealed by the reaction of TiO₂@SiO₂ nanocomposites with Ca(OH)₂. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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15 pages, 3779 KiB

Open AccessArticle

An Investigation of the Mechanical and Physical Characteristics of Cement Paste Incorporating Different Air Entraining Agents using X-ray Micro-Computed Tomography

by Mohamed Abd Elrahman, Mohamed E. El Madawy, Sang-Yeop Chung, Stanisław Majer, Osama Youssf and Pawel Sikora

Crystals 2020, 10(1), 23; https://doi.org/10.3390/cryst10010023 - 06 Jan 2020

Cited by 8 | Viewed by 3142

Abstract

Improving the thermal insulation properties of cement-based materials is the key to reducing energy loss and consumption in buildings. Lightweight cement-based composites can be used efficiently for this purpose, as a structural material with load bearing ability or as a non-structural one for [...] Read more.

Improving the thermal insulation properties of cement-based materials is the key to reducing energy loss and consumption in buildings. Lightweight cement-based composites can be used efficiently for this purpose, as a structural material with load bearing ability or as a non-structural one for thermal insulation. In this research, lightweight cement pastes containing fly ash and cement were prepared and tested. In these mixes, three different techniques for producing air voids inside the cement paste were used through the incorporation of aluminum powder (AL), air entraining agent (AA), and hollow microspheres (AS). Several experiments were carried out in order to examine the structural and physical characteristics of the cement composites, including dry density, compressive strength, porosity and absorption. A Hot Disk device was used to evaluate the thermal conductivity of different cement composites. In addition, X-ray micro-computed tomography (micro-CT) was adopted to investigate the microstructure of the air-entrained cement pastes and the spatial distribution of the voids inside pastes without destroying the specimens. The experimental results obtained showed that AS specimens with admixture of hollow microspheres can improve the compressive strength of cement composites compared to other air entraining admixtures at the same density level. It was also confirmed that the incorporation of aluminum powder creates large voids, which have a negative effect on specimens’ strength and absorption. Full article

(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)

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