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13 pages, 7239 KiB

Open AccessArticle

A Study on the Healing Performance of Solid Capsules for Crack Self-Healing of Cementitious Composites

by Yong Jic Kim, Yun Wang Choi and Sung-Rok Oh

Crystals 2022, 12(7), 993; https://doi.org/10.3390/cryst12070993 - 17 Jul 2022

Cited by 1 | Viewed by 1785

Abstract

The purpose of this study is to investigate the healing performance of solid capsules made of cement as a basis for manufacturing self-healing capsules that can heal cracks in cementitious composites. The solid capsules were mixed with 5%, 10%, and 15% concentrations on [...] Read more.

The purpose of this study is to investigate the healing performance of solid capsules made of cement as a basis for manufacturing self-healing capsules that can heal cracks in cementitious composites. The solid capsules were mixed with 5%, 10%, and 15% concentrations on the cement. The self-healing performance of cementitious composites with solid capsules was investigated through three evaluations. First, the mechanical strength-healing performance was evaluated through a re-loading test. Second, the durability-healing performance was evaluated through a permeability test. Finally, the crack-healing performance was examined by observing the crack widths. Through evaluation of the healing performance of the solid capsules, the healing performance of the compressive strength was found to be high when the capsule proportion was 10% and its size was within the range of 300 μm to 850 μm. Furthermore, the splitting tensile strength showed a high healing performance when the capsule proportion mixed was 15% and its size was 850 μm. In the case of the permeability test, a capsule size of 850 μm showed a healing effect greater than 95%. Cracks with a width of up to 200 μm tended to heal using capsules with a size of 600 μm to 850 μm. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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21 pages, 4463 KiB

Open AccessArticle

Influence of Fly Ash Denitrification on Properties of Hybrid Alkali-Activated Composites

by Lukáš Procházka, Jana Boháčová and Barbara Vojvodíková

Crystals 2022, 12(5), 633; https://doi.org/10.3390/cryst12050633 - 28 Apr 2022

Cited by 2 | Viewed by 1497

Abstract

This article deals with the possibility of partial replacement of blast furnace slag (GGBFS) with fly ash after denitrification (FAD) in alkali-activated materials. Physical-mechanical and durability properties were tested, hydration reaction was monitored, and infrared spectroscopy was performed. Results were compared between mixtures [...] Read more.

This article deals with the possibility of partial replacement of blast furnace slag (GGBFS) with fly ash after denitrification (FAD) in alkali-activated materials. Physical-mechanical and durability properties were tested, hydration reaction was monitored, and infrared spectroscopy was performed. Results were compared between mixtures prepared with fly ash without denitrification (FA), and also with a mixture based only on GGBFS. The basic result is that hybrid alkali-systems with FAD show similar trends to FA. The significant effect of fly ash is manifested in terms of its resistance to freeze-thaw processes. Reactions in a calorimeter show a slower development of reactions with increasing replacement of GGBFS due to the lower reactivity of the fly ash. Through testing the leaching resistance, a decrease in flexural strength was found. This may be due to the descaling of the main hydration product, C–(A)–S–H gel. After 28 days of maturation, compressive strengths of all monitored mixtures ranged from 96 to 102 MPa. The flexural strengths ranged from 6.8 to 8.0 MPa. After 28 days of maturation, the higher strengths reached mixtures without replacing GGBFS. In terms of resistance to freeze-thaw processes, the largest decrease (almost 20%) of flexural strength was achieved by a mixture with 30% of GGBFS replacement by FA. No fundamental differences were found for the mixtures in the FTIR analysis. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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14 pages, 8804 KiB

Open AccessArticle

Activation of Blast Furnace Slag with CFB Fly Ash as a Supplementary Binder Material: Hydration Products and Effects of Sulfate Attack

by Guan-Yu Chen and Wei-Hsing Huang

Crystals 2022, 12(1), 41; https://doi.org/10.3390/cryst12010041 - 28 Dec 2021

Cited by 3 | Viewed by 1873

Abstract

Circulating Fluidized Bed (CFB) combustion is a clean technology for burning, with advantages of adapting to a large variety of fuel, high combustion efficiency, lower NOx emissions, and stable operation. The residue collected from the ash-hoppers of the electrostatic precipitator of the CFB [...] Read more.

Circulating Fluidized Bed (CFB) combustion is a clean technology for burning, with advantages of adapting to a large variety of fuel, high combustion efficiency, lower NOx emissions, and stable operation. The residue collected from the ash-hoppers of the electrostatic precipitator of the CFB boiler is called CFB fly ash. This paper presents the hydration development on the application of CFB fly ash to activating blast furnace slag (BFS) as a supplementary binder material (SBM) for replacement of Portland cement in making concrete. Investigation of the hydration products of cement pastes prepared with combinations of BFS and CFB fly ash were conducted by means of X-ray diffraction, thermal gravimetric analysis, and scanning electronic microscope. Test results show that the main hydration products of the CFB fly ash-BFS blended pastes were found to be hydrated calcium silicate (C-S-H), ettringite, gypsum, and some portlandite. Considering that CFB fly ash produced from the combustion of high-sulfur coke has high SO₃ contents, the volume stability of mortar made from CFB fly ash-activated BFS was subjected to tests in accordance with ASTM C1012 and ASTM C1038 for evaluating the internal and external sulfate attack, respectively. The results indicate that, due to the high sulfur (SO₃) content of CFB fly ash, the expansion caused by internal sulfate attack (ISA) increased with increasing proportion of CFB fly ash in the mixture. In contrast, no significant expansion was observed in the external sulfate attack (ESA) test, regardless of the proportion of CFB fly ash in the mixture. In order for the CFB fly ash to serve as a supplementary binder material and to maintain adequate volume stability, the amount of CFB fly ash used for the activation of BFS is recommended to be no more than 20% of the SBM. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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15 pages, 5158 KiB

Open AccessArticle

Effect of Nitrate/Bromide on the Hydration Process of Cement Paste Mixed with Alkali Free Liquid Accelerator at Low Temperature

by Yongdong Xu and Tingshu He

Crystals 2021, 11(12), 1585; https://doi.org/10.3390/cryst11121585 - 19 Dec 2021

Cited by 8 | Viewed by 2681

Abstract

The effects of different inorganic salt accelerators (CaBr₂, NaBr, Ca(NO₃)₂, NaNO₃) and an alkali-free liquid accelerator were researched at a low temperature of 10 °C. The results showed the effects of 1.5% NaBr and 1.5% [...] Read more.

The effects of different inorganic salt accelerators (CaBr₂, NaBr, Ca(NO₃)₂, NaNO₃) and an alkali-free liquid accelerator were researched at a low temperature of 10 °C. The results showed the effects of 1.5% NaBr and 1.5% NaNO₃ inorganic accelerator were pronounced. The 1-d compressive strengths of the mortar with these two inorganic salts were increased by 185.8% and 184.2%, respectively, and the final setting times were shortened from 7.74 to 6.08 min and 6.12 min, respectively. The hydration temperatures at 10 °C were measured, and the promotion effects of the inorganic accelerators were calculated: the relationship between the hydration degree was α_{AS + NN} > α_{AS + NB} > α_{AS + CB} > α_{AS + CN} > α_AS. In addition, the reaction of C₃A with NaBr and NaNO₃ was used to analyze the products in an ettringite phase, i.e., Ca₄Al₂O₆Br₂10·H₂O, 3CaOAl₂O₃Ca(NO₃)₂X·H₂O. The formation of these phases was detected in the hydration products of the cement paste hydration for 12 h, 24 h, and 28 d. Combined with the mass loss of the ettringite phase at 90–120 °C, determined using TG/DTG, the synergetic acceleration mechanism of the inorganic accelerators was comprehensively inferred. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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18 pages, 11955 KiB

Open AccessArticle

Effects of Fluorogypsum and Flue-Gas Desulfurization Gypsum on the Hydration and Hardened Properties of Alkali Slag Cement

by Cheng Wang, Hang He, Yuli Wang and Wenyue Xue

Crystals 2021, 11(12), 1475; https://doi.org/10.3390/cryst11121475 - 27 Nov 2021

Cited by 12 | Viewed by 2571

Abstract

In order to explore the influence of the types of waste gypsum on the properties of alkali slag cement, fluorogypsum (FG) and flue-gas desulfurization (FGD) gypsum were comparatively investigated. Moreover, the action mechanisms of FG and FGD gypsum on the properties of alkali [...] Read more.

In order to explore the influence of the types of waste gypsum on the properties of alkali slag cement, fluorogypsum (FG) and flue-gas desulfurization (FGD) gypsum were comparatively investigated. Moreover, the action mechanisms of FG and FGD gypsum on the properties of alkali slag cement were analyzed. The results show that both the FG and FGD gypsum prolonged the setting time of the alkali slag cement paste. However, the prolongation effect of FG was more pronounced than the FGD gypsum. When the compressive strength was maximum, the contents of FG and FGD gypsum were 5 and 6 wt.%, respectively. At 3 and 28 days, compared to the control sample, the compressive strengths increased by 59.3% and 24.3%, and 66.9% and 33.9%, respectively. Furthermore, the XRD, TG-DTA and SEM-EDS results showed that, with the increase in the contents of FG and FGD gypsum, ettringite was more easily produced and the hydration products were more abundant in the system. The greater the gypsum content of the paste, the less accumulated was the heat of hydration. The change of micro-structure caused by the formation of ettringite was the main reason for the difference in the properties of cement. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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16 pages, 4843 KiB

Open AccessArticle

The Effect of Incorporating Ultra-Fine Spherical Particles on Rheology and Engineering Properties of Commercial Ultra-High-Performance Grout

by Wei-Ting Lin, Wen-Que Zhao, Yi-Hua Chang, Jiann-Shi Yang and An Cheng

Crystals 2021, 11(9), 1040; https://doi.org/10.3390/cryst11091040 - 29 Aug 2021

Cited by 4 | Viewed by 2577

Abstract

In this study, ultra-fine spherical particles of silica fume and reactive ultra-fine fly ash were added to a mixture of commercial ultra-high-performance grout (UHPG) with the aim of enhancing the rheological properties, compressive strength, compactness, and permeability. This commercial UHPG study was conducted [...] Read more.

In this study, ultra-fine spherical particles of silica fume and reactive ultra-fine fly ash were added to a mixture of commercial ultra-high-performance grout (UHPG) with the aim of enhancing the rheological properties, compressive strength, compactness, and permeability. This commercial UHPG study was conducted in collaboration with Triaxis Corporation (Changsha city, Hunan province, China). A water-to-binder ratio of 0.21 and a binder-to-fine aggregates ratio of 1.17 were used as fixed parameters, and the binders were a combination of type-II Portland cement, sulphoaluminate cement, silica fume, and reactive ultra-fine fly ash (RUFA). Polycarboxylate superplasticizer powder was used to control the rheology. The results revealed excellent compressive strength, volume stability, and resistance to chloride penetration. Mercury intrusion porosimetry and scanning electron microscopy tests revealed that the medium-sized RUFA particles with small silica fume particles completely filled the spaces between large cement particles to achieve optimal densification. This mixture also produced dense hydration and calcium-silicate-hydrates colloids, which filled the microstructures of the UHPG resulting in excellent engineering properties and durability. This commercially available UHPG mix responded to excellent compressive strengths approaching 120 MPa and exhibited good workability with a loss of slump-flow rate up to 33% after 60 min. It also exhibited very low abrasion resistance (0.5%), stable shrinkage and expansion rates (stabilization over 10 days), very low chloride diffusion coefficient (less than 0.1 × 10⁻¹⁴ m²/s) with a denser microstructure. This commercial UHPG (UHPG-120) has been developed to meet the needs of the market. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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21 pages, 7998 KiB

Open AccessArticle

Effect of Ultrafine Additives on the Morphology of Cement Hydration Products

by Grigory Yakovlev, Rostislav Drochytka, Gintautas Skripkiūnas, Larisa Urkhanova, Irina Polyanskikh, Igor Pudov, Ekaterina Karpova, Zarina Saidova and Ali E. M. M. Elrefai

Crystals 2021, 11(8), 1002; https://doi.org/10.3390/cryst11081002 - 22 Aug 2021

Cited by 9 | Viewed by 3120

Abstract

The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of [...] Read more.

The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of the research, the modification of ordinary Portland cement was performed by the suspension of multi-walled carbon nanotubes (MWCNTs), carbon black (CB) paste, and silica fume (SF). Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, thermal analysis, and Fourier-transform infrared (FTIR) spectroscopy were used to study cement hydration products. The morphology of hardened cement paste depends on the chemical reactivity of additives, their geometry, and their genesis. The action mechanism of the inert carbon-based additives and pozzolanic silica fume were considered. The cement hydration products formed in the process of modification by both types of ultrafine additives are described. In the case of the modification of cement paste by inert MWCNTs and CB paste, the formation of cement hydration products on their surface without strong adhesion was observed, whereas in the case of the addition of SF separately and together with MWCNTs, the strong adhesion of additives and cement hydration products was noted. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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21 pages, 7369 KiB

Open AccessArticle

Mechanical Properties of High Strength Concrete Containing Nano SiO₂ Made from Rice Husk Ash in Southern Vietnam

by Huu-Bang Tran, Van-Bach Le and Vu To-Anh Phan

Crystals 2021, 11(8), 932; https://doi.org/10.3390/cryst11080932 - 12 Aug 2021

Cited by 11 | Viewed by 3607

Abstract

This paper presents the experimental results of the production of Nano-SiO₂ (NS) from rice husk ash (RHA) and the engineering properties of High Strength Concrete (HSC) containing various NS contents. Firstly, the mesoporous silica nanoparticles were effectively modulated from RHA using NaOH [...] Read more.

This paper presents the experimental results of the production of Nano-SiO₂ (NS) from rice husk ash (RHA) and the engineering properties of High Strength Concrete (HSC) containing various NS contents. Firstly, the mesoporous silica nanoparticles were effectively modulated from RHA using NaOH solution, and subsequently precipitated with HCl solution until the pH value reached 3. The optimum synthesis for the manufacture of SiO₂ nanoparticles in the weight ratio of RHA/NaOH was 1:2.4, and the product was calcined at 550 °C for 2 h. The EDX, XRD, SEM, TEM, FT-IR, and BET techniques were used to characterize the NS products. Results revealed that the characteristics of the obtained NS were satisfactory for civil engineering materials. Secondly, the HSC was manufactured with the aforementioned NS contents. NS particles were added to HSC at various replacements of 0, 0.5, 1.0, 1.5, 2.0, and 2.5% by the mass of the binder. The water-to-binder ratio was remained at 0.3 for all mixes. The specimens were cured for 3, 7, 28, 25 days under 25 ± 2 °C and a relative humidity of 95% before testing compressive and flexural strengths. Chloride ion permeability was investigated at 28 and 56 days. Results indicated that the addition of NS dramatically enhanced compressive strength, flexural strength, chloride ion resistance, and reduced chloride ion permeability compared to control concrete. The optimal NS content was found at 1.5%, which yielded the highest strength and lowest chloride ion permeability. Next, the development of flexural and compressive strengths with an age curing of 3–28 days can be analytically described by a logarithmic equation with R² ≥ 0.74. The ACI code was used, and the compressive strength at t-day was determined based on 28 days with R² ≥ 0.95. The study is expected to solve the redundancy of waste RHA in southern Vietnam by making RHA a helpful additive when producing high-strength concrete and contributing meaningfully to a sustainable environment. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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14 pages, 5153 KiB

Open AccessArticle

Synergistic Use of Fly Ash and Silica Fume to Produce High-Strength Self-Compacting Cementitious Composites

by Muhammad Tausif Arshad, Saeed Ahmad, Anwar Khitab and Asad Hanif

Crystals 2021, 11(8), 915; https://doi.org/10.3390/cryst11080915 - 5 Aug 2021

Cited by 15 | Viewed by 3518

Abstract

High-performance cementitious composites with self-compacting characteristics are gaining due importance in meeting the challenges of the modern world. This experimental study deals with developing high-strength self-compacting cement mortar composites containing a binary blend of silica fume and fly ash. Seven specimens series were [...] Read more.

High-performance cementitious composites with self-compacting characteristics are gaining due importance in meeting the challenges of the modern world. This experimental study deals with developing high-strength self-compacting cement mortar composites containing a binary blend of silica fume and fly ash. Seven specimens series were prepared with fly ash (FA), ranging from 17.5% to 25%, and silica fume (SF), from 1.25% to 7.5% of the cement mass. The control specimen powder content consists of 80% ordinary portland cement (OPC), 20% FA, and 0% SF; in the remaining six series of specimens, OPC is kept constant, whereas FA is reduced by 1% and SF is increased by 1% subsequently. Rheological behavior, mechanical properties, and microstructural characteristics of the developed high-performance composites were evaluated. The optimum binary blend for achieving the maximum flow spread and flow rate of the cement mortar is reported as 80% FA and 20% SF. For superior mechanical characteristics, optimum powder content was found as 80% OPC, 17.5% FA, and 2.5% SF. Using the proposed binary blend for construction applications will produce high-strength composites and promote sustainable development due to the use of industrial wastes as OPC replacement. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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9 pages, 1669 KiB

Open AccessCommunication

X-ray Diffraction of Alkali-Activated Materials with Cement By-Pass Dust

by Barbara Vojvodíková, Lukáš Procházka and Jana Boháčová

Crystals 2021, 11(7), 782; https://doi.org/10.3390/cryst11070782 - 5 Jul 2021

Cited by 4 | Viewed by 2460

Abstract

Alkali-activated materials are alternative building binders, where secondary raw materials are processed. The possibility of using landfilled waste materials in the building industry increases their potential application in construction practice, and they are therefore subject to extensive research, especially in recent years. This [...] Read more.

Alkali-activated materials are alternative building binders, where secondary raw materials are processed. The possibility of using landfilled waste materials in the building industry increases their potential application in construction practice, and they are therefore subject to extensive research, especially in recent years. This paper briefly summarizes the interesting results of an experiment aimed at verifying the possibility of applying cement by-pass dust (CBPD) in the preparation of alkali-activated materials. The research was focused on the possibilities of using these wastes for the preparation of small elements of garden architecture. This work also briefly summarized the interesting results of an experiment aimed at verifying the possibility of applying cement by-pass dust (CBPD) in the preparation of alkali-activated materials. In the experiment, a mixture of blast furnace granulated slag, fly ash and cement by-pass dust was alkali activated with sodium metasilicate. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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26 pages, 8184 KiB

Open AccessArticle

Effects of Recycled Fine Aggregates and Inorganic Crystalline Materials on the Strength and Pore Structures of Cement-Based Composites

by Sung-Ching Chen, Si-Yu Zou and Hui-Mi Hsu

Crystals 2021, 11(6), 587; https://doi.org/10.3390/cryst11060587 - 23 May 2021

Cited by 7 | Viewed by 2286

Abstract

Concrete is porous; the partial pores in the internal structure of concrete are generated by hydration products, such as calcium hydroxide, dissolved in water. External harmful substances in the form of gases or aqueous solutions can penetrate concrete. The destruction of the internal [...] Read more.

Concrete is porous; the partial pores in the internal structure of concrete are generated by hydration products, such as calcium hydroxide, dissolved in water. External harmful substances in the form of gases or aqueous solutions can penetrate concrete. The destruction of the internal structure of concrete leads to problems such as shortening of the service life of concrete as well as the corrosion and poor durability of steel. To improve the pore structure of concrete, a material can be added to concrete mixtures to cause the secondary hydration of the hydration products of cement. This reaction is expected to reduce the pore volume and increase the density of concrete. For existing concrete structures, inorganic crystalline materials can be used to protect the surface and reduce the intrusion of external harmful substances. In this study, the water–binder ratio was 0.4 and 0.6. Three inorganic crystalline materials and recycled fine aggregates (0%, 10%, 20%, and 30% replacement of natural aggregates by weight) were used in the same cement-based composites. The results indicated that all specimens had a high total charge-passed value, and inorganic crystalline material C provided superior protection for green cement-based composites. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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13 pages, 3784 KiB

Open AccessArticle

Mechanical Properties of Glass-Based Geopolymers Affected by Activator and Curing Conditions under Optimal Aging Conditions

by Tai-An Chen

Crystals 2021, 11(5), 502; https://doi.org/10.3390/cryst11050502 - 2 May 2021

Cited by 5 | Viewed by 1916

Abstract

Inorganic polymeric materials react slowly at room temperature and therefore, usually require high-temperature curing. This study determined the correlation between temperature and duration in high-temperature curing. The results revealed optimal values for each alkali equivalent of an activator (weight ratio of Na₂ [...] Read more.

Inorganic polymeric materials react slowly at room temperature and therefore, usually require high-temperature curing. This study determined the correlation between temperature and duration in high-temperature curing. The results revealed optimal values for each alkali equivalent of an activator (weight ratio of Na₂O/glass powder), curing temperature, and curing duration. Increasing the curing duration and curing temperature had positive effects when the alkali equivalent was lower than the optimal percentage. However, over-curing resulted in the visible cracking of the specimens. Furthermore, despite being initially high, the compressive strength of specimens gradually diminished after standing in air. To ensure the durability of glass-based geopolymers, the curing temperature and duration should not exceed 70 °C, and 1 day, respectively. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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13 pages, 3096 KiB

Open AccessArticle

Standardized Procedure of Measuring the pH Value of Cement Matrix Material by Ex-Situ Leaching Method (ESL)

by Wei-Chien Wang, Wei-Hsing Huang, Ming-Yu Lee, Hoang Trung Hieu Duong and Ya-Hui Chang

Crystals 2021, 11(4), 436; https://doi.org/10.3390/cryst11040436 - 17 Apr 2021

Cited by 13 | Viewed by 3708

Abstract

According to the Spanish National Research Council (CSIC) report, the ex-situ leaching method (ESL) is more appropriate and accurate than other methods for measuring pH value in terms of repeatability and reproducibility. In this study, the ESL method was used to measure the [...] Read more.

According to the Spanish National Research Council (CSIC) report, the ex-situ leaching method (ESL) is more appropriate and accurate than other methods for measuring pH value in terms of repeatability and reproducibility. In this study, the ESL method was used to measure the pH value of cement matrix materials. The design test process aimed to avoid underestimating the variation in pH during the process of solution stirring and pH measurement without using both argon and nitrogen to block the specimen contact with air, with good repeatability and reproducibility. This study also considered the influence of the dryness of the specimen before crushing, the size of the powder, the air-exposed specimen, the air-exposed solution, the temperature of the solution, etc. After testing and analysis, a standard procedure for detecting the pH value of cement matrix materials was established which is known as the S-ESL method. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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Review

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22 pages, 8205 KiB

Open AccessReview

Production of Biochar and Its Potential Application in Cementitious Composites

by Anwar Khitab, Sajjad Ahmad, Riaz Akhtar Khan, Muhammad Tausif Arshad, Waqas Anwar, Junaid Tariq, Ali Sikandar Rasheed Khan, Raja Bilal Nasar Khan, Affan Jalil and Zeesshan Tariq

Crystals 2021, 11(5), 527; https://doi.org/10.3390/cryst11050527 - 10 May 2021

Cited by 20 | Viewed by 4003

Abstract

In cement composites, usually, reinforcement is provided to restrict the crack development and their further propagation under service conditions. Typically, reinforcements utilized in cementitious composites range from nanometer scale to millimeter scale by using nano-, micro-, and millimeter-sized fibers and particles. These reinforcements [...] Read more.

In cement composites, usually, reinforcement is provided to restrict the crack development and their further propagation under service conditions. Typically, reinforcements utilized in cementitious composites range from nanometer scale to millimeter scale by using nano-, micro-, and millimeter-sized fibers and particles. These reinforcements provide the crack arresting mechanisms at the nano/microscale and restrict the growth of the cracks under service loads, but usually, the synthesis of nano/microfibers, and afterward their dispersion in the cementitious materials, pose difficulty, thus limiting their vast application in the construction industry. Carbonaceous inerts are green materials since they are capable of capturing and storing carbon, thus limiting the emission of CO₂ to the atmosphere. In the present study, a comprehensive review of the synthesis of low cost and environmentally friendly nano/micro carbonaceous inerts from pyrolysis of different agricultural/industrial wastes, and afterward, their application in the cementitious materials for producing high performance cementitious composites is presented, which have the potential to be used as nano/micro reinforcement in the cementitious matrix. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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30 pages, 35481 KiB

Open AccessReview

Rice Husk Ash-Based Concrete Composites: A Critical Review of Their Properties and Applications

by Mugahed Amran, Roman Fediuk, Gunasekaran Murali, Nikolai Vatin, Maria Karelina, Togay Ozbakkaloglu, R. S. Krishna, Ankit Kumar Sahoo, Shaswat Kumar Das and Jyotirmoy Mishra

Crystals 2021, 11(2), 168; https://doi.org/10.3390/cryst11020168 - 8 Feb 2021

Cited by 93 | Viewed by 17754

Abstract

In the last few decades, the demand for cement production increased and caused a massive ecological issue by emitting 8% of the global CO₂, as the making of 1 ton of ordinary Portland cement (OPC) emits almost a single ton of [...] Read more.

In the last few decades, the demand for cement production increased and caused a massive ecological issue by emitting 8% of the global CO₂, as the making of 1 ton of ordinary Portland cement (OPC) emits almost a single ton of CO₂. Significant air pollution and damage to human health are associated with the construction and cement industries. Consequently, environmentalists and governments have ordered to strongly control emission rates by using other ecofriendly supplemental cementing materials. Rice husk is a cultivated by-product material, obtained from the rice plant in enormous quantities. With no beneficial use, it is an organic waste material that causes dumping issues. Rice husk has a high silica content that makes it appropriate for use in OPC; burning it generates a high pozzolanic reactive rice husk ash (RHA) for renewable cement-based recyclable material. Using cost-effective and commonly obtainable RHA as mineral fillers in concrete brings plentiful advantages to the technical characteristics of concrete and to ensure a clean environment. With RHA, concrete composites that are robust, highly resistant to aggressive environments, sustainable and economically feasible can be produced. However, the production of sustainable and greener concrete composites also has become a key concern in the construction industries internationally. This article reviews the source, clean production, pozzolanic activity and chemical composition of RHA. This literature review also provides critical reviews on the properties, hardening conditions and behaviors of RHA-based concrete composites, in addition to summarizing the research recent findings, to ultimately produce complete insights into the possible applications of RHA as raw building materials for producing greener concrete composites—all towards industrializing ecofriendly buildings. Full article

(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)

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