Editorial

Jump to: Research

Open AccessEditorial

Durability and Sustainability of Cement and Concrete Composites

by

Jin Yang

and

Xingyang He

Materials 2023, 16(16), 5693; https://doi.org/10.3390/ma16165693 - 19 Aug 2023

Viewed by 334

Abstract

Durability and sustainability are important objectives within the development of cement and concrete composites [...] Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

Research

Jump to: Editorial

Open AccessArticle

Exploration of the Compressive Strength and Microscopic Properties of Portland Cement Taking Attapulgite and Montmorillonite Clay as an Additive

by

,

,

,

and

Materials 2023, 16(5), 1794; https://doi.org/10.3390/ma16051794 - 22 Feb 2023

Cited by 1 | Viewed by 761

Abstract

The effects of attapulgite and montmorillonite calcinated at 750 °C for 2 h as supplementary cementing materials (SCMs) on the working properties, mechanical strength, phase composition, morphology, hydration and heat release of ordinary Portland cement (OPC) were studied. The results show that pozzolanic [...] Read more.

The effects of attapulgite and montmorillonite calcinated at 750 °C for 2 h as supplementary cementing materials (SCMs) on the working properties, mechanical strength, phase composition, morphology, hydration and heat release of ordinary Portland cement (OPC) were studied. The results show that pozzolanic activity increased with time after calcination, and with the increase in content of calcined attapulgite and calcined montmorillonite, the fluidity of cement paste exhibited a downward trend. Meanwhile, the calcined attapulgite had a greater effect on the decrease in the fluidity of cement paste than calcined montmorillonite, and the maximum reduction was 63.3%. Within 28 days, the compressive strength of cement paste with calcined attapulgite and montmorillonite was higher than that of the blank group in the later stage, and the optimum dosages of calcined attapulgite and montmorillonite were 6% and 8%, respectively. In addition, the compressive strength of these samples reached 85 MPa 28 days later. The introduction of calcined attapulgite and montmorillonite increased the polymerization degree of silico-oxygen tetrahedra in C-S-H gels during cement hydration, thereby contributing to accelerating the early hydration process. In addition, the hydration peak of the samples mixed with calcined attapulgite and montmorillonite was advanced, and the peak value was lower than that of the control group. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Freeze/Thaw Resistance of Mortar with Recycled Tyre Waste at Varying Particle Sizes

by

Riccardo Maddalena

Materials 2023, 16(3), 1301; https://doi.org/10.3390/ma16031301 - 03 Feb 2023

Cited by 1 | Viewed by 1379

Abstract

There is a growing concern for finding alternative solutions to construction materials in order to minimise their environmental impact as well as enhancing their service life. This study investigated the durability of cementitious mortars prepared by replacing fine aggregate (sand) with recycled tyre [...] Read more.

There is a growing concern for finding alternative solutions to construction materials in order to minimise their environmental impact as well as enhancing their service life. This study investigated the durability of cementitious mortars prepared by replacing fine aggregate (sand) with recycled tyre shreds and crumbs, aiming at providing an alternative outlet to tyre waste disposal. Tyre shreds obtained at different particle sizes, from fibres of 0.5–5.0 mm to crumbs of 0.1–0.85 mm in diameter, were used as fine aggregate replacement at 20% by volume. The strength of the mortar samples, their thermal conductivity and their water absorption rate were tested at the age of 28 days and after 20 freeze/thaw cycles. The results showed that the mortar containing tyre crumbs at lower particle sizes resulted in negligible shrinkage, improved freeze/thaw resistance, a reduced water absorption by up to 52% and an improved thermal resistivity. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Effects of Fines Content on Durability of High-Strength Manufactured Sand Concrete

by

Sunbo Zheng

,

Jiajian Chen

and

Wenxue Wang

Materials 2023, 16(2), 522; https://doi.org/10.3390/ma16020522 - 05 Jan 2023

Cited by 2 | Viewed by 675

Abstract

Manufactured sand is one of the effective ways to alleviate the extreme shortage of natural sand in the construction industry. This paper uses granite and limestone manufactured sand to study the effect of high fines content on the durability of high-strength manufactured sand [...] Read more.

Manufactured sand is one of the effective ways to alleviate the extreme shortage of natural sand in the construction industry. This paper uses granite and limestone manufactured sand to study the effect of high fines content on the durability of high-strength manufactured sand concrete, and analyzes its influence mechanism by combining macro and micro test methods. The results show that the carbonation depth of manufactured sand concrete is the smallest when the fines content is 10%. When the fines content is less than 15%, the chloride and sulfate impermeability of concrete are improved effectively. Through macroscopic and microscopic tests, it is found that the main reason why fines can improve the durability of concrete is the filling effect. Too much fines will inhibit the hydration of cement and adversely affect the durability of concrete. Therefore, the fines content of high-strength manufactured sand concrete should be controlled within 5~15%, and the durability is the best when the fines content is 10%. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Effect of Waste Glass as Fine Aggregate on Properties of Mortar

by

,

,

,

and

Materials 2022, 15(23), 8499; https://doi.org/10.3390/ma15238499 - 29 Nov 2022

Cited by 2 | Viewed by 926

Abstract

Currently, most cities landfill most waste glass, resulting in the waste of resources and environmental pollution. Therefore, to realize the recycling of waste glass, solid waste glass was recycled and broken. Waste glass sand was prepared according to the gradation of natural river [...] Read more.

Currently, most cities landfill most waste glass, resulting in the waste of resources and environmental pollution. Therefore, to realize the recycling of waste glass, solid waste glass was recycled and broken. Waste glass sand was prepared according to the gradation of natural river sand particles and the fineness modulus screening. It was used as an alternative material to natural river sand and mixed with mortar materials with different replacements. Analysis of the mortar with different replacements (0%, 20%, 40%, 60%, 80%) was conducted by combining macro and micro tests on the change law and influence mechanism of permeability, mechanical properties, and microstructure. The results showed that: the replacement of waste glass sand effectively improved the gas permeation resistance of mortar; with the increase of replacement, the gas permeation resistance of mortar roughly showed a trend of increasing first and then decreasing. The replacement of waste glass sand at 20% can better promote cement’s hydration so that the mortar’s porosity is reduced by 16.5%. The gas permeability decreases by 57.4%; the compressive strength increases by 3%, and the elastic modulus increases by 5.9%. When the replacement rate of glass sand is 20%, the test performance of mortar is the best among the five groups. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Research on the Working Performance and the Corresponding Mechanical Strength of Polyaluminum Sulfate Early Strength Alkali-Free Liquid Accelerator Matrix Cement

by

,

,

,

and

Materials 2022, 15(22), 8086; https://doi.org/10.3390/ma15228086 - 15 Nov 2022

Cited by 3 | Viewed by 679

Abstract

Liquid accelerating agents have the advantages of simple operation and fast construction, and have become indispensable admixtures in shotcrete. However, most liquid accelerating agents in the market at present contain alkali or fluorine, which adversely affect concrete and seriously threaten the physical and [...] Read more.

Liquid accelerating agents have the advantages of simple operation and fast construction, and have become indispensable admixtures in shotcrete. However, most liquid accelerating agents in the market at present contain alkali or fluorine, which adversely affect concrete and seriously threaten the physical and mental health of workers. Therefore, in view of the above deficiencies, it is necessary to develop a new type of alkali-free fluorine-free liquid accelerating agent. In this paper, the polyaluminum sulfate early strength alkali-free liquid accelerator is prepared using polymeric aluminum sulfate, diethanolamine, magnesium sulfate heptahydrate and nano-silica. The influence of this agent on the setting time of fresh cement paste and compressive strength of the corresponding cement mortar is determined. Thermogravimetric analysis curves, X-ray diffraction and scanning electron microscopy images are obtained to investigate the mechanism. Findings show that the initial setting time and the final setting time of cement paste are 2 min 30 s and 7 min 25 s. The compressive strengths of cement mortar cured for 1 d, 28 d and 90 d are 2.4 MPa, 52.2 MPa and 54.3 MPa respectively. Additionally, the corresponding flexural strengths are 3.4 MPa, 9.8 MPa, 11.8 MPa. When the mass rate of accelerator is 7%, the mechanical strengths of cement mortar are the highest. The additions of fly ash and blast furnace slag can affect the mechanical of cement mortar mixed with accelerator. When the mass ratio of the fly ash and blast furnace slag is 15%, the mechanical strengths of cement mortar reach the highest. Moreover, the hydration heat release rate of cement is increased by the accelerator and the corresponding time of hydration heat peak is decreased by the accelerator. The accelerator can decrease the amount of needle-like hydration products and improve the compactness. The mechanical strengths are improved by consuming a large amount of Ca(OH)₂ and forming more compact hydration products. It is recommended that the optimum dosage range of the polyaluminum sulfate early strength alkali-free liquid accelerator is 7%. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Preparation and Experimental Investigations of Low-Shrinkage Commercial Concrete for Tunnel Annular Secondary Lining Engineering

by

,

,

,

,

,

,

and

Materials 2022, 15(19), 6848; https://doi.org/10.3390/ma15196848 - 02 Oct 2022

Cited by 3 | Viewed by 1024

Abstract

Secondary lining concrete is frequently used in underground tunnels. Due to the internal restriction of the annular concrete segment, micro-cracks may be caused by temperature stress and volume deformation, thus affecting the safe transportation of the tunnel. The purpose of this study is [...] Read more.

Secondary lining concrete is frequently used in underground tunnels. Due to the internal restriction of the annular concrete segment, micro-cracks may be caused by temperature stress and volume deformation, thus affecting the safe transportation of the tunnel. The purpose of this study is to provide a concrete experimental basis with low hydration heat and low shrinkage for tunnel engineering with different construction requirements. Different amounts of expansion agent (EA), shrinkage-reducing agent (SRA), and superabsorbent polymer (SAP) were considered in commercial concrete. It was found that EA elevated the degree of hydration and the hydration exothermic rate, while SRA and SAP showed the opposite regularity. SRA has the optimum shrinkage reduction performance with a 79% reduction in shrinkage, but the strength decreases significantly compared to EA and SAP groups. The effect of the combination of different shrinkage reducing components in commercial concrete is instructive for the hydration rate and shrinkage compensation in secondary lining engineering. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Heating Rate Effect on Gas Permeability and Pore Structure of Mortar under High Temperature

by

,

,

,

,

and

Materials 2022, 15(19), 6505; https://doi.org/10.3390/ma15196505 - 20 Sep 2022

Cited by 3 | Viewed by 803

Abstract

This experimental study investigated the effect of heating rate on mortar gas permeability and microstructure. The mortar was heated to three target temperatures (400 °C, 500 °C, and 600 °C) at three heating rates (5 °C/min,10 °C/min, and 15 °C/min). The variations of [...] Read more.

This experimental study investigated the effect of heating rate on mortar gas permeability and microstructure. The mortar was heated to three target temperatures (400 °C, 500 °C, and 600 °C) at three heating rates (5 °C/min,10 °C/min, and 15 °C/min). The variations of gas permeability and porosity were measured simultaneously at different confining pressures, and the changes in mortar microstructure were analyzed by NMR and SEM techniques. The results show that the porosity and gas permeability increase with an increase in temperature and heating rate. The gas permeability and porosity continue to decrease as confinement is increased due to a reduction in the pore volume. The microstructure observed by SEM indicates that the high heating rate induces some microcracks at 500 °C and 600 °C. The fractal dimension based on NMR can quantitatively characterize the complexity of the mortar pore structure and shows a quadratic decreasing relationship with gas permeability and porosity. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Effect of Temperature on the Physical Salt Attack of Cement Mortars under Repeated Partial Immersion in Sodium Sulfate Solution

by

,

,

and

Materials 2022, 15(18), 6234; https://doi.org/10.3390/ma15186234 - 08 Sep 2022

Cited by 1 | Viewed by 851

Abstract

Physical salt attack (PSA) is one of the dominant durability issues of cement-based materials, where salt crystallization pressure is the driving force inducing damage. However, research on the temperature-related deterioration behavior of cement-based materials is limited. In this study, salt-contaminated cement mortars were [...] Read more.

Physical salt attack (PSA) is one of the dominant durability issues of cement-based materials, where salt crystallization pressure is the driving force inducing damage. However, research on the temperature-related deterioration behavior of cement-based materials is limited. In this study, salt-contaminated cement mortars were rewetted at different temperatures. The assessment criteria were based on the visual appearance, weight evolution and size distribution of scaled materials, and the alterations in the microstructure were investigated by microscopy, thermal and mineralogical analyses. The results indicated that more severe damage developed at 5 °C than that at 20 °C due to the greater crystallization pressure caused by the conversion from thenardite (Na₂SO₄) to mirabilite (Na₂SO₄·10H₂O) at the lower temperature. No damage was observed at 35 °C, since the repeated dissolution and re-crystallization of thenardite were harmless for the specimens. In addition, two distinct damage patterns were observed for PSA performed at 5 °C and 20 °C, namely, granular disintegration and contour scaling. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

The Influence of CaO and MgO on the Mechanical Properties of Alkali-Activated Blast Furnace Slag Powder

by

,

,

,

,

and

Materials 2022, 15(17), 6128; https://doi.org/10.3390/ma15176128 - 03 Sep 2022

Cited by 4 | Viewed by 1094

Abstract

CaO and MgO are both reported as effective activators for blast furnace slag. However, the synergistic effect of these two components on the mechanical properties of alkali-activated blast furnace slag remains unclear. In this study, the flexural and compressive strengths of alkali-activated blast [...] Read more.

CaO and MgO are both reported as effective activators for blast furnace slag. However, the synergistic effect of these two components on the mechanical properties of alkali-activated blast furnace slag remains unclear. In this study, the flexural and compressive strengths of alkali-activated blast furnace slag powder with MgO and CaO range from 0% to 30% by the mass ratio of alkali-activated blast furnace slag powder are investigated. Moreover, the dry shrinkage rate of alkali-activated blast furnace slag powder is measured. One percent refractory fibers by volume of binder materials are added in the alkali-activated blast furnace slag. Some refractory fibers are treated with water flushing, meanwhile, some refractory fibers are directly used without any treatment. Finally, the scanning electron microscope, the thermogravimetric analysis curves and the XRD diffraction spectrums are obtained to reflect the inner mechanism of the alkali-activated blast furnace slag powder’s mechanical properties. The water-binder ratios of the alkali-activated blast furnace slag powder are 0.35 and 0.42. The curing ages are 3 d, 7 d and 28 d. The measuring temperature for the specimens ranges from 20 °C to 800 °C. Results show that the flexural and compressive strengths increase with the increased curing age, the decreased water-binder ratio and the addition of refractory fibers. The water-treated refractory fibers can improve the mechanical strengths. The mechanical strengths increase in the form of a quadratic function with the mass ratio of MgO and CaO, when the curing age is 3 d, the increasing effect is the most obvious. A higher water-binder ratio leads to an increasing the drying shrinkage rate. The activated blast furnace slag powder with CaO shows a higher drying shrinkage rate. The mechanical strengths decrease with the increasing testing temperature. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

Improvement of CO₂-Cured Sludge Ceramsite on the Mechanical Performances and Corrosion Resistance of Cement Concrete

by

,

,

,

,

and

Materials 2022, 15(16), 5758; https://doi.org/10.3390/ma15165758 - 20 Aug 2022

Cited by 3 | Viewed by 820

Abstract

The application of CO₂ curing on sludge ceramsite may improve its mechanical properties, and then increase the corresponding corrosion resistance. In this study, the influence of CO₂-cured sludge ceramsite on the strength and long-term properties of cement concrete is investigated. [...] Read more.

The application of CO₂ curing on sludge ceramsite may improve its mechanical properties, and then increase the corresponding corrosion resistance. In this study, the influence of CO₂-cured sludge ceramsite on the strength and long-term properties of cement concrete is investigated. CO₂ curing time ranges from 0 h to 2 d. The cylinder compressive strength and water absorption rate of CO₂-cured sludge ceramsite are first determined. Additionally, the flexural and compressive strengths, the chloride permeability and the freeze—thaw damage, as well as the corresponding thermal conductivity of cement concrete, are tested. Furthermore, the corrosion resistance of reinforcement inner-sludge-ceramsite cement concrete is measured. Finally, the scanning electron microscope photos of sludge ceramsite are obtained. Results show that the cylinder compressive strength of CO₂-cured sludge ceramsite is 15.1, ~34.2% higher than that of sludge ceramsite. Meanwhile, the water absorption rate of CO₂-cured sludge ceramsite is 39.6, ~82.4% higher than that of sludge ceramsite. The compressive strength and the flexural strength of cement concrete with CO₂-cured sludge ceramsite are 11.4 and 18.7, ~21.6% and ~31.5% higher than the cement concrete with sludge ceramsite, respectively. The resistance of NaCl freeze—thaw cycles, determined by comparing the mass loss rate and the loss rates of mechanical strengths, is effectively improved by CO₂ curing, while the thermal conductivity of cement concrete is decreased by CO₂ curing. The corrosion resistance of inner reinforcement is improved by the application of CO₂ curing on sludge ceramsite. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessArticle

The Corrosion Resistance of Reinforced Magnesium Phosphate Cement Reactive Powder Concrete

by

,

,

and

Materials 2022, 15(16), 5692; https://doi.org/10.3390/ma15165692 - 18 Aug 2022

Cited by 2 | Viewed by 888

Abstract

Magnesium phosphate cement-based reactive powder concrete (MPC-RPC) is a cement-based material with early strength, high strength and excellent durability. The slump flow and setting time of steel fibers reinforced MPC-RPC are investigated. Meanwhile, the flexural strength, the compressive strength, the ultrasonic velocity and [...] Read more.

Magnesium phosphate cement-based reactive powder concrete (MPC-RPC) is a cement-based material with early strength, high strength and excellent durability. The slump flow and setting time of steel fibers reinforced MPC-RPC are investigated. Meanwhile, the flexural strength, the compressive strength, the ultrasonic velocity and the electrical resistivity of specimens cured for 3 h, 1 day, 3 days and 28 days are determined. Moreover, the corresponding corrosion resistance reinforced MPC-RPC exposing to NaCl freeze-thaw (F-T) cycles and dry-wet (D-W) alternations is researched. In this study, the steel fibers used are 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% by the volume of MPC-RPC. The corrosion of the inner reinforcement is reflected using the mass loss, electrical resistivity, ultrasonic velocity, and the AC impedance spectrum. Researching findings show that the steel fibers lead to decreasing the slump flow and setting time. The flexural strength, the compressive strength and ultrasonic velocity of MPC-RPC cured for 3 h are higher than 45% of the MPC-RPC cured for 28 days. Moreover, when the MPC-RPC is cured for 7 days, the flexural strength, the compressive strength and ultrasonic velocity of MPC-RPC are higher than 85% of the specimens cured for 28 days. The electrical resistance decreases in a quadratic function as the volume ratio of steel fibers increases. The corrosion resistance of the internal reinforcement can be improved by adding steel fibers at appropriate dosages. The reinforcement inner MPC-RPC corrodes more seriously under the NaCl D-W alternations than NaCl F-T cycles. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Open AccessEditor’s ChoiceArticle

Effect of Ultrafine Fly Ash and Water Glass Content on the Performance of Phosphorus Slag-Based Geopolymer

by

,

,

,

,

,

and

Materials 2022, 15(15), 5395; https://doi.org/10.3390/ma15155395 - 05 Aug 2022

Cited by 4 | Viewed by 1072

Abstract

Phosphorus slag (PS), an industrial waste slag, has been used in geopolymers because it is rich in silicon and calcium. The poor performance of phosphorus slag-based geopolymer is due to its aluminum deficiency. In this work, low-calcium fly ash, treated by a wet-grinding [...] Read more.

Phosphorus slag (PS), an industrial waste slag, has been used in geopolymers because it is rich in silicon and calcium. The poor performance of phosphorus slag-based geopolymer is due to its aluminum deficiency. In this work, low-calcium fly ash, treated by a wet-grinding process, named wet-grinding ultrafine fly ash (WUFA) was used as an Al supplement to replace some of the phosphorus slag, and the wet-grinding, ultrafine fly ash-phosphorus slag (WUFA-PS)-based geopolymer was prepared. The effects of the substitution amount of WUFA and the activator dosage on the hydration properties, mechanical properties, pore structure and SEM of the WUFA-PS geopolymer were discussed in detail. The results indicate that WUFA and more activators contribute to the Al and high alkalinity environment, which positively induces the production of more geopolymer gels, thus releasing more heat and optimizing the pore structure of the matrix. The compressive strength increased by up to 28.1%. The enhanced performance of the WUFA-PS-based geopolymer may also arise from the filling effect and activity improvement of WUFA. This study has proved the feasibility of preparing a geopolymer by blending wet-grinding ultrafine fly ash and phosphorus slag and has provided references for the ratio and performance evaluation of WUFA-PS-based geopolymer concrete. Full article

(This article belongs to the Special Issue Durability and Sustainability of Cement and Concrete Composites)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Special Issue "Durability and Sustainability of Cement and Concrete Composites"

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (13 papers)

Editorial

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI