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Open AccessArticle

Effect of Retarders on the Reactivity and Hardening Rate of Alkali-Activated Blast Furnace Slag Grouts

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Materials 2023, 16(17), 5824; https://doi.org/10.3390/ma16175824 - 25 Aug 2023

Viewed by 289

Abstract

Sodium silicate-activated slags have the potential to harden quickly, which limits their practical use in grouting and deep soil mixing works. The open time of grouts is defined as the time period when their rheological properties allow their storage, pumping, and injection into [...] Read more.

Sodium silicate-activated slags have the potential to harden quickly, which limits their practical use in grouting and deep soil mixing works. The open time of grouts is defined as the time period when their rheological properties allow their storage, pumping, and injection into the soil. In this work, the impact of the H₂O/Na₂O ratio and two acids (citric and boric acid) on the reactivity and hardening rates of slag-based grouts was studied. The H₂O/Na₂O ratio had a minimal impact on the open time but prolonged the setting time, as observed by ultrasonic characterization. Both acids were effective in delaying the structuration time, as revealed by oscillatory rheology and reaction advancement; however, they caused a decrease in the elastic modulus. Adding the acids resulted in a decrease in the pH of the medium, which may be linked to the extended open time. The analysis of the ion concentration of Ca, Si, and Al disclosed the mode of action of the two retarders. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

The Effect of Natural and Synthesised Zeolites on Cement-Based Materials Hydration and Hardened State Properties

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Giedrius Girskas

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Ina Pundienė

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Jolanta Pranckevičienė

Materials 2023, 16(16), 5608; https://doi.org/10.3390/ma16165608 - 13 Aug 2023

Viewed by 322

Abstract

The synthesis of zeolites from difficult-to-utilise waste materials facilitates the creation of more financially attractive and efficient synthetic zeolites. These can be incorporated into construction materials, resulting in a reduction in cement usage and the production of superior, clean, and sustainable construction materials. [...] Read more.

The synthesis of zeolites from difficult-to-utilise waste materials facilitates the creation of more financially attractive and efficient synthetic zeolites. These can be incorporated into construction materials, resulting in a reduction in cement usage and the production of superior, clean, and sustainable construction materials. The potential to enhance the hydration rate of fresh cement paste by substituting up to 10% of the cement with two synthetic zeolites—one commercially produced and the other synthesised from waste and natural zeolite—was explored. Due to a higher Al/Na ratio, newly sintered waste-based zeolite possesses six times higher electrical conductivity compared to industrially produced 4A zeolite and more than 20 times higher electrical conductivity compared to natural zeolite. As the sequence of this fact, substituting up to 10% of the cement with AX zeolite cement paste accelerates the maximum heat release rate time and increases the total heat by 8.5% after 48 h of hydration. The structure, compressive strength, and water absorption of the hardened cement paste depends on the Al/Na ratio, pH, and electrical conductivity values of the zeolite used. The findings revealed that AX zeolite, due to presence of mineral gibbsite, which speeds up hydration products, such as CSH development, increases the compressive strength up to 28.6% after 28 days of curing and reduces the water absorption by up to 1.5%. Newly synthesised waste-based AX zeolite is cheap because its production is based on waste materials and is mostly promising due to superior properties of created construction materials compared to the other presented zeolites. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Interaction of Nitrite Ions with Hydrated Portlandite Surfaces: Atomistic Computer Simulation Study

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Evgeny V. Tararushkin

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Vasily V. Pisarev

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Andrey G. Kalinichev

Materials 2023, 16(14), 5026; https://doi.org/10.3390/ma16145026 - 16 Jul 2023

Viewed by 524

Abstract

The nitrite admixtures in cement and concrete are used as corrosion inhibitors for steel reinforcement and also as anti-freezing agents. The characterization of the protective properties should account for the decrease in the concentration of free NO₂⁻ ions in the pores [...] Read more.

The nitrite admixtures in cement and concrete are used as corrosion inhibitors for steel reinforcement and also as anti-freezing agents. The characterization of the protective properties should account for the decrease in the concentration of free NO₂⁻ ions in the pores of cement concretes due to their adsorption. Here we applied the classical molecular dynamics computer simulation approach to quantitatively study the molecular scale mechanisms of nitrite adsorption from NaNO₂ aqueous solution on a portlandite surface. We used a new parameterization to model the hydrated NO₂⁻ ions in combination with the recently upgraded ClayFF force field (ClayFF-MOH) for the structure of portlandite. The new NO₂⁻ parameterization makes it possible to reproduce the properties of hydrated NO₂⁻ ions in good agreement with experimental data. In addition, the ClayFF-MOH model improves the description of the portlandite structure by explicitly taking into account the bending of Ca-O-H angles in the crystal and on its surface. The simulations showed that despite the formation of a well-structured water layer on the portlandite (001) crystal surface, NO₂⁻ ions can be strongly adsorbed. The nitrite adsorption is primarily due to the formation of hydrogen bonds between the structural hydroxyls on the portlandite surface and both the nitrogen and oxygen atoms of the NO₂⁻ ions. Due to that, the ions do not form surface adsorption complexes with a single well-defined structure but can assume various local coordinations. However, in all cases, the adsorbed ions did not show significant surface diffusional mobility. Moreover, we demonstrated that the nitrite ions can be adsorbed both near the previously-adsorbed hydrated Na⁺ ions as surface ion pairs, but also separately from the cations. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Preparation and Properties of Low-Carbon Foamed Lightweight Soil with High Resistance to Sulphate Erosion Environments

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Materials 2023, 16(13), 4604; https://doi.org/10.3390/ma16134604 - 26 Jun 2023

Viewed by 372

Abstract

Foamed lightweight soil (FLS) is a lightweight cementitious material containing a large number of tiny closed pores and has been widely used as a filler in places such as railways, roads and airports. However, there has been little research into the resistance of [...] Read more.

Foamed lightweight soil (FLS) is a lightweight cementitious material containing a large number of tiny closed pores and has been widely used as a filler in places such as railways, roads and airports. However, there has been little research into the resistance of FLS to sulphate attack in practical engineering applications. The performance of FLS against different sulphate erosion concentrations was studied to elucidate the engineering characteristics of using large volumes of FLS as fill material for the road base in the construction of intelligent networked vehicle test sites. The results showed that the compressive strength of FLS prepared using 30% Portland cement (C), 30% granulated blast furnace slag (GBFS), 40% fly ash (FA) and a small amount of a concrete antiseptic agent (CA) as cementitious materials reached 0.8 and 1.9 MPa at 7 and 28 d, respectively, when the wet density was about 600 kg/m³, which met the design requirements. The FLS prepared via the above-mentioned cementitious system had a low carbon emission, with a CO₂ emission reduction rate of up to 70%. It also had excellent sulphate attack resistance: the corrosion resistance coefficient of the cementitious material system reached 0.97, which was considerably better than that of C (0.83). For an erosion medium environment with SO₄²⁻ concentrations of less than 1000 mg/L (moderate), 40% GBFS or FA can be used to prepare FLS. When the concentration of SO₄²⁻ is less than 4000 mg/L (severe), 30% C, 30% GBFS and 40% FA can be used as cementitious materials, preferably in combination with an appropriate amount of CA, to prepare FLS. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Combined Effect of Ceramic Waste Powder Additives and PVA on the Structure and Properties of Geopolymer Concrete Used for Finishing Facades of Buildings

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Evgenii M. Shcherban’

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Materials 2023, 16(8), 3259; https://doi.org/10.3390/ma16083259 - 20 Apr 2023

Viewed by 878

Abstract

Currently, there is great interest in geopolymer composites as an alternative and environmentally friendly basis for compositions for restoring the facades of historical and modern buildings. Although the use of these compounds is much smaller than conventional concrete, replacing their main components with [...] Read more.

Currently, there is great interest in geopolymer composites as an alternative and environmentally friendly basis for compositions for restoring the facades of historical and modern buildings. Although the use of these compounds is much smaller than conventional concrete, replacing their main components with ecological geopolymer counterparts still has the potential to significantly reduce the carbon footprint and reduce the amount of greenhouse gas emitted into the atmosphere. The study aimed to obtain geopolymer concrete with improved physical, mechanical, and adhesive characteristics, designed to restore the finishing of building facades. Regulatory methods, chemical analysis, and scanning electron microscopy were applied. The most optimal dosages of additives of ceramic waste powder (PCW) and polyvinyl acetate (PVA) have been established, at which geopolymer concretes have the best characteristics: 20% PCW introduced into the geopolymer instead of a part of metakaolin, and 6% PVA. The combined use of PCW and PVA additives in optimal dosages provides the maximum increase in strength and physical characteristics. Compressive strength increased by up to 18%, bending strength increased by up to 17%, water absorption of geopolymer concretes decreased by up to 54%, and adhesion increased by up to 9%. The adhesion of the modified geopolymer composite is slightly better with a concrete base than with a ceramic one (up to 5%). Geopolymer concretes modified with PCW and PVA additives have a denser structure with fewer pores and microcracks. The developed compositions are applicable for the restoration of facades of buildings and structures. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

The Influence of Concrete Sludge from Residual Concrete on Fresh and Hardened Cement Paste Properties

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Edvinas Pocius

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Džigita Nagrockienė

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Ina Pundienė

Materials 2023, 16(6), 2531; https://doi.org/10.3390/ma16062531 - 22 Mar 2023

Viewed by 970

Abstract

In the concrete manufacturing industry, a large amount of waste is generated. Such waste can be utilised in the production of more sustainable products with a low carbon footprint. In this study, concrete sludge, a difficult-to-utilise waste that is obtained from residual concrete [...] Read more.

In the concrete manufacturing industry, a large amount of waste is generated. Such waste can be utilised in the production of more sustainable products with a low carbon footprint. In this study, concrete sludge, a difficult-to-utilise waste that is obtained from residual concrete by washing a concrete truck, was investigated. During washing, aggregates from the concrete mixture are separated, and the remaining insoluble fine particles combine with water to form concrete sludge. Dried and wet concrete sludge were used in the tests. Samples with different compositions were produced with dried and wet concrete sludge, cement, superplasticiser, and tap water. Seven cement pastes with different compositions were made by partially replacing cement with dried concrete sludge (0%, 5%, 10%, 15%, 20%, 25%, and 30%). In compositions with wet concrete sludge, cement was replaced by the same amounts as in the case of dried concrete sludge. The slump, setting time, and their changes with different amounts of concrete sludge were determined for fresh cement pastes. It was found that with different forms of concrete sludge, the technological properties of the mixtures change, and the setting time decreases. The density and compressive and flexural strength results were confirmed by SEM and XRD tests. The research results show that dry concrete sludge causes the deterioration of the mechanical properties of cement stone, while wet concrete sludge improves the mechanical properties of cement stone. However, it was found that replacing 5% cement with dry concrete sludge does not significantly affect the properties of hardened cement stone. In mixes with wet concrete sludge, the recommended amount of replaced cement is 10%, because the technological properties of the mixture are strongly influenced by larger amounts. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

The Effect of Milled Municipal Solid Waste Incineration Bottom Ash on Cement Hydration and Mortar Properties

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Jurgita Malaiškienė

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Edmundas Spudulis

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Rimvydas Stonys

Materials 2023, 16(6), 2528; https://doi.org/10.3390/ma16062528 - 22 Mar 2023

Viewed by 720

Abstract

Large amounts of municipal solid waste incineration bottom ash (MSWI BA) are formed worldwide, and this quantity is growing because of the establishment of new waste-to-energy plants. This waste is generally kept in landfills but can be used for the manufacturing of cementitious [...] Read more.

Large amounts of municipal solid waste incineration bottom ash (MSWI BA) are formed worldwide, and this quantity is growing because of the establishment of new waste-to-energy plants. This waste is generally kept in landfills but can be used for the manufacturing of cementitious building materials. This article analyzes the use of MSWI BA as a microfiller in cement mortars. The effects of MSWI BA on the properties of cement binder and mortar were analyzed by using them separately or in combination with other microfillers: milled quartz sand, metakaolin, milled glass, and microsilica. This article investigates the flowability of cement-based mixtures, the volume change as a result of the evolution of hydrogen gas, cement hydration, XRD, TG, the physical and mechanical properties of the mortar samples, and leaching. The addition of milled MSWI BA in cement mortars was found to significantly increase slump flow; therefore, MSWI BA can be used as a microfiller. The addition of metakaolin changed the kinetics of H₂, which evolved due to the reaction between Al and alkali, and had a positive effect on the mechanical properties of cement mortar. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

The Impact of Ions Contained in Concrete Pore Solutions on Natural Zeolites

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Przemysław Czapik

Materials 2023, 16(4), 1416; https://doi.org/10.3390/ma16041416 - 08 Feb 2023

Cited by 1 | Viewed by 796

Abstract

This article investigates the relationships between different chemical compositions of simulated cement concrete pore solutions and changes on the surface of zeolite rock with potassium clinoptilolite as its main component. The changes were studied using X-ray diffraction (XRD), thermal analysis (DTA-TG) and scanning [...] Read more.

This article investigates the relationships between different chemical compositions of simulated cement concrete pore solutions and changes on the surface of zeolite rock with potassium clinoptilolite as its main component. The changes were studied using X-ray diffraction (XRD), thermal analysis (DTA-TG) and scanning electron microscopy (SEM). Zeolite powder samples and a ground section of 16–64 mm grain were tested. The simulated pore solutions were based on Ca, Na, K hydroxides and K₂SO₄. It was found that 100% of Ca(OH)₂ in the systems could react between 7 and 180 days of hydration due to pozzolanic and side reactions. As the degree of clinoptilolite conversion increased, it became more difficult to detect it in X-ray patterns. At the same time, various microstructural changes could be observed. As a result of the reactions that occurred, hydrated calcium silicates, sulfate and carbonate compounds were formed. Potassium hydroxide had a more substantial effect on clinoptilolite reactivity than sodium hydroxide. This effect can be enhanced by the presence of SO₂³⁻ ions in the solution. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Foam Glass Granule Usage in Tile Glue Mixtures That Use a Reduced Portland Cement Amount

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Ramune Zurauskiene

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Lijana Navickiene

Materials 2023, 16(3), 1269; https://doi.org/10.3390/ma16031269 - 02 Feb 2023

Viewed by 850

Abstract

In the last few years, ceramic tiles and tiles from natural rock with higher measurements were used. A huge amount of tile glue is used for high-measurement tile gluing due to a special gluing technology, which is characterized by a thicker glue layer. [...] Read more.

In the last few years, ceramic tiles and tiles from natural rock with higher measurements were used. A huge amount of tile glue is used for high-measurement tile gluing due to a special gluing technology, which is characterized by a thicker glue layer. Due to this, a higher and higher amount of tile glue is used up during decorating. Regular tile glue mixture uses up to about 50–60% cement (according to mixture mass). In carried-out experiments, a lower amount of cement was used in tile glue mixture production (30%). Additionally, 5%, 10%, 15%, 20% and 25% of sand was replaced with small foam glass granules. These granules are made from glass waste. By using foam glass granules, lighter tile glue mixtures were produced, while reducing the cement amount can lower energy usage and CO₂ emissions into the atmosphere. The main properties of tile glue were investigated as follows: flow of mixture, density, compressive strength, bending strength, tensile-adhesive strength, slip and water absorption. The properties obtained during the research prove that newly produced tile glue mixtures fulfill all requirements given to these types of mixtures. A total of 25% of foam glass granule from filler mass can be used in tile glue production. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Life Cycle Environmental Impact Assessment and Applicability of Synthetic Resin Formwork

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Kyung-Yong Nam

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Myung-Kwan Lim

Materials 2023, 16(2), 696; https://doi.org/10.3390/ma16020696 - 10 Jan 2023

Viewed by 970

Abstract

In this study, the environmental impacts of the production and field application of synthetic resin formwork were quantitatively compared to the Euro form. The noise test results showed an average of 107.3 dB (A) for the Euro form and 99.7 dB (A) for [...] Read more.

In this study, the environmental impacts of the production and field application of synthetic resin formwork were quantitatively compared to the Euro form. The noise test results showed an average of 107.3 dB (A) for the Euro form and 99.7 dB (A) for the synthetic resin formwork. Additionally, when the number of uses was considered, the CO₂ emissions from the synthetic resin formwork were approximately 32% lower than the Euro form. Based on these results, it is expected that the use of synthetic resin formwork will reduce material production by half and reduce CO₂ emissions compared to channel formwork. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Extraction of Alkalis from Silicate Materials PART 2—Crystalline Silicate Materials

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Galyna Kotsay

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Wiktor Szewczenko

Materials 2022, 15(17), 6059; https://doi.org/10.3390/ma15176059 - 01 Sep 2022

Cited by 1 | Viewed by 595

Abstract

A feature of silicate materials is that they can exist in two antagonistic states—amorphous and crystalline. In both cases, alkalis, which are always present in chemical compositions, play an important role. A feature of alkalis in the composition of silicate materials is that [...] Read more.

A feature of silicate materials is that they can exist in two antagonistic states—amorphous and crystalline. In both cases, alkalis, which are always present in chemical compositions, play an important role. A feature of alkalis in the composition of silicate materials is that at certain stages of the synthesis of products, they play a positive role, reducing the temperature of synthesis, but worsening the properties of these products at the stage of their operation. Synthesis products should be understood as important building materials such as building glass and cement. It is known that the performance properties of glass and cement can be improved by the extraction of alkalis. In the first part of the article, the issues of extraction of alkalis in amorphous silicate materials-inorganic glasses were considered. This article presents the results of studies on the extraction process of alkalis in crystalline silicate materials-cement. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Experimental and Numerical Analysis of the Concrete Maturation Process with Additive of Phase Change Materials

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Mahmoud Hsino

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Tomasz Jankowiak

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Józef Jasiczak

Materials 2022, 15(13), 4687; https://doi.org/10.3390/ma15134687 - 04 Jul 2022

Viewed by 1141

Abstract

The article presents selected types of phase change materials (PCM) and their properties in terms of applications in various fields of science such as construction and concrete technology. The aim of the article is to present a comparative analysis between the results of [...] Read more.

The article presents selected types of phase change materials (PCM) and their properties in terms of applications in various fields of science such as construction and concrete technology. The aim of the article is to present a comparative analysis between the results of the laboratory tests and numerical simulations. The analysis contains two types of PCM (powder and in liquid), which were dosed in a hybrid system to the concrete mix. The purpose of using PCM is to allow the technological barrier to be exceeded in hot and dry climate conditions, enabling the construction of non-cracking concrete structures. The paper presents a parametric analysis of the influence of various modeling elements on the obtained results. The procedure of generating and absorbing heat caused by the applied PCM was also implemented using user subroutine into finite element code (Abaqus/Standard). The numerically obtained results are consistent with the experimental results. The presented results demonstrate that the use of PCM improves the conditions of concrete maturation by reducing the average temperature of the mixture in its entire volume. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

The Effect of Municipal Solid Waste Incineration Ash on the Properties and Durability of Cement Concrete

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Marija Vaičienė

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Elvinas Simanavičius

Materials 2022, 15(13), 4486; https://doi.org/10.3390/ma15134486 - 25 Jun 2022

Cited by 4 | Viewed by 993

Abstract

The aim of this study is to investigate the effect of municipal solid waste incineration bottom ash from a cogeneration plant on the physical and mechanical properties and durability of cement concrete. Part of the cement in concrete mixtures tested was replaced with [...] Read more.

The aim of this study is to investigate the effect of municipal solid waste incineration bottom ash from a cogeneration plant on the physical and mechanical properties and durability of cement concrete. Part of the cement in concrete mixtures tested was replaced with 0%, 3%, 6%, 9%, and 12% by weight of municipal solid waste incineration bottom ash. Concrete modified with 6% of bottom ash had a higher density (2323 kg/m³), compressive strength at 28 days (36.1 MPa), ultrasonic pulse velocity (3980 m/s), and lower water absorption rate (3.93%). The tests revealed that frost resistance, determined in all-sided testing directions, of concrete modified with 6%, 9%, and 12% of bottom ash added by weight of cement corresponds to strength grade F100. Such concrete can be used in construction works. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Use of Natural Zeolite and Glass Powder Mixture as Partial Replacement of Portland Cement: The Effect on Hydration, Properties and Porosity

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Dalius Kriptavičius

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Giedrius Girskas

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Gintautas Skripkiūnas

Materials 2022, 15(12), 4219; https://doi.org/10.3390/ma15124219 - 14 Jun 2022

Cited by 5 | Viewed by 1184

Abstract

The study investigates effect of the additive consisting of natural zeolite (clinoptilolite) and soda lime glass powder on the hydration, mechanical properties and porosity of Portland cement concrete. The effect of mineral additive on the technological, physical-mechanical properties and porosity of the mortar [...] Read more.

The study investigates effect of the additive consisting of natural zeolite (clinoptilolite) and soda lime glass powder on the hydration, mechanical properties and porosity of Portland cement concrete. The effect of mineral additive on the technological, physical-mechanical properties and porosity of the mortar was investigated by increasing the content of natural zeolite and glass powder added to the mortar up to 20% by weight of cement in increments of 5% and different particles size of natural zeolite. The mixes with the best technological and mechanical properties were identified and further studies were conducted by replacing 10% and 15% of cement with natural zeolite and soda lime glass with an average grain size of 59.3 μm, 29.0 μm or 3.6 μm of zeolite, and 29.6 μm of glass powder. The hydration process and microstructure of hardened cement paste modified with the aforementioned mineral additives was analysed by microcalorimetry, X-ray diffraction tests and thermogravimetric analysis. The optimal composition of cement paste and particle size distribution of natural zeolite were determined to achieve the higher flexural and compressive strength and lower open porosity. The mixture of mineral additives has the highest effect in terms of flexural and compressive strength and open porosity when added at the proportion 75:15:10 (cement:natural zeolite:soda lime glass) and when zeolite with an average particle size of about 3.6 μm is used Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Synthesis of High Crystallinity 1.13 nm Tobermorite and Xonotlite from Natural Rocks, Their Properties and Application for Heat-Resistant Products

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Materials 2022, 15(10), 3474; https://doi.org/10.3390/ma15103474 - 12 May 2022

Cited by 6 | Viewed by 1316

Abstract

The main measure to reduce energy losses is the usage of insulating materials. When the temperature exceeds 500 °C, silicate and ceramic products are most commonly used. In this work, high-crystallinity 1.13 nm tobermorite and xonotlite were hydrothermally synthesized from lime and Ca–Si [...] Read more.

The main measure to reduce energy losses is the usage of insulating materials. When the temperature exceeds 500 °C, silicate and ceramic products are most commonly used. In this work, high-crystallinity 1.13 nm tobermorite and xonotlite were hydrothermally synthesized from lime and Ca–Si sedimentary rock, opoka. By XRD, DSC, TG and dilatometry methods, it has been shown that 1.13 nm tobermorite becomes the predominant compound in stirred suspensions at 200 °C after 4 h of synthesis in the mixture with a molar ratio CaO/SiO₂ = 0.83. It is suitable for the production of insulating products with good physical–mechanical properties (average density < 200 kg·m⁻¹, compressive strength ~0.9 MPa) but has a limited operating temperature (up to 700 °C). Sufficiently pure xonotlite should be used to obtain materials with a higher operating temperature. Even small amounts of semi-amorphous C–S–H(I) significantly increase its linear shrinkage during firing. It has also been observed that an increase in the strength values of the samples correlated well with the increase in the size of xonotlite crystallites. The optimal technological parameters are as follows: molar ratio of mixture CaO/SiO₂ = 1.2; water/solid ratio W/S = 20.0; duration of hydrothermal synthesis at 220 °C—8 h, duration of autoclaving at 220 °C—4 h. The average density of the samples was ~180 kg·m⁻¹, the operating temperature was at least 1000 °C, and the compressive strengths exceeded 1.5 MPa. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Influence of Industrial Metakaolin Waste on Autoclaved Fiber Cement Properties Changes in Standard Fire Environment

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Materials 2022, 15(10), 3455; https://doi.org/10.3390/ma15103455 - 11 May 2022

Cited by 1 | Viewed by 911

Abstract

An investigation was conducted on the influence that industrial metakaolin waste (IMW) has on the properties of autoclaved fiber cement composition (FCC) samples. FCC samples were made from fiber cement plate’s typical components using the same proportions. In samples, IMW was used instead [...] Read more.

An investigation was conducted on the influence that industrial metakaolin waste (IMW) has on the properties of autoclaved fiber cement composition (FCC) samples. FCC samples were made from fiber cement plate’s typical components using the same proportions. In samples, IMW was used instead of cement in 10%, 20%, 30% proportions and in 50%, 100% proportions instead of ground quartz. Differential thermal analysis (DTG), thermogravimetric analysis (TGA), ultrasound pulse velocity (UPV), density, porosity and optical microscope (OM) research methods were used to identify the micro and macrostructure of samples. Mechanical properties were evaluated using flexural and compressive strength research methods. It was established that IMW was used instead of cement in fiber cement composition samples up to 10% and in fiber cement composition samples instead of ground quartz forms density microstructure structure because of Al-rich tobermorite. As a result, the flexural and compressive strength increased. Samples with higher content of IMW instead of cement had unreacted IMW and a less dense microstructure. In this case, flexural and compressive strength decreased. All FCC samples were fired in a standard fire curve (ISO 842) for 30 min. Samples of mechanical properties were established by doing flexural and compressive strength tests, and which results showed the same trends. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Study of the Course of Cement Hydration in the Presence of Waste Metal Particles and Pozzolanic Additives

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Ina Pundienė

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Jolanta Pranckevičienė

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Modestas Kligys

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Giedrius Girskas

Materials 2022, 15(8), 2925; https://doi.org/10.3390/ma15082925 - 17 Apr 2022

Cited by 1 | Viewed by 1193

Abstract

As the construction of hydrotechnical and energy facilities grows worldwide, so does the need for special heavyweight concrete. This study presents the analysis of the influence of waste-metal particle filler (WMP) on Portland cement (PC) paste and mortars with pozzolanic (microsilica and metakaolin) [...] Read more.

As the construction of hydrotechnical and energy facilities grows worldwide, so does the need for special heavyweight concrete. This study presents the analysis of the influence of waste-metal particle filler (WMP) on Portland cement (PC) paste and mortars with pozzolanic (microsilica and metakaolin) additives in terms of the hydration process, structure development, and physical–mechanical properties during 28 days of hardening. Results have shown that waste-metal particle fillers prolong the course of PC hydration. The addition of pozzolanic additives by 37% increased the total heat value and the ultrasound propagation velocity (UPV) in WMP-containing paste by 16%; however, in the paste with only WMP, the UPV is 4% lower than in the WMP-free paste. The density of waste-metal particle fillers in the free mortar was about two times lower than waste-metal particle fillers containing mortar. Due to the lower water absorption, the compressive strength of WMP-free mortar after 28 days of hardening achieved 42.1 MPa, which is about 14% higher than in mortar with waste-metal particle filler. The addition of pozzolanic additives decreased water absorption and increased the compressive strength of waste-metal particle filler containing mortar by 22%, compared to pozzolanic additive-free waste-metal particle fillers containing mortar. The pozzolanic additives facilitated a less porous matrix and improved the contact zone between the cement matrix and waste-metal particle fillers. The results of the study showed that pozzolanic additives can solve difficulties in local waste-metal particle fillers application in heavyweight concrete. The successful development of heavyweight concrete with waste-metal particle fillers and pozzolanic additives can significantly expand the possibility of creating special concrete using different local waste. The heavyweight concrete developed by using waste-metal particle fillers is suitable for being used in load balancing and in hydrotechnical foundations. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

The Effect of Active Additives and Coarse Aggregate Granulometric Composition on the Properties and Durability of Pervious Concrete

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Materials 2022, 15(3), 1035; https://doi.org/10.3390/ma15031035 - 28 Jan 2022

Cited by 6 | Viewed by 2028

Abstract

Pervious concrete (PCO) has many advantages and applications, such as water pooling reduction, noise attenuation, replenishment of groundwater reserves, etc. However, the use of pervious concrete is limited due to its low compressive strength and durability, especially as a result of portlandite leaching [...] Read more.

Pervious concrete (PCO) has many advantages and applications, such as water pooling reduction, noise attenuation, replenishment of groundwater reserves, etc. However, the use of pervious concrete is limited due to its low compressive strength and durability, especially as a result of portlandite leaching from concrete exposed to flowing water. The effects of active additives (nano SiO₂ (NS) spent catalyst generated at the fluid catalytic cracking unit (FCCCw) and paper sludge waste burned at 700 °C (PSw)) along with particle size distribution of the coarse aggregate on the properties and durability of pervious concrete were determined in the research. Active additives used in the binder were found to reduce portlandite leaching from concrete exposed to flowing water to significantly increase the resistance of concrete to freezing and thawing cycles and to increase sound absorption, compressive strength and infiltration rate. In addition, industrial waste (FCCCw and PSw) used as active additives significantly reduced the use of clinker in concrete applied in the construction of water pervious systems. The coarse aggregate size distribution had the greatest effect on the density, ultrasound pulse velocity (UPV), porosity, compressive strength and infiltration rate of pervious concrete. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessArticle

Influence of Inter-Particle Distances on the Rheological Properties of Cementitious Suspensions

by

Rajagopalan Sam Rajadurai

and

Su-Tae Kang

Materials 2021, 14(24), 7869; https://doi.org/10.3390/ma14247869 - 19 Dec 2021

Cited by 1 | Viewed by 1541

Abstract

Supplementary cementitious materials (SCMs), such as fly ash (FA), blast furnace slag (BS), and silica fume (SF), have been mostly used as a replacement for Portland cement (PC). Replacing the SCMs with cement can provide improved strength characteristics; however, their applicability depends on [...] Read more.

Supplementary cementitious materials (SCMs), such as fly ash (FA), blast furnace slag (BS), and silica fume (SF), have been mostly used as a replacement for Portland cement (PC). Replacing the SCMs with cement can provide improved strength characteristics; however, their applicability depends on the flow characteristics of the fresh mixtures. In this study, the rheological performance of cementitious suspensions in paste scale with different water-to-solid (W/S) volume ratios, varied from 1.25, 1.50, 1.75, 2.00, 2.25, to 2.50, was evaluated. As a result of the rheological tests, the yield stress and plastic viscosity of PC, FA, BS, and SF suspensions decreased as the W/S ratio increased. This study also estimated the inter-particle distances of the cementitious suspensions, and their relationship to the rheological properties was established. The inter-particle distances of the PC, FA, BS, and SF suspensions were in the ranges of 5.74~14.67 µm, 5.18~11.66 µm, 3.82~9.34 µm, and 0.107~0.27 µm, respectively. For very fine particles with a large surface area, the sensitivity to the rheological properties was high and the sensitivity was low when the particle sizes increased, indicating that the rheological properties were more sensitive to fine particles. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Open AccessEditor’s ChoiceArticle

Modification of the Structure and Properties of Lightweight Cement Composite with PVA Fibers

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Materials 2021, 14(20), 5983; https://doi.org/10.3390/ma14205983 - 11 Oct 2021

Cited by 6 | Viewed by 1364

Abstract

This study addresses the application of polyvinyl alcohol (PVA) fibers to improve the performance of lightweight cement composites with pozzolans. Blended cement mixes based on expanded glass granules were modified with PVA fibers (Type A: Ø40 µm, L = 8 mm and Type [...] Read more.

This study addresses the application of polyvinyl alcohol (PVA) fibers to improve the performance of lightweight cement composites with pozzolans. Blended cement mixes based on expanded glass granules were modified with PVA fibers (Type A: Ø40 µm, L = 8 mm and Type B: Ø200 µm, L = 12 mm). The following research methods were used to analyse the effect of the fibers on the structure of cement matrix and physical-mechanical properties of lightweight composite: SEM, XRD, DTG, calorimetry tests, and standard test methods of physical and mechanical properties. Results from the tests showed that a denser layer of hydrates was formed around the PVA fiber and the amounts of portlandite, CSH, and CASH formed in the specimens with PVA were found to be higher. PVA fibers of Type A accelerated hydration of the cement paste, slightly increased the compressive strength of the lightweight composite, but had no significant effect on the values of density, ultrasonic pulse velocity and flexural strength. The shrinkage of cement composite was significantly reduced using both types of PVA fiber and both types of PVA fibers increased the fracture energy of lightweight cement composite with expanded granules. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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Review

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Open AccessReview

Recent Advances in C-S-H Nucleation Seeding for Improving Cement Performances

by

Ana Cuesta

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Alejandro Morales-Cantero

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Angeles G. De la Torre

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Miguel A. G. Aranda

Materials 2023, 16(4), 1462; https://doi.org/10.3390/ma16041462 - 09 Feb 2023

Cited by 10 | Viewed by 1815

Abstract

Reducing cement CO₂ footprint is a societal need. This is being achieved mainly by replacing an increasing amount of Portland clinker by supplementary cementitious materials. However, this comes at a price: lower mechanical strengths at early ages due to slow pozzolanic reaction(s). [...] Read more.

Reducing cement CO₂ footprint is a societal need. This is being achieved mainly by replacing an increasing amount of Portland clinker by supplementary cementitious materials. However, this comes at a price: lower mechanical strengths at early ages due to slow pozzolanic reaction(s). This is being addressed by using accelerator admixtures. In this context, calcium silicate hydrate nucleation seeding seems to have a promising future, as it can accelerate cement and pozzolanic reactions at early ages, optimising their microstructures, without compromising late strength and durability performances. In fact, these features could even be improved. Moreover, other uses are low temperature concreting, precasting, shotconcrete, etc. Here, we focus on reviewing recent reports on calcium silicate hydrate seeding using commercially available admixtures. Current knowledge on the consequences of nucleation seeding on hydration reactions and on early and late mechanical strengths is discussed. It is noted that other features, in addition to the classic alite hydration acceleration, are covered here including the enhanced ettringite precipitation and the very efficient porosity refinement, which take place in the seeded binders. Finally, because the seeded binders seem to be denser, durability properties could also be enhanced although this remains to be properly established. Full article

(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research)

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