Materials

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23 pages, 6749 KiB

Open AccessArticle

A Study of the Influence of Thermoactivated Natural Zeolite on the Hydration of White Cement Mortars

by Ventseslav Stoyanov, Vilma Petkova, Katerina Mihaylova and Maya Shopska

Materials 2024, 17(19), 4798; https://doi.org/10.3390/ma17194798 - 29 Sep 2024

Viewed by 523

One trend in the development of building materials is the partial or complete replacement of traditional materials that have a high carbon footprint with eco-friendly ecological raw materials and ingredients. In the present work, the influence of replacing cement with 10 wt% thermally [...] Read more.

One trend in the development of building materials is the partial or complete replacement of traditional materials that have a high carbon footprint with eco-friendly ecological raw materials and ingredients. In the present work, the influence of replacing cement with 10 wt% thermally activated natural zeolite on the structural and physical-mechanical characteristics of cured mortars based on white Portland cement and river sand was investigated. The phase compositions were determined by wavelength dispersive X-ray fluorescence (WD-XRF) analysis, X-ray powder diffraction (PXRD), diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS), and scanning electron microscopy (SEM), as well as thermogravimetric analysis simultaneously with differential scanning calorimetry (TG/DTG-DSC). The results show that the incorporation of zeolite increases the amount of pores accessible with mercury intrusion porosimetry by about 40%, but the measured strengths are also higher by over 13%. When these samples were aged in an aqueous environment from day 28 to day 120, the amount of pores decreased by about 10% and the compressive strength increased by nearly 15%, respectively. The microstructural analysis carried out proves that these results are due to hydration with a low content of crystal water and the realization of pozzolanic reactions that last over time. Replacing some of the white cement with thermally activated natural zeolite results in the formation of a greater variety of crystals, including new crystalline CSH and CSAH phases that allow better intergrowth and interlocking. The results of the investigations allow us to present a plausible reaction mechanism of pozzolanic reactions and of the formation of new crystal hydrate phases. This gives grounds to claim that the replacement of part of the cement with zeolite improves the corrosion resistance of the investigated building solutions against aggressive weathering. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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13 pages, 3183 KiB

Open AccessArticle

Impact of Superplasticizers on the Performance of Low-Grade Limestone-Based Cement Mixes

by Murugan Muthu, Boddapati Ganesh Kumar, Neven Ukrainczyk, Łukasz Sadowski and Eddie Koenders

Materials 2024, 17(11), 2500; https://doi.org/10.3390/ma17112500 - 22 May 2024

Viewed by 702

Abstract

Low-grade limestone (LGL) is not used to produce cement clinker, but this leftover material in cement quarries increases the water demand when used as a filler in concrete production. In this study, the effect of six commercial superplasticizers on the performance of cement [...] Read more.

Low-grade limestone (LGL) is not used to produce cement clinker, but this leftover material in cement quarries increases the water demand when used as a filler in concrete production. In this study, the effect of six commercial superplasticizers on the performance of cement mixes containing 35% LGL and 2% gypsum was investigated. The optimal doses of these superplasticizers were found in a range of different water/binder (w/b) ratios by conducting several Marsh cone and mini-slump tests. The addition of a superplasticizer with a higher active solid content produced a maximum cement flow, regardless of the w/b ratios. The LGL-based mortar samples admixed with this superplasticizer obtained a maximum compressive strength of about 36 MPa at the end of 28 days. SEM and XRD results showed the formation of a new calcium-rich mineral in their microstructure. These findings highlight the impact of the type and properties of superplasticizers on the performance of concrete mixes containing LGL as a supplementary cementitious material. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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23 pages, 12345 KiB

Open AccessArticle

Mechanism of Rapid Curing Pile Formation on Shoal Foundation and Its Bearing Characteristic

by Wei Li, Feng Liu, Yizhong Tan, Mengjun Chen, Yi Cai and Jiayu Qian

Materials 2024, 17(10), 2416; https://doi.org/10.3390/ma17102416 - 17 May 2024

Viewed by 631

Abstract

This study explores the application effect of the new non-isocyanate polyurethane curing agent on the rapid curing mechanism and bearing characteristics of piles in beach foundations. Through laboratory tests and field tests, the effects of the curing agent on the physical and mechanical [...] Read more.

This study explores the application effect of the new non-isocyanate polyurethane curing agent on the rapid curing mechanism and bearing characteristics of piles in beach foundations. Through laboratory tests and field tests, the effects of the curing agent on the physical and mechanical properties of sand were systematically analyzed, including compressive strength, shear strength, and elastic modulus, and the effects of water content and cement–sand mass ratio on the properties of sand after curing were investigated. The results show that introducing a curing agent significantly improves the mechanical properties of sand, and the cohesion and internal friction angle increase exponentially with the sand mass ratio. In addition, the increase in water content leads to a decrease in the strength of solidified sand, and the microstructure analysis reveals the change in the bonding effect between the solidified gel and the sand particles. The field static load tests of single piles and pile groups verify the effectiveness of the rapid solidification pile in beach foundations and reveal the significant influence of pile length and pile diameter on the bearing capacity. This study provides a theoretical basis and technical support for the rapid solidification and reinforcement of tidal flat foundations and provides important guidance for related engineering applications. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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34 pages, 14637 KiB

Open AccessArticle

Study on Static Mechanical Properties and Numerical Simulation of Coral Aggregate Seawater Shotcrete with Reasonable Mix Proportion

by Yuxuan Peng, Liyuan Yu, Wei Li, Tao Zhang, Linjian Ma, Dongyang Wu, Changan Wu and Linjie Zhou

Materials 2024, 17(10), 2353; https://doi.org/10.3390/ma17102353 - 15 May 2024

Viewed by 813

Abstract

This study aims to explore the static mechanical characteristics of coral aggregate seawater shotcrete (CASS) using an appropriate mix proportion. The orthogonal experiments consisting of four-factor and three-level were conducted to explore an optimal mix proportion of CASS. On a macro-scale, quasi-static compression [...] Read more.

This study aims to explore the static mechanical characteristics of coral aggregate seawater shotcrete (CASS) using an appropriate mix proportion. The orthogonal experiments consisting of four-factor and three-level were conducted to explore an optimal mix proportion of CASS. On a macro-scale, quasi-static compression and splitting tests of CASS with optimal mix proportion at various curing ages employed a combination of acoustic emission (AE) and digital image correlation (DIC) techniques were carried out using an electro-hydraulic servo-controlled test machine. A comparative analysis of static mechanical properties at different curing ages was conducted between the CASS and ordinary aggregate seawater shotcrete (OASS). On a micro-scale, the numerical specimens based on particle flow code (PFC) were subjected to multi-level microcracks division for quantitive analysis of the failure mechanism of specimens. The results show that the optimal mix proportion of CASS consists of 700 kg/m³ of cementitious materials content, a water–binder ratio of 0.45, a sand ratio of 60%, and a dosage of 8% for the accelerator amount. The tensile failure is the primary failure mechanism under uniaxial compression and Brazilian splitting, and the specimens will be closer to the brittle material with increased curing age. The Brazilian splitting failure caused by the arc-shaped main crack initiates from the loading points and propagates along the loading line to the center. Compared with OASS, the CASS has an approximately equal early and low later strength mainly because of the minerals’ filling or unfilling effect on coral pores. The rate of increase in CASS is swifter during the initial strength phase and decelerates during the subsequent stages of strength development. The failure in CASS is experienced primarily within the cement mortar and bonding surface between the cement mortar and aggregate. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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21 pages, 46062 KiB

Open AccessArticle

The Influence of the Addition of Basalt Powder on the Properties of Foamed Geopolymers

by Michał Łach, Barbara Kozub, Sebastian Bednarz, Agnieszka Bąk, Mykola Melnychuk and Adam Masłoń

Materials 2024, 17(10), 2336; https://doi.org/10.3390/ma17102336 - 14 May 2024

Cited by 2 | Viewed by 884

Abstract

Geopolymers are binder materials that are produced by a chemical reaction between silica or aluminum compounds with an alkaline activating solution. Foamed geopolymer materials are increasingly being cited as a viable alternative to popular organic insulation materials. Since the foaming process of geopolymers [...] Read more.

Geopolymers are binder materials that are produced by a chemical reaction between silica or aluminum compounds with an alkaline activating solution. Foamed geopolymer materials are increasingly being cited as a viable alternative to popular organic insulation materials. Since the foaming process of geopolymers is difficult to control, and any achievements in improving the performance of such materials are extremely beneficial, this paper presents the effect of the addition of basalt powder on the properties of foamed geopolymers. This paper presents the results of physicochemical studies of fly ash and basalt, as well as mechanical properties, thermal properties, and structure analysis of the finished foams. The scope of the tests included density tests, compressive strength tests, tests of the thermal conductivity coefficient using a plating apparatus, as well as microstructure tests through observations using light and scanning microscopy. Ground basalt was introduced in amounts ranging from 0 to 20% by mass. It was observed that the addition of basalt powder contributes to a reduction in and spheroidization of pores, which directly affect the density and pore morphology of the materials tested. The highest density of 357.3 kg/m³ was characterized by samples with a 5 wt.% basalt powder addition. Their density was 14% higher than the reference sample without basalt powder addition. Samples with 20 wt.% basalt addition had the lowest density, and the density averaged 307.4 kg/m³. Additionally, for the sample containing 5 wt.% basalt powder, the compressive strength exceeded 1.4 MPa, and the thermal conductivity coefficient was 0.1108 W/m × K. The effect of basalt powder in geopolymer foams can vary depending on many factors, such as its chemical composition, grain size, content, and physical properties. The addition of basalt above 10% causes a decrease in the significant properties of the geopolymer. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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24 pages, 10851 KiB

Open AccessArticle

Influence of TiO₂ Nanoparticles on the Physical, Mechanical, and Structural Characteristics of Cementitious Composites with Recycled Aggregates

by Carmen Teodora Florean, Horațiu Vermeșan, Timea Gabor, Bogdan Viorel Neamțu, Gyorgy Thalmaier, Andreea Hegyi, Alexandra Csapai and Adrian-Victor Lăzărescu

Materials 2024, 17(9), 2014; https://doi.org/10.3390/ma17092014 - 25 Apr 2024

Cited by 3 | Viewed by 781

Abstract

The aim of this study is to analyze the effect of the addition of TiO₂ nanoparticles (NTs) on the physical and mechanical properties, as well as the microstructural changes, of cementitious composites containing partially substituted natural aggregates (NAs) with aggregates derived from [...] Read more.

The aim of this study is to analyze the effect of the addition of TiO₂ nanoparticles (NTs) on the physical and mechanical properties, as well as the microstructural changes, of cementitious composites containing partially substituted natural aggregates (NAs) with aggregates derived from the following four recycled materials: glass (RGA), brick (RGB), blast-furnace slag (GBA), and recycled textolite waste with WEEE (waste from electrical and electronic equipment) as the primary source (RTA), in line with sustainable construction practices. The research methodology included the following phases: selection and characterization of raw materials, formulation design, experimental preparation and testing of specimens using standardized methods specific to cementitious composite mortars (including determination of apparent density in the hardened state, mechanical strength in compression, flexure, and abrasion, and water absorption by capillarity), and structural analysis using specialized techniques (scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS)). The analysis and interpretation of the results focused primarily on identifying the effects of NT addition on the composites. Results show a decrease in density resulting from replacing NAs with recycled aggregates, particularly in the case of RGB and RTA. Conversely, the introduction of TiO₂ nanoparticles resulted in a slight increase in density, ranging from 0.2% for RTA to 7.4% for samples containing NAs. Additionally, the introduction of TiO₂ contributes to improved compressive strength, especially in samples containing RTA, while flexural strength benefits from a 3–4% TiO₂ addition in all composites. The compressive strength ranged from 35.19 to 70.13 N/mm², while the flexural strength ranged from 8.4 to 10.47 N/mm². The abrasion loss varied between 2.4% and 5.71%, and the water absorption coefficient varied between 0.03 and 0.37 kg/m²m^0.5, the variations being influenced by both the nature of the aggregates and the amount of NTs added. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) analysis showed that TiO₂ nanoparticles are uniformly distributed in the cementitious composites, mainly forming CSH gel. TiO₂ nanoparticles act as nucleating agents during early hydration, as confirmed by EDS spectra after curing. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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11 pages, 4780 KiB

Open AccessArticle

Experimental Study of the Moisture Resistance of Cement Mortar Using Pozzolan Materials and Calcium Stearate

by Jang Hyun Park and Chang Bok Yoon

Materials 2024, 17(5), 1014; https://doi.org/10.3390/ma17051014 - 22 Feb 2024

Viewed by 998

Abstract

Nanosilica and diatomite are pozzolanic resources rich in SiO₂. In this study, the purpose of this study was to improve the moisture resistance of the specimen by producing a mixed material using pozzolanic materials and calcium stearate and adding it to [...] Read more.

Nanosilica and diatomite are pozzolanic resources rich in SiO₂. In this study, the purpose of this study was to improve the moisture resistance of the specimen by producing a mixed material using pozzolanic materials and calcium stearate and adding it to cement mortar while stirring. The results showed that the hydration reaction was not activated when calcium stearate adhered to the fine particles of nanosilica; it existed simply in the form of a filler inside the specimen. Diatomite, due to its atypical particles and porosity, may have greater water tightness than nanosilica because of the pozzolanic reaction in particles to which calcium stearate is not attached. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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19 pages, 5067 KiB

Open AccessArticle

Analysis of Durability of Watertight Concretes Modified with the Addition of Fly Ash

by Janina Adamus and Bogdan Langier

Materials 2023, 16(17), 5742; https://doi.org/10.3390/ma16175742 - 22 Aug 2023

Cited by 1 | Viewed by 1052

Abstract

The growing demand for watertight concrete structures is conducive to the development of research in this area, but their results are rarely published. In order to partially fill this gap, the authors of the publication present the results of research into the effect [...] Read more.

The growing demand for watertight concrete structures is conducive to the development of research in this area, but their results are rarely published. In order to partially fill this gap, the authors of the publication present the results of research into the effect of fly ash addition on the watertightness of concrete. Prior to the tests, a recipe for a concrete mix with the addition of a sealing admixture modified with fly ash was developed. The following properties were analyzed: consistency of the concrete mix, air content in the concrete mix, compressive strength of concrete, depth of penetration of water under pressure, and frost resistance of concrete for F150 level. The work meets the expectations of the construction industry with respect to the production of concrete structures resistant not only to the penetration of water into concrete but also resistant to aggressive substances dissolved in water that accelerate the destruction of concrete and corrosion of reinforcement bars. Based on the test results, it was found that the addition of fly ash to the concrete mix enhances the positive impact of the applied sealing admixture, increasing the tightness of the concrete. It reduces the depth of penetration of water under pressure and therefore increases the frost resistance of concrete. Full article

(This article belongs to the Special Issue Effect of Additives/Admixtures on the Properties of Concretes and Cementitious Composites)

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