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Open AccessArticle

A Simplified Model for Shear Behavior of Mortar Using Biomimetic Carbonate Precipitation

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Materials 2023, 16(16), 5613; https://doi.org/10.3390/ma16165613 - 13 Aug 2023

Viewed by 524

Abstract

As a common molecule in biomineralization, L-aspartic acid (L-Asp) has been proven to be able to induce in vitro CaCO₃ precipitation, but its application in sand reinforcement has never been studied. In this study, L-Asp was employed in sand reinforcement for the [...] Read more.

As a common molecule in biomineralization, L-aspartic acid (L-Asp) has been proven to be able to induce in vitro CaCO₃ precipitation, but its application in sand reinforcement has never been studied. In this study, L-Asp was employed in sand reinforcement for the first time through the newly developed biomimetic carbonate precipitation (BCP) technique. Specimens with different number of BCP spray cycles were prepared, and a series of direct shear tests were conducted to investigate the impact of spray number on shear strength, critical displacement, and residual strength. Then a simplified power model for shear stress–displacement behavior was established and calibrated with the measured data. The results show that BCP can significantly improve the shear strength of sand. As the number of spray cycles increases, both the shear strength and residual strength increase, while the critical displacement decreases. Such variations can be described with two sigmoid models and a linear model, respectively. The simplified power model performs well in most cases, especially at higher spray numbers. This study is expected to provide a practical model for the shear behavior of BCP-treated mortar. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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Open AccessFeature PaperArticle

Lightweight SCC Development in a Low-Carbon Cementitious System for Structural Applications

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Galal Fares

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Ahmed K. El-Sayed

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Abdulrahman M. Alhozaimy

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Abdulaziz I. Al-Negheimish

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Abdulrahman S. Albidah

Materials 2023, 16(12), 4395; https://doi.org/10.3390/ma16124395 - 14 Jun 2023

Viewed by 511

Abstract

The utilization of manufactured lightweight aggregates adds another dimension to the cost of the preparation of self-compacting concrete (SCC). The common practice of adding absorption water to the lightweight aggregates before concreting leads to inaccurate calculations of the water-to-cement ratio. Moreover, the absorption [...] Read more.

The utilization of manufactured lightweight aggregates adds another dimension to the cost of the preparation of self-compacting concrete (SCC). The common practice of adding absorption water to the lightweight aggregates before concreting leads to inaccurate calculations of the water-to-cement ratio. Moreover, the absorption of water weakens this interfacial bond between aggregates and the cementitious matrix. A particular type of black volcanic rock with a vesicular texture known as scoria rocks (SR) is utilized. With an adapted sequence of additions, the occurrence of water absorption can be minimized to overcome the issue of calculating the true water content. In this study, the approach of preparing the cementitious paste first with adjusted rheology followed by the addition of fine and coarse SR aggregates enabled us to circumvent the need for adding absorption water to the aggregates. This step has improved the overall strength due to the enhanced bond between the aggregate and the cementitious matrix, rendering a lightweight SCC mix with a target compressive strength of 40 MPa at 28 days, which makes it appropriate for structural applications. Different mixes were prepared and optimized for the best cementitious system that achieved the goal of this study. The optimized quaternary cementitious system included silica fume, class F fly ash, and limestone dust as essential ingredients for low-carbon footprint concrete. The rheological properties and parameters of the optimized mix were tested, evaluated, and compared to a control mix prepared using normal-weight aggregates. The results showed that the optimized quaternary mix satisfied both fresh and hardened properties. Slump flow, T50, J-ring flow, and average V-funnel flow time were in the ranges of 790–800 mm, 3.78–5.67 s, 750–780 mm, and 9.17 s, respectively. Moreover, the equilibrium density was in the range of 1770–1800 kg/m³. After 28 days an average compressive strength of 42.7 MPa, a corresponding flexural load of over 2000 N, and a modulus of rupture of 6.2 MPa were obtained. The conclusion is then drawn that altering the sequence of mixing ingredients becomes a mandatory process with scoria aggregates to obtain high-quality lightweight concrete for structural applications. This process leads to a significant improvement in the precise control of the fresh and hardened properties, which was unachievable with the normal practice used with lightweight concrete. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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Open AccessArticle

Effect of Basalt Powder on Hydration, Rheology, and Strength Development of Cement Paste

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Materials 2022, 15(23), 8632; https://doi.org/10.3390/ma15238632 - 03 Dec 2022

Viewed by 773

Abstract

Basalt materials (e.g., basalt powder, aggregate, and fiber) are commonly used in cement-based materials. To understand the mechanism of the influence of basalt on the properties of cement-based materials (i.e., fluidity, hydration, and strength), zeta potential tests with different Ca2⁺ concentrations were [...] Read more.

Basalt materials (e.g., basalt powder, aggregate, and fiber) are commonly used in cement-based materials. To understand the mechanism of the influence of basalt on the properties of cement-based materials (i.e., fluidity, hydration, and strength), zeta potential tests with different Ca2⁺ concentrations were carried out using basalt powder (BP). It is found that BP has a weaker absorption for Ca2⁺ compared to cement and quartz particles, which is directly related to its surface chemical properties. This weak absorption has a significant influence on the rheology and early-age hydration of cement paste. Moreover, the morphology of hydrate on the surface of the material observed by scanning electron microscope (SEM) also shows that the growth of CSH on the surface of BP particles is smaller than that of cement particles, indicating that BP delays the formation of CSH. Rheological tests showed that the reduction of BP’s adsorption of calcium ions weakened the electrostatic repulsion between particles, which led to the reduction of rheological properties. The influence of BP on the strength of cement paste was studied through crack characterization and fracture observation. The results show that the interfacial strength between BP and hydration products is very weak and does not increase with the hydration process, and the chemical reaction of BP is not obvious. In addition, the substitution of BP for cement leads to a dilution effect. These factors cause the strength of cement paste to decrease. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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Open AccessArticle

Using Fumed Silica to Develop Thermal Insulation Cement for Medium–Low Temperature Geothermal Wells

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Materials 2022, 15(14), 5087; https://doi.org/10.3390/ma15145087 - 21 Jul 2022

Cited by 2 | Viewed by 1401

Abstract

During geothermal energy development, the bottom high-temperature fluid continuously exchanges heat with the upper low-temperature wellbore and the stratum during its rising process. Thermal insulation cement (TIC) can increase the outlet temperature, thus effectively reducing the heat loss of the geothermal fluid and [...] Read more.

During geothermal energy development, the bottom high-temperature fluid continuously exchanges heat with the upper low-temperature wellbore and the stratum during its rising process. Thermal insulation cement (TIC) can increase the outlet temperature, thus effectively reducing the heat loss of the geothermal fluid and improving energy efficiency. In this study, vitrified microbubbles (VMB) were screened out by conducting an orthogonal test of compressive strength (CS) and thermal conductivity (TC) on three inorganic thermal insulation materials (VMB, expanded perlite (EP), and fly-ash cenosphere (FAC)). Fumed silica (FS) was introduced into the cement with VMBs, as its significant decreasing effect on the TC. Moreover, a cement reinforcing agent (RA) and calcium hydroxide [CH] were added to further improve the CS of TIC at 90 °C. The fresh properties, CS, TC, hydration products, pore-size distribution, and the microstructure of the cement were investigated. As a result, a TIC with a TC of 0.1905 W/(m·K) and CS of 5.85 MPa was developed. The main conclusions are as follows: (1) Increasing the mass fraction of the thermal insulation material (TIM) is an effective method to reduce TC. (2) The CH content was reduced, but the C–S–H gel increased as FS content increased due to the pozzolanic reaction of the FS. (3) As the C–S–H gel is the main product of both the hydration and pozzolanic reactions, the matrix of the cement containing 60% FS and VMBs was mainly composed of gel. (4) The 10% RA improved the cement fluidity and increased the CS of TIC from 3.5 MPa to 5.85 MPa by promoting hydration. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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Open AccessArticle

Effect of Aggregate Type on Properties of Ultra-High-Strength Concrete

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Anna Szcześniak

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Jarosław Siwiński

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Adam Stolarski

Materials 2022, 15(14), 5072; https://doi.org/10.3390/ma15145072 - 21 Jul 2022

Cited by 2 | Viewed by 1365

Abstract

In this work, we present an analysis of natural fine aggregates’ influence on the properties of ultra-high-strength concrete. The reference concrete mix was made of natural sand with the addition of fly ash and microsilica. It was assumed to obtain concrete with a [...] Read more.

In this work, we present an analysis of natural fine aggregates’ influence on the properties of ultra-high-strength concrete. The reference concrete mix was made of natural sand with the addition of fly ash and microsilica. It was assumed to obtain concrete with a very high strength without the addition of fibers and without special curing conditions, ensuring the required workability of the concrete mix corresponding to the consistency of class S3. The reference concrete mix was modified by replacing sand with granite and basalt aggregate in the same fractions. Five series of concrete mixes made with CEM I 52.5R cement were tested. Experimental investigations were carried out regarding the consistency of the concrete mix, the compressive strength, the flexural strength and the water absorption by hardened concrete. A comparative analysis of the obtained results indicated significant improvement in the concrete strength after the use of basalt aggregate. The strength of the concrete series based on basalt aggregate, BC1, allowed it to be classified as ultra-high-performance concrete. Concrete based on sand, SC1, was characterized by the lowest compressive and flexural strength but obtained the best workability of the mix and the lowest water absorption. The results presented in the paper, show a significant influence of the type of aggregate used on the mechanical and physical properties of ultra-high strength concrete. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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Open AccessArticle

Prediction of the Compressive Strength for Cement-Based Materials with Metakaolin Based on the Hybrid Machine Learning Method

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Jiandong Huang

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Mengmeng Zhou

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Hongwei Yuan

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Mohanad Muayad Sabri Sabri

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Xiang Li

Materials 2022, 15(10), 3500; https://doi.org/10.3390/ma15103500 - 13 May 2022

Cited by 11 | Viewed by 1262

Abstract

Cement-based materials are widely used in construction engineering because of their excellent properties. With the continuous improvement of the functional requirements of building infrastructure, the performance requirements of cement-based materials are becoming higher and higher. As an important property of cement-based materials, compressive [...] Read more.

Cement-based materials are widely used in construction engineering because of their excellent properties. With the continuous improvement of the functional requirements of building infrastructure, the performance requirements of cement-based materials are becoming higher and higher. As an important property of cement-based materials, compressive strength is of great significance to its research. In this study, a Random Forests (RF) and Firefly Algorithm (FA) hybrid machine learning model was proposed to predict the compressive strength of metakaolin cement-based materials. The database containing five input parameters (cement grade, water to binder ratio, cement-sand ratio, metakaolin to binder ratio, and superplasticizer) based on 361 samples was employed for the prediction. In this model, FA was used to optimize the hyperparameters, and RF was used to predict the compressive strength of metakaolin cement-based materials. The reliability of the hybrid model was verified by comparing the predicted and actual values of the dataset. The importance of five variables was also evaluated, and the results showed the cement grade has the greatest influence on the compressive strength of metakaolin cement-based materials, followed by the water-binder ratio. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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Open AccessEditor’s ChoiceArticle

Effect of Alkali Salts on the Hydration Process of Belite Clinker

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Valeriia Iliushchenko

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Materials 2022, 15(10), 3424; https://doi.org/10.3390/ma15103424 - 10 May 2022

Cited by 2 | Viewed by 992

Abstract

Belite-rich cement is a low carbon footprint binder. However, its use is accompanied by a low initial rate of hydration. This can be partially eliminated by grinding to a high specific surface or through the addition of admixtures (mineralizators or activators). The influence [...] Read more.

Belite-rich cement is a low carbon footprint binder. However, its use is accompanied by a low initial rate of hydration. This can be partially eliminated by grinding to a high specific surface or through the addition of admixtures (mineralizators or activators). The influence of alkaline activators CaSO₄, Na₂SO₄ and Na₂CO₃ (in the amount of 5 wt.% related to the clinker weight) on the hydration course, as well as the quantity of hydration products in belite-rich cements, were investigated in this paper. Belite-rich clinker was laboratory-synthetized and ground together with activators to prepare various belite-rich cements. Next, the hydration kinetics and the hydrated phase assemblage were investigated using isothermal calorimetry, X-ray powder diffraction and thermogravimetric and differential thermal analyses. The use of selected admixtures allowed us to obtain belite-rich cements with higher hydraulic activity in the initial period. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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Open AccessReview

Calcium-Based Binders in Concrete or Soil Stabilization: Challenges, Problems, and Calcined Clay as Partial Replacement to Produce Low-Carbon Cement

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Angham Ali Mohammed

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Haslinda Nahazanan

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Noor Azline Mohd Nasir

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Ghasan Fahim Huseien

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Ahmed Hassan Saad

Materials 2023, 16(5), 2020; https://doi.org/10.3390/ma16052020 - 28 Feb 2023

Cited by 1 | Viewed by 1785

Abstract

Calcium-based binders, such as ordinary Portland cement (OPC) and lime (CaO), are the most common artificial cementitious materials used worldwide for concrete and soil improvement. However, using cement and lime has become one of the main concerns for engineers because they negatively affect [...] Read more.

Calcium-based binders, such as ordinary Portland cement (OPC) and lime (CaO), are the most common artificial cementitious materials used worldwide for concrete and soil improvement. However, using cement and lime has become one of the main concerns for engineers because they negatively affect the environment and economy, prompting research into alternative materials. The energy consumption involved in producing cementitious materials is high, and the subsequent CO₂ emissions account for 8% of the total CO₂ emissions. In recent years, an investigation into cement concrete’s sustainable and low-carbon characteristics has become the industry’s focus, achieved by using supplementary cementitious materials. This paper aims to review the problems and challenges encountered when using cement and lime. Calcined clay (natural pozzolana) has been used as a possible supplement or partial substitute to produce low-carbon cement or lime from 2012–2022. These materials can improve the concrete mixture’s performance, durability, and sustainability. Calcined clay has been utilized widely in concrete mixtures because it produces a low-carbon cement-based material. Owing to the large amount of calcined clay used, the clinker content of cement can be lowered by as much as 50% compared with traditional OPC. It helps conserve the limestone resources used in cement manufacture and helps reduce the carbon footprint associated with the cement industry. Its application is gradually growing in places such as Latin America and South Asia. Full article

(This article belongs to the Special Issue Advanced and Sustainable Low Carbon Cement and Concrete Materials)

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