Research

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32 pages, 8687 KiB

Open AccessArticle

Bond Strength and Fracture Toughness of Alkali Activated Self-Compacting Concrete Incorporating Metakaolin or Nanosilica

by Radhwan Alzeebaree

Sustainability 2022, 14(11), 6798; https://doi.org/10.3390/su14116798 - 01 Jun 2022

Cited by 11 | Viewed by 1655

Abstract

This study aims to evaluate the effect of nanosilica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened characteristics of slag (GGBS)-based alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes, with and without metakaolin, were prepared, as well as [...] Read more.

This study aims to evaluate the effect of nanosilica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened characteristics of slag (GGBS)-based alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes, with and without metakaolin, were prepared, as well as mixes with and without NS incorporation. In the production of A-ASCC mixes, GGBS was used as a binder material. The fresh properties of A-ASCC were determined using the L-box, V-funnel, T50 value, and slump flow tests, while the hardened properties were examined using compressive strength, bonding strength (pullout test), fracture toughness, and flexural tensile strength tests. A relationship analysis was also conducted on the A-ASCC experimental data. The experimental results showed that NS and MK had a negative effect on the fresh properties of GGBS-based A-ASCC mixtures, whereas metakaolin had a greater influence. The addition of 1% and 2% NS, on the other hand, improved the mechanical performance of the A-ASCC specimens significantly. The use of more than 2% NS had a harmful effect on the mechanical properties of A-ASCC. A 5% replacement ratio of metakaolin improved the mechanical properties of A-ASCC. The use of metakaolin at ratios of more than 5% had a negative effect on the properties of A-ASCC. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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29 pages, 8320 KiB

Open AccessArticle

Performance of Alkali-Activated Self-Compacting Concrete with Incorporation of Nanosilica and Metakaolin

by Alaa Mohammedameen

Sustainability 2022, 14(11), 6572; https://doi.org/10.3390/su14116572 - 27 May 2022

Cited by 10 | Viewed by 1824

Abstract

This study aims to analyze the influence of nano-silica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened performance of alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes with and without metakaolin were prepared, as well as mixes with [...] Read more.

This study aims to analyze the influence of nano-silica (NS) and metakaolin (MK) as binder replacement materials on the fresh and hardened performance of alkali-activated self-compacting concretes (A-ASCC). Therefore, nine A-ASCC mixes with and without metakaolin were prepared, as well as mixes with and without NS inclusion. Slump flow, v-funnel, L-box, and T50 value tests were used to investigate the fresh properties of A-ASCC. While the hardened performance was examined using compressive strength, bonding strength (pullout test), fracture toughness and flexural tensile strength tests. A relationship analysis was also conducted on the A-ASCC experimental data. The experimental results showed that the addition of NS and MK had a negative influence on the fresh characteristics of fly ash-based A-ASCC mixtures, while the addition of metakaolin had a higher effect. The addition of 1% and 2% NS, on the other hand, significantly enhanced the mechanical performance of the A-ASCC specimens. The use of more than 2% of NS had a negative influence on the mechanical properties of A-ASCC. The mechanical properties of A-ASCC were improved significantly by metakaolin replacement ratios. The A-ASCC bond strength showed the highest improvement. Furthermore, using NS and/or MK significantly increased the A-ASCC setting time and may be used to produce A-ASCC at ambient environment. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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24 pages, 72993 KiB

Open AccessArticle

Performance of Fiber-Reinforced Alkali-Activated Mortar with/without Nano Silica and Nano Alumina

by Mahmood Hunar Dheyaaldin, Mohammad Ali Mosaberpanah and Radhwan Alzeebaree

Sustainability 2022, 14(5), 2527; https://doi.org/10.3390/su14052527 - 22 Feb 2022

Cited by 16 | Viewed by 2620

Abstract

The current study is aimed to evaluate the effect of nanomaterials (nano alumina (NA) and nano silica (NS) on the mechanical and durability performance of fiber-reinforced alkali-activated mortars (FRAAM). Polypropylene fiber (PPF) was added to the binders at 0.5% and 1% of the [...] Read more.

The current study is aimed to evaluate the effect of nanomaterials (nano alumina (NA) and nano silica (NS) on the mechanical and durability performance of fiber-reinforced alkali-activated mortars (FRAAM). Polypropylene fiber (PPF) was added to the binders at 0.5% and 1% of the volume of the alkali-activated mortar (AAM). Design-expert software was used to provide the central composite design (CCD) for mix proportions. This method categorizes variables into three stages. The number of mixes was created and evaluated with varied proportions of variables. The primary binders in this experiment were 50% fly ash (FA) and 50% ground granulated blast slag (GGBS). The alkali-activated solution to binder ratio was 0.5, and the sodium hydroxide (NaOH) concentration was 12 molarity. The sodium silicate to sodium hydroxide ratio was 2.5. The cubic specimens and prisms were evaluated in an ambient atmosphere at 23 + 3 °C room temperature at the ages of 7 and 28 days. The mechanical performance of AAM was indicated through evaluation of the compressive and flexural strength, flowability, and unit weight of the alkali activator mortar. In addition, the durability performance and microstructure analysis were also evaluated. The experiments demonstrated that the AAM without fibers and nanomaterials had a higher flow rate than the other mixtures. However, the flowability of all mixtures was acceptable. The highest compressive strength was deducted through the use of 2% NA and higher flexural tensile strength was obtained for mixtures included 1% NS and 0.5% PPF. The lower water absorption was noted through the combination of 2% nano silica and 1% polypropylene fiber. Whereas, the combination of 2% nano silica, 1% nano alumina, and 0.5% polypropylene fiber had the lower sorptivity. In addition, the microstructure analysis indicated that the nanomaterials significantly improved the matrix and the porosity of the matrix was considerably reduced. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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23 pages, 24149 KiB

Open AccessArticle

Systematic Multiscale Models to Predict the Compressive Strength of Cement Paste as a Function of Microsilica and Nanosilica Contents, Water/Cement Ratio, and Curing Ages

by Chiya Y. Rahimzadeh, Ahmed Salih and Azeez A. Barzinjy

Sustainability 2022, 14(3), 1723; https://doi.org/10.3390/su14031723 - 02 Feb 2022

Cited by 10 | Viewed by 1905

Abstract

Sustainable construction requires high-strength cement materials that additives with silica content could provide the requirements as well. In this study, the effect of the micro and nano-size of silica on the compressive strength of cement paste using different mathematical approaches is investigated. This [...] Read more.

Sustainable construction requires high-strength cement materials that additives with silica content could provide the requirements as well. In this study, the effect of the micro and nano-size of silica on the compressive strength of cement paste using different mathematical approaches is investigated. This study compares the strength of preferentially replaced cement pastes with microsilica (MS) and nanosilica (NS) incorporation by proposing several mathematical models. In this study, 205 data were extracted from the literature and analyzed. The modeling processes considered the most significant variables as input variables that influence the compression strength, such as curing time, which ranged between 3 and 90 days, the water-cement ratio, which varied between 0.4 and 0.85, and NS ranged between 0 and 15%. MS ranged between 0 and 40% based on the weight of cement. In this process, the compressive strength of cement paste modified with NS and MS was modeled using four different models, including the Linear Regression Model (LR), Nonlinear Model (NLR), Multi-Logistic Regression Model (MLR), and artificial neural network (ANN). The efficiency of the suggested models was evaluated using different statistical assessments, such as the Root Mean Squared Error (RMES), the Mean Absolute Error (MAE), Scatter Index (SI), Objective value (OBJ), and coefficient of determination (R²). The findings revealed that the ANN model conducted better performance for predicting compressive strength for cement paste than the other models based on the statistical assessment. In addition, based on the statistical assessment of the sensitivity of parameters, NS had more of an effect on the compressive strength of cement paste, with 6.3% more than MS. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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26 pages, 9295 KiB

Open AccessArticle

Multiple Analytical Models to Evaluate the Impact of Carbon Nanotubes on the Electrical Resistivity and Compressive Strength of the Cement Paste

by Nzar Shakr Piro, Ahmed Salih Mohammed and Samir Mustafa Hamad

Sustainability 2021, 13(22), 12544; https://doi.org/10.3390/su132212544 - 13 Nov 2021

Cited by 18 | Viewed by 2541

Abstract

Cement paste is the most common construction material being used in the construction industry. Nanomaterials are the hottest topic worldwide, which affect the mechanical properties of construction materials such as cement paste. Cement pastes containing carbon nanotubes (CNTs) are piezoresistive intelligent materials. The [...] Read more.

Cement paste is the most common construction material being used in the construction industry. Nanomaterials are the hottest topic worldwide, which affect the mechanical properties of construction materials such as cement paste. Cement pastes containing carbon nanotubes (CNTs) are piezoresistive intelligent materials. The electrical resistivity of cementitious composites varies with the stress conditions under static and dynamic loads as carbon nanotubes are added to the cement paste. In cement paste, electrical resistivity is one of the most critical criteria for structural health control. Therefore, it is essential to develop a reliable mathematical model for predicting electrical resistivity. In this study, four different models—including the nonlinear regression model (NLR), linear regression model (LR), multilinear regression model (MLR), and artificial neural network model (ANN)—were proposed to predict the electrical resistivity of cement paste modified with carbon nanotube. Furthermore, the correlation between the compressive strength of cement paste and the electrical resistivity model has also been proposed in this study and compared with models in the literature. In this respect, 116 data points were gathered and examined to develop the models, and 56 data points were collected for the proposed correlation model. Most critical parameters influencing the electrical resistivity of cement paste were considered during the modeling process—i.e., water to cement ratio ranged from 0.2 to 0.485, carbon nanotube percentage varied from 0 to 1.5%, and curing time ranged from 1 to 180 days. The electrical resistivity of cement paste with a very large number ranging from 0.798–1252.23 Ω.m was reported in this study. Furthermore, various statistical assessments such as coefficient of determination (R2), mean absolute error (MAE), root mean square error (RMSE), scatter index (SI), and OBJ were used to investigate the performance of different models. Based on statistical assessments—such as SI, OBJ, and R2—the output results concluded that the artificial neural network ANN model performed better at predicting electrical resistivity for cement paste than the LR, NLR, and MLR models. In addition, the proposed correlation model gives better performance based on R2, RMSE, MAE, and SI for predicting compressive strength as a function of electrical resistivity compared to the models proposed in the literature. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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16 pages, 2343 KiB

Open AccessEditor’s ChoiceArticle

Predicting the Compressive Strength of Rubberized Concrete Using Artificial Intelligence Methods

by Amedeo Gregori, Chiara Castoro and Giri Venkiteela

Sustainability 2021, 13(14), 7729; https://doi.org/10.3390/su13147729 - 11 Jul 2021

Cited by 16 | Viewed by 2371

Abstract

In this study, support vector machine (SVM) and Gaussian process regression (GPR) models were employed to analyse different rubbercrete compressive strength data collected from the literature. The compressive strength data at 28 days ranged from 4 to 65 MPa in reference to rubbercrete [...] Read more.

In this study, support vector machine (SVM) and Gaussian process regression (GPR) models were employed to analyse different rubbercrete compressive strength data collected from the literature. The compressive strength data at 28 days ranged from 4 to 65 MPa in reference to rubbercrete mixtures, where the fine aggregates (sand fraction) were substituted with rubber aggregates in a range from 0% to 100% of the volume. It was observed that the GPR model yielded good results compared to the SVM model in rubbercrete strength prediction. Two strength reduction factor (SRF) equations were developed based on the GPR model results. These SRF equations can be used to estimate the compressive strength reduction in rubbercrete mixtures; the equations are provided. A sensitivity analysis was also performed to evaluate the influence of the w/c ratio on the compressive strength of the rubbercrete mixtures. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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17 pages, 34849 KiB

Open AccessArticle

Sustainable Use of Waste Polypropylene Fibres to Enhance the Abrasion and Skid Resistance of Two-Stage Concrete

by Rayed Alyousef

Sustainability 2021, 13(9), 5200; https://doi.org/10.3390/su13095200 - 06 May 2021

Cited by 2 | Viewed by 1772

Abstract

Two-stage concrete (TSC), also known as prepacked aggregate concrete (PAC), differs from traditional concrete in terms of site application and manufacturing process. Although this type of concrete is not a replacement for conventional concrete applications, it is an ideal option for unusual and [...] Read more.

Two-stage concrete (TSC), also known as prepacked aggregate concrete (PAC), differs from traditional concrete in terms of site application and manufacturing process. Although this type of concrete is not a replacement for conventional concrete applications, it is an ideal option for unusual and difficult placing conditions, especially for repairing existing concrete structures. In other words, this type of concrete is a newly developed concrete and made by placing and packing coarse aggregates and fibres in a designed formwork, then injecting a cement grout mixture into the free spaces between the aggregate particles using gravity or a pump device. For the mentioned system and others, concrete components used as floors or pavements must have an adequate degree of roughness during service life when exposed to skid and abrasion. Thus, this research work introduced a new concrete method (prepacked aggregates fibre-reinforced concrete—PAFRC) with high abrasion and skid resistance reinforced with waste polypropylene (PP) fibres from the carpet industry. The effects of PP fibres at 0–1% dosages on the mechanical properties, abrasion resistance, and skid resistance of PAFRC mixes were studied. The results revealed that the addition of PP fibres reduces the compressive strength of concrete mixtures. Nonetheless, the presence of PP fibres results in PAFRC mixes having higher tensile strength, abrasion resistance, and skid resistance than plain concrete. It was detected that in both grouting methods (gravity and pump), with the addition of PP fibre up to a specific dosage, the resistance against abrasion and skid was increased by about 26% compared to plain PAC mix. Additionally, the outcomes indicated that PAFRC is a promising material for applications such as pavements with high abrasion and skid resistance. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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Review

Jump to: Research

33 pages, 11195 KiB

Open AccessReview

A Review of the Combined Effect of Fibers and Nano Materials on the Technical Performance of Mortar and Concrete

by Twana Hussein, Rawaz Kurda, Mohammad Mosaberpanah and Rayed Alyousef

Sustainability 2022, 14(6), 3464; https://doi.org/10.3390/su14063464 - 16 Mar 2022

Cited by 6 | Viewed by 2025

Abstract

Nowadays, both nanomaterials and fibers have tremendous application in various industries, and they are a significant research area in the construction industry particularly. Thus, it is critical to have a comprehensive review to show the simultaneous impact of fibers and nanomaterials on the [...] Read more.

Nowadays, both nanomaterials and fibers have tremendous application in various industries, and they are a significant research area in the construction industry particularly. Thus, it is critical to have a comprehensive review to show the simultaneous impact of fibers and nanomaterials on the technical performance of different types of main construction materials such as mortar and concrete. The current work accomplishes this by providing a comprehensive review of the relevant literature on various nanomaterials and fibers through using a literate experimental database of conducted studies that have at least a type of fiber with one nanomaterial in the same mix. Accordingly, the collected data were analyzed, and they were compared to their control mixes in which no fiber and nanomaterials were used. The study majorly focuses on the effects of fibers and nanomaterials on fresh and hardened properties of produced mixes in terms of density, workability, mechanical and durability performance with consideration of microstructure and electrical resistivity as well. The study outcome provides a systematic knowledge and thorough guide to selecting and combining different fibers with nanoparticles to improve concrete/mortar performance effectively, in which not only the optimum percentage for the use of both fiber and nanomaterials are identified, but also is helpful to promote further research. Full article

(This article belongs to the Special Issue Towards Advanced Sustainable Recycled Materials and Technology)

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