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16 pages, 3588 KiB

Open AccessArticle

Effects of an Amphiphilic Micelle of Diblock Copolymer on Water Adsorption of Cement Paste

by Lei Dong, Fei Meng, Pan Feng, Qianping Ran, Chonggen Pan and Jianming He

Materials 2023, 16(6), 2190; https://doi.org/10.3390/ma16062190 - 9 Mar 2023

Cited by 1 | Viewed by 1223

Abstract

To reduce the inhibiting effects of polystyrene-based emulsion on the hydration process and strength development of cementitious materials, an amphiphilic diblock copolymer polystyrene-block-poly(acrylic acid) (PS-b-PAA) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and demonstrated in cement paste [...] Read more.

To reduce the inhibiting effects of polystyrene-based emulsion on the hydration process and strength development of cementitious materials, an amphiphilic diblock copolymer polystyrene-block-poly(acrylic acid) (PS-b-PAA) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and demonstrated in cement paste system for improving the resistance to water absorption without significantly reducing 28-day compressive strength. Firstly, the dissolved PS-b-PAA was added into water, and it quickly self-assembled into amphiphilic 80 nm-sized micelles with hydrophobic polystyrene-based core and hydrophilic poly(acrylic acid)-based shell. The improved dispersion compared to that of polystyrene emulsion may minimize the inhibiting effects on strength development, as the effects of PS-b-PAA micelle as hydrophobic admixtures on rheological properties, compressive strength, water absorption, hydration process, and pore structure of 28-day cement pastes were subsequently investigated. In comparison with the control sample, the saturated water absorption amount of cement pastes with 0.4% PS-b-PAA was reduced by 20%, and the 28-day compressive strength was merely reduced by 2.5%. Besides, the significantly increased hydrophobicity instead of slightly decreased porosity of cement paste with PS-b-PAA may contribute more to the reduced water adsorption characteristics. The study based on prepared PS-b-PAA micelle suggested a promising alternative strategy for fabricating polystyrene-modified concrete with reduced water absorption and unaffected compressive strength. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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16 pages, 3846 KiB

Open AccessArticle

The Preparation of a Novel Hyperbranched Antifouling Material and Application in the Protection of Marine Concrete

by Junhao Xie, Shuai Qi, Qianping Ran and Lei Dong

Materials 2022, 15(23), 8402; https://doi.org/10.3390/ma15238402 - 25 Nov 2022

Cited by 2 | Viewed by 1330

Abstract

Marine fouling on concrete has become one of the severest problems that damage the surface and even cause internal corrosion of marine concrete. Dissimilarly to the previous abuse of toxic antifoulants, developing hydrophobic waterborne antifouling materials could be regarded as one of the [...] Read more.

Marine fouling on concrete has become one of the severest problems that damage the surface and even cause internal corrosion of marine concrete. Dissimilarly to the previous abuse of toxic antifoulants, developing hydrophobic waterborne antifouling materials could be regarded as one of the most environment-friendly and potential directions to protect marine concrete. However, the insufficient hydrophobicity, antifouling, and mechanical properties limit their application. Herein, we reported a series of hybrid coatings combining hyperbranched polyglycerol (HPG) decorated waterborne fluoro silicone polyurethane (H) and HPG-grafted graphene oxide (G-HPG) that improve the hydrophobicity, antifouling, and mechanical properties. The hybrid materials were modified by the hyperbranched polyglycerol synthesized based on the anionic-ring-opening reaction between glycerol and ethylene glycol or polyethylene glycol. Remarkably, the hydrophobicity (115.19°) and antifouling properties (BSA absorption of 2.33 μg/cm² and P. tricornutum attachment of 1.289 × 10⁴ CFU/cm²) of the materials could be developed by the modification of HPG with higher generation numbers and backbone molecular weights. Moreover, the mechanical properties negligibly decreased (tensile strength decreased from 11.29 MPa to 10.49 MPa, same pencil hardness and adhesion grade as H of 2H and grade 2). The results revealed that the HPG of higher generation numbers and backbone molecular weights could benefit materials with enhanced antifouling properties and hydrophobicity. The method of hyperbranched modification can be regarded as potentially effective in developing the durability and antifouling properties of marine antifouling materials. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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12 pages, 5418 KiB

Open AccessArticle

Preparation and Properties of Different Polyether-Type Defoamers for Concrete

by Min Qiao, Jingzhi Wu, Nanxiao Gao, Guangcheng Shan, Fei Shen, Jian Chen and Bosong Zhu

Materials 2022, 15(21), 7492; https://doi.org/10.3390/ma15217492 - 25 Oct 2022

Cited by 5 | Viewed by 1989

Abstract

In this study, a series of polyether-type defoamers for concrete which consist of the same alkyl chain (hydrophobic part) but different polyether chains (hydrophilic part) was prepared, and the structure–property relationship of the defoamers was investigated for the first time. Using oleyl alcohol [...] Read more.

In this study, a series of polyether-type defoamers for concrete which consist of the same alkyl chain (hydrophobic part) but different polyether chains (hydrophilic part) was prepared, and the structure–property relationship of the defoamers was investigated for the first time. Using oleyl alcohol (OA) as the starting agent (alkyl chain), the polyether defoamers with different polyether chains were prepared by changing the amount and sequence of ethylene oxide (EO) and propylene oxide (PO) units. The properties of different defoamers were tested in aqueous solutions, and fresh and hardened mortars; the structure–property relationship of the defoamers was thus studied. The results indicated that the defoaming capacity of the polyether defoamers decreased with an increased EO amount, and the defoamers linked with both EO and PO units (PO before EO) had a stronger defoaming capacity than those linked with EO only. This study is beneficial for the development and applications of novel synthetic polyether-type defoamers for concrete. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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19 pages, 6545 KiB

Open AccessArticle

Inhibition Effect of Hydrophobic Functional Organic Corrosion Inhibitor in Reinforced Concrete

by Jinzhen Huang, Jie Hu, Jinshun Cai, Haoliang Huang, Jiangxiong Wei and Qijun Yu

Materials 2022, 15(20), 7124; https://doi.org/10.3390/ma15207124 - 13 Oct 2022

Cited by 1 | Viewed by 1294

Abstract

Using an admixed organic corrosion inhibitor is one of the most efficient strategies to enhance the corrosion resistance and durability of reinforced concrete. However, traditional admixed organic corrosion inhibitors only increase the corrosion resistance of the embedded reinforcing steel, and the optimization effect [...] Read more.

Using an admixed organic corrosion inhibitor is one of the most efficient strategies to enhance the corrosion resistance and durability of reinforced concrete. However, traditional admixed organic corrosion inhibitors only increase the corrosion resistance of the embedded reinforcing steel, and the optimization effect on the pore structure and the impermeability of concrete is very limited. In this study, in order to evaluate the corrosion-inhibition effect of a novel hydrophobic functional organic corrosion inhibitor, the adsorption behavior of a hydrophobic functional organic corrosion inhibitor and its related effect on the electrochemical behavior of the reinforcing steel was investigated. In addition, this paper further discusses the effect of a hydrophobic functional organic corrosion inhibitor on pore structure and hydrophobic properties, as well as the impermeability of concrete. The results indicated that the hydrophobic functional organic corrosion inhibitor was effectively adsorbed on the surface of the steel bar, and the higher adsorption content was relevant to the higher inhibitor dosage. On one hand, the hydrophobic functional organic corrosion inhibitor exhibited both a pore-blocking effect and a hydrophobic effect on concrete, leading to a refined pore structure and reduced capillary water absorption amount; on the other hand, the hydrophobic functional organic corrosion inhibitor exhibited an excellent corrosion-inhibition effect on the reinforcement embedded in the concrete, presenting an inhibition efficiency higher than 90% with a concentration of 4 wt.%. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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14 pages, 1823 KiB

Open AccessArticle

Synthesis and Performances of Shrinkage-Reducing Polycarboxylate Superplasticizer in Cement-Based Materials

by Shiyu Li, Xiao Liu, Yurui Xu, Guanghong Lai, Yungchin Ding, Yichen Chen, Chunlei Xia, Ziming Wang and Suping Cui

Materials 2022, 15(19), 7002; https://doi.org/10.3390/ma15197002 - 9 Oct 2022

Cited by 1 | Viewed by 1633

Abstract

Reducing or eliminating cracks caused by shrinkage of cementitious materials remains a daunting challenge for construction engineers. Drying shrinkage and autogenous shrinkage are the main shrinkage types in the service process of cement-based materials, which have a great impact on engineering applications. If [...] Read more.

Reducing or eliminating cracks caused by shrinkage of cementitious materials remains a daunting challenge for construction engineers. Drying shrinkage and autogenous shrinkage are the main shrinkage types in the service process of cement-based materials, which have a great impact on engineering applications. If cracks in concrete generate by drying or autogenous shrinkage, the mechanical properties, water resistance and durability of concrete will be also affected. It is an effective method to use chemical admixtures to inhibit the shrinkage of cement-based materials. Polycarboxylate plasticizer (PCE) is an important chemical admixture in cement-based materials and is widely used in practical engineering. It can bring great value by reducing the shrinkage effect through molecular design. Through our innovative design, a series of shrinkage-reducing polycarboxylate superplasticizers (SRPs) were synthesized, their molecular structures were confirmed by Fourier transform infrared spectroscopy (FTIR) and their molecular properties were determined by gel permeation chromatography (GPC). Furthermore, the shrinkage performances at different ages of the mortars containing the synthesized SRPs with different structures were systematically evaluated. The results showed that compared with the blank sample, the dry shrinkage rate and free shrinkage rate of the mortars containing SRP decreased by over 20% and 15%, respectively. Additionally, the shrinkage rates of the mortars containing SRP were significantly lower than that of the mortar containing conventional PCE, and moreover, the water-reducing performance was improved compared to conventional PCE. Based on the experimental results of surface tension and evaporation rate of different SRP solutions, the mechanism of the shrinkage-reducing effect was probed, as expected to provide guidance for the design and development of new shrinkage-reducing admixtures. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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12 pages, 2683 KiB

Open AccessArticle

Influence of Sulfates on Formation of Ettringite during Early C₃A Hydration

by Yong Yang, Qianqian Zhang, Xin Shu, Xiumei Wang and Qianping Ran

Materials 2022, 15(19), 6934; https://doi.org/10.3390/ma15196934 - 6 Oct 2022

Cited by 3 | Viewed by 1465

Abstract

The hydration of C₃A-gypsum systems was studied in the presence of various types of sulfates such as gypsum, hemihydrate and Na₂SO₄ in the first hour. The BET method combined with a DSC analysis enabled us to quantitatively characterize [...] Read more.

The hydration of C₃A-gypsum systems was studied in the presence of various types of sulfates such as gypsum, hemihydrate and Na₂SO₄ in the first hour. The BET method combined with a DSC analysis enabled us to quantitatively characterize the amount of precipitated ettringite and its specific surface area along the hydration. It was found that sulfates not only affected the formation rate of ettringite, but also had a significant impact on the morphology of ettringite. For all the C₃A-gypsum systems, a large part of the ettringite precipitated within the first 20 min and the specific surface area of the hydrated sample strongly increased within the first 5 min, whereas the specific surface area of ettringite gradually decreased along the C₃A hydration reaction. Incorporating a small amount of Na₂SO₄ in the C₃A-gypsum system could greatly promote the formation rate of ettringite in the first 20 min, and significantly decrease the specific surface area of ettringite. As hemihydrate was added to the C₃A-gypsum system, two processes of ettringite precipitation and gypsum precipitation occurred. The nucleation and growth process of ettringite and gypsum resulted in the complex changes in the specific surface area of the hydrated sample, which first increased at the very beginning, then decreased and, finally, increased. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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14 pages, 3223 KiB

Open AccessArticle

The Influence of Alkali-Free Shotcrete Accelerators on Early Age Hydration and Property Development within Cement Systems

by Wei Wang, Luping Zeng, Shuang Du, Min Qiao, Junsong Chen and Bosong Zhu

Materials 2022, 15(19), 6907; https://doi.org/10.3390/ma15196907 - 5 Oct 2022

Cited by 4 | Viewed by 1382

Abstract

Fluoride-containing alkali-free setting accelerators are a common type of admixture used in tunnel shotcrete but few studies in the literature focus on the effect of their fluoride compounds on the setting and hardening properties of accelerated cement paste under low environment temperatures. Tunnel [...] Read more.

Fluoride-containing alkali-free setting accelerators are a common type of admixture used in tunnel shotcrete but few studies in the literature focus on the effect of their fluoride compounds on the setting and hardening properties of accelerated cement paste under low environment temperatures. Tunnel shotcrete in cold regions or winter construction periods would be obviously influenced by low environment temperatures, especially for its fast setting and quick support applications. The objective of this work is to evaluate the early age hydration behavior of different accelerated cement pastes under 20 °C and 5 °C environment temperatures. In this study, setting time measurement, early age strength development, hydration ion leaching concentration, isothermal calorimetry, X-ray diffraction, and ESEM were performed on cement systems prepared with a non-fluoride alkali-free accelerator (aluminum sulfate solution with over 60% solid content) and a designed fluoride-containing alkali-free setting accelerator (aluminum sulfate and fluoride compound). The results showed that the fluorides obtained in alkali-free accelerators promote C3S dissolution and massive ettringite needles together with monosulfoaluminate (AFm) hydrate formation, thus leading to a quicker setting effect and low sensitivity to low environment temperatures than in non- fluoride groups. However, the rate of mechanical strength development of cement pastes hydrated within 24 h was decreased obviously when fluorine-containing alkali-free accelerator was used. This phenomenon is mainly related to the crystallization of thin-plate shape calcium fluoride (CaF₂) formations and promoted conversion of ettringite to monosulfoaluminate hydrate in the accelerating period, thus weakening the denseness of C-S-H gel and inhibiting alite further hydration. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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11 pages, 1574 KiB

Open AccessArticle

Influence of a Nano-Hydrophobic Admixture on Concrete Durability and Steel Corrosion

by Jingshun Cai, Qianping Ran, Qi Ma, Hao Zhang, Kai Liu, Yang Zhou and Song Mu

Materials 2022, 15(19), 6842; https://doi.org/10.3390/ma15196842 - 1 Oct 2022

Cited by 8 | Viewed by 1456

Abstract

Steel corrosion is major reason of the deterioration of reinforced concrete structures. Decreasing the transportation of erosion ions in concrete is one of effective methods to protect the steel from corrosion. In the present work, a novel nano-hydrophobic admixture is introduced to improve [...] Read more.

Steel corrosion is major reason of the deterioration of reinforced concrete structures. Decreasing the transportation of erosion ions in concrete is one of effective methods to protect the steel from corrosion. In the present work, a novel nano-hydrophobic admixture is introduced to improve the ion-diffusion properties and the corrosion resistance of reinforced steel. Compared with unmodified concrete, the nano-hydrophobic admixture effectively decreases the water adsorption, water evaporation, and chloride ions transport in a concrete structure, and then improved the concrete’s durability. The concrete’s water adsorption decreased more than 78%, and the initial corrosion time of reinforced steel is prolonged more than one time by treatment with the nano-hydrophobic admixture. The inhibition penetration of the medium in concrete modified by hydrophobic nanoparticles is the key to provide the protective properties of steel reinforcement from chloride erosion. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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14 pages, 2015 KiB

Open AccessArticle

Synergistic Effect of Polycarboxylate Superplasticiser and Protein Retarders in Cementitious Materials Containing Na- Montmorillonite: Effect of Addition Methods

by Zhenhe Tian, Jun Ren, Hao Li, Xusheng Wang, Yang Feng, Wei Xiong, Jialing Yang, Shengye Xu and Zengle Ren

Materials 2022, 15(19), 6614; https://doi.org/10.3390/ma15196614 - 23 Sep 2022

Cited by 2 | Viewed by 1486

Abstract

Polycarboxylate superplasticiser (PCE) is notably sensitive towards Na-Montmorillonite (Na-Mmt), an impurity generated from the manufacturing of concrete aggregate due to the chemical intercalation and poor surface adsorption. In order to improve the poor compatibility of PCE, the protein-based retarders were applied as the [...] Read more.

Polycarboxylate superplasticiser (PCE) is notably sensitive towards Na-Montmorillonite (Na-Mmt), an impurity generated from the manufacturing of concrete aggregate due to the chemical intercalation and poor surface adsorption. In order to improve the poor compatibility of PCE, the protein-based retarders were applied as the sacrificial agents, and its synergetic effects in cementitious materials containing Na-Mmt were investigated. The protein-based retarders were applied as the sacrificial agents and its synergetic effects in cementitious materials containing Na-Mmt were investigated. In addition to test rheology, minislump, and setting time, the adsorption behaviour and intercalation were characterised via Total Organic Carbon, X-ray photoelectron spectroscopy, and X-ray diffraction. The results revealed that the incorporation of protein-retarders improved the performance of PCE in terms of workability, and the rheological behaviour of cement with Na-Mmt. Moreover, compared to simultaneous addition, the application of separate addition further increased the workability and improved workability retention, with best dispersion performance obtained by prior adding the retarders, which could be due to the lessened intercalation between the layers of Na-Mmt. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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Review

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16 pages, 39126 KiB

Open AccessReview

Deformation and Cracking Resistance of MgO-Incorporated Cementitious Material: A Review

by Jinyuan Lu, Pan Feng, Hua Li and Qian Tian

Materials 2023, 16(2), 500; https://doi.org/10.3390/ma16020500 - 4 Jan 2023

Viewed by 914

Abstract

In China, MgO-based expansive agent (MEA) has been used for concrete shrinkage compensation and cracking control for over 40 years. The expansive behavior of MEA in cementitious materials could be manipulated to some extent by adjusting the calcination process of MEA and influenced [...] Read more.

In China, MgO-based expansive agent (MEA) has been used for concrete shrinkage compensation and cracking control for over 40 years. The expansive behavior of MEA in cementitious materials could be manipulated to some extent by adjusting the calcination process of MEA and influenced by the restraint condition of the matrix. It is key to investigate the factors related to deformation and cracking resistance so that the desired performance of MEA in certain concrete structures could be achieved. This paper reviews the influence of key parameters such as hydration reactivity, dosage, and calcination conditions of MEA, the water-to-binder ratio, supplementary cementitious material, aggregates, and curing conditions on the deformation and cracking resistivity of cement paste, mortar, and concrete with an MEA addition. The numerical simulation methods and deformation prediction models are then summarized and analyzed for more reasonable estimations. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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31 pages, 4966 KiB

Open AccessReview

Advances in Organic Rheology-Modifiers (Chemical Admixtures) and Their Effects on the Rheological Properties of Cement-Based Materials

by Qianqian Zhang, Jian Chen, Jiang Zhu, Yong Yang, Dongliang Zhou, Tao Wang, Xin Shu and Min Qiao

Materials 2022, 15(24), 8730; https://doi.org/10.3390/ma15248730 - 7 Dec 2022

Cited by 5 | Viewed by 2597

Abstract

Organic rheology modifiers, especially superplasticizers and viscosity-modifying admixtures (VMAs), have become key components for the workability optimization of modern concrete. The development of these admixtures is crucial to the further performance improvement of modern concrete under different casting and service conditions. Many of [...] Read more.

Organic rheology modifiers, especially superplasticizers and viscosity-modifying admixtures (VMAs), have become key components for the workability optimization of modern concrete. The development of these admixtures is crucial to the further performance improvement of modern concrete under different casting and service conditions. Many of the former reviews have summarized research advances in respect of these admixtures from chemical and material perspectives, focusing on the effects of structure and the performance. In this paper, from a rheological perspective, an overview is provided of the microscale behavior of polycarboxylate (PCE) superplasticizers and VMAs (e.g., adsorption, conformation, and bridging) in terms of the evolution of the microstructure of the paste, the effect of chemical structure on the yield stress, the apparent viscosity and thixotropy of cement-based materials, and the structure design of these admixtures. Most importantly, in addition to a general discussion with assumptions (monolayer adsorption of a “flat” conformation, with each molecule on a single particle; statistical polymer composition), special conditions (e.g., preferential adsorption, depletion effects, hydration modification effects, and the polydispersity of the polymer composition) are discussed. Newly developed admixtures, realized through regulation of the microscale behavior, and by the modification of adsorption, topological structure, and molecular frame, are introduced. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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24 pages, 97785 KiB

Open AccessReview

Bubble Evolution under the Action of Polycarboxylate and Air-Entraining Agent and Its Effects on Concrete Properties—A Review

by Shuncheng Xiang, Yansheng Tan, Yingli Gao, Zhen Jiang, Bin Liu and Wei Zeng

Materials 2022, 15(20), 7053; https://doi.org/10.3390/ma15207053 - 11 Oct 2022

Cited by 3 | Viewed by 2351

Abstract

In order to improve the performance of concrete, it is of great significance to have a better understanding the mechanism and main influencing factors of concrete bubble evolution under the action of polycarboxylate and air-entraining agents. In the present review, with respect to [...] Read more.

In order to improve the performance of concrete, it is of great significance to have a better understanding the mechanism and main influencing factors of concrete bubble evolution under the action of polycarboxylate and air-entraining agents. In the present review, with respect to the generation, growth, stability, and rupture of concrete bubbles under the action of polycarboxylate and air-entraining agents, this paper discusses the influence of bubble characteristics on concrete performance and studies bubble regulation by air-entraining agents and polycarboxylate (PCE) superplasticizer. The results show that the acid-to-ether ratio, sulfonic acid group, ester group, and the type of air entraining agent of the polycarboxylate acid structure have a significant impact on the bubbles. The bubble size, specific area, spacing factor, and bubble content have a significant impact on the rheological properties and related mechanical properties of fresh concrete and also affect the appearance quality of concrete. The problems with the experimental methods and theoretical models of concrete bubble research were analyzed, and future research ideas were put forward. Full article

(This article belongs to the Special Issue Advances of Chemical Admixtures for Modern Concrete)

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