Preface

Hewlett, P. C.; Líška, Martin

doi:10.1016/b978-0-08-100773-0.09998-6

Cited by 27 publications

(59 citation statements)

References 0 publications

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“…The interaction between nonionic surfactant and cement particles is very weak. The interaction between cement particles and surfactant molecules leads directly to an interaction between cement particles and air bubbles, which plays a significant role in the air-entraining behavior [ 17 , 85 ]. When solid particles are attached to air bubbles, these air bubbles are strengthened.…”

Section: Resultsmentioning

confidence: 99%

Study of the Air-Entraining Behavior Based on the Interactions between Cement Particles and Selected Cationic, Anionic and Nonionic Surfactants

2020

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The essential role of the air void size distribution in air-entrained cementitious materials is widely accepted. However, how the air-entraining behavior is affected by features such as the molecular structure of air-entraining agents (AEAs), the type of solid particles, or the chemical environment of the pore solution in fresh mortars is still not well understood. Besides, methods to assess the interaction between AEAs and cement particles are limited. Thus, in this study, the air-entraining behaviors of three kinds of surfactant (cationic, anionic, and nonionic) were examined. The general working mechanisms of these surfactants were studied by zeta potential and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Results indicate that the cationic surfactant entrains improper coarse air voids due to the strong electrical interaction between air bubbles formed by the cationic surfactant and negatively charged cement particles. The anionic surfactant interacts with the positively charged part of cement particles, and thus entrains finer air voids. The interaction between the nonionic surfactant and cement particles is very weak; as a result, the nonionic surfactant entrains the finest and homogeneous air voids.

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Section: Resultsmentioning

confidence: 99%

Study of the Air-Entraining Behavior Based on the Interactions between Cement Particles and Selected Cationic, Anionic and Nonionic Surfactants

2020

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“…However, most of them focused the impact of nanomaterials on the hydration of tricalcium silicate (C 3 S) only [ 3 ], not on tricalcium aluminate (C 3 A), which is the most intense hydration mineral component in cement. Though the typical proportion of C 3 A in cement is only about 10 wt.% [ 4 ], it is the most reactive component of the Portland cement.…”

Section: Introductionmentioning

confidence: 99%

“…Compared to C 3 S, the hydration of C 3 A is significantly faster, forming calcium hydroaluminates and other phases such as calcium hydroaluminate-ferrite, commonly called AFm [ 5 ]. However, the fast reaction, often named “flash setting” [ 6 ], will reduce the workability and strength of the final products, which is usually avoided by adding gypsum [ 4 , 5 ]. The sulfate in gypsum binds C 3 A, generating sulfoaluminates instead of calcium hydroaluminates [ 7 ].…”

Section: Introductionmentioning

confidence: 99%

Hydration Characteristics of Tricalcium Aluminate in the Presence of Nano-Silica

et al. 2021

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Tricalcium aluminate (C3A) is the most reactive component of the Portland cement and its hydration has an important impact on the workability and early strength of concrete. Recently, nanomaterials such as nano-silica (nano-SiO2) have attracted much attention in cement-based materials because of its pozzolanic reactivity and the pore-filling effect. However, its influence on the hydration of C3A needs to be well understood. In this study, the hydration kinetics of C3A mixed with different percentages of nano-SiO2 were studied and compared with pure C3A. The hydration products were examined by different characterization techniques including XRD, XPS, and NMR spectroscopy and isothermal calorimetry analyses. The XRD results showed that the addition of nano-SiO2 promoted the conversion of the intermediate product C4AH13. The isothermal calorimetry results showed that the addition of nano-SiO2 significantly reduced the hydration exotherm rate of C3A from 0.34 to less than 0.1 mW/g. With the presence of nano-SiO2, the peaks for Q1 were observed in 29Si MAS-NMR measurements, and the content of Q1 increased from 6.74% to 30.6% when the nano-SiO2 content increased from 2 wt.% to 8 wt.%, whereas the proportion of Q4 gradually decreased from 89.1% to 63.6%. These results indicated a pozzolanic reaction provoked by the nano-SiO2 combined with aluminate structures generating C-A-S-H gel.

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“…It accelerates the cement hydration by the nucleation effect and subsequently fills the voids [ 32 , 33 , 34 ]. Calcium carbonate was observed to react with C 3 A to form calcium carboaluminate (CCA), which tended to increase the compressive strength [ 29 , 35 , 36 , 37 ].…”

Section: Introductionmentioning

confidence: 99%

Eco-UHPC as Repair Material—Bond Strength, Interfacial Transition Zone and Effects of Formwork Type

et al. 2020

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A reduced carbon footprint and longer service life of structures are major aspects of circular economy with respect to civil engineering. The aim of the research was to evaluate the interfacial bond properties between a deteriorated normal strength concrete structure and a thin overlay made of Eco-UHPC containing 50 wt% of limestone filler. Two types of formwork were used: untreated rough plywood and surface treated shuttering plywood. The normal strength concrete elements were surface scaled using water jets to obtain some degradation prior to casting of the UHPC overlay. Ultrasonic pulse velocity (UPV), bond test (pull-off test), and Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectrometry (EDS) were used for analysis. Elements repaired with the Eco-UHPC showed significantly improved mechanical properties compared to the non-deteriorated NSC sample which was used as a reference. The bond strength varied between 2 and 2.7 MPa regardless of the used formwork. The interfacial transition zone was very narrow with only slightly increased porosity. The untreated plywood, having a rough and water-absorbing surface, created a surface friction-based restraint which limited microcracking due to autogenous shrinkage. Shuttering plywood with a smooth surface enabled the development of higher tensile stress on the UHPC surface, which led to a more intensive autogenous shrinkage cracking. None of the formed microcracks penetrated through the entire thickness of the overlay and some were partly self-healed when a simple water treatment was applied. The project results showed that application of UHPC as repair material for concrete structures could elongate the lifespan and thus enhance the sustainability.

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Preface

Cited by 27 publications

References 0 publications

Study of the Air-Entraining Behavior Based on the Interactions between Cement Particles and Selected Cationic, Anionic and Nonionic Surfactants

Study of the Air-Entraining Behavior Based on the Interactions between Cement Particles and Selected Cationic, Anionic and Nonionic Surfactants

Hydration Characteristics of Tricalcium Aluminate in the Presence of Nano-Silica

Eco-UHPC as Repair Material—Bond Strength, Interfacial Transition Zone and Effects of Formwork Type

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