scholarly journals MODIFICATION OF CEMENTITIOUS MATRIX OF RAPID-HARDENING HIGH-PERFORMANCE CONCRETES

2021 ◽  
Vol 2021 (1) ◽  
pp. 79-84
Author(s):  
Iryna Kirakevych ◽  
◽  
Myroslav Sanytsky ◽  
Orest Shyiko ◽  
Roman Kagarlitsky ◽  
...  
Keyword(s):  
High Performance ◽  
Rapid Hardening ◽  
Cementitious Matrix ◽  
Active Alumina ◽  
Early Loading ◽  
Physico Chemical ◽  
Cementitious System ◽  
Cementitious Systems ◽  
Mineral Additives ◽  
Active Mineral Additives

The paper presents the results of research concerning the peculiarities of modern High Performance Concretes based on cementitious systems "Portland cement – active mineral additives – micro fillers – superplasticizers – accelerators of hardening". Physico-chemical regularities of structure formation of super plasticized cementitious systems are established. It is shown that the formation of secondary fine ettringite due to the interaction of active alumina with calcium hydroxide and gypsum in the non-clinker part of the binder because of the effect of "self-reinforcement" compensates for shrinkage and increases the strength of the cementitious system. The modification of the cementitious matrix makes it possible to obtain Rapid Hardening High Performance Concretes that provide early loading and turnover of the formwork of monolithic constructions.

scholarly journals Self-Сompacting Сoncretes, which hardening at different temperature conditions

2020 ◽  
Vol 2020 (2) ◽  
pp. 107-112
Author(s):  
Iryna Kirakevych ◽  
◽  
Myroslav Sanytsky ◽  
Igor Margal ◽  
◽  
...  
Keyword(s):  
Portland Cement ◽  
Structure Formation ◽  
Quality Parameters ◽  
Production Cycle ◽  
Temperature Conditions ◽  
Early Loading ◽  
Physico Chemical ◽  
Vibration Technology ◽  
Cementitious Systems ◽  
Mineral Additives

In the article the features of reinforced concrete hardening at different temperature conditions and the current issues of preparation technology of Self-Сompacting Сoncretes (SCC) on the basis of superplasticized cementitious systems, combining knowledge of structure and modifying Portland cement compositions "Portland cement – active mineral additives – microfiller – superplasticizer – accelerator of hardening" to search for rational making provision of technical and building properties of concrete in the changing factors of its composition, technology and exploitation are shown. The physico-chemical peculіarities of hydration and hardening processes of superplasticized cementitious systems were established. The problem of obtaining Self-Compacting mixtures and Rapid-Hardening Concretes on their basis by the direct structure formation of cementitious matrix was solves. The optimization of Self-Compacting Concretes composition on the base of superplasticized cementitious systems with high early strength was carried out. The quality parameters of developed concretes were investigated and the effectiveness of their using in different temperature conditions was shown. The results of the studies found that the use of the superplasticized cementitious systems allows to influence on technological properties and kinetics of structure formation and create concrete structure with improved construction and technical properties at a different temperature conditions. Technological solutions designing of superplasticized cementitious systems that solves the problem of obtaining the Self-Сompacting Сoncretes (SCC) on their basis with using non-vibration technology are established. This creates an opportunity allows to solve the problem of obtaining for enabling early loading, reducing the production cycle, increasing turnover and formwork acceleration of monolithic buildings and structures at different temperature conditions.

Electrochemical Deposition of Polypyrrole Nanostructures for Energy Applications: A Review

2020 ◽  
Vol 16 (4) ◽  
pp. 462-477 ◽  
Author(s):  
Patrizia Bocchetta ◽  
Domenico Frattini ◽  
Miriana Tagliente ◽  
Filippo Selleri
Keyword(s):  
Lithium Batteries ◽  
High Performance ◽  
Relevant Literature ◽  
Chemical Parameters ◽  
Energy Devices ◽  
Energy Applications ◽  
Physico Chemical ◽  
Potential Applications ◽  
Template Free ◽  
Cathodic Polymerization

By collecting and analyzing relevant literature results, we demonstrate that the nanostructuring of polypyrrole (PPy) electrodes is a crucial strategy to achieve high performance and stability in energy devices such as fuel cells, lithium batteries and supercapacitors. In this critic and comprehensive review, we focus the attention on the electrochemical methods for deposition of PPy, nanostructures and potential applications, by analyzing the effect of different physico-chemical parameters, electro-oxidative conditions including template-based or template-free depositions and cathodic polymerization. Diverse interfaces and morphologies of polymer nanodeposits are also discussed.

scholarly journals Physico-chemical deformations of solidifying cementitious systems: multiscale modelling

2009 ◽  
Vol 43 (1-2) ◽  
pp. 151-165 ◽  
Author(s):  
F. Grondin ◽  
M. Bouasker ◽  
P. Mounanga ◽  
A. Khelidj ◽  
A. Perronnet
Keyword(s):  
Multiscale Modelling ◽  
Physico Chemical ◽  
Cementitious Systems

Preparation and Photocatalytic Activity of Mixed Phase Anatase/rutile TiO2 Nanoparticles for Phenol Degradation

2014 ◽  
Vol 70 (2) ◽  
Author(s):  
Mohamad Azuwa Mohamed ◽  
Wan Norharyati Wan Salleh ◽  
Juhana Jaafar ◽  
Norhaniza Yusof
Keyword(s):  
Photocatalytic Activity ◽  
Tio2 Nanoparticles ◽  
High Performance ◽  
Sol Gel ◽  
Phenol Degradation ◽  
Chemical Properties ◽  
Mixed Phase ◽  
Rutile Tio2 ◽  
Physico Chemical ◽  
Degussa P25

The evolution of desirable physico-chemical properties in high performance photocatalyst materials involves steps that must be carefully designed, controlled, and optimized. This study investigated the role of key parameter in the preparation and photocatalytic activity analysis of the mixed phase of anatase/rutile TiO2 nanoparticles, prepared via sol-gel method containing titanium-n-butoxide Ti(OBu)4 as a precursor material, nitric acid as catalyst, and isopropanol as solvent. The prepared TiO2 nanoparticles were characterized by means of XRD, SEM, and BET analyses, and UV-Vis-NIR spectroscopy. The results indicated that the calcination temperature play an important role in the physico-chemical properties and photocatalytic activity of the resulting TiO2 nanoparticles. Different calcination temperatures would result in different composition of anatase and rutile. The photocatalytic activity of the prepared mixed phase of anatase/rutile TiO2 nanoparticles was measured by photodegradation of 50 ppm phenol in an aqueous solution. The commercial anatase from Sigma-Aldrich and Degussa P25 were used for comparison purpose. The mixed phase of anatase/rutile TiO2 nanoparticles (consists of 38.3% anatase and 61.7% rutile) that was prepared at 400°C exhibited the highest photocatalytic activity of 84.88% degradation of phenol. The result was comparable with photocatalytic activity demonstrated by Degussa P25 by 1.54% difference in phenol degradation. The results also suggested that the mixed phase of anatase/rutile TiO2 nanoparticles is a promising candidate for the phenol degradation process. The high performance of photocatalyst materials may be obtained by adopting a judicious combination of anatase/rutile and optimized calcination conditions.

scholarly journals Effect of water/cement ratio on micro-nanomechanical properties of the interface between cementitious matrix and steel microfibers in ultra-high performance cementitious composites

2021 ◽  
Vol 14 (4) ◽  
Author(s):  
Vanessa Fernandes Cesari ◽  
Fernando Pelisser ◽  
Philippe Jean Paul Gleize ◽  
Milton Domingos Michel
Keyword(s):  
Transition Zone ◽  
Cement Paste ◽  
Calcium Silicate ◽  
High Performance ◽  
Calcium Silicate Hydrate ◽  
Interfacial Transition Zone ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Nanomechanical Properties ◽  
Cementitious Matrix

abstract: Ultra-high performance concretes with steel microfibers have been studied in depth with the aim of producing more efficient and durable structures. The performance of these materials depends on the characteristics of the interface between microfibers and cementitious matrix. This research investigates the micro-nanomechanical properties of the interfacial transition zone between the steel microfibers and the matrix of ultra-high performance cementitious composite. The effect of the water/cement ratio and distance from the microfiber were analyzed. The results confirm the formation of high-density calcium-silicate-hydrate (HD C-S-H) matrix at higher concentrations than low-density calcium-silicate-hydrate (LD C-S-H) for w/c ratios of 0.2 and 0.3. The properties in cementitious matrix interface with steel microfibers were very similar to that measured for the cement paste, and no significant difference was observed regarding the distance to the microfibers in relation to the elastic modulus, hardness and chemical composition. Thus, the authors can conclude that the formation of a less resistant region does not occur at the interfacial transition zone cement paste/microfibers.

Research on the Effect of Polycarboxylate Superlasticizers on Reheology Properties of Compound Cementitious System

2011 ◽  
Vol 477 ◽  
pp. 151-156 ◽  
Author(s):  
Dong Min Wang ◽  
Zhi Hua Liu ◽  
Wei Feng Xiong
Keyword(s):  
Molecular Structure ◽  
Rheological Property ◽  
Rheological Properties ◽  
Molecular Structures ◽  
Mineral Admixture ◽  
Dispersion Property ◽  
Cementitious System ◽  
Adsorption Amount ◽  
Polymer Surfactants ◽  
Cementitious Systems

The rheological property is the best method which can directly reflect the dispersion property of polymer surfactants. In this paper, the rheological properties in the systems of pure cement, cement/fly ash and cement/silica fume with polycarboxylate superplasticizers of different molecular structures were studied. The effect of molecular structure on shear sress, apparent viscosity and thixotropy in compound cementitious systems was expatiated. At last, the rules of mineral admixture to the system’ rheological property and the relations between adsorption amount and rheological properties were put forward.

Comparative Study of Physico-Chemical Properties of Pure Polyurethane and Polyurethane Based on Castor Oil

2014 ◽  
Vol 983 ◽  
pp. 39-43
Author(s):  
M. A. Alaa ◽  
Kamal Yusoh ◽  
S.F. Hasany
Keyword(s):  
Castor Oil ◽  
High Performance ◽  
In Situ Polymerization ◽  
Chemical Properties ◽  
Strength Properties ◽  
Hydroxyl Group ◽  
Physico Chemical ◽  
Analysis Technique ◽  
Hydrophobic Nature ◽  
Poly Propylene

Petroleum based polyurethanes are contributing major portions in the world requirement. To overcome the environmental issues and price adaptability, there is always a massive demand of utilization of renewable resources for polyurethane synthesis with comparable physico-chemical properties. Castor oil is the only major natural vegetable oil that contains a hydroxyl group (-OH) and unsaturated double bonds (C=C) in its organic chain and therefore can be employed with or without modification due to the excellent properties derived from the hydrophobic nature of triglycerides. In this study, physico-chemical properties of high performance polyurethane synthesized from Poly propylene glycol (PPG) in comparison with a combination of PPG and Castor oil (a renewable source), by in situ polymerization technique has been studied. The variations in properties of both types of polyurethanes are evaluated by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric analysis technique (TGA). Tensile strength properties were investigated by Film Tensile testing equipment. Results indicated the presence of large-CH stretching in castor oil mixed polyurethane with a larger oxidative thermal stability, over a pure PPG polyurethanes. Tensile properties were found almost comparable in pure and mixed polymers, which signify the usage of mixed polymer in coming future, to overcome the environmental and economical crisis in polyurethanes synthesis.

scholarly journals Fluorescence Microscopic Investigations of the Retarding Effect of Superplasticizers in Cementitious Systems of UHPC

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1057 ◽  
Author(s):  
Johannes Arend ◽  
Alexander Wetzel ◽  
Bernhard Middendorf
Keyword(s):  
Molecular Structure ◽  
High Performance ◽  
High Performance Concrete ◽  
Ultra High Performance Concrete ◽  
Adsorption Characteristic ◽  
Beneficial Effects ◽  
Retarding Effect ◽  
Cementitious Systems ◽  
Mixing Water

The adsorption of superplasticizer molecules to particle surfaces in cementitious systems is a very important aspect for the desired liquefaction of pastes and concretes. This way, the comb shaped polymers shield attractive forces between the particles and induce a well-dispersed, homogeneous suspension. These admixtures allow the usage of fine fillers even in combination with low amounts of mixing water, and thus, are the basis for modern high performance concretes. However, the adsorption does not cause beneficial effects only: The polymer covered particle surfaces, especially clinker, are hindered to interact with water, thus hydration is retarded. This is the reason for lower early strength and is very disadvantageous for certain applications. Today it is known that the molecular structure of the polymers, for instance the chain length and charge density, affects the retardation strongly. The complexity and diversity of cementitious systems is the main reason why research in this field is quite empiric and time as well as cost intensive. To investigate the adsorption of superplasticizers in various systems in-situ, a fluorescence microscopic approach was applied: By staining the polymers with fluorescent dye they become localizable and the adsorption quantifiable. This work shows the influence of molecular structure to adsorption characteristic of different polymers and the correlation to the retarding effect of superplasticizers, especially concerning the presence of silica fume, which is indispensable for ultra-high performance concrete (UHPC).

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