Microstructure and Flow Behaviior of Fresh Cement Paste

1992 ◽  
Vol 289 ◽  
Author(s):  
W. Jiang ◽  
D.M. Roy
Keyword(s):  
Cement Paste ◽  
Scientific Information ◽  
External Factors ◽  
Processing Conditions ◽  
Flow State ◽  
Flow Properties ◽  
Structure Development ◽  
Micro Structure ◽  
Emission Signal ◽  
Theological Properties

AbstractCharacteristics of aqueous cement suspensions and the packing nature during setting were investigated as keys controlling the microstructure and density of a cement paste. The theological properties of the paste were studied as functions of hydration and setting; these properties are influenced by a variety of external factors, which are discussed. The objective of this paper is to sketch a new atomistic approach to a group of rheological phenomena which are as interesting from a scientific viewpoint as they are important for technology. The experiments were carried out by a HAAKE rheometer and an acoustic ultrasonic system. At different flow state, the acoustic emission signal generated from micro-structure is transformed due to wave propagation and due to the transducer response. The scientific information obtained through this study is expected to contribute the establishment of concept of setting processing. The measurements of flow properties relating to flocculation and coagulation were evaluated with respect to the effects of processing conditions on structure development in cement paste.

Novel Ultrasonic Technology for Devulcanization of Waste Rubbers

1995 ◽  
Vol 68 (2) ◽  
pp. 267-280 ◽  
Author(s):  
A. I. Isayev ◽  
J. Chen ◽  
A. Tukachinsky
Keyword(s):  
Mechanical Properties ◽  
Structural Characteristics ◽  
Three Dimensional ◽  
Ultrasonic Waves ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Processing Conditions ◽  
Laboratory Reactor ◽  
Plant Level ◽  
Theological Properties

Abstract A novel patented process and several reactors have been developed for devulcanization of waste rubbers. The technology is based on the use of the high power ultrasonics. The ultrasonic waves of certain levels in the presence of pressure and heat rapidly break up the three-dimensional network in crosslinked rubbers. The devulcanized rubber can be reprocessed, shaped and revulcanized in much the same way as a virgin rubber. The first laboratory reactor has been scaled up to pilot-plant level by the National Feedscrew and Machining, Inc. Various devulcanization experiments were carried out with model styrene-butadiene rubber (SBR) and with ground rubber tire (GRT). Curing behavior, Theological properties, and structural characteristics of rubbers devulcanized at various processing conditions were studied, as well as mechanical properties of revulcanized rubber samples. A possible mechanism of the devulcanization is discussed. The performed measurements indicate that the rubbers are partially devulcanized, and the devulcanization process is accompanied by certain degradation of the macromolecular chains. In spite of these observations, the processing conditions are identified at which the retention of the mechanical properties is found to be good. A further work is in progress to find the optimal conditions of devulcanization and to improve the selectivity of the process towards breaking up the chemical network only.

scholarly journals Effect of Ground Slag on Mechanical Properties of Concrete under Low Temperature

2021 ◽  
Vol 2109 (1) ◽  
pp. 012019
Author(s):  
Xuelian Yuan ◽  
Jie Hu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Compressive Strength ◽  
Low Temperature ◽  
Cement Paste ◽  
High Volume ◽  
Hardened Cement ◽  
Micro Structure ◽  
Hardened Cement Paste ◽  
Fracture Properties

Abstract Through using cube resisting compression test, fracture properties and micro-structure, the mechanical properties of high volume ground slag concrete under low temperature are studied in this paper. The results show that low temperature can improve the compressive strength of high volume ground slag concrete. And strength increased with the decreased of temperature. Low temperature can also improve the fracture energy and fracture toughness. Not only can ground slag reduce the content of calcium hydroxide in hardened cement paste, but ground slag can improve the compactness of hardened cement paste, reduce porosity and improve the strength of the interface.

Chemo-Micro-Dilatation Modeling of Carbonation Shrinkage Phenomenon of the Porous Mortars

2011 ◽  
Vol 261-263 ◽  
pp. 680-684 ◽  
Author(s):  
T. X. Dinh ◽  
J. Jeong ◽  
H. Ramézani ◽  
Z. Q. Feng
Keyword(s):  
Cement Paste ◽  
Cement Mortar ◽  
Ph Value ◽  
Empirical Method ◽  
Micro Structure ◽  
Unknown Parameters ◽  
Scientific Goal ◽  
Different Types ◽  
Semi Empirical ◽  
Carbonation Shrinkage

In this paper, we investigate the CO2 carbonation on porous materials such as the cement paste mortar. Our scientific goal is to model the CO2 carbonation effect on the porous cement mortar by the micro-dilatation theory and to determine the chemo-mechanical stress development due to the chemical reactions. In fact, this phenomenon will modify not only the pH value of the cement paste but also the micro-structure due to collapsing pore-network. Based upon the micro-dilatation theory originally proposed by Cowin and Nunziato, four unknown parameters related to the micro-structure will be determined for the cement mortar using the semi-empirical method and numerical modeling. The experimental carbonation tests on two different types of cement paste (CEMI and CEMIII) have been realized to capture carbonated affected zones and to measure their shrinkage deformations.

Effect of Processing Conditions on the Microstructure and Electromechanical Response of PVDF TrFE CTFE Terpolymers

2014 ◽  
Author(s):  
Nirmal Shankar Sigamani ◽  
Saad Ahmed ◽  
Zoubeida Ounaies
Keyword(s):  
Annealing Time ◽  
Annealed Film ◽  
Relaxor Ferroelectric ◽  
Processing Conditions ◽  
Structure Property ◽  
Micro Structure ◽  
Electromechanical Properties ◽  
Structure Property Relationships ◽  
Α Phase ◽  
Enthalpy Of Melting

Effect of annealing time on the micro structure and electromechanical properties PVDF TrFE CTFE terpolymer with 7.8 mol % CTFE was investigated to better understand structure-property relationships in these polymers. DSC results show that the 9 hr-annealing time gives the maximum enthalpy of melting which suggests the crystallinity of the polymer is increased. WAXS results show that annealing increases the proportion of the γ-phase with the ratio of the intensity of γ-phase to α-phase increases with more annealing time. Dielectric spectroscopic study of 9hr-annealed film also suggests that the film shows complete relaxor ferroelectric behavior with a maximum electrostrictive strain up to 4.4 % compared to 4.1 % for the 2.5 hr-annealed film. Finally, annealing time higher than 9 hrs result in a decrease in the electrostrictive strain.

Effects of nonionic surfactants and external factors on stability of latex in cement paste

2017 ◽  
Vol 135 (10) ◽  
pp. 45946 ◽  
Author(s):  
Dongdong Han ◽  
Weideng Chen ◽  
Shiyun Zhong ◽  
Yan He
Keyword(s):  
Cement Paste ◽  
Nonionic Surfactants ◽  
External Factors

scholarly journals Measuring Rheological Properties of Cement Pastes: Most common Techniques, Procedures and Challenges

2017 ◽  
Vol 2 ◽  
pp. 129-135 ◽  
Author(s):  
Dimitri Feys ◽  
Rolands Cepuritis ◽  
Stefan Jacobsen ◽  
Karel Lesage ◽  
Egor Secrieru ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Rheological Properties ◽  
Cement Paste ◽  
Testing Procedure ◽  
Phenomenological Description ◽  
Flow Properties ◽  
Cement Pastes ◽  
Fundamental Investigation

The science of rheology is increasingly used to describe the properties of fresh cement paste. Compared to standard workability tests, rheological properties allow for more fundamental investigation, more precise phenomenological description of flow properties and serve as input for numerical simulations. Standard commercially available rheometers are typically used to perform those measurements. However, the results of the measurement depend on the geometry, testing procedure and a number of potential artefacts which may occur. This technical letter describes the most common techniques and procedures used to assess the rheological properties of cement paste, as well as challenges during measurements and actions to counter these challenges.

Effect of processing conditions on structure development and mechanical response of Si–Mn ‘TRIP’ steel

2008 ◽  
Vol 483-484 ◽  
pp. 71-75 ◽  
Author(s):  
Jozef Zrnik ◽  
Ondrej Muransky ◽  
Ondrej Stejskal ◽  
Peter Lukáš ◽  
Peter Hornak
Keyword(s):  
Trip Steel ◽  
Mechanical Response ◽  
Processing Conditions ◽  
Structure Development
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