Evolution of Various States of Water in Blended Cementitious Materials

2012 ◽  
Vol 193-194 ◽  
pp. 389-392
Author(s):  
An Ming She ◽  
Wu Yao ◽  
Wan Cheng Yuan
Keyword(s):  
Fly Ash ◽  
Cement Paste ◽  
Bound Water ◽  
Transverse Relaxation Time ◽  
Quantitative Relationship ◽  
Cementitious Materials ◽  
Relative Content ◽  
Cement Matrix ◽  
Transverse Relaxation ◽  
In Series

Low field NMR, as a nondestructure and noninvasive method was employed to study the evolution of various states of water in blended cementious materials added with fly ash during hydration from 1 day to 100 days. The relative content of water held in series of pores in cement matrix, e.g. capillary pore, mesopore and gel pore, was determined based on the quantitative relationship between transverse relaxation time, T2, and pore dimension. The results indicated that the relative content of chemically bound water was higher at long-term cure of 100 days compared with the neat cement paste. The water distributed in various pores was also influenced by the pozzolanic reactions between fly ash and calcium hydroxide. The gel water and mesopore water increased dramatically during the short-term age of 1 to 7 days in blended matrix, but then decreased gradually after 28 days, unlike that in pure cement paste. Due to the lower hydration degree in blended matrix, there was still amount of capillary water residual in paste to supply for the further hydration of fly ash.

Creep of Cement Pastes with Content of Fly Ash one Year Old

2015 ◽  
Vol 732 ◽  
pp. 385-388
Author(s):  
Pavel Padevět ◽  
Petr Bittnar
Keyword(s):  
Fly Ash ◽  
Cement Paste ◽  
Material Properties ◽  
Bound Water ◽  
Basic Creep ◽  
Cement Pastes ◽  
One Year ◽  
Creep Measurement ◽  
Ratio Of Components

The paper discusses the creep cement pastes with addition of fly ash. The evolution of the creep was observed in age of one year, for length one month. The size of the creep is influenced by the amount the creep physically bound water. The material properties depend on the ratio of components from which the cement paste is composed. The paper presents the results of creep measurement for the ratio of cement and fly ash 70:30, 60:40 and 50:50. The basic creep and creep of the saturated cement paste were calculated from measurements.

Hydration Dynamics of Portland Cement Studied by Magnetic Resonance

2012 ◽  
Vol 193-194 ◽  
pp. 509-512 ◽  
Author(s):  
An Ming She ◽  
Wu Yao ◽  
Wan Cheng Yuan
Keyword(s):  
Portland Cement ◽  
Initial Period ◽  
Bound Water ◽  
Transverse Relaxation Time ◽  
Rate Of Change ◽  
Individual Stage ◽  
Transverse Relaxation ◽  
Low Field ◽  
Low Field Nmr ◽  
Hydration Dynamics

Hydration dynamics of Portland cement was investigated by low field NMR, a technique with advantage of continuous and nondestructure monitor. The transverse relaxation time, T2, and signals intensity arising from the physically bound water in paste were measured. Their evolution with the hydration time could be used well to describe the hydration dynamics. Three successive periods, comprising of initial period, accelerated period and steady period, were defined according the different rate of change. The reactions and mechanism for individual stage were disscussed based on the cement chemistry theory.

Low Field-NMR in Measuring Water Mobility and Distribution in Beef Granules during Drying Process

2012 ◽  
Vol 550-553 ◽  
pp. 3406-3410 ◽  
Author(s):  
Xin Li ◽  
Li Zhen Ma ◽  
Yuan Tao ◽  
Bao Hua Kong ◽  
Pei Jun Li
Keyword(s):  
Bound Water ◽  
Free Water ◽  
Transverse Relaxation Time ◽  
Water Mobility ◽  
Drying Process ◽  
Transverse Relaxation ◽  
Low Field ◽  
Different Temperatures ◽  
Low Field Nmr ◽  
Lf Nmr

Low field-nuclear magnetic resonance (LF-NMR) was employed in this study to evaluate water mobility and distribution in beef granules during drying process due to its fast and nondestructive detection. Beef granules were dried in a blast drying oven at different temperatures (40, 50 and 60 °C) to a final moisture content around 21% after cooking. Results showed that it took about 150, 90 and 60 min for the samples dried at 40, 50 and 60 °C to get to the drying destination, respectively. The immobilized water was transformed into bound water with lower association degree and free water during drying at different conditions. Drying also resulted in a proportion increase of bound water; what’s more, the proportion of bound water is the largest when drying at 50 °C compared to 40 and 60 °C. After the drying destination was reached, the transverse relaxation time for bound water and immobilized water appeared significant change. It revealed that LF-NMR was an effective tool to assess water mobility and distribution during food drying process.

Effect of Fly Ash and nanoCaCO3 on the Setting Time of Cement Paste

2013 ◽  
Vol 405-408 ◽  
pp. 2885-2888
Author(s):  
Zhi Qin Zhao ◽  
Zhi Ge ◽  
Ren Juan Sun ◽  
Gong Feng Xin ◽  
Da Wei Huang
Keyword(s):  
Experimental Study ◽  
Fly Ash ◽  
Cement Paste ◽  
Setting Time ◽  
Test Group ◽  
Cementitious Materials ◽  
Ash Content ◽  
Setting Times

This paper presents an experimental study to evaluate the effects of fly ash and nanoCaCO3 on setting time of cement paste. The test group included the contents of fly ash was 30%, 40%, 50%, 60% and content of nanoCaCO3 was 2.5%, 5%, 10%, 20%. Results indicate that setting time was increased with the incorporation of fly ash, shortened with the incorporation of nanoCaCO3. The incorporation of 5% nanoCaCO3 by mass of cementitious materials reduced initial and final setting times by 60 and 70 min, respectively. In comparison to the referenced paste with 40% fly ash. The best fly ash content appear to be 40% when nanoCaCO3 was added.

Changes of the Properties of Cement Paste with Fly Ash Exposed to the High Temperature

2016 ◽  
Vol 677 ◽  
pp. 138-143
Author(s):  
Romana Lovichová ◽  
Pavel Padevět ◽  
Jindřich Fornůsek
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
High Temperature ◽  
Fly Ash ◽  
Cement Paste ◽  
Material Properties ◽  
Bound Water ◽  
Material Structure ◽  
Cement Pastes ◽  
Strength In Bending

This paper describes influence of exposure to high temperatures on material properties of cement paste with addition of fly ash. The properties of cement pastes are significant to the assumption behaviour of concrete and concrete structures. In the cement paste containing fly ash, the effect of high temperature up to 600 ° C causes the changes of content in physically bound water and the change in the material structure. The results of research indicate changes that are reflected in the material properties of the cement paste as compressive strength, tensile strength in bending.

scholarly journals The impact of metakaolin, silica fume and fly ash on the temperature resistance of high strength cement paste

2021 ◽  
Author(s):  
Nabil Abdelmelek ◽  
Eva Lubloy
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Cement Paste ◽  
Elevated Temperatures ◽  
High Strength ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Temperature Resistance ◽  
Maximum Temperatures ◽  
The Impact

AbstractThe effects of elevated temperatures on the properties of high-strength cement paste (HSCP) based on metakaolin (MK), silica fume (SF), and fly ash (FA) were studied in the current experimental research. The resistance of HSCP against elevated temperatures was evaluated as well. The new method is expressed by the total area under each curve of strength, known as “temperature resistance”, is adopted. Results of the HSCP mixtures containing MK, SF, and FA with replacements ratios of 9%, 6% and 15% have shown excellent temperature resistance at all levels of maximum temperatures, respectively. Properties added to HSCP by these supplementary cementitious materials (SCM) such as decreasing the amount of CaO and increasing the amounts of SiO2 and Al2O3 have minimized the harmful effects of the use of pure ordinary Portland cement (OPC) at elevated temperatures. The results have shown also that the grinding fineness of OPC influences the amount of optimum replacement of the used SCM on HSCP at elevated temperatures. Hence, the amount of optimum replacement of MK blended with CEM I 42.5 N was 9% whereas, the amount of optimum replacement of MK blended with CEM I 52.5 N shifted to 3%. Finally, the fineness of cement of 4500 cm2 g−1 has shown a better-elevated temperature resistance compared to the cement with a fineness of 4000 cm2 g−1 in case of using pure OPC.

Mesoscale Modeling of Nonlinear Influence of Ambient Relative Humidity on Drying Shrinkage of Concrete

2016 ◽  
Vol 825 ◽  
pp. 129-134
Author(s):  
Petr Havlásek ◽  
Milan Jirásek
Keyword(s):  
Relative Humidity ◽  
Cement Paste ◽  
Viscoelastic Model ◽  
Nonlinear Function ◽  
Nonlinear Behavior ◽  
Drying Shrinkage ◽  
Cementitious Materials ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Ambient Relative Humidity

Creep and shrinkage are complicated time-dependent processes taking place in cementitious materials. In typical concretes, the most significant part of shrinkage is represented by drying shrinkage; it is caused by a decrease in relative humidity of pores which leads to an increase in capillary tension of pore water and in the solid surface tension at pore walls.Experimental data indicate that the ultimate value of drying shrinkage measured on concrete and mortar specimens is a nonlinear function of the ambient relative humidity. The nonlinear behavior is partially caused by microcracking, and partially by creep of the cement matrix. On the other hand, drying shrinkage of hardened cement paste, measured on very thin specimens at gradually decreasing relative humidity, is found to be a linear function of relative humidity.The aim of this paper is to assess the nature of the macroscopic shrinkage computed employing finite element simulations at the meso-scale level in which the drying cement paste is described by a viscoelastic model with tensile cracking and with a constant shrinkage coefficient.

Effect of ground granulated blast funrnace slag and fly ash on strength, permeability, and under-water abrasion of fine-grained concrete

2020 ◽  
Vol 71 (7) ◽  
pp. 775-788
Author(s):  
Quyet Truong Van ◽  
Sang Nguyen Thanh
Keyword(s):  
Fly Ash ◽  
Concrete Strength ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Chloride Permeability ◽  
Cement Replacement ◽  
Fine Grained ◽  
Granulated Blast Furnace Slag ◽  
Compressive Strength Test ◽  
Economic Ground

The utilisation of supplementary cementitious materials (SCMs) is widespread in the concrete industry because of the performance benefits and economic. Ground granulated blast furnace slag (GGBFS) and fly ash (FA) have been used as the SCMs in concrete for reducing the weight of cement and improving durability properties. In this study, GGBFS at different cement replacement ratios of 0%, 20%, 40% and 60% by weight were used in fine-grained concrete. The ternary binders containing GGBFS and FA at cement replacement ratio of 60% by weight have also evaluated. Flexural and compressive strength test, rapid chloride permeability test and under-water abrasion test were performed. Experimental results show that the increase in concrete strength with GGBFS contents from 20% to 40% but at a higher period of maturity (56 days and more). The chloride permeability the under-water abrasion reduced with the increasing cement replacement by GGBFS or a combination of GGBFS and FA

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