scholarly journals Physical and Chemical Aspects of the Nucleation of Cement-Based Materials

10.14311/1668 ◽  
2012 ◽  
Vol 52 (6) ◽  
Author(s):  
Pavel Demo ◽  
Alexey Sveshnikov ◽  
Šárka Hošková ◽  
David Ladman ◽  
Petra Tichá
Keyword(s):  
Cement Paste ◽  
Energy Barrier ◽  
Critical Size ◽  
Time Lag ◽  
Point Of View ◽  
Cement Ratio ◽  
Initial Stage ◽  
Water To Cement Ratio ◽  
Cement Based Materials ◽  
Physical And Chemical

A theoretical model of the nucleation of portlandite is proposed, and the critical size of a portlandite cluster and the energy barrier of nucleation are determined. The steady state nucleation rate and the time lag of the nucleation of portlandite are estimated for a pure solution of Ca(OH)2 in water. Possible connections with the corresponding properties for cement paste are discussed. A new method is developed for experimentally determining the concentration of Ca2+ ions during the initial stage of hydration of a cement paste. The time dependence of Ca2+ ions is measured for various water-to-cement ratio values. The results are discussed from the point of view of existing models of the induction period.

scholarly journals CO2 Curing Efficiency for Cement Paste and Mortars Produced by a Low Water-to-Cement Ratio

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3883
Author(s):  
Seong Ho Han ◽  
Yubin Jun ◽  
Tae Yong Shin ◽  
Jae Hong Kim
Keyword(s):  
Cement Paste ◽  
Pressure Vessel ◽  
Gas Pressure ◽  
Strength Development ◽  
Co2 Uptake ◽  
Cement Pastes ◽  
Co2 Gas ◽  
Cement Ratio ◽  
Mix Proportion ◽  
Water To Cement Ratio

Curing by CO2 is a way to utilize CO2 to reduce greenhouse gas emissions. Placing early-age cement paste in a CO2 chamber or pressure vessel accelerates its strength development. Cement carbonation is attributed to the quickened strength development, and CO2 uptake can be quantitatively evaluated by measuring CO2 gas pressure loss in the pressure vessel. A decrease in CO2 gas pressure is observed with all cement pastes and mortar samples regardless of the mix proportion and the casting method; one method involves compacting a low water-to-cement ratio mix, and the other method comprises a normal mix consolidated in a mold. The efficiency of the CO2 curing is superior when a 20% concentration of CO2 gas is supplied at a relative humidity of 75%. CO2 uptake in specimens with the same CO2 curing condition is different for each specimen size. As the specimen scale is larger, the depth of carbonation is smaller. Incorporating colloidal silica enhances the carbonation as well as the hydration of cement, which results in contributing to the increase in the 28-day strength.

Dispersion and Absorption of SBR Latex in the System of Mono-Dispersed Cement Particles in Water

2013 ◽  
Vol 687 ◽  
pp. 347-353 ◽  
Author(s):  
Xiao Xin Shi ◽  
Ru Wang ◽  
Pei Ming Wang
Keyword(s):  
Cement Hydration ◽  
Single Layer ◽  
Optical Microscope ◽  
Solution Phase ◽  
Environmental Scanning ◽  
Cement Particle ◽  
Microstructure Formation ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Cement Based Materials

This paper investigates the dispersion of cement particles in water at different mix proportions using optical microscope, and the dispersion and absorption of SBR latex in the system of mono-dispersed cement particles in water using environmental scanning electron microscope (ESEM). The results show that the mono-dispersed cement can be well obtained at the water to cement ratio (mw/mc) of 10:1. The ESEM images present that SBR latex is dispersed on the surface of the cement particles as well as the solution phase. SBR latex does not prefer to be absorbed on the cement particles in spite of their opposite electric charge but chooses to be dispersed in the system proportionally. In addition, SBR particles are single-layer absorbed on the surface of cement particles in all the SBR latex to cement ratios (mp/mc). Several SBR particles absorbed on the surface of cement particle get close enough to form groups at the mp/mc of 15% and 20%. The results of this paper provide some bases for analyzing the influence of polymer on cement hydration and the microstructure formation of polymer-modified cement-based materials in a new view.

Prediction of Elastic Modulus of Cement-Based Materials Based on Power’s Volume Model

2012 ◽  
Vol 253-255 ◽  
pp. 474-477 ◽  
Author(s):  
Lang Wu ◽  
Bing Yan ◽  
Bin Lei
Keyword(s):  
Elastic Modulus ◽  
Elastic Properties ◽  
Cement Paste ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Micromechanics Model ◽  
Volume Model ◽  
Cement Based Materials ◽  
Hydrated Products ◽  
Multi Phase

The hydrated products, unhydrated cement and water (capillary pores) in the cement paste are seen as matrix, inclusion, Equivalent medium respectively, We used the micromechanics theories and Power’s Volume model to develop a multi-phase micromechanics model capable of simulating the elastic properties of cement-based materials, and the evolution of elastic properties in the hydration process was calculated at different water-cement ratio. The final experimental results show that this model can be used to predict the elastic properties of cement-based materials.

scholarly journals Effective Absorption Capacity Examined by Isothermal Calorimetry: Effect of Pore Structure and Water-to-Cement Ratio

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Joo-Ha Lee ◽  
Do Guen Yoo ◽  
Bo Yeon Lee
Keyword(s):  
Activated Carbon ◽  
Carbon Fibre ◽  
Pore Structure ◽  
Isothermal Calorimetry ◽  
Absorption Capacity ◽  
Cement Ratio ◽  
Effective Absorption ◽  
Water To Cement Ratio ◽  
Cement Based Materials ◽  
Activated Carbon Fibre

The accurate measurement of effective absorption capacity is crucial for highly absorptive materials when they are used within cement-based materials. In this study, a method for examining effective absorption capacity using isothermal calorimetry is reviewed and investigated in detail to accommodate different circumstances. Specifically, the effect of different pore structures and water-to-cement ratios in determining effective absorption capacity is experimentally examined using activated carbon fibre and powdered activated carbon. The results suggest that the method may be suitable for porous materials with micropores but not suitable for those with mesopores. Also, the results indicate that the effective absorption capacity value can change with the water-to-cement ratio used. These findings can be used to find the effective absorption capacity of highly absorptive materials more accurately using the isothermal calorimetry method.

Quantitative Characterization of Effective Porosity in Cement-Based Composite Materials

2010 ◽  
Vol 163-167 ◽  
pp. 3174-3179
Author(s):  
Guo Wen Sun ◽  
Jin Yang Jiang ◽  
Yun Sheng Zhang ◽  
Cai Hui Wang
Keyword(s):  
Composite Materials ◽  
Cement Paste ◽  
Pore Diameter ◽  
Effective Porosity ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Pore Characteristics ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Second Peak

The method of the second intrusion mercury in MIP was used to investigate the pore characteristics of hardened cement paste with w/c ratio 0.23, 0.35 and 0.53, respectively, in order to research the quantitative relationship between transport properties and pore characteristics in cement-based composite materials. The results show the second intrusion mercury could well determine the effective pore structure parameters, and effective porosity accounts for 25% to 50% of total porosity in cement paste. At the same time, the existence of the first and second peak in pore size distribution curves is confirmed by MIP, such as, the first peak in hardened cement paste with water to cement ratio 0.53 is very distinct, however, with the decrease of water to cement ratio, the first peak gradually disappears. The pore diameter corresponding to the first and second peak is critical pore diameter of capillary pore and gel pore, respectively.

Effect of Heat-Treatment on Microstructure and Mechanical Properties of Magnesium Phosphate Cement

2016 ◽  
Vol 680 ◽  
pp. 447-450
Author(s):  
Xin Tao ◽  
Jia Chen Liu ◽  
Ming Chao Wang
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Compressive Strength ◽  
Magnesium Phosphate ◽  
Cement Ratio ◽  
Heat Treated ◽  
Water To Cement Ratio ◽  
Heating Up ◽  
Physical And Chemical ◽  
Made In

Magnesium phosphate cement with M/P of 6, borax content of 4.8 wt% and water-to-cement ratio of 0.12, were made in this study. Heat-treatment was conducted from 200 °C to 1200 °C, and the physical and chemical evolution in the process of heating up was investigated via TG/DSC, XRD and SEM. Besides, the compressive strength, density and porosity of the heat-treated specimen were measured and the influence of treating temperature was discussed. The results show that magnesium phosphate cement possesses good chemical stability at 1200 °C and the strength has reduced only by 32.2% compared with none-treating specimens.

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