scholarly journals Effect of nano-SnO2 on early-age hydration of Portland cement paste

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985194 ◽  
Author(s):  
Jianping Zhu ◽  
Genshen Li ◽  
Ruijie Xia ◽  
Huanhuan Hou ◽  
Haibin Yin ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Strength Development ◽  
Early Age ◽  
Test Machine ◽  
Portland Cement Paste ◽  
Scanning Electron

Nanomaterial, as a new emerging material in the field of civil engineering, has been widely utilized to enhance the mechanical properties of cementitious material. Nano-SnO2 has presented high hardness characteristics, but there is little study of the application of nano-SnO2 in the cementitious materials. This study mainly investigated the hydration characteristics and strength development of Portland cement paste incorporating nano-SnO2 powders with 0%, 0.08%, and 0.20% dosage. It was found that the early-age compressive strength of cement paste could be greatly improved when nano-SnO2 was incorporated with 0.08% dosage. The hydration process and microstructure were then measured by hydraulic test machine, calorimeter, nanoindentation, X-ray diffraction, scanning electron microscope, and mercury intrusion porosimetry. It was found that the cement hydration process was promoted by the addition of nano-SnO2, and the total amount of heat released from cement hydration is also increased. In addition, the addition of nano-SnO2 can promote the generations of high density C-S-H and reduce the generations of low density C-S-H indicating the nucleation effect of nano-SnO2 in the crystal growth process. The porosity and probable pore diameter of cement paste with 0.08% nano-SnO2 were decreased, and the scanning electron microscopic results also show that the cement paste with 0.08% nano-SnO2 promotes the densification of cement microstructure, which are consistent with the strength performance.

scholarly journals Effects of Highly Crystalized Nano C-S-H Particles on Performances of Portland Cement Paste and Its Mechanism

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 816
Author(s):  
Yuli Wang ◽  
Huijuan Lu ◽  
Junjie Wang ◽  
Hang He
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Setting Time ◽  
Tricalcium Silicate ◽  
Strength Development ◽  
Early Age ◽  
Hydration Products ◽  
X Ray ◽  
Early Strength ◽  
Portland Cement Paste

In order to improve the early age strength of ordinary Portland cement-based materials, many early strength agents were applied in different conditions. Different from previous research, the nano calcium silicate hydrate (C-S-H) particles used in this study were synthesized through the chemical reaction of CaO, SiO2, and H2O under 120 °C using the hydrothermal method, and the prepared nano C-S-H particles were highly crystalized. The influences of different amounts of nano C-S-H particles (0%, 0.5%, 1%, 2% and 3% by weight of cement) on the setting time, compressive strength, and hydration heat of cement paste were studied. The hydration products and microstructure of the cement paste with different additions of nano C-S-H particles were investigated through thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), and scanning electron microscope (SEM) tests. The results show that the nano C-S-H particles could be used as an early strength agent, and the early strength of cement paste can be increased by up to 43% through accelerating the hydration of tricalcium silicate (C3S). However, the addition of more than 2% nano C-S-H particles was unfavorable to the later strength development due to more space being left during the initial accelerated hydration process. It is suggested that the suitable content of the nano C-S-H particles is 0.5%−1% by weight of cement.

Scanning Electron Microscopy in the Studies of Hydrated Cementitious Materials Microstructure Formed in the Presence of some Heavy Metals Containing Admixtures

2015 ◽  
Vol 231 ◽  
pp. 145-153 ◽  
Author(s):  
Wiesława Nocuń-Wczelik ◽  
Barbara Trybalska
Keyword(s):  
Electron Microscopy ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Early Age ◽  
Silicate Phase ◽  
Small Individual ◽  
Calorimetric Measurements ◽  
Individual Particles ◽  
Scanning Electron ◽  
Nitrate Solutions

The calorimetric measurements together with microscopic observations and analyses relating to the interaction of cement paste with sulfate and nitrate solutions of various concentration were carried out. These salts modify the rate of cement hydration at early age. In the presence of sulfates the formation of some well crystallized calcium sulfates or calcium sulfoaluminates can be found. In case of nitrates there is no additional products. However, one can observe that the calcium silicate phase becomes less fibrous but more compact, with very small individual particles, as the nucleation from the liquid phase is disturbed. There are the accompanying cations incorporated in this product.

scholarly journals Effects of graphene oxide on early-age hydration and electrical resistivity of Portland cement paste

2017 ◽  
Vol 136 ◽  
pp. 506-514 ◽  
Author(s):  
Wengui Li ◽  
Xiangyu Li ◽  
Shu Jian Chen ◽  
Yan Ming Liu ◽  
Wen Hui Duan ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Graphene Oxide ◽  
Portland Cement ◽  
Cement Paste ◽  
Early Age ◽  
Portland Cement Paste ◽  
Early Age Hydration

Modeling cement hydration by connecting a nucleation and growth mechanism with a diffusion mechanism. Part II: Portland cement paste hydration

2016 ◽  
Vol 23 (6) ◽  
pp. 605-615 ◽  
Author(s):  
Xueyu Pang ◽  
Christian Meyer
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Growth Mechanism ◽  
Rate Constants ◽  
Cement Hydration ◽  
Diffusion Mechanism ◽  
Nucleation And Growth ◽  
Curing Temperature ◽  
Nucleation And Growth Mechanism ◽  
Portland Cement Paste

AbstractA particle-based C3S hydration model with only three rate constants developed in Part I of this study is further developed and applied to Portland cement paste hydration. Experimental data are obtained with chemical shrinkage tests of cement pastes prepared with different water to cement (w/c) ratios (0.3–0.5), and cured at different temperatures (24°C–63°C) and pressures (0.69–51.7 MPa). The proposed model produces exceptionally good fits to test data. The fitted results indicate that the entire process of cement hydration can be modeled by connecting a nucleation and growth mechanism with a diffusion mechanism. Furthermore, the results reveal that the deceleration period of cement hydration may be due to the gradual transition of the rate-controlling mechanisms of different particles. The fitted rate constants generally follow basic chemical kinetics laws in terms of their dependencies on curing temperature and pressure, and appear to be largely independent of w/c ratio.

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