Experimental observations of early-age drying of Portland cement paste under low-pressure conditions

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.

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Mathematical modeling of accelerated carbonation curing of Portland cement paste at early age

Cement and Concrete Research ◽

10.1016/j.cemconres.2019.03.025 ◽

2019 ◽

Vol 120 ◽

pp. 187-197 ◽

Cited By ~ 28

Author(s):

Tiefeng Chen ◽

Xiaojian Gao ◽

Ling Qin

Keyword(s):

Mathematical Modeling ◽

Portland Cement ◽

Cement Paste ◽

Early Age ◽

Accelerated Carbonation ◽

Carbonation Curing ◽

Portland Cement Paste

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

Crystals ◽

10.3390/cryst10090816 ◽

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.

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