scholarly journals Evaluation of test methods for determination of normal consistency and setting time or portland cement paste part I

1968 ◽  
Author(s):  
N G Zoldners ◽  
G G Carette
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Setting Time ◽  
Test Methods ◽  
Portland Cement Paste

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.

Determination of Low Levels of Chloride in Hardened Portland Cement Paste, Mortar, and Concrete

1975 ◽  
Vol 3 (3) ◽  
pp. 208 ◽  
Author(s):  
SF Etris ◽  
YR Fiorini ◽  
KC Lieb ◽  
IC Moore ◽  
AL Batik ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Low Levels ◽  
Portland Cement Paste

scholarly journals Comparison of Effects of Sodium Bicarbonate and Sodium Carbonate on the Hydration and Properties of Portland Cement Paste

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1033 ◽  
Author(s):  
Yuli Wang ◽  
Fengxia He ◽  
Junjie Wang ◽  
Qianku Hu
Keyword(s):  
Compressive Strength ◽  
Sodium Bicarbonate ◽  
Portland Cement ◽  
Cement Paste ◽  
Sodium Carbonate ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
Sprayed Concrete ◽  
Final Setting Time ◽  
Portland Cement Paste

Carbonates and bicarbonates are two groups of accelerators which can be used in sprayed concrete. In this study, the effects of the two accelerators sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) (0%, 1%, 2%, 3%, and 4% by weight of ordinary Portland cement OPC) on the properties of OPC paste were compared. The results show that both of them could accelerate the initial and final setting time of OPC paste, but the effect of the two accelerators on the compressive strength were different. After 1 day, sodium bicarbonate at 3% had the highest strength while sodium carbonate at 1% had the highest strength. After 7 days, both of the two accelerators at 1% had the highest compressive strength. After 28 days, the compressive strength decreased with the increase of the two. The improved strength at 1 and 7 days was caused by the accelerated formation of ettringite and the formation of CaCO3 through the reactions between the two with portlandite. The decrease of strength was caused by the Na+ could reduce the adhesion between C-S-H gel by replacing the Ca2+. NaHCO3 was found be a better accelerator than Na2CO3.

Using High Temperature for Improve Compressive Strength of Ordinary Portland Cement Paste (OPC) – A New Approach

2014 ◽  
Vol 894 ◽  
pp. 70-76
Author(s):  
Abdoullah Namdar ◽  
Fadzil Mat Yahaya ◽  
Mashita Mohd Yusoff
Keyword(s):  
Surface Roughness ◽  
Compressive Strength ◽  
Portland Cement ◽  
Cement Paste ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
New Approach ◽  
Force Microscopy ◽  
Atomic Force ◽  
Portland Cement Paste

Cement paste was replaced with kaolin-bentonite. The specimens were exposed to elevated temperature for 3 hours in a ceramic furnace and cooled down to room temperature. After cooling, the effect of kaolin-bentonite (particles sized of < 45μm) on hydration, rehydration, surface roughness and compressive strength of ordinary Portland cement (OPC) paste were investigated. Atomic Force Microscopy (AFM) was used to study surface roughness of OPC paste-additive mixture. The application of fire on OPC paste was analyzed. The results showed imposed heat (500 oC for 3 hours) accelerates the hydration process of OPC, and reduces setting time. Increased heat to 1000 oC, leads to zero compressive strength of specimens, the compressive strength of OPC continuously reduces after specimen has fully cooled down. A method for recovery of compressive strength of OPC after offing fire has been suggested. The method of offing fire has important effects on the compressive strength of concrete. The best results for specimen content are cement-kaolin-bentonite paste, exposure to 500 o C, after 90 days of curing, and cooling down in water. In this case the compressive strength has been increased around 60 % compared to not using additive and not exposing to heat.

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