scholarly journals Effect of C-S-H Nucleating Agent on Cement Hydration

2021 ◽  
Vol 11 (14) ◽  
pp. 6638
Author(s):  
Wenhao Zhao ◽  
Xuping Ji ◽  
Yaqing Jiang ◽  
Tinghong Pan
Keyword(s):  
Fractal Dimension ◽  
Cement Hydration ◽  
Nucleating Agent ◽  
Crystal Nucleation ◽  
Enhancement Effect ◽  
Hydration Products ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Cement Mortars ◽  
Early Strength

This work aims to study the effect of a nucleating agent on cement hydration. Firstly, the C-S-H crystal nucleation early strength agent (CNA) is prepared. Then, the effects of CNA on cement hydration mechanism, early strength enhancement effect, C-S-H content, 28-days hydration degree and 28-days fractal dimension of hydration products are studied by hydration kinetics calculation, resistivity test, BET specific surface area test and quantitative analysis of backscattered electron (BSE) images, respectively. The results show that CNA significantly improves the hydration degree of cement mixture, which is better than triethanolamine (TEA). CNA shortens the beginning time of the induction period by 49.3 min and the end time of the cement hydration acceleration period by 105.1 min than the blank sample. CNA increases the fractal dimension of hydration products, while TEA decreases the fractal dimension. CNA significantly improves the early strength of cement mortars; the 1-day and 3-days strength of cement mortars with CNA are more than the 3-days and 7-days strength of the blank sample. These results will provide a reference for the practical application of the C-S-H nucleating agent.

Cement Hydration Kinetics Research Based on Center-Particles Hydration Model

2012 ◽  
Vol 204-208 ◽  
pp. 3634-3638
Author(s):  
Lang Wu ◽  
Bing Yan ◽  
Bin Lei
Keyword(s):  
Cement Hydration ◽  
Free Water ◽  
Interfacial Area ◽  
Hydration Products ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Hydration Rate ◽  
Variation Curve ◽  
Hydration Model ◽  
Relationship Of

Abstract: Based on the center-particles hydration dynamic model proposed by Park, a micro-structural hydration model of Portland cement that was built considering the decrease of the hydration rate due to the reduction of free water and the reduction of the interfacial area of contact between the free water and the hydration products. It can be used to predict the variation relationship of the hydration rate increases with the change of hydration degree. The results showed that: the revised model can simulate the variation curve of the cement hydration speed with hydration degree in this paper and the model results agree well with the experimental results.

Cement Hydration Models Research Based on Composition Content of each Phase of Minerals

2012 ◽  
Vol 204-208 ◽  
pp. 3639-3643
Author(s):  
Chun Hua Rao ◽  
Lang Wu ◽  
Bin Lei
Keyword(s):  
Cement Hydration ◽  
Curing Temperature ◽  
Kinetics Model ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Hydration Rate ◽  
Chemical Phase ◽  
Temperature Water

Abstract: Based on the cement hydration kinetics model proposed by R.Berliner, taking into account the factors such as each chemical phase of minerals, curing temperature, water-cement ratio, the final hydration degree and fineness of cement, a theoretical hydration kinetics equations was established in this paper. It can be used to predict the hydration rate and the change of hydration degree.

Preparation and Mechanism Analysis of High-Efficiency early Strength Agent

2012 ◽  
Vol 535-537 ◽  
pp. 2483-2487 ◽  
Author(s):  
Ming Sheng Zhang
Keyword(s):  
Cement Hydration ◽  
High Efficiency ◽  
Calcium Nitrate ◽  
Xrd Analysis ◽  
Mechanism Analysis ◽  
Hydration Products ◽  
Mineral Formation ◽  
Early Strength ◽  
Further Development

High-efficiency early strength agents were obtained which included triethanolamine, glycol and calcium nitrate. Then it was tested for concrete. Though text, we find that the compressive strength and flexural strength of the specimen, use of the high-efficiency early strength agent is greatly improved than with its much better not to use high-efficiency early strength agent. With time go on, high-efficiency early strength agent added does not make the strength of concrete worse, but better. Using SEM and XRD analysis technology text high-efficiency early strength agent by adding performances of concrete, including the degree of cement hydration, the morphology of hydration products and the composition of mineral formation. Analysis of the role of high-efficiency early strength agents from the perspective of the mechanism. Identified high-efficiency early strength agent impact on the cement hydration, for the further development of early strength agent to provide a theoretical basis.

Physical and Chemical Influence of Polyacrylate Latex on Cement Mortars

2011 ◽  
Vol 261-263 ◽  
pp. 807-811 ◽  
Author(s):  
Ye Tian ◽  
Zong Jin Li ◽  
Hong Yan Ma ◽  
Xian Yu Jin ◽  
Nan Guo Jin
Keyword(s):  
Pore Structure ◽  
Cement Hydration ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Air Entrainment ◽  
Hydration Products ◽  
Cement Mortars ◽  
Cement Based Materials ◽  
Physical And Chemical ◽  
Chemical Influence

In this research, the physical and chemical influence of polyacrylate (PA) latex on cement-based materials were studied using polymer modified mortars with polymer/cement (P/C) ratios of 0%, 5% and 10%. Physically, the mechanical performance of PA latex modified mortars was investigated with compression toughness energy and bending strength. Further more, a comparison of the pore structure and porosity between PA latex modified and unmodified mortars was conducted. The chemical reactions between PA polymer and cement hydrates were clarified with thermogravimetric (TG) analysis. It can be concluded from this research that PA polymer can refine the pore structure of cement mortars and link the cement hydration products together chemically. While, at the same time, PA latex addition can cause air entrainment which will weaken the physical behavior of cement mortars. So there is an optimum P/C ratio to achieve the best mechanical properties. And in this research, the optimum P/C ratio is 5%.

scholarly journals The Optimization of Calcareous Fly Ash-Added Cement Containing Grinding Aids and Strength-Improving Additives

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Gökhan Kaplan ◽  
Sadık Alper Yildizel ◽  
Selçuk Memiş ◽  
Ali Uğur Öztürk
Keyword(s):  
Fly Ash ◽  
Ash Content ◽  
Early Age ◽  
Economic Factors ◽  
Hydration Products ◽  
Chemical Additive ◽  
Cement Production ◽  
Grinding Aids ◽  
Cement Mortars ◽  
Early Strength

This is an experimental study which explores the physical, mechanical, and economic factors involved in the production of type CEM II A-B/W cement. In this context, 4 cement additives were used in two different dosages (200 and 800 g/t). Class C fly ash was used for composite cement production at ratios of 5%, 20%, and 35%. It was shown that Blaine fineness increases with the increasing fly ash content. The use of fly ash at ratios of 5% and 20% was not found to have any unfavorable effects on the compressive strength at the early days. It is found that the use of additive for improving the early-age strength is preferable when fly ash is used. It is possible to produce Class 52.5 N cement using additives to improve early strength and 20% fly ash. Loss in strength was observed in cement mortars produced using glycol-based grinding aid. Increasing the dosage of chemical additive also led to loss in strength due to nonhomogeneous distribution of hydration products. As a result, grinding fly ash with clinker and the use of cement chemicals contribute to the cement sector in terms of sustainability. It is possible to produce cements with improved mechanical properties especially with the use of 20% fly ash.

Effect of Superplasticizers on the Cement Hydration Process

2015 ◽  
Vol 1100 ◽  
pp. 3-6
Author(s):  
Michal Matysík ◽  
Tomáš Vymazal ◽  
Iveta Plšková
Keyword(s):  
Cement Hydration ◽  
Exothermic Reaction ◽  
Storage Period ◽  
Thermal Capacity ◽  
Hydration Heat ◽  
Time Interval ◽  
Hydration Degree ◽  
Hydration Kinetics ◽  
Heat Development ◽  
Time Plot

The cement hydration is an exothermic reaction. The hydration heat is characterizing quantitatively the clinker hydration degree. Monitoring its time response makes it possible to determine not only the heat released during a certain time interval but also the concrete mix setting onset, the cement hydration degree (when evaluating the cement applicability after a long storage period) etc. The measurement of the hydration heat or the temperature versus time plot for a hydrating mix makes it possible to identify the effect of the different additives and admixtures on the mix hydration kinetics. This paper deals with the effect of adding two different super-plasticizers (lignin-sulphonate-based and naphthalene-sulphonate-based) on the hydration heat development progress. A set of iso-peribolic calorimeters was used to measure the hydration heat development process. The measurement proper consisted in monitoring and recording the temperature versus time plot for the specimen under test. The released heat amount was determined by calculation from the temperature gradient, the ambience specific thermal losses, the material thermal capacity and the test specimen mass.

scholarly journals Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1938
Author(s):  
Luís Urbano D. Tambara Júnior ◽  
Janaíde C. Rocha ◽  
Malik Cheriaf ◽  
Pilar Padilla-Encinas ◽  
Ana Fernández-Jiménez ◽  
...  
Keyword(s):  
Cement Hydration ◽  
Hydration Products ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Calcium Sulfoaluminate Cement ◽  
Hydration Kinetics ◽  
Sodium Salts ◽  
X Ray ◽  
Calcium Sulfoaluminate ◽  
Ettringite Formation

This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na2SO4, Na2CO3, and Na2SiO3) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH3, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. Na2SO4 induces cracking in the ≥28-d pastes due to post-hardening gypsum and ettringite formation from the excess SO42– present. Anhydrite dissolves more rapidly in the presence of Na2CO3, prompting carbonation. Na2SiO3 raises compressive strength and exhibits strätlingite as one of its reaction products.

scholarly journals Ultrafast transfer strength of reinforced concrete sleepers by Using complex additives

2021 ◽  
pp. 44-63
Author(s):  
Andrii Plugin ◽  
Olena Kaliuzhna ◽  
Olga Borziak ◽  
Oleksii Plugin ◽  
Oleksandr Savchenko
Keyword(s):  
Energy Intensity ◽  
Cement Hydration ◽  
Experimental Investigations ◽  
Cement Stone ◽  
Hydration Products ◽  
Heat Regime ◽  
Electron Microscopic ◽  
Initial Stage ◽  
Early Strength ◽  
Mineral Additives

The influence of superplasticizers-polycarboxylates and their complex additives withaccelerants - electrolytes and dispersion of calcium hydroxylates on the early strength of concretefor concrete of concrete sleepers has been studied. It was found that the use of superplasticizerspolycarboxylates can improve the early strength of the concrete after heat treatment, but eachadditive must be checked for consistency with the cement used. Approx Complex additives withaccelerators in conditions of natural hardening ensure an increase in the early strength of concrete,but some of them, which accelerate natural hardening, can reduce the strength after WWTP and mustbe checked before use. Electron-microscopic examinations of the structure of cement stone withadditives were carried out and it was found that the additive of only policarboxylate does not changethe structure of hydration products. Complex additives lead to formation of additional number ofcrystalline hydrates of AFm- and/or AFt-phases. The scheme of development of the cement hardeningprocess and the initial stage of cement hardening without or with additives has been developed. Bymeans of which the highest accelerating effect of the complex addition of polycarboxylate andcalcium hydroxylate dispersions was established by experimental investigations, Dispersion particlesincrease surface area where crystallization (condensation) of cement hydration products takes placeand ensures faster filling of spaces between cement particles (mineral additives) with them, fillers)with establishment of lances with electro-heterogeneous contacts. As a result of potentiodynamic andmicroscopic investigations it was established that the tested additives in the dosages do not causecorrosion effect on the steel reinforcement bars. Transmission strength values of 32 MPa for sleepersafter 24 years of hardening under low-heat regime and after 2 days of natural hardening have beenachieved. The formula for economic efficiency of using additives to reduce the energy intensity ofproduction of concrete sleepers has been proposed.

scholarly journals Enhancing carbonation and chloride resistance of autoclaved concrete by incorporating nano-CaCO3

2020 ◽  
Vol 9 (1) ◽  
pp. 998-1008
Author(s):  
Guo Li ◽  
Zheng Zhuang ◽  
Yajun Lv ◽  
Kejin Wang ◽  
David Hui
Keyword(s):  
Cement Hydration ◽  
Mercury Intrusion Porosimetry ◽  
Hardened Concrete ◽  
Optimal Dosage ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Carbonation Depth ◽  
X Ray ◽  
Chloride Resistance

AbstractThree nano-CaCO3 (NC) replacement levels of 1, 2, and 3% (by weight of cement) were utilized in autoclaved concrete. The accelerated carbonation depth and Coulomb electric fluxes of the hardened concrete were tested periodically at the ages of 28, 90, 180, and 300 days. In addition, X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry were also performed to study changes in the hydration products of cement and microscopic pore structure of concrete under autoclave curing. Results indicated that a suitable level of NC replacement exerts filling and accelerating effects, promotes the generation of cement hydration products, reduces porosity, and refines the micropores of autoclaved concrete. These effects substantially enhanced the carbonation and chloride resistance of the autoclaved concrete and endowed the material with resistances approaching or exceeding that of standard cured concrete. Among the three NC replacement ratios, the 3% NC replacement was the optimal dosage for improving the long-term carbonation and chloride resistance of concrete.

Effect of Heavy Metals and Leaching Toxicity of Magnesium Potassium Phosphate Cement

2011 ◽  
Vol 117-119 ◽  
pp. 1080-1083 ◽  
Author(s):  
Bao Guo Ma ◽  
Jing Ran Wang ◽  
Xiang Guo Li
Keyword(s):  
Heavy Metals ◽  
Cement Hydration ◽  
Potassium Phosphate ◽  
National Standard ◽  
Magnesium Phosphate ◽  
Toxicity Tests ◽  
Hydration Products ◽  
Obvious Effect ◽  
Leaching Toxicity ◽  
Magnesium Potassium Phosphate Cement

Solidification / stabilization (S/S) is a popular method for treating solid wastes containing heavy metals. In recent years, it shows positive results of magnesium potassium phosphate cement as stabilizing agent. In the work, the influence of heavy metal Cu、Zn and Pb on magnesium phosphate cement and the leaching behavior of magnesium phosphate cement were studied. Two proportions of cements were employed with hard burned magnesia and potassium phosphate. The hydration products were analyzed by XRD showing that: Cu、Zn and Pb would not take on obvious effect during magnesium phosphate cement hydration process. Leaching toxicity tests showed that: Cu、Zn and Pb were immobilized within cement hydration products through physical fixation, adsorption mechanisms, and the results were far lower than that of the National Standard in China.

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