scholarly journals Changes in the immitance spectra of the cement paste in the initial period of hardening

2021 ◽  
Vol 1198 (1) ◽  
pp. 012014
Author(s):  
V A Zhuravlev ◽  
D O Ugodenko ◽  
A V Zhuravlev ◽  
V I Suslyaev ◽  
I A Prischepa ◽  
...  
Keyword(s):  
Cement Paste ◽  
Initial Period ◽  
Equivalent Circuits ◽  
Electrophysical Properties ◽  
Frequency Range ◽  
Cement Slurry ◽  
Electrical Circuits ◽  
Electrode Layer ◽  
Measuring Cell ◽  
Interface Phenomena

Abstract The paper analyzes changes in the impedance and admittance spectra of the cement slurry during hardening. The spectra were measured in the frequency range from 20 Hz to 2 MHz on a precision RLC meter Agilent E4890A using a homemade capacitor measuring cell. The studies in order to establish the optimal equivalent electrical circuits describing the transformation of the electrophysical properties of the cement slurry and interface phenomena in the near-electrode layer of the measuring cell from the time of hardening were carried out. The sensitivity of the parameters of equivalent circuits to different stages of cement slurry hardening has been established.

The Flowability and Adsorption of Low Sulfate Cement with Superplasticizers

2013 ◽  
Vol 477-478 ◽  
pp. 904-907
Author(s):  
Ming Zhe An ◽  
Song Han
Keyword(s):  
Charge Density ◽  
Cement Paste ◽  
Water Demand ◽  
Cement Slurry ◽  
Sulfate Content ◽  
Standard Dosage ◽  
Slump Test ◽  
Adsorbed Amount ◽  
Lower Charge

The compatibility of low sulfate cement with naphthalene (NS) and polycarboxylate (PCE) type superplasticizers was discussed. The flowability of slurry and the adsorption of superplasticizers (SP) were investigated by mini slump test and TOC. The results show that severe compatibility degeneration is caused by low sulfate content in cement slurry. The water demand of slurry, the standard dosage and adsorbed amount of SPs were dramatically raised. In the cement slurry with low sulfate content, polycarboxylate type superplasticizers presents better performance than naphthalene type. The PCE with lower charge density presents better robustness. It is recommended in the preparation of concrete to avoid the incompatibility problems caused by lack of sulfate in cement paste.

scholarly journals Studying of dielectric spectra of YCu0.15Mn0.85O3 solid solution with the use of complex conductivity

2021 ◽  
pp. 2160013
Author(s):  
A. V. Nazarenko ◽  
A. V. Pavlenko ◽  
Y. I. Yurasov
Keyword(s):  
Solid Solution ◽  
Electrical Conductivity ◽  
Model Description ◽  
Complex Conductivity ◽  
Electrophysical Properties ◽  
Approximation Model ◽  
Frequency Range ◽  
Dielectric Parameters ◽  
Frequency Behavior ◽  
Complex Electrical Conductivity

This work presents the results of studying the electrophysical properties of the YCu[Formula: see text]Mn[Formula: see text]O3 solid solution in the range of temperatures of [Formula: see text] = 26–400[Formula: see text]C and frequency range of [Formula: see text] = 102–105 Hz. A model description of the revealed dispersion of dielectric parameters in the material is made. The nonclassical modified Havriliak–Negami model written for complex electrical conductivity was used as an approximation model. It is shown that the application of this model almost exactly describes the frequency behavior of the dielectric constant [Formula: see text]/[Formula: see text], the dielectric loss tangent tg[Formula: see text] as well as the real and imaginary parts of complex conductivity [Formula: see text] and [Formula: see text]. The results of this work are an important step in identifying the opportunities and understanding the applications of this model.

Carbon Dioxide Corrosion and Corrosion Prevention of Oil Well Cement Paste Matrix in Deep Wells

2014 ◽  
Vol 692 ◽  
pp. 433-438 ◽  
Author(s):  
Jing Fu Zhang ◽  
Jin Long Yang ◽  
Kai Liu ◽  
Bo Wang ◽  
Rui Xue Hou
Keyword(s):  
Carbon Dioxide ◽  
Compressive Strength ◽  
Cement Paste ◽  
Oil Wells ◽  
Oil Well ◽  
Cement Slurry ◽  
Corrosion Prevention ◽  
Oil Well Cement ◽  
Oil Well Cement Paste ◽  
Well Cement

Carbon dioxide CO2could corrode the oil well cement paste matrix under agreeable moisture and pressure condition in deep oil wells, which could decrease the compressive strength and damage the annular seal reliability of cement paste matrix. The problem of oil well cement paste matrix corrosion by CO2was researched in the paper for obtain the feasible corrosion prevention technical measures. The microstructure and compressive strength of corroded cement paste matrix were examined by scanning electron microscopeSEMand strength test instrument etc. under different corrosion conditions. The mechanism and effect law of corrosion on oil well cement paste matrix by CO2were analyzed. And the suitable method to protect CO2corrosion in deep oil wells was explored. The results show that the corrosion mechanism of cement paste matrix by CO2was that the wetting phase CO2could generate chemical reaction with original hydration products produced from cement hydration, which CaCO3were developed and the original composition and microstructure of cement paste matrix were destroyed. The compressive strength of corrosion cement paste matrix always was lower than that of un-corrosion cement paste matrix. The compressive strength of corrosion cement paste matrix decreased with increase of curing temperature and differential pressure. The corroded degree of cement paste matrix was intimately related with the compositions of cement slurry. Developing and design anti-corrosive cement slurry should base on effectively improving the compact degree and original strength of cement paste matrix. The compounding additive R designed in the paper could effectively improve the anti-corrosive ability of cement slurry.

scholarly journals Effect of Acid Activation-Hydrophilic-Modified Sepiolite on Comprehensive Properties of Oil-Well Cement

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Yihang Zhang ◽  
Miao He ◽  
Mingbiao Xu ◽  
Peng Xu
Keyword(s):  
Cement Paste ◽  
Oil Well ◽  
Acid Activation ◽  
Cement Slurry ◽  
Comprehensive Properties ◽  
Oil Well Cement ◽  
Before And After ◽  
Sepiolite Fiber ◽  
Well Cement ◽  
Agent Treatment

In this paper, sepiolite was treated by acid activation, coupling agent treatment, and sulfonation modification. The purpose of this study was to explore the changes in the fluidity and mechanical properties of sepiolite cement slurry before and after modification. Therefore, the comprehensive properties of unmodified sepiolite fiber (HPS) and acid activation-coupling agent treatment-sulfonated sepiolite fiber (S-O-H-HPS) in oil-well cement slurry were evaluated. FT-IR and microscopic mechanism of cement paste fracture surface before and after sepiolite modification were analyzed. The results showed that HPS can effectively improve the toughness of cement paste, but when the content of HPS was more than 1%, the fluidity of cement paste deteriorated sharply and the compressive strength decreased gradually. The addition of S-O-H-HPS can significantly improve the fluidity and stability of HPS slurry. Without affecting the compressive strength, it can effectively improve the flexural strength and impact strength and reduce the elastic modulus of cement paste. The mechanism analysis showed that S-O-H-HPS can not only form network structure in cement paste but also improve the toughness of cement paste by forming a bridge. This also explains why the strength of S-O-H-HPS cement paste does not decrease significantly with the increase of S-O-H-HPS.

The Performance Evaluation of New Low Temperature early Strength Agent ZL-1

2013 ◽  
Vol 470 ◽  
pp. 842-846
Author(s):  
Ji Gang Wang ◽  
An Qi Tong ◽  
Zhen Zhong Fan ◽  
Qing Wang Liu
Keyword(s):  
Performance Evaluation ◽  
Low Temperature ◽  
Silica Fume ◽  
Cement Paste ◽  
Cement Slurry ◽  
Hydration Rate ◽  
Anionic Polymers ◽  
Temperature Conditions ◽  
Chlorine Ions ◽  
Early Strength

Low temperature early strength cement slurry is a slurry in order to meet the well cementation in low-temperature conditions. Daqing weather is characterized by the silica fume, solid alcohols, amines and anionic polymers prepared a certain proportion, got a new low temperature early strength agent, It can greatly accelerate the hydration rate of cement and promote the formation of the cement paste early strength; and no chlorine ions, able to overcome the problem caused by traditional chlorine early strength agent casing corrosion.

scholarly journals Experimental Study of Reinforcing Broken Gangues by Colloid Cement Slurry

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Xin Lyu ◽  
Ke Yang ◽  
Qiang Fu ◽  
Zhen Wei ◽  
Shuai Liu
Keyword(s):  
Failure Mode ◽  
Cement Paste ◽  
Failure Modes ◽  
Axial Strain ◽  
Optimal Choice ◽  
Strengthening Effect ◽  
Reinforcement Effect ◽  
Cement Slurry ◽  
Load Bearing ◽  
Failure Patterns

Studies on jet grouting materials mainly focus on the aggregates in cement or the environment where they are maintained and rarely deal with the cohesiveness, reinforcement load-bearing characteristics, and surface spalling. In this study, cement slurries with different colloid contents were prepared to explore the characteristics and reinforcement effect of broken gangues. These were then subjected to mechanical testing to measure the strength and axial strain performance, and the failure modes and failure patterns were discussed. The results indicated that the colloid component has a significant strengthening effect on the early strength of the samples. As the age increased, the sample axial strain and elastic modulus of the colloid cement paste increased as the colloid component provides viscoelasticity when it resists deformation. The sample strength of cement paste decreases after the addition of broken gangue while the strength of class E samples increases significantly during each age. The cement paste sample showed penetrating splitting failure, the colloidal component effectively controlled the peeling of sample surface, and the failure mode after adding gangue was relatively complicated. The instability modes of the samples are divided into dispersed load-bearing instability and cumulative load-bearing instability, and the content of colloid components affects the failure mode of the samples. A colloid component proportion of 23.33% is the optimal choice, which has an obvious reinforcement effect on the broken gangue.

Development and Change of Compressive Strength for Class G Oil Well Cement under High Temperature

2014 ◽  
Vol 941-944 ◽  
pp. 1441-1444 ◽  
Author(s):  
Jing Fu Zhang ◽  
Kai Liu ◽  
Rui Xue Hou ◽  
Bo Wang ◽  
Jin Long Yang
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Initial Period ◽  
Strength Development ◽  
Oil Well ◽  
Curing Time ◽  
Cement Slurry ◽  
Critical Temperatures ◽  
Oil Well Cement ◽  
Well Cement

The compressive strength of oil well cement would be damaged by high temperature in deep oil wells, which was caused by the obvious change of the components and microstructure of cement hydration products. The adaptability of common oil well cement for cementing under higher temperatures was confined by above reasons. Characteristics of development and change of compressive strength of Class G oil well cement were studied under different temperatures by using Static Gel Strength Analyzer and High Temperature-High Pressure curing chamber. The influence law of temperature and silica sands on compressive strength was analyzed. The results showed that the critical temperatures at which the compressive strength begun to decline were about 110°C and 150°C respectively; The compressive strength increased with curing time during the initial period and would reduced after it reached a certain value when temperature exceeded 110°C; For cement with silica sands, the compressive strength development trend was in the shape of two-stage form with increase of curing time within the range of 110~150°C, but for 160~200°C temperature range the development form was in the shape of single stage; The reasonable amounts of silica sands which would be added to cement slurry to enhance the compressive strength of hardening paste were determined to be 30%~40%.

scholarly journals A Low-Cost and Low-Density Cement Slurry System Suitable for a Shallow Unconsolidated Stratum

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Jiaping Yue ◽  
Zhaonian Liu ◽  
Jie Wang ◽  
Ting Sun ◽  
Zhiqiang Wu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Oil And Gas ◽  
Low Cost ◽  
Low Density ◽  
Cement Slurry ◽  
Oil And Gas Fields ◽  
Slurry System ◽  
Gas Fields ◽  
Offshore Oil

The shallow unconsolidated stratum in the offshore oilfield is characterized by large porosity, low temperature, and weak formation and often faces problems such as low density and poor compressive strength of a cement slurry, among others, which pose serious challenges to construction. A high-performance low-density cement slurry system must be used for cementing to ensure the safety of subsequent drilling and mining on-site and to reduce the cost of cement slurry for the efficient development of oil and gas fields. Based on these problems, according to the principle of particle gradation, a mixture with a high accumulation rate and low density composed of five types of mineral materials, i.e., artificial microbeads, floating beads, microsilicon, fly ash, and slag, has been developed through a large number of indoor experiments, and a set of low-cost and low-density cement slurry systems has been developed; these systems are suitable for the shallow loose formations of offshore oil fields. The cement slurry system meets the requirements of the cementing operation conducted under different temperatures and pressures. The density range is 1.4–1.7 g/cm3, which can be adjusted. The cement slurry is stable and exhibits good fluidity. The thickening time meets the requirements of cementing construction. Moreover, the compressive strength of the cement paste is high, and the compressive strength of cement paste is greater than 12 MPa for 24 h and 14 MPa for 48 h of curing at 50°C, which maximizes the economic benefits. The research results provide technical support for the safe and efficient development of offshore oil and gas fields.

Phase transitions and interface phenomena in the cryogenic temperature domain of a niobate nanostructured ceramic

2014 ◽  
Vol 43 (28) ◽  
pp. 10983-10998 ◽  
Author(s):  
S. Lanfredi ◽  
C. Darie ◽  
F. S. Bellucci ◽  
C. V. Colin ◽  
M. A. L. Nobre
Keyword(s):  
Phase Transitions ◽  
Cryogenic Temperature ◽  
Unit Cell ◽  
Equivalent Circuits ◽  
Sem Image ◽  
Interface Phenomena ◽  
Nanostructured Ceramic

The SEM image of the KSr2Nb5O15 nanoceramic based on grains G1, G2 and G3 (90 to 500 nm) with the plot of the unit cell of KSr2Nb5O15 and the set of equivalent circuits representing the several interfaces of the nanostructured ceramic.

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