scholarly journals Multiphase Model for Predicting the Thermal Conductivity of Cement Paste and Its Applications

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4525
Author(s):  
Yuanbo Du ◽  
Yong Ge
Keyword(s):  
Thermal Conductivity ◽  
Cement Paste ◽  
Simulation Method ◽  
Curing Temperature ◽  
Multiphase Model ◽  
Test Results ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Concrete Testing ◽  
Curing Age

Thermal conductivity plays a significant role in controlling thermal cracking of cement-based materials. In this study, the thermal conductivity of cement paste at an early age was measured by the hot plate method. The test results showed that the thermal conductivity of cement paste decreased with the increase of water/cement ratio and curing age. Meanwhile, a multiphase model for the thermal conductivity of cement paste was proposed and used to study the influence of saturation and curing temperature on the thermal conductivity of cement paste. To determine the parameters involved in this model, the thermal conductivity of each phase in cement paste was calculated by the molecular dynamic simulation method, and the hydration of cement was simulated by the Virtual Cement and Concrete Testing Laboratory. The inversion results showed that the relative error between experimental and simulation results lay between 1.1% and 6.5%. The thermal conductivity of paste in the saturated condition was 14.9–32.3% higher than that in the dry state. With the curing temperature increasing from 10 °C to 60 °C, the thermal conductivity of cement paste decreased by 3.9–4.9% depending on the water/cement ratio.

Evaluating the Two-Point Probability Function of Capillary Pores by Computer Simulation

2011 ◽  
Vol 261-263 ◽  
pp. 905-908
Author(s):  
Jian Jun Zheng ◽  
Yao Jun Huang ◽  
Xin Zhu Zhou
Keyword(s):  
Computer Simulation ◽  
Numerical Method ◽  
Cement Paste ◽  
Probability Function ◽  
Simulation Method ◽  
Hydration Time ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Chloride Diffusivity ◽  
Quantitative Manner

To more exactly predict the chloride diffusivity of cement paste, it is essential to determine the two-point probability function of capillary pores. The intention of the paper is to present a computer simulation method for evaluating the two-point probability function of capillary pores. By introducing three physical quantities to quantify the mutual interference between neighboring cement particles, the microstructure evolution of cement paste is simulated. Based on the simulated microstructure of cement paste, a numerical method is developed for evaluating the two-point probability function of capillary pores. After verifying the numerical method with the experimental results obtained from the literature, the effect of the hydration time and water/cement ratio on the two-point probability function is assessed in a quantitative manner. It is found that the two-point probability function decreases with the increase of the hydration time for a given water/cement ratio, but increases with an increase in water/cement ratio for a given hydration time.

scholarly journals Effect of water/cement ratio on micro-nanomechanical properties of the interface between cementitious matrix and steel microfibers in ultra-high performance cementitious composites

2021 ◽  
Vol 14 (4) ◽  
Author(s):  
Vanessa Fernandes Cesari ◽  
Fernando Pelisser ◽  
Philippe Jean Paul Gleize ◽  
Milton Domingos Michel
Keyword(s):  
Transition Zone ◽  
Cement Paste ◽  
Calcium Silicate ◽  
High Performance ◽  
Calcium Silicate Hydrate ◽  
Interfacial Transition Zone ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Nanomechanical Properties ◽  
Cementitious Matrix

abstract: Ultra-high performance concretes with steel microfibers have been studied in depth with the aim of producing more efficient and durable structures. The performance of these materials depends on the characteristics of the interface between microfibers and cementitious matrix. This research investigates the micro-nanomechanical properties of the interfacial transition zone between the steel microfibers and the matrix of ultra-high performance cementitious composite. The effect of the water/cement ratio and distance from the microfiber were analyzed. The results confirm the formation of high-density calcium-silicate-hydrate (HD C-S-H) matrix at higher concentrations than low-density calcium-silicate-hydrate (LD C-S-H) for w/c ratios of 0.2 and 0.3. The properties in cementitious matrix interface with steel microfibers were very similar to that measured for the cement paste, and no significant difference was observed regarding the distance to the microfibers in relation to the elastic modulus, hardness and chemical composition. Thus, the authors can conclude that the formation of a less resistant region does not occur at the interfacial transition zone cement paste/microfibers.

scholarly journals Effect of Phenolic Particles on Mechanical and Thermal Conductivity of Foamed Sulphoaluminate Cement-Based Materials

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3596 ◽  
Author(s):  
Xiuzhi Zhang ◽  
Qing Yang ◽  
Qinfei Li ◽  
Heng Chen ◽  
Guofa Zheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pore Structure ◽  
Dry Density ◽  
Mechanical And Thermal Properties ◽  
Foaming Agent ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Performance Indexes ◽  
Foamed Concrete ◽  
Inorganic Matrix

Foamed concrete materials based on sulpoaluminate cement were prepared by the chemical foaming method. The effects of water–cement ratio, foaming agent, and foaming stabilizer on the mechanical and thermal properties of foamed concrete were studied. Meanwhile, a portion of cement was replaced with foamed phenolic particles to further optimize the performance of foamed concrete; the results show that when the water–cement ratio was 0.53, the foaming agent content was 5%, the foam stabilizer was 1%, and the substitution of phenolic particles was 20%, the performance indexes of foamed concrete were the best. Methods, describing briefly the main methods or treatments applied: dry density was 278.4 kg/m3, water absorption was 19.9%, compressive strength was 3.01 MPa, and thermal conductivity was 0.072 W/(m·K). By the pore structure analysis of the foamed concrete suing Micro-CT, it was found that when the replacement amount of phenolic particles was 20%, the pore size of foamed concrete was relatively uniform, the minimum D90 was 225 μm respectively. The combination of organic and inorganic matrix and optimized pore structure improved the performance of foamed concrete.

Microstructure of High Strength Cement Paste Systems

1984 ◽  
Vol 42 ◽  
Author(s):  
M. Regourd
Keyword(s):  
Cement Paste ◽  
Ultrafine Particles ◽  
High Strength ◽  
Interfacial Bond ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Composite Systems ◽  
Crystalline Hydrates ◽  
Low Porosity

AbstractHigh strength cement pastes include hot pressed, autoclaved, impregnated low water/cement ratio, macrodefect free, ultrafine particles arrangement systems. The densification of the microstrucure is mainly related to a low porosity and to the formation of poorly crystalline hydrates. In composite systems like mortars and concretes, the interfacial bond between the cement paste and aggregates is moreover less porous and more finely crystallized than the normal “auréole de transition”.

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.

Evaluation of initial setting time due to superplasticizers

2017 ◽  
Vol 8 (2) ◽  
pp. 65
Author(s):  
Abhishek Singh ◽  
Shobha Ram ◽  
Alok Verma
Keyword(s):  
Water Content ◽  
Cement Paste ◽  
Setting Time ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Initial Setting Time ◽  
Initial Setting

This paper shows how polycarboxylate based superplasticizer affects the initial setting time of cement paste. Three superplasticizers are used in this study with different properties and aiming to determine the delay in initial setting time due to superplasticizer. Initial setting time is calculated as per IS: 4031-PART 5-1988 with different SP dosages (0.5%, 0.75%, 1.0% and 1.5% of weight of cement). Superplasticizer is an admixture which reduces the water-cement ratio or increase the workability at the same water content. This paper deals with the evaluation of initial setting time due to superplasticizers.

scholarly journals Strength and Deformability of Fiber Reinforced Cement Paste on the Basis of Basalt Fiber

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Yury Barabanshchikov ◽  
Ilya Gutskalov
Keyword(s):  
Crack Resistance ◽  
Cement Paste ◽  
Basalt Fiber ◽  
Fiber Content ◽  
Fiber Reinforced ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Particulate Reinforcement ◽  
Reinforced Cement ◽  
Basaltic Fiber

The research object of the paper is cement paste with the particulate reinforcement of basalt fiber. Regardless of fibers’ length at the same fiber cement mix workability and cement consumption equality compressive solidity of the specimens is reduced with increasing fiber content. This is due to the necessity to increase the water-cement ratio to obtain a given workability. The flexural stability of the specimens with increasing fiber content increments in the same conditions. There is an optimum value of the fibers’ dosage. That is why stability has a maximum when crooking. The basaltic fiber particulate reinforcement usage can abruptly increase the cement paste level limiting extensibility, which is extremely important in terms of crack resistance.

Regression Analysis on Bonding Test of Polypropylene Fiber

2014 ◽  
Vol 638-640 ◽  
pp. 1378-1382
Author(s):  
Wei Hong Xuan ◽  
Yan Wang ◽  
Yu Zhi Chen
Keyword(s):  
Regression Analysis ◽  
Polypropylene Fiber ◽  
Pullout Test ◽  
Cement Matrix ◽  
Test Results ◽  
Pullout Force ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Factor Regression ◽  
Force Displacement

Base on the data that gained from pullout test of Polypropylene fiber, multi-factor regression analysis considering water cement ratio and age of cement matrix, length and angle of embedded fiber was carried out. Then, a practical function of pullout force-displacement was proposed, which is well agreed with the test results.

Prediction of Elastic Modulus of Cement-Based Materials Based on Power’s Volume Model

2012 ◽  
Vol 253-255 ◽  
pp. 474-477 ◽  
Author(s):  
Lang Wu ◽  
Bing Yan ◽  
Bin Lei
Keyword(s):  
Elastic Modulus ◽  
Elastic Properties ◽  
Cement Paste ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Micromechanics Model ◽  
Volume Model ◽  
Cement Based Materials ◽  
Hydrated Products ◽  
Multi Phase

The hydrated products, unhydrated cement and water (capillary pores) in the cement paste are seen as matrix, inclusion, Equivalent medium respectively, We used the micromechanics theories and Power’s Volume model to develop a multi-phase micromechanics model capable of simulating the elastic properties of cement-based materials, and the evolution of elastic properties in the hydration process was calculated at different water-cement ratio. The final experimental results show that this model can be used to predict the elastic properties of cement-based materials.

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