Evolution of microstructures of cement paste via continuous-based hydration model of non-spherical cement particles

2020 ◽  
Vol 185 ◽  
pp. 107795 ◽  
Author(s):  
Zhigang Zhu ◽  
Wenxiang Xu ◽  
Huisu Chen ◽  
Zhijun Tan
Keyword(s):  
Cement Paste ◽  
Hydration Model

scholarly journals An Efficient Approach of Predicting the Elastic Property of Hydrating Cement Paste

2021 ◽  
Vol 8 ◽  
Author(s):  
Baoyu Ma ◽  
Guansuo Dui ◽  
Zhenglin Jia ◽  
Bo Yang ◽  
Chunyan Yang ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Cement Paste ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Empirical Method ◽  
Elastic Behavior ◽  
Engineering Practice ◽  
Proposed Model ◽  
Hydration Model ◽  
Semi Empirical

Although elastic properties of hydrating cement paste are crucial in concrete engineering practice, there are only a few widely available models for engineers to predict the elastic behavior of hydrating cement paste. Therefore, in this paper, we derive an analytical model to efficiently predict the elastic properties (e.g., Young’s modulus) of hydrating cement paste. Notably, the proposed model provides the prediction of hydration, percolation, and homogenization of the cement paste, enabling the study of the early age elasticity evolution in cement paste. A hydration model considering the mineral composition and the initial w/c ratio was used, while the percolation threshold was calculated adopting a phenomenological semi-empirical method describing the effects of the solid volume fraction and the w/c ratio. An efficient mixing rule based on the degree of solid connectivity was then adopted to calculate the elastic properties of the hydrating cement paste. Moreover, for ordinary Portland cement, a simplified model was built using Powers’ hydration model. The obtained modeling results are following experimental data and other numerical results available in the literature.

scholarly journals Simulation of Permeation of Saturated Cement Paste Based on a New Meso-scale Pore Network Model

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Yong Zhou ◽  
Yuxuan Yang ◽  
Bigya Gyawali ◽  
Weiping Zhang
Keyword(s):  
Network Model ◽  
Cement Paste ◽  
Pore Network ◽  
Pore Network Model ◽  
Cement Particle ◽  
Hydrated Cement ◽  
Network Construction ◽  
Water Permeation ◽  
Model And Simulation ◽  
Hydration Model

AbstractThis paper presents the simulation of the permeation of saturated cement paste based on a novel pore network model. First, a 2D hydration model of cement particles was developed by extending the work of Zheng et al. 2005 to provide the background for the network construction. Secondly, the establishment of the pore network model and simulation of permeation of saturated cement paste were carried out. The irregular pores between any two hydrated cement particles were linearized with clear distances as the diameters of pores. The straight tubular pores were interconnected with one another to form the network model. During this process, the weighted Voronoi diagram was employed to operate on the graphical expression of the hydrated cement particles. Water permeation in saturated cement paste was simulated to verify the pore network model. Finally, the factors including water–cement ratio, reaction temperature, reaction time and cement particle size that would influence water permeation were numerically investigated.

scholarly journals Effects of Nano-SiO2 and SAP on Hydration Process of Early-Age Cement Paste Using LF-NMR

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Haitao Zhao ◽  
Yi Wan ◽  
Jun Xie ◽  
Kaidi Jiang ◽  
Donghui Huang ◽  
...  
Keyword(s):  
Cement Paste ◽  
Bound Water ◽  
Hydration Process ◽  
Early Age ◽  
Superabsorbent Polymer ◽  
Test Results ◽  
Low Field ◽  
Water To Cement Ratio ◽  
Hydration Model ◽  
Zero Points

The effects of nano-SiO2 and superabsorbent polymer on the hydration process of early-age cement paste are investigated through the physically bound water evolution test by means of the low-field nuclear magnetic resonance technology. The test results show that the hydration process can be characterized by four-stage patterns based on the zero points of the second-order differential hydration curve, i.e., the initial, accelerated, decelerated, and steady periods. The beginning time of each stage is postponed and the hydration duration is prolonged with an increasing water to cement ratio. The beginning time of each stage and the hydration duration are shortened with an increasing content of nano-SiO2. And the beginning time of each stage and the hydration duration are prolonged with an increasing content of superabsorbent polymer. Based on the test data and the Avrami–Erofeev model, a modified hydration model taking the influence of nano-SiO2 and SAP into account is proposed, and the predicted results are consistent with the test results.

Diffusivity of cement paste via a continuum-based microstructure and hydration model: influence of cement grain shape

2021 ◽  
pp. 103920
Author(s):  
Zhigang Zhu ◽  
Wenxiang Xu ◽  
Huisu Chen ◽  
Yuan Wang ◽  
Xiaofan Gou ◽  
...  
Keyword(s):  
Cement Paste ◽  
Grain Shape ◽  
Hydration Model

scholarly journals Hydration of Early Age Cement Paste with Nano-CaCO3 and SAP by LF-NMR Spectroscopy: Mechanism and Prediction

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Haitao Zhao ◽  
Gaoyang Sun ◽  
Lu Yu ◽  
Kaidi Jiang ◽  
Xiaodong Chen ◽  
...  
Keyword(s):  
Cement Paste ◽  
Initial Period ◽  
Bound Water ◽  
Hydration Process ◽  
Early Age ◽  
Starting Time ◽  
Water To Cement Ratio ◽  
Acceleration Period ◽  
Hydration Model ◽  
Lf Nmr

In this paper, by testing the evolution of the physically bound water using the low-field nuclear magnetic resonance (LF-NMR) technology, the hydration process of cement paste with nano-CaCO3 (NC) and superabsorbent polymer (SAP) at early age is investigated. Results indicate that the hydration process can be divided into four periods according to the zero points of the second-order differential hydration curve: initial period, acceleration period, deceleration period, and steady period. Firstly, with the increase in the water to cement ratio, the starting time of the hydration period is delayed, and the duration becomes longer. Secondly, the addition of NC leads to the speedy arrival of each period and shortens the duration of each period in the hydration process, and the optimal NC content is 1.5%. Thirdly, with the increase in SAP content, the starting time of the hydration period is delayed and the duration becomes longer. Finally, based on the experimental results and the existing hydration model, the modified hydration model considering the content of NC and SAP is proposed.

Numerical Simulation of Autogenous Shrinkage in High-Performance Cement Paste Based on a Multi-Component Hydration Model

2008 ◽  
Vol 385-387 ◽  
pp. 629-632
Author(s):  
Seung Min Lim ◽  
Han Seung Lee ◽  
Xiao Yong Wang
Keyword(s):  
Numerical Simulation ◽  
Cement Paste ◽  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Curing Temperature ◽  
Hydration Process ◽  
Material System ◽  
Water Mixture ◽  
Hydration Model

Autogenous shrinkage is the term for the bulk deformation of a closed, isothermal, cement-based material system not subjected to external forces. It is associated with the internal volume reduction of cement/water mixture in the course of the hydration process. However, addition of blended components to cement, especially such as fly ash or silica fume, for the high-performance concrete will lead to a densification of the microstructure. The autogenous shrinkage deformation will increase and the following autogenous shrinkage crack will do harm to durability of concrete structure. In this paper, numerical simulation is suggested to predict autogenous shrinkage of high performance cement paste. The simulation is originated from a multicomponent hydration model. The numerical program considers the influence of water to cement ratio, curing temperature, particle size distribution, cement mineral components on hydration process and autogenous shrinkage. The prediction result agrees well with experiment result.

scholarly journals DISTRIBUTION OF HYDRATION PRODUCTS IN THE MICROSTRUCTURE OF CEMENT PASTES

2020 ◽  
Vol 27 ◽  
pp. 84-89
Author(s):  
Michal Hlobil
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Numerical Study ◽  
Hardened Cement ◽  
Spatial Gradient ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Cement Pastes ◽  
Hydration Model

This case study focuses on the quantification of the amorphous hydrate distribution in the microstructure of hardened cement paste. Microtomographic scans of the hardenend cement paste were thresholded based on histogram image analysis combined with microstructural composition obtained from CEMHYD3D hydration model, to separate unhydrated cement grains, crystalline and amorphous hydrates, and capillary pores. The observed spatial distribution of the amorphous hydrate exhibited a strong spatial gradient as the amorphous gel tended to concentrate around dissolving cement grains rather than precipitate uniformly in the available space. A comparative numerical study was carried out to highlight the effect of the spatially (non)uniform hydrate distribution on the compressive strength of the hardened cement paste.

Prediction of the Elastic Modulus of Cement Paste as a Kinetic Hydration Model

2007 ◽  
Vol 348-349 ◽  
pp. 421-424 ◽  
Author(s):  
Ki Bong Park ◽  
Han Seung Lee ◽  
Xiao Yong Wang ◽  
Seung Min Lim
Keyword(s):  
Elastic Modulus ◽  
Cement Paste ◽  
Three Dimensional ◽  
Unit Cell ◽  
Element Analysis ◽  
Degree Of Hydration ◽  
Total Displacement ◽  
The Finite Element Analysis ◽  
Model Predictions ◽  
Hydration Model

This paper describes a numerical method for estimating the elastic modulus of cement paste. The cement paste is modeled as a unit cell, which consists of three parts: dehydrated cement grain, gel, and capillary pore. In the unit cell, the volume fractions of the constituents are quantified with a single kinetic function of the degree of hydration. The elastic modulus of cement paste was calculated from the total displacement of constituents when the uniform pressure was applied to the gel contact area in cement paste assumed a homogenous isotropic matrix. Numerical simulations were conducted through the finite element analysis of the three-dimensional periodic unit cell. The model predictions were compared with experimental results. The predicted trends agree with experimental observations. The approach and some of the results might also be relevant for other technical applications.

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