Autogenous Shrinkage of Cement Paste Interpreted by Electrical Resistivity and Capillary Stress at Early Age

2018 ◽  
Vol 47 (1) ◽  
pp. 20170117 ◽  
Author(s):  
Jiayin Tao ◽  
Xiaosheng Wei ◽  
Lei Fu
Keyword(s):  
Electrical Resistivity ◽  
Cement Paste ◽  
Autogenous Shrinkage ◽  
Early Age ◽  
Capillary Stress

Microstructural modelling of autogenous shrinkage in Portland cement paste at early age

2020 ◽  
Vol 37 (9) ◽  
pp. 3171-3186
Author(s):  
Huy Quang Do ◽  
Shashank Bishnoi ◽  
Karen Louise Scrivener
Keyword(s):  
Cement Paste ◽  
Autogenous Shrinkage ◽  
Early Age ◽  
Variable Load ◽  
Good Prediction ◽  
Content Type ◽  
Capillary Stress ◽  
Microstructural Modelling ◽  
Creep And Shrinkage ◽  
Autogeneous Shrinkage

Purpose This paper aims to develop a numerical, micromechanical model to predict the evolution of autogenous shrinkage of hydrating cement paste at early age (up to 7 days). Autogeneous shrinkage can be important in high-performance concrete characterized by low water to cement (w/c) ratios. The occurrence of this phenomenon during the first few days of hardening may result in early-age cracking in concrete structures. A good prediction of autogeneous shrinkage is necessary to achieve better understanding of the mechanisms and the deployment of effective measures to prevent early-age cracking. Design/methodology/approach Three-dimensional digital microstructures from the hydration modelling platform μic of cement paste were used to simulate macroscopic autogenous shrinkage based on the mechanism of capillary tension. Elastic and creep properties of the digital microstructures were calculated by means of finite element (FE) method homogenization. Autogenous shrinkage was then estimated as the average hydrostatic strain resulting from the capillary stress that was globally applied on the simulated digital microstructures. For this estimation, two approaches of homogenization technique, i.e. analytical poro-elasticity and numerical creep-superposition were used. Findings The comparisons of between the simulated and experimentally measured deformations indicate that the creep-superposition approach is more reasonable to estimate shrinkage at different water to cement ratios. It was found that better estimations could be obtained at low degrees of hydration, by assuming a loosely packed calcium silicate hydrates (C-S-H) growing in the microstructures. The simulation results show how numerical models can be used to upscale from microscopic characteristics of phases to macroscopic composite properties such as elasticity, creep and shrinkage. Research limitations/implications While the good predictions of some cement paste properties from the microstructure at early age were obtained, the current models have several limitations that are needed to overcome in the future. Firstly, the limitation of pore-structure representation is not only from lack understanding of C-S-H structure but also from the computational complexity. Secondly, the models do not consider early-age expansion that usually happens in practice and appears to be superimposed on an underlying shrinkage as observed in experiments. Thirdly, the simplified assumptions for mechanical simulation do not accurately reflect the solid–liquid interactions in the real partially saturated system, for example, the globally applying capillary stress on the boundary of the microstructure to find the effective deformation, neglecting water flow and the pore pressure. Last but not least, the models, due to the computational complexities, use many simplifications such as FE approximation, mechanical phase properties and creep statistical data. Originality/value This study holistically tackles the phenomenon of autogeneous shrinkage through microstructural modelling. In a first such attempt, the authors have used the same microstructural model to simulate the microstructural development, elastic properties, creep and autogeneous shrinkage. The task of putting these models together was not simple. The authors have successfully handled several problems at each step in an elegant manner. For example, although several earlier studies have pointed out that discrete models are unable to capture the late setting times of cements due to mesh effects, this study offers the most effective solution yet on the problem. It is also the first time that creep and shrinkage have been modelled on a young evolving microstructure that is subjected to a time variable load.

scholarly journals A Mathematical Model for the Electrical Resistivity of Cement Paste at Early Ages Considering the Partially Saturated State

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3306 ◽  
Author(s):  
Ye Tian ◽  
Xin Xu ◽  
Haodong Ji ◽  
Zushi Tian ◽  
Xianyu Jin ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Electrical Resistivity ◽  
Cement Paste ◽  
Isothermal Calorimetry ◽  
Setting Time ◽  
Degree Of Saturation ◽  
Early Age ◽  
Saturation State ◽  
Partially Saturated ◽  
Saturated State

For cementitious materials, electrical resistivity is often used in the study of the cement hydration process at early age, as one of the few indicators that can be continuously and non-destructively monitored. Variation characteristics of resistivity are widely reported to interact with the early-age performance of cement paste, such as hydration kinetics parameters and setting time. However, there is no reasonable mathematical model to predict the resistivity at early ages, especially within the first 24 h, due to significant changes in the porosity and degree of saturation. In this work, a mathematical model was developed by considering the partially saturated state and density change of C-S-H (calcium silicate hydrate). To verify the model, two experimental methods were chosen, including the non-contact electrical resistivity test and isothermal calorimetry test. The hydration heat and resistivity of cement paste with a water–cement ratio of 0.35 and 0.45 were continuously monitored for 3 days. In the resistivity test, embedded temperature sensors were used to monitor the internal temperature and temperature correction was treated carefully in order to obtain accurate data. The test results prove that the mathematical model can accurately predict electrical resistivity and describe the saturation state of early-age cement pastes under sealed curing.

scholarly journals Can the maturity concept be used to separate the autogenous shrinkage and thermal deformation of a cement paste at early age?

2002 ◽  
Vol 32 (9) ◽  
pp. 1443-1450 ◽  
Author(s):  
Philippe Turcry ◽  
Ahmed Loukili ◽  
Laurent Barcelo ◽  
Jean Michel Casabonne
Keyword(s):  
Cement Paste ◽  
Thermal Deformation ◽  
Autogenous Shrinkage ◽  
Early Age

scholarly journals Effects of graphene oxide on early-age hydration and electrical resistivity of Portland cement paste

2017 ◽  
Vol 136 ◽  
pp. 506-514 ◽  
Author(s):  
Wengui Li ◽  
Xiangyu Li ◽  
Shu Jian Chen ◽  
Yan Ming Liu ◽  
Wen Hui Duan ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Graphene Oxide ◽  
Portland Cement ◽  
Cement Paste ◽  
Early Age ◽  
Portland Cement Paste ◽  
Early Age Hydration

scholarly journals Autogenous shrinkage of Eco-cement paste and mortar at early age

2002 ◽  
Vol 13 (3) ◽  
pp. 29-37
Author(s):  
Hiroshi HIRAO ◽  
Masao ISHIDA
Keyword(s):  
Cement Paste ◽  
Autogenous Shrinkage ◽  
Early Age

scholarly journals Investigation of the early-age performance and microstructure of nano-C–S–H blended cement-based materials

2021 ◽  
Vol 10 (1) ◽  
pp. 1374-1382
Author(s):  
Wei He ◽  
Gang Liao
Keyword(s):  
Cement Paste ◽  
Pore Diameter ◽  
Autogenous Shrinkage ◽  
Blended Cement ◽  
Cement Matrix ◽  
Early Age ◽  
Early Hydration ◽  
Characterization Methods ◽  
Gradual Loss ◽  
Cement Based Materials

Abstract Nano calcium silicate hydrate (nano-C–S–H) has become a novel additive for advanced cement-based materials. In this paper, the effect of nano-C–S–H on the early-age performance of cement paste has been studied, and some micro-characterization methods were used to measure the microstructure of nano-C–S–H-modified cement-based material. The results showed that the initial fluidity of cement paste was improved after addition of nano-C–S–H, but the fluidity gradual loss increased with the dosage of nano-C–S–H. The autogenous shrinkage of cement paste can be reduced by up to 42% maximum at an appropriate addition of nano-C–S–H. The mechanical property of cement paste was enhanced noticeably after adding nano-C–S–H, namely, the compressive strengths were improved by 52% and 47.74% at age of 1 day and 7 days, respectively. More hydration products were observed and pore diameter of cement matrix was refined after adding nano-C–S–H, indicating that the early hydration process of cement was accelerated by nano-C–S–H. This was mainly attributed to seed effect of nano-C–S–H. The detailed relationship between microstructure and early-age performance was also discussed.

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