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Cracking behavior of concrete caused by early age drying shrinkage is simulated based on a multi-scale computational system. The original analysis indicates that the deformation of a restrained concrete cannot be well simulated, and micro-crack status at surface is greatly overestimated. Therefore, a local tensile strength model treating micro-pore...
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... analysis is cracked case, on the other hand is non-cracked case. The cracked case assumes that when the tensile stress exceeds tensile strength, cracks occur in the element, and the strain-stress relationship afterwards follows the tension softening law (Figure 2). The tensile strength f' t used in cracked case is derived from compressive strength f' c , and the equation is given as following JSCE code (Japan Society of Civil Engineering 2007). ...
Context 2
... creep. Referring back to Figure 2, the deformation of restrained concrete relies on not only tensile strength but also the strain-stress relationship after local cracking. Unlike uniaxial tensile test, the penetrating cracking of restrained specimen is progress as long as tens of days. ...
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Citations
... In addition, it is essential to consider the molar volume differences between the hydration products and clinker minerals. This difference leads to a phenomenon known as chemical shrinkage, where the total volume of the hydration products is less than the total volume of the clinker minerals; this phenomenon contributes to self-desiccation and autogenous contraction in cementitious systems [51,52]. Previous studies have often overlooked or assumed constant percentages of reacted cement; however, this can have implications in accurately Table 3 Coefficients for computing the hydration degree of the clinker phases [44,45]. ...
This study presents a systematic model to optimise nano-silica utilisation in cement paste and predict its nonlinear behaviour. The model integrates a hydration model, which calculates the dissolution rate of each clinker mineral, with a thermodynamic model that simulates the hydration reaction and interaction between hydrates and nano-silica. The investigation considered different replacement levels of nano-silica (2 and 4% by weight of cement) to analyse the phase assemblages and porosity of nano-silica reinforced cement paste. The reaction between nano-silica and the hydrate (portlandite) was meticulously accounted for by incorporating the formation of calcium-silica-hydrate (C-S-H) with a realistic transition from jennite-type C-S-H (Si/Ca ratio of 0.58) to tobermorite C-S-H (Si/Ca ratio of 0.67). The coupled model was validated against the experimental results obtained from thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy, ensuring its reliability. Subsequently, the model was used to compute the volume fractions of various phases including hydrates, unhydrated clinkers, pores, and unreacted nano-silica. A representative volume element (RVE) was formulated for the cement pastes with and without nano-silica using MATLAB. The RVE was further evaluated through finite element analysis using COMSOL Multiphysics, enabling the computation of homogenised material properties such as compressive strength, and this aligned well with experimental findings. In summary, the proposed systematic model provides a realistic prediction of the nonlinear behaviour of cement pastes with different nano-silica replacement levels. Its applicability extends to the optimisation of cement-based composites for diverse engineering applications.
... In addition, in the model, the strength prediction of concrete accounted for the factors like water-to-binder ratio, mineral composition of cement, curing temperature, internal porosity and admixtures (silica fume). Even though the strength predictability of the DuCOM model was verified with available literature with 2.95 N/mm 2 of standard deviation, the model did not account for the fundamental factors that affect the concrete strength such as aggregate properties (strength), interfacial transition zone (ITZ), air content, etc. [117,119]. However, the DuCOM model which is among the several strength prediction model, directly correlate the strength of cement paste to the strength of concrete, which features extend its wide applications. ...
... A schematic representation of the multi-scale approach in the DuCOM model[119]. ...
In Civil Engineering field, the compressive strength of concrete is a key parameter to design concrete structures and evaluate existing structures. Conventionally the measurement of the strength requires a considerable amount of time (~28 days) and cost. Thus, this paper comprehensively reviews the literature on strength prediction models focusing on the prediction mechanism and its prediction precision. The literature demonstrates that various techniques including mathematics and statistics, analytical, numerical, computational, homogenization and multi-scale model have been employed to develop a model. An analytical model which simply correlates compressive strength and strength influencing factors was first introduced based on a statistical analysis of experimental data and the ideology of concrete technology. With the advancement of concrete technology, those analytical models fail to account for the complexity of strength affecting factors and compute less accurate results. Although Machine Learning (ML) techniques have proven superior accuracy for estimating the mixture proportions and mechanical properties of novel concrete with complex cementitious material, the prediction mechanism is being ‘black box’ which limits its wide application. Since the microstructure of hydrated cement paste was identified as a strength controlling factor in concrete, several models have been developed simulating the hydration of cementitious materials and thus bridging between nano and macro properties such as compressive strength and young’s modulus of concrete. Even though those microstructural models give comparable results with experimental data, various assumptions and hypotheses were considered during the model development. In addition, some of the models could not directly correlate the macro properties of concrete. The review presented in this paper is strong evidence of the need for a powerful model which realistically predicts the mechanical properties of concrete incorporating fundamental physics and chemistry, thermodynamic consideration, bonding and packing arrangement between particles.
... In this section, FE analysis of multi-layer composite experiments is performed. In the analysis, moisture migration and thermodynamic equilibrium are calculated by considering concrete composition, [34,35]. Table 3 lists the main mechanical models incorporated in the constitutive model. ...
The shear resistant mechanism along cracks of concrete changes as localized shear deformation progresses. The aggregate interlock mechanism shifts to the Coulomb friction mechanism. A disintegration model considering the transient shear transfer has been proposed. In this study, the applicability of this constitutive model to low and normal strength concrete was verified through experiments and post-peak analysis. As a conclusion, it is clarified that when this graveling formation progresses along the localized shear bands in structures, it is necessary to consider the transition of shear disintegration and the proposed model has fair consistency with the experimental results. Moreover, the average frictional coefficient of disintegrated cementitious composite is inversely idealized about 1.0 for concrete and about 0.4 for mortar. It is expected that the proposed model will increase the accuracy of analyzing the structural restoring force characteristics of reinforced concrete and its post-peak behaviors.
... The multi-scale thermo-hygral simulation, which integrates micro-scale events of cement hydration and moisture migration with macro-scale structure responses, has been applied. Then, the effect of autogenous and drying shrinkage of concrete was taken into account (Maekawa et al. 2009;Yoneda et al. 2013) for Cases II and III. The input values of each case are summarized in Table 3. ...
Shear failure experiments of concrete beams containing a weak layer were conducted with a focus on the bifurcation of shear localization appearing at the boundary between structure and soil foundation. Low-strength concrete, which is analogous to artificial soft rocks and strengthened foundation, was used to create a weak layer that caused dispersal and bifurcation of the shear localization area, resulting in ductile fracturing of members. Pulverization of hardened cement paste and gravelization (the loss of aggregate particle's cementation) were observed in shear planes appearing in the weak layer. This confirmed the difficulty of simulating bifurcating shear localization solely by the constitutive law of concrete, which assumes firm cementation by hardened cement paste. In reference to the simulation of the disintegrated concrete slabs for bridge decks under fatigue loads, the transient model from hardened concrete to gravelized assembly was proposed , and it was successfully applied to the bifurcating shear localization of weak layers of low-strength concrete.
... Yuan and Wan completed a numerical procedure based on a micromechanical model and empirical formulas with consideration of creep, hydration, and moisture transport [3]. Yoneda et al. proposed a local tensile strength model treating micropore water pressure as prestress and applied the model to cracking criterion [9]. ...
Due to the low hydration rate of high-volume fly ash (HVFA) concrete at early age, the temperature gradient between the concrete core and surfaces could be effectively reduced. However, the low hydration rate results in a lack of hydration degree for early-age HVFA concrete. Thus, during curing, compared to the strength of ordinary Portland cement (OPC), a subsequent lower one of HVFA concrete leads to a more sensitive response to inner stresses induced by thermal and moisture loads. Based on ABAQUS, in this paper, user subroutines in the temperature and moisture fields were developed, with regard to the hydration degree, for simulation of the temperature and moisture influences on concrete. Additionally, the Double Power Law (DPL) model was used to depict early-age deformations of concrete in the mechanical field. Combined with the extended finite element method (XFEM), another subroutine for early-age cracking analysis in the mechanical field was then developed. Together with aforementioned subroutines, a thermo-hygro-mechanical model is derived. For evaluation of early-age cracking initiation and propagation of a pier composed of HVFA concrete, the model was implemented with XFEM. The obtained results show that (1) temperature and restraints are the main causes of cracking; (2) moisture loss affects surface cracks on structures at early age; and (3) although the temperature difference between the core and surfaces is not much obvious due to the reduced rate of heat dissipation from hydration, cracking of early-age HVFA concrete is still likely to happen for its low early strength. Thus, timely curing is critical to prevent early cracking.
... Several THM analysis methodologies have been developed or used, for serviceability analyses of restrained RC members (Gasch et al. 2016;Nakamura et al. 2006;Sciumè et al. 2012;Yoneda et al. 2013). However, none of those have analysed the crack propagation in thick, restrained, RC members, since the early ages until the long-term, considering the imposed deformations due to cement hydration and shrinkage. ...
Preface: This special issue of the Journal of Advanced Concrete Technology presents seven invited journal papers, which were selected on basis of outstanding conference contributions during the International RILEM/COST conference SynerCrete’18, held on 24-26 October 2018 in Funchal, Madeira Island, Portugal, which gathered 183 participants. The selection was made by the scientific committee and the chairpersons among 184 contributions. The conference itself dealt with interdisciplinary approaches for cement-based materials and structural concrete, intending to provide added value through collaborations across the entire field of structural concrete – ranging from concrete technology, over simulation and structural design, production and building, up to operation, monitoring and maintenance. Exciting fields of research such as performance-based design, 3D modelling for analysis/design, Building Information Modelling and even robotics (e.g. digital fabrication or robotics design) were included, while retaining focus on multi-scale approaches at time and spatial levels. Overall, the hereby promoted journal papers are representative for the successful balance act between a great versatility of the conference contributions and the targeted synergizing of expertise aiming on the ultimate goal of reliable and durable concrete structures. SynerCrete’18 also marked the end of COST Action TU1404 “Towards the next generation of standards for service life of cement-based materials and structures” (www.tu1404.eu), offering a final forum to the discussions raised during the funded period of the Action from 2014 to 2018. A sense of accomplishment was felt by all the members of the Action, in the view of the important achievements of networking tools that were brought about by the extended Round Robin Testing Programme (RRT+), the Numerical Benchmarking Activities and 24 Short Term Scientific Missions (STSMs). Some of the selected papers in this special issue are the result of fruitful collaborations initiated by COST Action TU1404. A further remark in regard to the wide international institutional support that this conference attained, is about the direct support of RILEM, fib, JCI and ACI. Specifically, with regard to the Japanese Concrete Institute, a mention is given to the special session dedicated to the most recent version of “JCI Guidelines for Control of Cracking of Mass Concrete”, as it was indeed one of the most inspiring documents that influenced the genesis of COST Action TU1404.
... Several THM analysis methodologies have been developed or used, for serviceability analyses of restrained RC members (Gasch et al. 2016;Nakamura et al. 2006;Sciumè et al. 2012;Yoneda et al. 2013). However, none of those have analysed the crack propagation in thick, restrained, RC members, since the early ages until the long-term, considering the imposed deformations due to cement hydration and shrinkage. ...
The calculation of crack width in thick, restrained, reinforced concrete (RC) members has relevance, either at the design stage or during the assessment of existing structures. This type of structural element exhibits a complex serviceability behaviour, due to the nonlinear self-induced deformations caused by cement hydration and shrinkage, and also the interaction between primary cracks and secondary cracks which do not fully penetrate in the cross section. In this context, this paper presents a staggered thermo-hygro-mechanical (THM) analysis methodology, based on the finite element method (FEM), for calculation of the long-term development of self-induced deformations, stresses and cracks, since casting, at the macro scale. A comprehensive approach is followed, in which the mechanical material models are defined as a function of the calculated thermal and hygral fields. This analysis methodology is applied in the study of the crack formation in end restrained slab-like RC members, with a thickness of 50 cm, a parametric analysis in conducted in order to gain insight about the influence of some relevant structural and material variables.
... If there is tensile stress developed in concrete, it will result in cracking because concrete can withstand compressive stresses. There are two restraint types; internal and external which are interconnected and generally to some extent exist in concrete members [1]. Three-dimension finite element simulation is presented to model the behavior of the concrete at an early age. ...
... Many numerical tools have been formulated to evaluate the acquired to reduce the cracking risk at an early age caused by drying shrinkage [1,2]. Based on mathematical models capable, these tools are taken to depict the coupling of thermal, moisture diffusion, chemical, and mechanical analysis. ...
Drying shrinkage can be defined as the reduction of volume that concrete undergoes as a result of the moisture relocation when exposed to a lower relative moist surrounding environment than the foremost one of its basic pore structure system. Finite element model(FEM) is developed and implemented, to simulate and analyses the early age restrained cracking behavior due to drying shrinkage. The Simulation focus on the evaluation of the impact of restrained edge distance on early age cracking due to deformation resulting from drying shrinkage. The FEM analysis Model deals with phenomena of temperature, humidity exchange, thermal diffusion, and mechanical behavior which can take a place at the three first days followed the concrete casting, to evaluate the diameter, distance effects on the early age crack. The effect of the diameter of the restricted steel ring was studied on the diameter of the concrete and the spacing between them. The results were compared with the results of the experiments discussed in the published literature; it was found that there is an excellent agreement for all the performed analysis.
... The continued deflection for a long time is clarified mainly due to the differential shrinkage of viaduct's flanges of different dimensions . Currently, the long-term excessive deflection can be estimated by thermo-hygral analysis (Ishida et al. 2007;Maekawa et al. 2008;Yoneda et al. 2015Yoneda et al. , 2013 which simulates the moisture migration and equilibrium coupled with mechanical models as shown in Fig. 1. ...
... Under the lapped curing, moisture loss through the surfaces is not computationally allowed. At the onset of exposure to out-door climate, the moisture transfer elements are placed on the surface and the moisture exchange between concrete and environments is made possible (Yoneda et al. 2015(Yoneda et al. , 2013. ...
Middle-scale box-sectional hollow PC ducts, which consist of heterogeneous concrete with different mix proportions, were exposed to natural environments for about three years, and the long-term curvature and axial mean deformation, which have much to do with deflection of long span bridge viaducts, was gaged for verification of coupled thermo-hygral and multi-scale models. The associated internal moisture and the local climate inside micro-pores were measured and the effect of precipitation was quantified over yearly four seasons. The moisture migration linked with concrete multi-scale
mechanics was analyzed and the simulation results are compared with the field exposure tests. The reliability of the thermo-hygral analysis, which has been used for estimating the long-term serviceability of bridges, was made firmer.
... The continued deflection for a long time is clarified mainly due to the differential shrinkage of viaduct's flanges of different dimensions . Currently, the long-term excessive deflection can be estimated by thermo-hygral analysis (Ishida et al. 2007;Maekawa et al. 2008;Yoneda et al. 2015Yoneda et al. , 2013 which simulates the moisture migration and equilibrium coupled with mechanical models as shown in Fig. 1. ...
... Under the lapped curing, moisture loss through the surfaces is not computationally allowed. At the onset of exposure to out-door climate, the moisture transfer elements are placed on the surface and the moisture exchange between concrete and environments is made possible (Yoneda et al. 2015(Yoneda et al. , 2013. ...
Middle-scale box-sectional hollow PC ducts, which consist of heterogeneous concrete with different mix proportions, were exposed to natural environments for about three years, and the long-term curvature and axial mean deformation, which have much to do with deflection of long span bridge viaducts, was gaged for verification of coupled thermo-hygral and multi-scale models. The associated internal moisture and the local climate inside micro-pores were measured and the effect of precipitation was quantified over yearly four seasons. The moisture migration linked with concrete multi-scale mechanics was analyzed and the simulation results are compared with the field exposure tests. The reliability of the thermo-hygral analysis, which has been used for estimating the long-term serviceability of bridges, was made firmer.
