Numerical Modelling of Field Test for Crack Risk Assessment of Early Age Concrete Containing Fly Ash

The high-strength/high-performance concretes are prone to cracking at early age due to low water/binder ratio. The replacement of cement with mineral additives such as fly ash and blast-furnace slag reduces the hydration heat during the hardening phase, but at the same time, it has significant influence on the development of mechanic and viscoelastic properties of early age concrete. Its potential benefit to minimize the cracking risk was investigated through a filed experiment carried out by the Norwegian Directorate of Roads. The temperature development and strain development of the early age concrete with/without the fly ash were measured for a “double-wall” structure. Based on experimental data and well-documented material models which were verified by calibration of restraint stress development in TSTM test, thermal-structural analysis was performed by finite element program DIANA to assess the cracking risk for concrete structures during hardening. The calculated and measured temperature and strain in the structure had good agreement, and the analysis results showed that mineral additives such as flay ash are beneficial in reducing cracking risk for young concrete. Furthermore, parameter studies were performed to investigate the influence of the two major factors: creep and volume change (autogenous shrinkage and thermal dilation) during hardening, on the stress development in the structure.

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Calibration of Material Models against TSTM Test for Crack Risk Assessment of Early-Age Concrete Containing Fly Ash

Advances in Materials Science and Engineering ◽

10.1155/2018/1069181 ◽

2018 ◽

Vol 2018 ◽

pp. 1-11 ◽

Cited By ~ 2

Author(s):

G. M. Ji ◽

T. Kanstad ◽

Ø. Bjøntegaard

Keyword(s):

Risk Assessment ◽

Fly Ash ◽

Blast Furnace Slag ◽

Restraint Stress ◽

Early Age ◽

Material Models ◽

Early Age Concrete ◽

Mineral Additives ◽

Cracking Risk ◽

Furnace Slag

Making reliable cracking risk assessment involves experimental testing and advanced modeling of the time- and temperature-dependent behavior of the properties, the restraint conditions of the structure, and the external environmental conditions. Mineral additives such as silica fume (SF), blast furnace slag (BFS), and fly ash (FA) have been used extensively in production of high performance concrete in the last decades. The mineral additives such as fly ash and blast furnace slag will reduce the hydration heat during the hardening phase, and the mineral additives also have significant influence on the development of mechanic and viscoelastic properties at early age. Within the NOR-CRACK project, extensive test programs were performed to investigate the material properties related to cracking risk of early-age concrete containing mineral additives. In current paper, the advanced modeling of the heat of hydration, volume changes (autogenous shrinkage and thermal dilation) during hardening, the development of mechanical properties (E-modulus, compressive strength, and tensile strength), and creep/relaxation properties are discussed. Tests were performed in “temperature stress testing machine” (TSTM) to measure the restraint stress, and well-documented material models were verified by performing 1-D analysis of restraint stress development in the TSTM (Ji, 2008).

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Studies of Fracture Toughness in Concretes Containing Fly Ash and Silica Fume in the First 28 Days of Curing

Materials ◽

10.3390/ma14020319 ◽

2021 ◽

Vol 14 (2) ◽

pp. 319

Author(s):

Grzegorz Ludwik Golewski ◽

Damian Marek Gil

Keyword(s):

Fracture Toughness ◽

Stress Intensity Factor ◽

Stress Intensity ◽

Fly Ash ◽

Critical Stress ◽

Critical Stress Intensity Factor ◽

Early Age ◽

Strength Parameters ◽

Cement Binder ◽

Mineral Additives

This paper presents the results of the fracture toughness of concretes containing two mineral additives. During the tests, the method of loading the specimens according to Mode I fracture was used. The research included an evaluation of mechanical parameters of concrete containing noncondensed silica fume (SF) in an amount of 10% and siliceous fly ash (FA) in the following amounts: 0%, 10% and 20%. The experiments were carried out on mature specimens, i.e., after 28 days of curing and specimens at an early age, i.e., after 3 and 7 days of curing. In the course of experiments, the effect of adding SF to the value of the critical stress intensity factor—KIcS in FA concretes in different periods of curing were evaluated. In addition, the basic strength parameters of concrete composites, i.e., compressive strength—fcm and splitting tensile strength—fctm, were measured. A novelty in the presented research is the evaluation of the fracture toughness of concretes with two mineral additives, assessed at an early age. During the tests, the structures of all composites and the nature of macroscopic crack propagation were also assessed. A modern and useful digital image correlation (DIC) technique was used to assess macroscopic cracks. Based on the conducted research, it was found the application of SF to FA concretes contributes to a significant increase in the fracture toughness of these materials at an early age. Moreover, on the basis of the obtained test results, it was found that the values of the critical stress intensity factor of analyzed concretes were convergent qualitatively with their strength parameters. It also has been demonstrated that in the first 28 days of concrete curing, the preferred solution is to replace cement with SF in the amount of 10% or to use a cement binder substitution with a combination of additives in proportions 10% SF + 10% FA. On the other hand, the composition of mineral additives in proportions 10% SF + 20% FA has a negative effect on the fracture mechanics parameters of concretes at an early age. Based on the analysis of the results of microstructural tests and the evaluation of the propagation of macroscopic cracks, it was established that along with the substitution of the cement binder with the combination of mineral additives, the composition of the cement matrix in these composites changes, which implies a different, i.e., quasi-plastic, behavior in the process of damage and destruction of the material.

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Effect of Reinforcement on Early-Age Concrete Temperature Stress: Preliminary Experimental Investigation and Analytical Simulation

Advances in Materials Science and Engineering ◽

10.1155/2015/231973 ◽

2015 ◽

Vol 2015 ◽

pp. 1-9 ◽

Cited By ~ 3

Author(s):

Jianda Xin ◽

Siqing Lin ◽

Nannan Shi ◽

Jianshu Ouyang ◽

Dahai Huang

Keyword(s):

Reinforced Concrete ◽

Temperature Stress ◽

Testing Machine ◽

Early Age ◽

Principle Of Superposition ◽

Stress Development ◽

Concrete Crack ◽

Analytical Simulation ◽

Concrete Temperature ◽

Early Age Concrete

For concrete under short-term loading, effect of reinforcement on concrete crack resistance capability is usually negligible; however, recent research results show that extension of this viewpoint to concrete under long-term loading (temperature variation) may be unsuitable. In order to investigate this phenomenon, this paper presents the experimental and analytical results of early-age reinforced concrete temperature stress development under uniaxial restraint. The experiments were carried out on a temperature stress testing machine (TSTM). Experimental results show that the coupling of reinforcement and concrete creep behavior influenced the concrete temperature stress development, and nearly 16% of concrete stress was reduced in the current research. Moreover, the cracking time of reinforced concrete was also delayed. Finally, based on the principle of superposition, analytical simulations of effect of reinforcement on concrete temperature stress have been performed.

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Finite-Element Modeling of Early-Age Concrete Stress Development

Journal of Materials in Civil Engineering ◽

10.1061/(asce)mt.1943-5533.0002988 ◽

2020 ◽

Vol 32 (1) ◽

pp. 04019338 ◽

Cited By ~ 1

Author(s):

Yalin Liu ◽

Anton K. Schindler

Keyword(s):

Finite Element ◽

Finite Element Modeling ◽

Early Age ◽

Stress Development ◽

Element Modeling ◽

Early Age Concrete ◽

Concrete Stress

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Crack Risk Evaluation of Early Age Concrete Based on the Distributed Optical Fiber Temperature Sensing

Advances in Materials Science and Engineering ◽

10.1155/2016/4082926 ◽

2016 ◽

Vol 2016 ◽

pp. 1-13 ◽

Cited By ~ 7

Author(s):

Nannan Shi ◽

Yanyu Chen ◽

Zhenbao Li

Keyword(s):

Thermal Stress ◽

Optical Fiber ◽

Risk Evaluation ◽

Temperature Sensing ◽

Thermal Parameters ◽

Early Age ◽

Controlling Measures ◽

Distributed Optical Fiber ◽

Early Age Concrete ◽

Cracking Risk

Cracks often appear in concrete arch dams, due to the thermal stress and low tensile strength of early age concrete. There are three commonly used temperature controlling measures: controlling the casting temperature, burying cooling pipe, and protecting the surface. However, because of the difficulty to obtain accurate temperature and thermal stress field of the concrete, the rationality and economy of these measures are not assessed validly before and after construction. In this paper, a crack risk evaluation system for early age concrete is established, including distributed optical fiber temperature sensing (DTS), prediction of temperature and stress fields, and crack risk evaluation. Based on the DTS temperature data, the back-analysis method is applied to retrieve the thermal parameters of concrete. Then, the temperature and thermal stress of early age concrete are predicted using the reversed thermal parameters, as well as the laboratory test parameters. Finally, under the proposed cracking risk evaluation principle, the cracking risk level of each concrete block is given; the preliminary and later temperature controlling measures were recommended, respectively. The application of the proposed system in Xiluodu super high arch dam shows that this system works effectively for preventing cracks of early age concrete.

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Evaluation of Thermal Properties of Early-Age Concrete Containing Fly Ash

Materials Science Forum ◽

10.4028/www.scientific.net/msf.865.157 ◽

2016 ◽

Vol 865 ◽

pp. 157-161

Author(s):

Petra Jarošová ◽

Stanislav Šťastník ◽

Jiří Vala

Keyword(s):

Fly Ash ◽

Thermal Characteristics ◽

Early Age ◽

Portland Cement Concrete ◽

Weak Formulation ◽

Reliable Prediction ◽

Engineering Structures ◽

Pozzolanic Material ◽

Least Squares Optimization ◽

Early Age Concrete

Fly ash, a by-product of burning pulverized coal in electrical generating stations, is used as a supplementary pozzolanic material in the production of Portland cement concrete. It improves, e.g., workability of a concrete mixture, suppresses bleeding, reduces the rate of production of hydration heat and delays finishing operations. Consequently experimental research, theoretical analysis, incorporating available microstructural data, and efficient numerical simulations are needed to understand the influence of early-age curing on later macroscopic mechanical, thermal, etc. material properties. This paper presents a proper experimental and computational approach to the evaluation of time-variable thermal characteristics of a hardening mixture, based on the weak formulation of the evolution problem and on the least squares optimization. Results of such types are necessary for reliable prediction of behaviour, performance and durability of buildings and engineering structures.

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Effect of fly ash on the strength of cement paste at early age

Journal of Mining and Earth Sciences ◽

10.46326/jmes.htcs2020.02 ◽

2020 ◽

Vol 61 (HTCS6) ◽

pp. 10-18

Author(s):

Dung Trong Nguyen ◽

Lam Van Tang ◽

Hung Xuan Ngo ◽

Phi Van Dang ◽

Cuong Anh Ho ◽

...

Keyword(s):

Mechanical Properties ◽

Fly Ash ◽

Cement Paste ◽

Power Plants ◽

Building Materials ◽

High Efficiency ◽

Thermal Power ◽

Early Age ◽

Technical Specifications ◽

Mineral Additives

In Vietnam, thermal power plants produce millions of tons of fly ash per year and cause a lot of problems for the environment. The re-use of fly ash as mineral additives in the production of building materials such as cement, concrete etc is a comprehensive solution that brings high socio-economic efficiency. However, to achieve high efficiency, the technical specifications index of fly ash needs to be studied and evaluated in detail because the content of added fly ash is very important for producing and manufacturing processes. This paper aims to study the influence of Formosa fly ash on the mechanical properties at the early age of cement paste. The mechanical properties of the samples which contain alternatively 10÷30% of fly ash was measured at the early ages (1, 3, and 7 days) by experimental methods. In addition, the microstructure analysis and differential thermal analysis methods have been used to interpret the obtained results.

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Complex Effect of Concrete Composition on the Thermo-Mechanical Behaviour of Mass Concrete

Materials ◽

10.3390/ma11112207 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2207 ◽

Cited By ~ 5

Author(s):

Barbara Klemczak ◽

Maciej Batog ◽

Zbigniew Giergiczny ◽

Aneta Żmij

Keyword(s):

Fly Ash ◽

Experimental Tests ◽

Early Age ◽

Mass Concrete ◽

Volume Deformation ◽

Complex Investigation ◽

Foundation Slab ◽

Early Age Concrete ◽

Composite Cements

The current work presents the complex investigation of the influence of cement and aggregate type on the thermo-mechanical behavior of mass concrete. Six types of cement with different amounts of non-clinker constituents and four types of aggregates are used in experimental tests. Particular attention was given to the low clinker cements with high amounts of siliceous fly ash and ground blast furnace slag. The experimental research covered the determination of thermal, mechanical, and rheological properties of early age concrete with different constituents. Experimental results have been used both to validate the numerical model and analysis of exemplary foundation slab. The results confirm the importance of the concrete mix composition and it has been shown that the early-age volume deformation and possible cracking is the result of the concerted action of thermal and mechanical properties of concrete. The obtained results indicate granite as the best aggregate for mass concrete. Considering the type of cement, much better behaviour of mass concrete has been noted for cements with fly ash and composite cements containing both fly ash and slags than cements only with slag.

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