Reinforced concrete tank walls and bridge abutments: Early-age behaviour, analytic approaches and numerical models

Batog²,

Giergiczny

et al. 2018

Materials

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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.

Section: Thermo-mechanical Analysismentioning

confidence: 99%

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

Batog²,

Giergiczny

et al. 2018

Materials

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“…Thus, the knowledge of the temperature sensitivity of the hydration process is crucial in many engineering tasks as accurate prediction of thermal gradients in massive concrete structures or assessment of early-age strength of concrete, which is influenced by curing temperature. For example, in modeling of exothermic temperature rise in massive concrete structures, the isothermal tests at 20°C are basically considered and they must be recalculated due to the developing temperature in each step of calculation [1][2][3][4]. The most common method applied for this purpose is an equivalent age approach, which is usually referred to Arrhenius concept.…”

Section: Introductionmentioning

confidence: 99%

Heat of hydration of low clinker cements

Batog

2015

J Therm Anal Calorim

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Part I of this paper has reported the results of the experimental tests and discussed the influence of mineral additives on the hydration heat evolution. The purpose of the Part II of the paper is to study the validity of the equivalent age approach and determine the apparent activation energy of low clinker cements with mineral additives. The concept of the equivalent age method and Arrhenius formulation for the temperature sensitivity of the hydration reaction is briefly presented. The evolution of the apparent activation energy as well as its single values is determined on the basis of the tests results presented in Part I of the paper. The low clinker cements with 30, 50 and 70 % substitution ratio by ground granulated blast furnace slag or siliceous fly ash were studied. Finally, the results of semi-adiabatic and isothermal tests at different temperatures were compared to assess the validity of the equivalent age method with determined and recommended values of activation energy in relation to low clinker cements with mineral additives.

“…Numerical validation of the presented analytical model was performed with the use of TEMWIL and MAFEM original software [24,25]. This software allows for 3D FE analysis of the behavior of massive foundation slabs in the early stages of concrete hardening.…”

Section: Numerical Validationmentioning

confidence: 99%

Analytical Method for Predicting Early Age Thermal Effects in Thick Foundation Slabs

2019

Materials

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Prediction of hydration temperature and induced stresses in mass foundation slabs, due to the hydration effects is a difficult task. The complexity of this issue is compounded by transient and non-linear thermo-mechanical phenomena as well by a significant number of contributing technological and material factors that affect the early-age volume changes. This is a probable reason for the limited number of simple analytical methods allowing for the estimation of these effects. This work presents a new proposal in the discussed field. The submitted analytical method for determining the hydration temperature rise, its differentials at a cross-section and induced thermal stresses in mass concrete foundation slabs considers the majority of important technological and material factors, such as the initial temperature of the concrete, the ambient temperature, the thermal properties of the concrete and the heat exchange conditions on the slab surfaces. In stress analysis, both self-balanced and restraint stresses are calculated. Finally, the method is validated in FE analysis conducted for the slabs with various heights and made of different types of cements, as well as by the thermal measurements from the construction site. Due to the limited number of methods allowing for the analytical estimation of the early age thermo-mechanical effects in slabs, this new proposal can be useful in the assessment of these effects.