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

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2207 ◽  
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.

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

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
G. M. Ji ◽  
T. Kanstad ◽  
Ø. Bjøntegaard
Keyword(s):  
Fly Ash ◽  
Wall Structure ◽  
Early Age ◽  
Measured Temperature ◽  
Finite Element Program ◽  
Stress Development ◽  
Thermal Dilation ◽  
Early Age Concrete ◽  
Mineral Additives ◽  
Cracking Risk

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.

Creep and thermal cracking of ultra-high volume fly ash mass concrete at early age

2019 ◽  
Vol 99 ◽  
pp. 191-202 ◽  
Author(s):  
Zhifang Zhao ◽  
Kejin Wang ◽  
David A. Lange ◽  
Hougui Zhou ◽  
Weilun Wang ◽  
...  
Keyword(s):  
Fly Ash ◽  
Thermal Cracking ◽  
High Volume ◽  
Early Age ◽  
Mass Concrete ◽  
High Volume Fly Ash

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

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.

Determination of Required Insulation for Preventing Early-Age Cracking in Mass Concrete Footings

2014 ◽  
Vol 2441 (1) ◽  
pp. 91-97 ◽  
Author(s):  
Tu A. Do ◽  
Adrian M. Lawrence ◽  
Mang Tia ◽  
Michael J. Bergin
Keyword(s):  
Early Age ◽  
Mass Concrete

Effect of Thermal Environment at Early Age on Hydration Phases Composition and Strength Development of Concrete Containing Fly Ash

2010 ◽  
Vol 168-170 ◽  
pp. 582-588
Author(s):  
Feng Chen Zhang ◽  
De Jian Shen ◽  
Ji Kai Zhou ◽  
Zhong Hua Li
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Thermal Environment ◽  
Ash Content ◽  
Splitting Tensile Strength ◽  
Curing Temperature ◽  
Strength Development ◽  
Early Age ◽  
Mass Concrete ◽  
Hydration Phases

Cement hydration at early age is sometimes in a certain thermal environment probably caused by hydration heat of mass concrete as well as cement productions curing at high temperature. And phases composition and strength development in thermal environment are commonly different from those in normal curing conditions. Phases composition and strength development of concrete containing different fly ash content curing in different thermal environment are studied in this paper. Experimental results show that compressive strengths of concrete with 0.3 water to binder ratio increase with the increase of curing temperature. Splitting tensile strength of concrete not containing any fly ash curing at about 50 is the highest among those curing at temperature between 40 and 80 . For concrete with different fly ash content, splitting tensile strengths increase approximately with the increse of curing temperature. Dehydration of ettringite and formation of monosulfate solid solution and AFm at higher temperature perhaps relate to the development of concrete splitting tensile strength along with different curing temperature. Adding fly ash to binder, curing temperature at which hydration phases change occurs is raised, which helps to explain that splitting tensile strengths of concrete with different fly ash content decrease little with the increase of curing temperature between 60 and 80 .

scholarly journals Investigation on Hydration and Mechanical Properties of Mortar Containing Limestone Powder and Fly Ash Based on the Coupled Chemical–Thermal–Mechanical Method

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4387
Author(s):  
Wei Zhou ◽  
Wenxiang Tian ◽  
Tianqi Qi ◽  
Shuhua Liu ◽  
Chuqiao Feng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Experimental Tests ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Limestone Powder ◽  
Superior Performance ◽  
Early Age ◽  
Mechanical Method ◽  
Engineering Structures

The composited cementitious materials usually have superior performance; for example, using limestone powder (LP) and fly ash (FA) as the admixtures of cement in concrete/mortar is a popular way of improving the properties of concrete/mortar structures. In this work, we performed experimental tests to study the hydration process and pore distribution in mortar containing different ratios of LP and FA. Based on the results of mercury intrusion porosimetry (MIP), a numerical mortar model with random pore is built. The model can reflect the synergistic hydration interaction and filling effect caused by the admixtures of LP and FA. After analyzing the hydration process, the coupled chemical–thermal–mechanical method was used to simulate the characteristics of mortar containing LP and FA. The coupling model can simulate the “hump-type” hydration acceleration stage of the mortar at early age, which is specifically caused by the LP, proved in the experimental test. Additionally, the special, “hump-type” stage is important to enhance the early strength of the mortar. At different levels of admixture content, the random pore model and coupled method can predict the evolution process of the mechanical properties well, at early age and for long-term strength. Both experimental and numerical results suggest that the mortar containing admixtures of the proper ratio of LP to FA have good mechanical properties, which can be applied to engineering structures.

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

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
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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