Description

During hardening of mass concrete structures (MCS) high amount of heat resulting from hydration and material’s shrinkage develop within concrete elements. This often results into formation of cracks and other failures which negatively influence quality, functionality, and durability of MCS. To effectively overcome the above problems, important issues have to be fulfilled, e.g. appropriate basic materials and design of mass concrete mixture, optimal building technology, accurate pre-calculation of the development of temperature field inside mass concrete element using real, actual characteristics of input materials, etc. To achieve the above requirements, the use of modern technology of design and placing of mass concrete mixtures is of paramount importance, together with the use of mineral and chemical admixtures in the composition of the material and correct and accurate experimental determination of the characteristics of basic materials. In addition to the basic mechanical properties (compressive and bending strength, elastic moduli, etc.), other characteristics have to be evaluated in the case of MCS, namely liberation of hydration heat, thermal conductivity, specific heat, coefficient of linear expansion, shrinkage and creep, concrete porosity, self-healing capability, etc. The above issues associated with designing and building MCS present the main motivation and introducing an appropriate technology with key measures a basic goal of the proposed project. In order to fulfil these issues, a maximum aggregate size in the composition of the material has to be reduced from generally used >63 mm to the site of 16-32 mm, which will affect overall quality of the material significantly and presents the beginning of a new, modern era of mass production of mass concrete mixtures with reduced aggregate size. To achieve these objectives, the project will be at its first stage divided into experimental and numerical part. However, it will be further divided into seven work packages. After initial part, three parts of experimental work will follow, dealing with characterization of input materials, design of concrete mixtures, and determination of properties of fresh and hardened materials using new advanced nondestructive techniques. A wide spectra of basic materials and their combinations will be studied, resulting into a comprehensive database of concrete mixtures. On the basis of the experiments and numerical model performed by the member of the project’s research group used to calculate adiabatic hydration curve of an arbitrary concrete mixture, optimal concrete mixtures will be chosen and further analysed to determine all their properties used to achieve a required quality and durability of MCS. Based on the real, actual values of the initial material parameters experimentally determined using advanced testing techniques, a complex numerical model for calculation of temperature field within MCS will be prepared, allowing determination of adiabatic hydration curve, calculation of fully coupled problem of water, moist air, and heat transfer and consequently prediction of shrinkage of the material. Moreover, the model will allow calculation of successive construction, i.e. determining optimal size of concrete segments as well as optimal time between constructing each segment . The above characteristics present important advantages over existing numerical models. With the objective to reduce environmental pollution, aggregate consisting of blast furnace slag will be used and detailed LCA analysis performed for all the developed mixtures.

Project goals

Objectives of the experimental part of the proposed project:

• reducing D_max in the composition of fresh mass concrete mixture from generally used >63 mm to the site of 16-32 mm and detailed analysis of the influence of this essential correction on the development of temperature field inside mass concrete structures – basic hypothesis 1,
• To perform detailed studies and analysis of the possibility of using previously described new, modern technology of designing and placing mass concrete mixtures with reduced maximum aggregate size – basic hypothesis 1
• To perform detailed studies of the possibility of using new, advanced testing techniques for determination of different essential properties of mass concrete mixtures which serve as input parameters in various numerical programs for calculation of temperature field inside mass concrete elements – basic hypothesis 2,
• The use of a new semi-adiabatic standard (DRAFT prEN 12390-14, January 2016) experimental procedure for determination of various new adiabatic hydration curves of mass concrete mixtures which will expand the range of applicability and usability of the self-developed numerical model for prediction of and adiabatic hydration curve of an arbitrary concrete mixture – basic hypothesis 3
• To perform detailed analysis of the influence of various waste materials (e.g. blast furnace slag, fly ash, etc.) in the composition of mass concrete mixtures with reduced maximum aggregate size and to study effectiveness of suitable advanced self-healing technologies for mass concrete – basic hypothesis 5.

Objectives of the numerical part of the proposed project:

• To expand the range of suitability of the developed ANN based model with the objective to accurately calculate adiabatic hydration curves of concrete mixtures with specific, locally available basic materials of concrete mixture,
• To upgrade the new numerical program with respect to include real, actual values of material input parameters experimentally determined using new, advanced testing techniques,
• To upgrade the new numerical program with respect to determine optimal construction scheduling using successive construction calculated on the basis of maximum temperature gradient and maximum temperature allowed,
• To perform a detailed LCA analysis with the objective to analyse the influence of all previously mentioned modifications of mass concrete technology on the environment.

Project work packages

Work Package 1: Initial materials characterization

Work Package 2: Mass concrete mixture design

Work Package 3: Measurements of fresh, hardening and hardened concrete properties

Work Package 4: Numerical modelling

Work Package 5: LCA

Work package 6: Dissemination of the results