Dunja Mikulić

Analysis of Thermal Properties of Cement Paste During Setting and Hardening

An experimental investigation is made in order to study changes of thermal properties of hardening cement paste. Using a hot disc principle for determination of thermal properties, specific heat capacity, effusivity and thermal conductivity are analyzed during first 4 days of hydration. Specific heat capacity value changed only slightly during hydration. Thermal conductivity decreased with the progress of hydration 20% compared to initial value. Hydration process was monitored using ultrasonic pulse velocity (UPV) test. A discussion of results is made taking into account porous nature of cement paste and transformation of liquid and hardened phases i.e. water and clinker minerals, into hardened structure.The motivation for conducted research is improvement of numerical models for calculating temperature changes in mass concrete structures using hydration dependant thermal properties. Also, another field of application could be the quality control of cement based materials.

Application of ultrasonic methods for early age concrete characterisation

Concrete setting and hardening process are the most critical phases during construction work, influencing to properties of concrete structure, so the application of efficiency non-destructive test methods for early age concrete properties determination is crucial. Penetrometer, pull out and Vicat needle methods are standardised methods for young concrete characterisation. Paper shows that ultrasound methods have potential to be used for these purposes. Measurements of longitudinal compressive wave velocity through concrete and mortar during hardening process are performed. For mixtures preparation different additives were used. Obtained results indicate possibility for hardening process monitoring and time of cementitous materials setting determination.

C-D-c-t diagrams for practical design of concrete durability parameters

Abstract Structures (especially bridges), in Croatian coastal marine environment, are exposed to influence of different aggressive factors. Since many old structures have to be repaired and since many new have to be constructed in that area, there is a special interest of both, experts and the public to perform works with high quality standards. In this paper we propose a method for durability design of structures built in marine environment based on space and time distribution of chloride ions in reinforced concrete structures. This method, which is developed as the computer program CHLODIF, is applied during the construction of new Maslenica bridge.

Quality Management Through Process Management in Construction

Each participant in a construction project manages a great number of processes, which are very much interdependent and always appears in three roles: as a supplier, a contractor and as a user. Thus, successful realization of construction project requires very developed organizational structure, determination of managerial and executive processes and the way of their realization, control and determination of efficiency. The quality management system simulates the development process approach - indentification of processes in construction, their analysis, measurement and continuous improvement. For each quality control process in civil engineering it is necessary to define control parameters to be measured, objectives and standards, necessary instruments, data to be noted, find out criteria and determine responsibility for each individual decision.

Service Life Prolongation by Rebar Corrosion Inhibition

Corrosion of reinforcement has been recognized as one of the most prevalent durability factors, which affects the largest group of reinforced concrete structures as bridges, parking garages etc. Corrosion could be put under control by application of the protective measure. One of the possibilities is the topical application of the migrating corrosion inhibitor. The application should be done at the right time before the end of the initiation period of the structures service life. This could be calculated by a computer program, and the example of such calculation is presented in this paper. The calculation is also used as the base for a maintenance plan during the structure design.