Papers by Keyword: Concrete Performance

Abstract: The main goal of transportation infrastructure management is to optimize the use of infrastructure in the most beneficiary way while respecting the predefined requirements. One of the crucial parts in management strategy is the prediction of behaviour of vital transportation elements. Used prediction models should accurately describe the process of degradation and allow forecasting of structural condition by considering environment, usage and maintenance actions. Deterioration models can be divided into mathematical (statistical), physical and empirical models. Statistical models are based on data that describe condition of structure, such as for example condition rating. Physical models describe damage-causing processes and empirical models are experience based. The focus of this paper is to present the physical model of carbonation in assessment of performance of existing reinforced concrete structures in transportation networks. Assessment is done through determining the probability of limit state of depassivation. In order to determine the carbonation without testing, a special attention has to be given to environmental and material parameter identification. Herein, the identification takes into account weather specifics and construction practice in Austria. Finally, the reliability of existing reinforced concrete structures for combination of different exposure classes and material characteristics is analysed. Based on the analysis of reliability, the carbonation nomogram for engineering use is presented, showing the reliability indices β for the service life of 50 years.

Abstract: A new low air-entraining polycarboxylate superplasticizer (denoted as L-PCE) was synthesized by using oxirane/epoxypropane (denoted as EO/PO) block-polyether as one of monomers. The molecular structure of EO/PO block-polyether monomer was characterized by proton nuclear magnetic resonance spectroscopy (denoted as ¹H NMR). The pore parameters, workability, and compressive strength of the concrete added with L-PCE were compared to that added with conventional polycarboxylate superplasticizer (denoted as G-PCE) or the G-PCE compounding with defoaming agent. The results demonstrate that the air entraining performance of the L-PCE has been greatly improved than the G-PCE and the G-PCE compounding with defoaming agent. Then the problems, which the workability and slumps of fresh concrete decrease when G-PCE compounding with defoaming agent are added, can be solved. What is more, the interior pore structure of concrete has been optimized. The spacing factor of hardened concrete added with the L-PCE is 27% lower than that added with the G-PCE compounding with defoaming agent. And the 28d strength of the concrete added with the L-PCE is 10% higher than that added with the G-PCE compounding with defoaming agent.

Abstract: This thesis first analyzes the necessity for the application of limestone powder produced in Lime Ridge from Xixia County, Henan Province. It also tests the concrete performance with different composition materials and does research on the influence of limestone powder on concrete strength by adding limestone powder instead of fly ash in fly ash concrete. It then finds out the reasonable volume of limestone powder to meet the concrete’s performance, in order to guarantee the scientific and effective use of limestone powder in concrete engineering.