Development Of Concrete Technology Research Articles

Performance Research on Ultra-High Performance Self-Compaction Concrete (UHP-SCC)

With development of concrete technology, the self-compaction concrete, as a green material, has been studied and widely applied thanks to its characteristics like self-leveling, self-compacting and desirable fillability. At present, high performance and ultra-high performance is an important trend in development of self-compaction concrete technology. Working performance, physical performance, endurance quality, ultra-high pumpability and microstructure of C100UHP-SCC are studied in this paper. The initial fluidity of studied UHP-SCC reaches above 550mm and maintains for 3h without loss, its compressive strength on 28d is more than 100MPa, which can ensure the architectural structure to last for 100 years and enable ultra-high pumping over 400m. The technical parameters mentioned above provide valuable reference for design and construction of super high-rise buildings which are above 1000m.

Simulation of the microstructure formation in hardening self-compacting cement paste containing limestone powder as filler via computer-based model

With the development of concrete technology, fillers are widely used in high performance concrete to improve its properties. Among them, limestone powder is popularly added in self-compacting concrete to gain good flowability. However, by lack of experimental data, several materials properties after the addition of limestone powder are still not sure, which actually yield some uncertainty for the further use of limestone powder in cement-based materials. In this study, by employing computer-based model, the microstructure of self-compacting cement paste containing limestone as filler is simulated and further used to investigate the role of limestone in hardening materials. To gain this goal, thermometric isothermal conduction calorimetry, thermal analysis and backscattered electron image acquisition were applied to understand the hydration kinetics with the addition of limestone filler. After that, a computational materials model based on HYMOSTRUC was developed to simulate the formation of microstructure in materials containing limestone powder. The predictive ability of the model was validated with the experimental test results. Then the developed model was employed to investigate the influence of several variables, such as water to cement ratio, limestone filler content and fineness, on the microstructure formation in hardening materials. The numerical experiments show that the addition of limestone filler could result in a denser microstructure at the initial hydration stage. With the proceeding of hydration, the limestone powder has a decreasing influence on the microstructure, and could obstruct somewhat the formation of a denser microstructure at later hydration stage. And it is found that computer-based modelling is an effective method to provide insights into the material behaviour, by relieving researchers from numerous repeated experiments.

我が国のコンクリートの研究史と技術の発展

我が国のコンクリートの研究史と技術の発展

Some results of the effect of carbonation on the porosity and pore size distribution of cement paste

The effect of carbonation has gained in significance during the development of concrete technology because of the usage of thinner structures and the more exact utilization of the real properties of concrete. It is known that carbonation changes the microstructure of cement paste and affects the strength and deformation properties of concrete. However, a knowledge of the phenomenon and its effects on concrete is still relatively poor and even contradictions in opinions exist. The research reported briefly in this paper is an investigation to elucidate the basic alterations in the microstructure of cement paste produced by carbonation. The results, although of tentative nature, indicate 1) that the total porosity of the carbonated cement paste is essentially smaller than the total porosity of non-carbonated cement paste, and 2) that the carbonation affects more the greater pores than the smaller ones.