Filtern
Erscheinungsjahr
- 2018 (2)
Dokumenttyp
Sprache
- Englisch (2) (entfernen)
Schlagworte
- Fast measurement (1)
- Heat treatment (1)
- Hydroxylellestadite (1)
- Sample holder (1)
- Spatial analyses (1)
- Tobermorite (1)
- Ultra-high performance concrete (1)
- Ultrahigh-performance concrete (UHPC) (1)
- X-ray diffraction (XRD) (1)
- Zonation (1)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (2)
- 7.1 Baustoffe (2)
By the combination of an optimized granulometry, a reduced water cement ratio and the use of superplasticizers ultra-high performance concrete achieves a compressive strength of over 150 N/mm2 and a high resistance regarding acids and water-soluble salts. In different Research projects the effect of an autoclavation on the mechanical strength and the phase composition was analyzed. In systematic studies, the concrete mix and the process parameters were varied.
The results show that autoclavation leads to an improved pozzolanic and hydraulic reaction and significantly improves the mechanical strength compared to a conventional thermal treatment. If a minimum time-span for hydration is ensured, the achievable strength level is not dependent on the prestorage time. However, the duration of the autoclaving is significant. After the Maximum strength is reached there is only a very slight decrease, even if unrealistically long autoclaving times are applied.
Powder X-ray diffraction is a time-consuming and challenging task, especially for preparation of sensitive phases like ettringite and calcium-silicate-hydrate (C-S-H) phases. Fine-grained ultrahigh-performance concrete (UHPC) with an average grain size <100 μm could be investigated directly without time-consuming milling. As a proof of concept, small UHPC cylinders with plain surfaces were investigated with a newly designed sample holder. The comparison with conventionally prepared powder shows the feasibility of fast qualitative phase analysis using this approach. As a great benefit, a depth-dependent analysis, as well as a comparison of surface layers and core material, was carried out.