Erfahrungsbericht 25 Jahre 'Werksstraße Knepper'

摘要

The concrete carriageway of the "Werksstraße Knepper" was designed from the start as a test section so that the effect of fly ash, used as an addition, on the durability of a road concrete could be investigated scientifically, especially during stressing by lorry traffic and alternating freezing and thawing in the presence of de-icing agents. Investigations into the condition of the carriageway and of the in-situ concrete were carried out repeatedly over the service life of about 25 years - recently also in respect of a possible alkali-silica reaction. The article describes the results of the investigations. After over 15 years in use the skid resistance of the concrete carriageway was still above the acceptance limits for a new concrete carriageway. The ma-crotexture and the surface evenness in the longitudinal and transverse directions determined in accordance with the criteria that apply to autobahns and trunk roads also confirmed the good condition of the concrete carriageway. At the most recent investigation after almost 25 years in use the concrete carriageway was still in good overall condition even though no repairs had been carried out in the meantime. No typical damage could be detected externally but this time, unlike the previous investigations, drill cores taken from the carriageway were examined for a possible alkali-aggregate reaction of the greywacke chippings used, and the alkali reactivity of the concretes was investigated. The results show that both concretes have a corresponding reaction potential but that this is significantly lower in the concrete containing fly ash than in the concrete without fly ash. The investigations confirm the practical suitability of fly ash for producing durable concrete carriageways for a service life of about 25 years.%Bis heute darf Flugasche in Betonen für Fahrbahndecken nach ZTV-Beton StB/TL Beton-StB nicht auf den Zementgehalt und den w/z-Wert angerechnet werden. Die Betonfahrbahn der „Werksstraße Knepper" wurde von Beginn an als Versuchsstrecke konzipiert, um den Einfluss von Flugasche als Zusatzstoff auf die Dauerhaftigkeit eines Straßenbetons insbesondere bei Beanspruchung durch Frost-Tauwechsel mit Taumitteln und Lkw-Verkehr wissenschaftlich untersuchen zu können. Über eine Nutzungsdauer von ca. 25 Jahren hinweg wurden mehrfach Untersuchungen zum Zustand der Fahrbahn und des eingebauten Betons durchgeführt - zuletzt auch mit Blick auf eine mögliche Alkali-Kieselsäure-Reaktion. Über die Ergebnisse der Untersuchungen wird im Folgenden berichtet.