The effect of reducing the clinker in the cement on the strength development and durability of the concrete was investigated. The effects of this substitution were to be minimized by optimising the particle size and component distributions, targeted use of superplasticizers and, where appropriate, adaptation of the concrete technology.
It should be possible to use cements containing reduced levels of Portland cement clinker for the production of normal structural concrete of medium strength, which accounts for the majority of concrete production. The exposure classes for interior and external structural elements (XC1 to XC4, XF1 and XF3) were taken into account.
The work initially concentrated on the investigation of mortar systems. Starting from normal cements complying with DIN EN 197-1 the clinker content was being reduced in steps with simultaneous optimisation of the particle size distribution. The workability properties and strength development were being tested. The mortar investigations were linked to the production of selected cements on an industrial scale. Particular attention was paid to cements containing high levels of limestone and cements made with different grades of limestone. Workability properties and strength development as well as durability parameters (resistance to carbonation, resistance to freeze-thaw cycles, chloride penetration resistance, shrinkage, creep) of the concretes was checked. The purpose of the investigations was to find out whether durable concretes could be produced with cements containing high levels of limestone. A strategy was devised to establish how concretes containing high proportions of limestone, possibly deviating from the existing standards, could be used. The results of the research project was then evaluated in a life cycle analysis.
