Self-compacting concrete for use in concrete road construction

Up to now, concrete pavements have been produced with slipform pavers. However, only stiff to very stiff concretes can be used for this purpose, as only these have sufficient dimensional stability and green strength just a few meters behind the paving site. Due to their consistency, however, such concretes have to be compacted intensively. For this purpose, internal vibrators are used which locally inject a high compaction energy into the concrete. This high local compaction can lead to an accumulation of fine mortar in the vibrating alleys, which can cause weak spots in the concrete cross-section. As a result, cracks can form preferentially in these vibrating alleys. This can be avoided by using self-compacting concrete (SCC). Due to its high flowability, however, conventional SCC is not suitable for processing with a slipform paver, as it would have to exhibit more or less contrary properties within a very short time. On the one hand, the SCC must have a sufficiently high flowability during paving and must compact or deaerate itself. On the other hand, the same concrete must have sufficient green strength or dimensional stability after leaving the slipform paver, i.e. after about two to five minutes. Based on these findings of a first orienting research project, the present research project will, on the one hand, pursue the approach described above. Furthermore, the subsequent addition of additives in a separate mixing process is to be investigated. These additives are to influence the flow properties of the fresh concrete in such a way that the flowability of the fresh concrete is reduced in a time-dependent manner, whereby a high green strength or dimensional stability can subsequently be achieved after a certain period of time. Various superabsorbent polymers (SAP) and superplasticizers based on naphthalene sulfonate (due to their interaction with PCE superplasticizers) are to be used as additives.