Improvement of the Adherence between Old and New Concrete in Road Construction – Procedures and Testing Methods

The mechanical adherence properties of new concrete bound with old concrete surfaces which had been pretreated in a conventional manner as well as with new techniques, have been studied uding fracture mechanical methods. It was shown that far better adherences are achieved with specially structured old concrete surfaces than with conventional surface treatments (like sand or water blasting). I he tracture mechanical elidiacterization of odhoronce compounds was performed with a new wedqe splitting procedure on cubic or drill-core specimens. This procedure allows -in contrast to the pull-off test- a quantitative answer to the question whether compound fracturing takes place in a "ductile" or in a "brittle" manner and if the crack growth resistance within the interface is high or low respectively. The new testiiuy piucedurcs and tho rocults are described and discussed.