ABSTRACT

Trenchmix is a slow setting slow hardening mixture consisting of “surplus fines from a recycling plant”, PFA (pulverized fuel ash) and lime. The slow setting properties of the lime/PFA combination gives Trenchmix a useable time of up to 12 h. Immediately after compaction, typically by vibrating plate, the mixture is mechanically stable and can support immediate surfacing and opening to traffic. In the long term, the material develops strength and stiffness akin to foamed concrete. The paper describes the laboratory evaluation of the mixture to optimize mixture proportions. In addition it reports on the use and performance of the mixture in two full-scale site trials, one successful the other unsuccessful, carried out during 2000 and describes the actions taken to establish why one trial was unsuccessful.