Erosion of Cement Treated Subbases Below Concrete Pavements

Laboratory tests have been carried out to examine the effect of the following parameters on the erosion behaviour in the case of cement treated subbases (CTB) below concrete pavements: aggregate mixture (gravel or sand), treatment (with wet treatment, without treatment), compressive strength requirement (varying cement content), arrangement of a geotextile layer, effect of cracks and notches in the CTB, behaviour of drain asphalt base courses. The full scale erosion test rig comprised a concrete slab with an opened joint, the CTB to be examined in a water bath, supported on an elastic rubber mat. About 5 to II million load cycles were applied hy means of the servohydraulic loading device at the joint edge. The observed erosion decreases with increasing cement content and increasing compressive strength of the CTB. Thus, a mean cylinder compressive strength 13D28 ~! 15 N/mm2 is proposed for the qualification test for determination of [lie !!eLcssa!'y ccmcnt content, as is required by th Technical Specification, ZTVT-StB 95 (Additional Technical Contract Terms and Guidelines for CTB in Road Construction). The treatment of the CTB is also important. Notches or cracks of CTB had no effect on the erosion behaviour. Insertion of a geotcxtilc in the interface of concrete slab and CTB prevented erosion. No stripping or lateral displacement was observed on the tested drain asphalt base courses.