Survey of drainage methods for concrete road pavements

In the Federal Republic of Germany, as in other countr~ es, concrete road pavements have in recent years been affected by deteriorative damage which is attributable to Lhe presence of wa ter in the pavement. lnvestigations which the Federal lnstitutefor Highway Englneerlng (Bundesanstalt für Strassenwesen) started in 1981 aimed at analysing the mechanisms of such damage and at seeking and testing effective ways and means of prevention. Surface water penetrates from above through joints and cracks and from the edges into the pavement; seepage water penetrates from the sides and capillary water from underneath. Discharge of this water takes place at three important levels: I surface of the concrete pavement II interface of concrete slab and sub-base III formation (surface of subgrade) Drainage at levels I and III has traditionally been a regular feature of road pavements. The well-established drainage arrangements are described in the code "RAS Entwässerunge~". rf defects develop here, they are mostly due to l.ncorrect construction and inadequate malntenance. Damage caused by build-up of water between the slab and the sub-base presents a new problem which is being investigated worldwide. Experiments by the Federal Institute for Highway Engineering with longitudlnal, polnt-type and area drainage systems at level II have, for new concrete pavements, resulted in - among others - a solution incorporating geotextile laid over the entire area on a cement-bound sub-base. The geotextlle functlons as a separating and draining layer between the slab and the sub-base and provides permanently uniform and unvarying bearing conditions for the slab. For this reason the system comprising concrete slab/geotextile/sub-base promises