Britpave: The British In-Situ Concrete Paving Association

Construction

Slipform paving

Unless specifically requested for a hand lay process, Pavement Quality concrete is optimised for paving via slipforming. Placement timing is critical and delivery rate should be calculated to minimise waiting time on site. The rate of supply must match the placing rate to ensure consistency in the timing of placement, compaction and finishing processes as well as joint sawing.
Where problems occur on site plant or in transit to site, good communication and feed back between site and supply plant is essential.

Hand lay

Where it is proposed to hand lay Pavement Quality concrete, some adjustments to the concrete mix design may be necessary to assist the laying gang:

  1. An increase in the level of consistence
  2. An increase fines content

In addition it is essential that the delivery rate is reduced to match the rate of production and laying of the hand laying gang. It may also be necessary to assess the type of delivery vehicle, where a tipper vehicle may be more suitable for a slipforming process; a ready mixed concrete mixer truck may be more suited to the hand lay process as the placement of the concrete discharge may be more accurately controlled.

Curing

All the cements and combinations require effective curing to develop optimum properties in the hardened concrete. Abrasion resistance is particularly sensitive to the early drying of the surface that may occur if curing is inadequate. The early strength development of concrete containing PFA or ggbs is slower in colder weather, so proper curing is important to prevent moisture loss, which may result in surface dusting and poorer abrasion resistance. It is therefore important to apply appropriate curing techniques as soon as practical after finishing is completed.