Recommended practice for winter sealing in South Africa

SANRAL, like many other road authorities, enforces an embargo on seal work during the winter period from May to August, both months included. The high demand for bitumen and aggregate during the summer period and problems arising from local refineries being unable to meet the South African demand consistently, result in project delays and available funds not being spent. A task team was appointed by SANRAL to investigate possible solutions and to develop an appropriate strategy to maximise seal work throughout the year. Following a study on current best practice local and international (sealing during cold periods), fifty three trial sections were designed and constructed during the winters of 2012 and 2013 in the coldest parts of South Africa. The experimental matrix included five different seal types, six bituminous binder types with zero to four percent cutter, high and low application rates and different distributions of binder within the seal structure i.e. tack coat (first binder application), penetration coat (second binder application) in the case of double seals and cover spray. Although all trial sections experienced sub-zero temperatures within days after construction, aggregate loss occurred only on one section. Fattiness visible after the first summer period on six trial sections is mainly related to embedment of aggregate and high application rates applied on bitumen rubber single seals. However, texture depths on these sections stabilised after one year, with a minimum of 1.4 mm. This paper summarises key aspects for sealing during the South African winter period and makes recommendations regarding the selection of low risk surfacings, design strategies and critical construction aspects.


  • English

Media Info

  • Pagination: 15p
  • Monograph Title: 11th Conference on Asphalt Pavements for Southern Africa: CAPSA15, 16-19 August 2015, Sun City, South Africa

Subject/Index Terms

Filing Info

  • Accession Number: 01597081
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ATRI
  • Created Date: Apr 22 2016 11:13AM