Featured

Steph Bredenhann summed up the Winter Seal Workshop held by SAT in April 2014 with some thoughts on the current scenario at the time and the way forward. For him the important steps in the success of winter seal applications include sharing of knowledge, planning, and attention to detail, bearing in mind that this is not an exact science. He also maps out a brief strategy for the future.

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This presentation covers the essentials of binder testing in winter seals, with focus on the properties of cutback binders used in cold temperatures in South Africa, the rheological effects of adding paraffin, site testing including getting cutter quantities right, gas chromatography and mass loss. Also get the lowdown from Johan O’Connell on evaluating the curing rate of winter seals.

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Kim Jenkins talks us through the key factors, including various test results that help practitioners to make informed decisions. The presentation touches on bitumen specifications and performance grading, BBS tests including adhesion/cohesion factors, hot applied binders versus emulsions, the influence of precoat, manufacturing temperature and more. Well informed decisions can be made when selecting materials for surface seals if BBS properties are known, Jenkins concludes.

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The A to Z of sealing, starting with the history of specifications developed in SA and proposed changes. The presentation continues with aggregate and bituminous binder specs for seals; plant and equipment required; methodology; construction considerations such as early trafficking, aggregate spread rate and road surface temperature; and finally contractual issues on when to include a winter seal option and payment items for winter sealing.

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Group Five Civil Engineering participated in winter seal trials on the N14 Section 7 between Kathu and Kuruman in the Northern Cape Province and Section 8 between Kuruman and the North West Province border. Thomas Moolman shares the trial specifications as well as observations on the outcomes. He concludes that winter seal construction can be used in South Africa to ensure a continuous flow of road and road rehabilitation projects and reduce/spread the demand on the manufacture and supply of bitumen and surfacing aggregates.

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Find out what lessons can be learned from sealwork trials – from seal geometry to binder aggregate contact and adhesion, to temperature and micro-climates, to cutters, precoating and bond strength, base preparation and viscosity. Gerrie provides practical recommendations for asphalt practitioners.

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