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The Art of laying quick set slurry seals on site-troubleshooting & workmanship

Siphamandla Mnguni, Colas Group


Abstract

Infrastructure maintenance and preservation are important activities for any developing city. Microsurfacing is a well known slurry seal surface maintenance technique that leverages the use of cationic quick setting slurry. The technique is considered by some practitioners to be more economic than other conventional surface treatment methods such as asphalt and chip seal. Micro surfacing seals could correct rutting defects, restore skid resistance, reduce pavement oxidation, help preserve water ingress, and in turn extend the surface life span. Quick setting slurries are preferred when working on urban roads where the specialised modified emulsion allows the seal to set quickly, building good cohesion and allowing opening to traffic within 2hrs (weather dependent). Work performed in urban areas during winter poses various challenges for micro surfacing seals due to shades on residential streets (low surface temperature). These conditions are usually mitigated through adjustment of the emulsion formulation to allow different setting/breaking times of the quick set product.

The success of a microsurfacing seals depends on careful pre-planning (using digital logging), surface preparation (sealing of cracks, potholes repairs, etc.); raw materials selection (emulsion and crusher dust); workmanship and fit for purpose equipment. The system can only be placed with a purpose designed microsurfacing machine and spreader box capable of continuously feeding accurate raw material proportions to ensure a consistent, high quality surfacing layer. The application process of quick set slurries is a complex and specialised operation requiring skilled supervision, specialised machine operators and skilled squeegee operators who understand quality requirements, on site trouble shooting, breaking times and time constraints with regards to workability and hand work.

Careful seal design & application techniques are critical for successfully achieving a quick setting slurry seal capable of accommodating light to medium traffic. This presentation addresses onsite challenges & solutions for laying microsurfacing systems.