2013 - World Bank - Otta Seal Workshop

Presentations from the World Bank session on Otta Seals.

Natural gravel materials have traditionally been used for upgrading earth to gravel roads or for regravelling  existing gravel roads. However, serious concerns have arisen regarding the continuous use of vast amounts of gravel - a non-renewable, finite resource - which is not only being rapidly depleted in many countries but is also unsustainable in the medium to long term. This has prompted road engineers to consider the use of low-cost bituminous surface treatments on these gravel roads as an alternative to regravelling. One type of surfacing that can provide an economic and practical alternative to traditional surfacings, such as the Chip seal, is the Otta seal. Unfortunately, lack of information regarding this relatively new type of bituminous surfacing has suppressed its more widespread use, despite its excellent performance in a number of countries.

 In view of the above, the first presentation provides state-of-the-art information on the provision of the Otta seal surfacing as an economic and practical alternative to the more traditional bituminous surface treatments. The presentation outlines the origin, properties, design and construction of the Otta seal and very briefly discusses its implementation impacts and the global use of the Otta seal.

 This type of bituminous seal was first introduced to Botswana in the late 1970s with design and construction being initially undertaken in-house and, subsequently, by the private sector. However, a somewhat haphazard approach to the transfer of this relatively new technology from the public to the private sector was largely responsible for initially suppressing the uptake of this innovative type of surfacing despite its eminent suitability for use with locally available, marginal quality aggregates. Many lessons have been learned from this experience which are likely to be useful to other countries where the introduction of the Otta seal is being contemplated.

 The second presentation highlights the critical importance of undertaking effective technology transfer to ensure the sustainability of any new type of technology, such as the Otta seal. The presentation considers the path from research to implementation of new technology, including the typical constraints and barriers that are faced in the African region. In the context of the Otta seal experience in Botswana then identifies typical barriers and constraints to its ready adoption by the private sector and proposes measures for overcoming them. The presentation concludes that a carefully crafted, pro-active approach to technology transfer is necessary to ensure the sustainability of the Otta seal in countries where it is being introduced for the first time.

 The Kingdom of Tonga’s road network, comprising approximately 640km of public roads, has had minimal road maintenance over the past decade. As a result, the road network is rapidly deteriorating. The World Bank funded Transport Sector Consolidation Project is supporting the Government of Tonga in implementing a road maintenance program to prolong the serviceability of the road network. However, due to the limited capacity of the local contracting industry, and a severe lack of quality road surfacing aggregate, traditional surfacing methods for periodic maintenance and road upgrading are not suitable. Innovative surfacing technologies, such as Otta Seals, were adopted to overcome the local limitations. The main objective of this presentation is to document the introduction of Otta Seals to Tonga and the experience to date. It will also briefly capture the applications, benefits and limitations of Otta Seals, and the reasons why they have been considered for Tonga. The paper provides a brief review of the local contracting industry and the availability of locally sourced aggregate in Tonga, and the effects that these have on the choice of pavement surfacing alternatives. The first trial sections were awarded to a local contractor in January 2012, and the works were started after the rainy season in July 2012. The process of introducing the new technology has to date been successful and progress of this project is being monitored by a number of other South Pacific countries that are faced with the similar constraints.

 This presentation covers the monitoring programme for several Otta Seal Trials in the South Pacific region.  In order for this technology to be accepted within the region, Otta Seal Trials were set up in order to a) introduce the technology to the region and b) to demonstrate the practicality and appropriateness of this technology within the geology, environment and traffic loading. A monitoring guideline that defines how to install a test section, and the protocol required to periodically monitor a test section, was developed.  The philosophy for these requirements was to develop procedures that required minimal training of assessors while at the same time would yield useful data that could be utilized for statistical analysis of the surface performance. The setting up of the Otta Seal Trials for the South Pacific Islands has confirmed a number of recommendations related to road performance experiments including:

· Clearly define the objectives for the trials with consideration for the region and the available resources (i.e., skilled labor, materials, equipment, etc.);

· Only collect the data needed to answer the objectives/questions; and,

· Trials should be designed within context of available resources for conducting the monitoring.