The 2008 Summer Olympics will be held from Aug 8th to Aug 24th in Beijing, China, and the city is preparing for the projected traffic of over 3-million cars and 18-million people using the streets and roads. The improvements to traffic in Beijing are expected to allow athletes to travel from the Olympic Village to every venue in the city in less than half an hour.Beijing is a metropolis that is 16,800 square kilometers in size, and contains 11 million inhabitants. A record number of over 22,000 new vehicles were registered in Beijing in the first 18 days of 2007 and car ownership has reached 1,898,000, with over 2,947,000 drivers. In addition, there are over 11 million non-motorized vehicles and a great deal of transit vehicles — 18,000 buses by 2008 — running in Beijing. This high level of traffic combines to make roadwork on the ring roads that encircle the city possible only at night. For this roadwork, polymer modified hot mix is being used, and a polymer modified tack coat was specified. This presented the problem — how to emulsify the highly modified base asphalt, and to design a quick setting tack coat recipe suitable for night work.

Michael Tan, of Akzo Nobel’s Singapore laboratory, worked with the Beijing department of transport and came up with an unusual solution. Redicote C-404, well established as a micro surfacing emulsifier, was used to form the tack coat emulsion. According to Michael, the base, which contained 3.5% Styrene-Butadiene Styrene (SBS) presented a particular problem to emulsify, but the chemistry of Redicote C-404 enabled a high level of emulsifier to be used sufficient to prepare a storage stable emulsion, yet gave the quick-setting characteristics needed for the night work. The tack coat, which was applied hot, could be trafficked in 10 minutes and was paved after one hour.