During April and May 2013 the full width of Industria road (9 m) was spread only during dry and working days according to the following calendar:
- Phase 1: 25% CMA aqueous solution (ICE & DUST-AWAY, Nordisk Aluminat) was spread on a 1400 m stretch in the morning of 16th, 17th and 18th April;
- Phase 2: 25% CMA aqueous solution was spread on a 2300 m stretch in the morning of 22nd, 23rd, 24th April and 2nd, 6th, 8th, 13th May;
- Phase 3: 20% MgCl2 aqueous solution was spread on a 2300 m stretch on 21st and 23rd May.
Both solutions were sprayed by means of a Springer SD210 spreader vehicle at a rate of 20g/m2 (Fig. 2). The spreader covers a 2.7 m wide area and it adjusts the flow according to
the speed of tractor in order to assure an even and constant application on road surface. The amount of CMA solution on road was monitored hourly at five spots, from 1 hour up to 7
hours after its application by means of the conductivity sensor (SOBO, Boschung) which was previously calibrated for the 25% CMA aqueous solution.
Spreading calendar was based on weather forecast (no rain, temperatures above 0ºC) and traffic activity (only working days). Given that the air quality benefit is expected to be short lived (www.life-cma.at; Barratt et al., 2012; Gustafsson et al., 2010), CMA and MgCl2 solutions were spread around between 5 and 9 am local time, in order to maximize its effectiveness during the most-polluted hours due to traffic emissions (7-9 am). Totally the duration of spreading was around 1 hour.
In order to avoid build-up of CMA on road surface, after each test a vacuum-assisted sweeping vehicle cleaned road surface starting from 23:00 of the same day or of the day after, so that the effectiveness of dust suppressant can be evaluated only on the first-day or of the first-2-days.
At high dosage, CMA solution may reduce friction between road pavement and tires (www.life-cma.at). For traffic safety a number of measures were taken: speed limit was decreased from 50 to 30 km/h, road signals were warned drivers of possible slippery conditions, friction tests were performed before and after the CMA application following the UNE-EN 13036-4:2012 protocol. This protocol allowed, providing fast information on slip resistance, the possibility of withdraw immediately the application of CMA.