Sunday, July 21, 2019

Sanchez: Road sustainability

Nature Speaks

DUTERTENOMICS, founded on a “build, build, build” agenda of infrastructure, could very well be one of Duterte’s defining legacies.

Aside from the war on drugs, you can see Duterte’s presence in Bacolod as well. Over the next decade, the government has embarked on a $180-billion infrastructure spending bonanza, set to transform the country’s economy.

His administration is looking at 75 flagship projects that include six airports, nine railways, three bus rapid transits, 32 roads and bridges, and four seaports that will help bring down the costs of production, improve rural incomes, encourage countryside investments, make the movement of goods and people more efficient, and create more jobs.

But here’s an old-new alternative: Asphalt based on recycled single-use sando bags.

These recycled plastic wastes can be turned into MR6 pellets, or small pellets of waste plastic that can replace bitumen, the material used to bind roads together (extracted from crude oil).

The main savings with the use of recycled plastics in costs are twofold. First, the optimum amount of plastic in plastic-bitumen roads is between eight and 10 percent, so on this point, the difference in price between what you would pay for bitumen and what you pay for the plastic is the cost savings.

If you have a cheap or free source of waste plastic, that could be quite a bit as bitumen currently goes for about P21,083.77-P26,349.66 per metric ton, varying by purchase location. Second, roads made with plastic added to it are showing a great deal more durability and resistance to water, so there are maintenance cost savings.

The entire process is very simple. The plastic waste material is first shredded into a particular size using a shredding machine. The aggregate mix is heated at 165°C and transferred to the mixing chamber, and the bitumen is heated to 160°C to result in good binding. It is important to monitor the temperature during heating.

The shredded plastic waste is then added to the aggregate. It gets coated uniformly over the aggregate within 30 to 60 seconds, giving it an oily look. The plastic waste-coated aggregate is mixed with hot bitumen and the resulting mix is used for road construction. The road laying temperature is between 110°C to 120°C. The roller used has a capacity of eight tons.

The process is easy and does not need any new machinery. For every kilo of stone, 50 grams of bitumen is used and 1/10th of this is plastic waste; this reduces the amount of bitumen being used. Plastic increases the aggregate impact value and improves the quality of flexible pavements. Wear and tear of the roads will decrease to a large extent.


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