Kudos to the Department of Public Works and Highways (DPWH) for approving the use of plastic bag waste in national road construction nationwide.
While not mandatory, I still believe this is a commendable decision. Using plastic additives can help improve overall road durability and, at the same time, help address the problem with plastic waste disposal.
In a statement, DPWH Secretary Manuel M. Bonoan said that under its Department Order No. 139, series of 2024, all its Regional Offices, District Engineering Offices, and Unified Project Management Office Clusters could now “utilize shredded plastic bag wastes to make longer-lasting national roads across the country.”
The order prescribes the specification for “bituminous concrete surface course with low-density polyethylene (LDPE) plastic bag waste, hot laid.” The DPWH said it aimed “to promote the recycling of LDPE plastic bag waste by shredding and using it as an additive to reduce the susceptibility to permanent deformation of bituminous concrete surface course or asphalt concrete.”
“This development is in line with the continuing efforts of the Department to support sustainable engineering and upgrade construction technology through adoption of successful research studies,” said Mr. Bonoan. The DPWH said the use of LDPE plastic bag waste in hot mix asphalt has successfully passed testing and met standards set by the agency.
DPWH Research and Development Engineer Neilsen Campit was reported by Spot.ph to have led the research into plastic additives, which started in 2018. It took the DPWH six years of laboratory and field testing to finally approve the use of LDPE waste plastic bags as an additive or modifier in road construction.
Spot.ph noted that the first trial was in January 2020, with plastic bag waste being added to the hot mix asphalt used to pave 149 meters across four southbound lanes of Taft Ave. in Ermita, Manila. In 2021, another 162 meters along President Quirino Ave. in Paco, Manila was paved with asphalt mixed with plastic waste. In all, the road work used around 1.6 tons of plastic waste.
As per DPWH specifications, “the LDPE plastic bag waste content shall not exceed 7.39% by weight of binder.” Also, “it shall consist of clean, dry, flexible, very lightweight, and relatively translucent plastic bag waste shredded into sizes varying from 6.35 mm to 12.7 mm.” Moreover, during mixing, plastic waste should be “added directly to the heated aggregates before adding the binder.”
In addition, “the mixture shall have a minimum compressive strength of 1.4 Mpa when tested by AASHTO T 167, Standard Method of Test for Compressive Strength of Hot Mix Asphalt and an Index of Retained Strength of not less than 70 when tested by AASHTO T 165, Standard Method of Test for Effect of Water on Compressive Strength of Compacted Bituminous Mixtures.”
I recall a previous report that in 2019, San Miguel Corp. (SMC) laid plastic-mixed asphalt on a 1,500-square meter pilot site in its logistics center in General Trias, Cavite. The road was said to have used 900 kilos of recycled plastic as a binder with bitumen to produce the asphalt. The road, meant to withstand heavily loaded trucks and equipment, is said to exceed Public Works standards.
Perhaps San Miguel can make public its experience with that project and how its “plastic road” has been doing so far. Is it performing better or worse than expected? Moreover, what were the specifications for that project? How does it exceed DPWH standards? Also, is San Miguel still using plastic in its ongoing road construction? Incidentally, prior to returning to the DPWH in 2022, Secretary Bonoan was president and chief executive officer of SMC Tollways.
In a previous column, I noted that mixing plastic waste with bitumen for road construction is a technology reportedly first credited to Professor Rajagopalan Vasudevan of Thiagarajar College of Engineering in Madurai. Plastic-bitumen composite is said to have better wear resistance than standard asphalt; does not absorb water; and, has better flexibility which results in smoother, lower-maintenance roads.
A study by the University of Baghdad, by researchers Zainab Ismail and Enas A Al-Hashmi, also used waste plastic in a concrete mixture as aggregate replacement. After 86 experiments and 254 tests, the research concluded that waste plastic could be used as a sand-substitution aggregate in concrete.
A similar conclusion was made by researchers at the University of Bath, who noted that plastic waste could be a viable partial replacement for sand in structural concrete. The Bath study, done in partnership with Goa Engineering College in India, found that plastic waste could pave the way for the sustainable use of a natural resource like sand.
Meantime, a study by Ahmad Jassim of the University of Basrah concluded that “plastic cement” could be produced from mixing high density polyethylene (HDPE) waste (used plastic bottles and food crates) and Portland cement. He also noted that this cement’s “density was decreased, ductility increased, and workability improved,” resulting in the production of “lightweight materials.”
The Basrah study focused on HDPE, while DPWH is now allowing the use of LDPE as an additive. LDPEs are used mostly in plastic bags, while HDPE are used in harder or stiffer plastic products like plastic bottles and plastic crates. Imagine if technology will allow the eventual use of HDPE-based plastic cement along with LDPE-based aggregates in road or housing construction.
“Plastic roads” already exist in the Indian cities of Pune, Bengaluru, and Jamshedpur; and, in Indonesia’s Bali, Surabaya, Bekasi, Makassar, Solo, and Tangerang. In 2018, the Dutch company Volkerwessels built a bicycle path made of recycled plastic in Zwolle, in northeast Netherlands. And in 2019, the UK Department of Transport started trying plastic road technology developed by Scottish reinforcement company MacRebur.
Two roads in Manila used 1.6 tons of waste plastic additives in 2020 and 2021. With the DPWH order this month setting the specifications for such use, perhaps more public roads will be paved with plastic in the future. The challenge, of course, is how to make sure that DPWH gets access to “clean, dry, flexible, very lightweight, and relatively translucent plastic bag waste.”
Marvin Tort is a former managing editor of BusinessWorld, and a former chairman of the Philippine Press Council
