Representative image of a California road paved with crushed recycled glass, showing the unusual material incorporated into the asphalt. Image Credits: ChatGPT.
In 1970, a street in Fullerton, California, became an unusual experiment in recycling when crushed waste glass was used as a major part of its asphalt surface. Instead of sending unwanted bottles to disposal, the material was processed and incorporated into a road mixture that covered part of a 600-foot stretch in the Fullerton Air Industrial Park. At the time, researchers were investigating whether discarded bottles could replace some or all of the conventional mineral aggregate used in asphalt. The Fullerton experiment provided an opportunity to observe how such a material behaved under actual traffic rather than only in laboratory tests.
Another test was done on the skid resistance of the road by the California Division of Highways in March 1971. The test found skid numbers of 61 to 69 at 25 miles per hour, equivalent to 54 to 62 at 40 miles per hour. As stated by the EPA summary for 1975, the field installations usually provided adequate skid resistance and satisfactory performance from a structural point of view; however, surface ravelling was observed in some cases. In a subsequent report issued by the Federal Highway Administration, the Fullerton trial installation was described as 600 feet long and made of asphalt material with 63 per cent of crushed glass in the aggregate composition.
There were no signs of excessive degradation of the aggregate on the Fullerton and Rolla roads, according to the EPA report. The inclusion of hydrated lime in the aggregate was intentional. The EPA study found that asphalt mixes could be produced with crushed glass aggregates and conventional paving equipment, though compaction was challenging. After a year, the surface showed some ravelling caused by fractures in the larger glass particles. Even so, the surface was still rated good, and the pavement performance was considered satisfactory. Later analysis provided additional evidence about aggregate performance. In Fullerton, the aggregate gradation change was minimal. An early experiment in glassphalt However, the use of glass-in-asphalt in Fullerton was not an isolated case. At about the same time, similar trials were carried out in Missouri, Ontario, Pennsylvania, and other regions. This does not mean the experiment proved waste glass was always a better alternative to traditional road aggregates. Rather, the experiment showed that used bottles could be converted into asphalt material and tested under real traffic conditions.
It had been previously discovered in laboratory testing that lime addition would enhance the water-resistance properties of glass-asphalt mixtures.
