Recyclers Offer Concrete Guidelines to L.A. County

In response to concrete recyclers’ complaints that the Los Angeles County Public Works (LACPW) department specification techniques favor natural aggregate producers, members of the Southern California Chapter of the Construction Materials Recycling Association (CMRA) recently met with department staff to discuss the problem.

Two key issues concerned the recyclers, as explained by CMRA regional director Kelly Ingalls: 1) LACPW issues specifications that call for crushed aggregate base (CAB) instead of crushed miscellaneous (CMB, the recycled product), and 2) LACPW has issued a specification for tract developments that requires a test report for every 100 tons of CMB produced before the material can be used on a tract project.

“Such testing is economically unfeasible for the recyclers,” says Ingalls. What essentially then happens, says Ingalls, is “LACPW is specifying CAB as a preferred material, and CMB producers are at a competitive disadvantage by not being able to bid on certain LACPW jobs.

“This is not specific to LACPW jobs,” adds Ingalls. “The CMRA has documented a list of about 10 localities that will not allow the use of CMB because they mimic LACPW. As a result, recyclers lose out on hundreds of thousands of dollars of public and private work every year.”

But LACPW countered that the compaction of CMB is not as good as CAB, with the latter able to reach 95 percent compaction, compared to 90 percent for recycled material.

On the other hand, an LACPW staff engineer pointed out that sometimes the compaction issue is a field problem, with contractors compacting CMB in the same way they would CAB. CMB uses a static mode with water, while CAB has a vibrator mode. The materials are different, and the problem could be resolved by using the proper mode and improving the placement and compaction methods when CMB is used.

As for tract developments, LACPW staff pointed out that this was used whenever wet clay was present and geotechnical fabric was being used. There are different gravel equivalent ratings between CMB and CAB, with CAB considered by LACPW to have better gravel equivalent. But all in attendance agreed that better empirical evidence is needed to see just what the differences are between CAB and CMB. In addition, as the spec for tract developments was written many years ago, LACPW agreed to review the language with the original author.

Then the LACPW staff claimed that there are more road failures when CMB is used, rather than CAB. The CMRA’s Ingalls, who also worked for the city of Los Angeles public works department for more than nine years, questioned this, saying that roads with CAB and CMB have the same level of failures. LACPW could not back up their claim, and agreed their needs to be studies done to compare the data.

Also, the recyclers suggested that perhaps a plant certification process could be developed for CMB recycling plants to certify the plants can make the material into the needed specifications.