Identifying Fine Aggregates Prone to Polishing in PCC Pavements

Surface polishing in portland cement concrete (PCC) pavements leads to higher incidences of skid-related accidents on highways. This type of failure is often associated with the usage of softer fine aggregate such as limestone sands. To identify polish resistance aggregates, state agencies like TxDOT have adopted tests such as the acid insoluble residue test (AI). Since calcium carbonate is soluble in acid, no carbonate sand passes the AI test which has a minimum limit of 60% in Texas. This paper describes research that was done to evaluate the polish resistance of aggregates using a laboratory concrete performance test. Concrete slabs made with different fine aggregates were evaluated for skid using a circular track meter (CTM), a dynamic friction tester (DFT), and a three-wheel-polishing device (TWPD). To ensure that the values obtained at the laboratory related to field performance, test sections constructed with 100% limestone sand and blended sands were also evaluated. Results show that some of the aggregates that failed the AI test performed as well as some of the siliceous fine aggregates that passed the AI test. Other aggregate tests such as the micro-Deval have shown to relate more closely to the concrete performance tests performed under laboratory conditions.