Because the specification has significant economic impact on aggregate producers and the Department, the P214 test must be repeatable and consistent. To be credible, the test should correlate with other recognized tests and, more importantly, with observed field performance. Although the Department has achieved a certain level of confidence with the test method and the specification, additional verification is desirable. The reasons for apparent discrepancies between results of different test methods must be understood. Correlation of test results with field performance and identification of other factors affecting field performance are also needed.
In the Departments last study, researchers recognized the possibility of pit variability, but limitations in study scope and duration prevented thorough investigation. It is not known whether the reactivity of sand sources varies significantly with depth or lateral location. Variability could frustrate attempts to maintain a consistently acceptable level of reactivity. Furthermore, it is not known whether certain reactive components could be mechanically separated from the sand to lessen its overall reactivity.
Finally, there is evidence that another chemical reaction, called alkali-carbonate reactivity, may be responsible for distress in some pavements. The extent and severity of alkali-carbonate reactions is unknown. Criteria for identification and verification are not established, nor are predictive tests determined. It is not known whether fine aggregates, coarse aggregates, or both contribute to this problem.