Expansive Limestone Aggregate in a Concrete Pavement

Recurrent blowups and surface cracking are common symptoms of distress in concrete pavements. Premature appearance of distress symptoms is alarming because the materials used in the concrete become suspect. Criteria for design, quality of materials, and construction are necessarily re-evaluated. Indeed, a dutiful effort to discover the cause(s) and to provide future safeguards is reasonably expected. The analysis of causative factors besetting I 65-1(13)13 was complicated by an intuitive notion that blowups and surface cracks might be separate and independent problems. The crack pattern resembled the configuration of the wire mesh -- which was vibrated into position after the concrete was spread and screeded. The blowups are, as the evidence presented here will show, attributable to expansive forces arising from a limestone aggregate which now has been identified with specific ledges in the source quarry. The nature of this aggregate was such that its deleterious or expansive character would not have been detected by the specification tests and routine safeguards then in effect. However, insights extending beyond specification requirements surely would have made the ledges suspect had they been brought to bear in this instance. This report includes a relevant history of the project and results from the several investigative tests undertaken.