Development of a Mortar Abrasion Test for Fine Aggregates and Wear Resistance of Concrete Pavements - Paper

The cost-effective design of a rigid pavement with exposed Portland cement concrete (PCC) must take into consideration the on-going life cycle costs of maintaining adequate macrotexture and microtexture characteristics, which are essential in providing surface friction. The longevity and durability of the pavement’s surface texture depends on the ability of the selected aggregates to resist polishing and of the total mix to resist abrasion. In PCC pavements, the composition and characteristics of the fine aggregate are a key component in controlling its ability to resist polishing and retain good microtexture. Macrotexture is imparted during construction, e.g., tining, dragging, or through scheduled maintenance, e.g., grinding and grooving. Macrotexture retention in PCC pavements will depend on a number of factors including aggregate type, mix design, and workmanship, e.g., depth of tining, curing.

Currently, there is insufficient development of an adequate test to directly measure the abrasion resistance of concrete as a function of the fine aggregate component and the retention of macrotexture which are directly related to the frictional performance of concrete pavements. Aggregate tests such as acid Insoluble Residue (IR) that evaluates carbonate mineral content and micro-Deval abrasion (MDA) that measures relative durability of fine aggregates are indirectly related to microtexture and macrotexture retention in concrete materials.

This paper presents the development and results of a testing program utilizing equipment originally designed for measuring the Aggregate Abrasion Value (AAV) of coarse aggregates according to British Standards BN ES 1097-8. Mortar coupons were tested on a mechanical wheel lap rotating at 30 revolutions per minute for a total of 500 revolutions while a dry abrasive charge was fed onto the lap at a rate of 800 g per minute in front of each specimen. The average mass loss of four specimens is reported as the mortar abrasion value (MAV). A total of thirty concrete fine aggregates from sources across Ontario were evaluated.

The abrasion loss for each fine aggregate mortar mix was determined at the ages of 7 and 28 days. Results were compared with the compressive strength, insoluble residue, micro-Deval abrasion loss and mineralogy of the aggregates. The determination of the mortar’s resistance to abrasion was dependent on the degree of hydration and bond strength of the cement as demonstrated in comparing 7 day vs 28 day test results. Test results show that sensitivity to abrasion was minimized due to the selected water:cement ratio of the mortar. As a result, with increased curing time, variation in MAV test values was reduced with respect to aggregates of different mineral hardness. Test results show that there was little correlation established between the MAV and the various other parameters tested.