MECHANISM OF LOAD TRANSFER-CRACK WIDTH RELATION IN JPCP: INFLUENCE OF COARSE AGGREGATE PROPERTIES

Aggregate interlock from continuous measurement of crack deflections for concrete slabs-on-grade subjected to wheel loading up to 40kN using a large-scale slab test system were analyzed in this paper. These results show that aggregate interlock is comprised of at least three significant components: (1) an initial slack or gap between crack surfaces, which exists prior to loading; (2) a sliding of the adjacent crack surfaces; and (3) an in-plane dilation of the crack if unrestrained, otherwise build-up of normal force. The significance of dilation forces increases with crack width and approaches the crack shear load in magnitude for large crack widths (e.g. 2.5mm). These mechanisms vary with crack width and roughness. Roughness in turn is controlled by timing of cracking (i.e. PCC strength), coarse aggregate type and size. Tough and large-size aggregate had reduced slack and sliding and maintained high load transfer.