Interface shear transfer of lightweight-aggregate concretes with different lightweight aggregates

This paper presents the results from the second phase of an ongoing investigation of the direct shear transfer across an interface of lightweight aggregate concretes. The lightweight concretes were made with different lightweight-aggregate materials (expanded shale, expanded clay, or expanded slate). The second phase of the experimental investigation included 52 push-off specimens. Test variables included concrete type (normalweight, sand-lightweight, or all-lightweight), lightweight-aggregate material, surface preparation of the shear interface, reinforcement ratio, and crack interface condition. Applied shear force-slip relations are presented and discussed. Peak shear forces are also compared. Current shear friction design provisions in ACI 318-14 and PCI Design Handbook are examined. Shear strengths computed by ACI 318-14 Eq. (22.9.4.2) and PCI Design Handbook Eq. (5-32a) using the coefficient of friction mu approach were conservative for the sand-lightweight and all-lightweight monolithic and cold joint specimens in this study. Revisions are proposed for shear friction design of a smooth interface condition.