ABSTRACT
The direct tensile strength is a parameter of significant interest for compacted concrete with a low w/c ratio used in constructing RCC dams under the procedure of spreading layers of this material of 30–50 cm thickness and roller compacting them. The maximum static vertical traction in the horizontal joints between layers used in the design of the seism is a project parameter which needs verification through laboratory tests. The correct execution of the direct tensile test with cylinder specimens of 15 × 30 cm (slenderness 2) have serious difficulties to guarantee the direct tension force application in pure axial direction and its transmission to the body of the test specimen. This issue can be resolved by performing consecutive tests until achieving a procedure that ensures the traction breakage around the center of the specimen body. In order to do so, it is necessary to design specific fastening tools and defining a preparation procedure of the circular specimen bases that allows the correct reception of the traction force. Different tests have been performed using specimens fabricated for this purpose and also using vertical cores extracted from the dams body. The direct tensile strength values obtained were in the 1–2MPa range for the fabricated specimens and around 1 MPa for the dam cores. It is frequently observed in the fracture surface the presence of aggregates of large size (60 × 70 cm and more) with unfastened mortar, soft aggregates (sandstones) cleaved and honeycombs.
