A New Test Method for Determining the Strength and Fracture Toughness of Cement Mortar and Concrete

The Spiral Notch Torsion Fracture Toughness Test (SNTT) was developed recently to determine the intrinsic fracture toughness (K_IC) of structural materials. The SNTT system operates by applying pure torsion to uniform cylindrical specimens with a notch line that spirals around the specimen at a 45° pitch. K_IC values are obtained with the aid of an in-house developed three-dimensional finite-element computer code, TOR3D-KIC. The SNTT method is uniquely suitable for testing a wide variety of materials used extensively in pressure vessel and piping structural components and weldments. Application of the method to metallic, ceramic, and graphite materials has been demonstrated. One important characteristic of SNTT is that neither a fatigue precrack nor a deep notch are required for the evaluation of brittle materials, which significantly reduces the sample size requirement. In this paper we report results for a Portland cement-based mortar to demonstrate applicability of the SNTT method to cementitious materials. The estimated K_IC of the tested mortar samples with compressive strength of 34.45 MPa was found to be 0.19 MPa √m.