Effects of Testing Methods and Specimen Dimensions on Compressive and Tensile Strength Evaluation of Ultra-High-Strength Grout for Wind Turbines

This study experimentally investigates the effects of testing methods, specimen shapes and sizes, and curing temperatures on the mechanical properties of 100 N/mm²-class ultra-high-strength grout used in onshore wind turbine foundations. Three types of imported grout were evaluated in terms of compressive strength and tensile strength based on JIS, EN and ASTM standards. The results revealed a pronounced size effect in the high-strength range, with smaller specimens showing greater sensitivity to accumulated temperature. Tensile strength was strongly influenced by the testing configuration, and the EN method using packing strips demonstrated improved stability and consistency. The tensile-to-compressive strength ratio was lower than that of conventional concrete, indicating distinctive brittle fracture characteristics of ultra-high-strength grout. These findings highlight that mechanical property evaluation is highly dependent on testing standards and specimen conditions, emphasizing the necessity of considering international differences in testing methods for reliable quality control and structural design.