Strength Development Properties of Core Specimens Taken from Structural Concrete Test Specimens Prepared All Over Japan

This paper investigates the strength development properties of core samples (range: 40–100 N/mm2) from concrete specimens prepared and tested at ready-mixed concrete plants all over Japan. Experimental data was obtained using cubic concrete blocks (1 m3) made of three types of cement, which were classified according to the time of year they were prepared to account for the influence of seasonal/temperature conditions (spring/fall, summer, winter). The study considered the maximum internal temperature of concrete blocks, the relationship of cement-to-water ratio and compressive strength, and differences in compressive strength between underwater (standard)-cured specimens and core specimens attributable to season and cement type. In addition, design parameters were derived for cement-to-water ratio in order to achieve certain target strengths for structural concrete members. The authors show the difference of strength development of core specimen by cement types.