Size effects on mechanical properties of recycled aggregate thermal insulation concrete

•GHBs have a significant influence on the size effect of concrete compressive strength.•A larger strength grade could make the size effect on compressive strength for RATIC specimens more prominent.•RATIC specimen section has more significant effect on the size effect of compressive strength than the slenderness ratio.•RATIC specimens has more prominent size effect on strengths than NC. The paper presents an experimental study on the effect of specimen size on the compressive strength, splitting tensile strength, and elastic modulus of recycled aggregate thermal insulation concrete (RATIC). Factors influencing size effect discussed in this paper include recycled coarse aggregate (RCA) replacement ratio, RATIC strength grade, and concrete type. Specimen size ranged between 50 and 200 mm for cubic specimens. The slenderness ratio for prismatic specimens ranged from 1.0 to 4.0 and the lateral dimension ranged from 100 mm to 200 mm. All specimens were tested after 28 days of curing. Results showed that RCA replacement ratio has slight effect on the size effect of compressive strength, splitting tensile strength, and elastic modulus. Concrete strength grade has a significant influence on size effect of compressive strength for RATIC. For a constant slenderness ratio (h/l = 2), the decreasing rate greatly depended on the RATIC strength grade. The compressive strength decreases with increasing slenderness ratio in prismatic specimen. For RATIC, the section of specimen size has more significant effect on the size effect of compressive strength than slenderness ratio. Conversion factors for the four concrete type are proposed for both compressive strength measurements. Refined models are presented to predict the prismatic compressive strength of RATIC specimens.