Tensile Creep of Metakaolin-Limestone Powder UHPC
Rodolfo Bonetti, Oguzhan Bayrak, Kevin Folliard, Thanos Drimalas
Appears on pages(s):
cast orientation; drying shrinkage; mix composition; tensile creep; UHPC
An investigation has been performed on the drying shrinkage and tensile drying creep characteristics of a non-proprietary ultra-high performance concrete (UHPC) mixture. The mixture was formulated using metakaolin as supplementary cementitious material (SCM) and limestone powder as mineral filler. Cylindrical specimens with dimensions of 52 x 400 mm (2.05 x 16 in.) were fabricated and loaded at 7 and 11 days from casting to various stress levels for 90 days. Additional specimens were fabricated from a proprietary mixture with a silica fume-ground quartz formulation to study the effects of mixture composition. Simultaneous free-drying shrinkage measurements were recorded in accompanying specimens placed in the same room environment. Attention was given to the effect of the casting orientation, age at loading, and mixture composition on the drying shrinkage and drying creep behavior of the samples. These tests show that the metakaolin-limestone powder mixture has significantly lower drying shrinkage and specific drying creep than the silica fume-ground quartz mixture. Additionally, the age at loading influences primary creep behavior while not affecting secondary creep at the same stress level. It seems that fiber orientation plays a significant role in the drying creep behavior of UHPC and that cracked UHPC under constant tensile stress undergoes a significant amount of fiber slip.