Title: Tensile Creep of Metakaolin-Limestone Powder Ultra-High- Performance Concrete

Author(s): Rodolfo Bonetti, Oguzhan Bayrak, Kevin Folliard, and Thanos Drimalas

Publication: Materials Journal

Volume: 120

Issue: 2

Appears on pages(s): 97-103

Keywords: casting orientation; drying shrinkage; mixture composition; tensile creep; ultra-high-performance concrete (UHPC)

DOI: 10.14359/51738492

Date: 3/1/2023

Abstract:
An investigation was performed on the drying shrinkage and tensile drying creep characteristics of a nonproprietary ultra-high-performance concrete (UHPC) mixture. The mixture was formulated using metakaolin as the supplementary cementitious material (SCM) and limestone powder as the 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.