Comparative study of proprietary and non-proprietary ultra-high performance concrete as partial-depth joint replacement

Abstract

Ultra-High Performance Concrete (UHPC) is a special type of concrete that has unique properties that are desirable for various types of construction projects. The most common form of UHPC used in the field is a proprietary UHPC product, which is much more costly than normal strength conventional concrete. Due to the expensive nature of the proprietary UHPC, research studies have been conducted to produce comparatively more affordable alternative non-proprietary UHPC made from local and readily available materials. This paper presents comparative studies of proprietary and non-proprietary UHPC as partial-depth bridge joint replacement. The proprietary UHPC product used in this study is manufactured by LafargeHolcim under the name Ductal® and the non-proprietary UHPC is the J3 mix developed previously at the University of Oklahoma. The nature of this study was comparative, hence all methods and tests performed were similar to previous studies conducted at the University of Oklahoma. Having reviewed relevant literature, six pairs of slab specimens were cast using normal-strength conventional concrete before joining each pair with a half-depth, heat cured UHPC joint once the conventional concrete slabs achieved the design strength. Three joint specimens were constructed using both proprietary and non-proprietary UHPC. These half-depth jointed slab specimens were tested both statically to failure and cyclically using service level loads. This research produced encouraging results regarding the UHPC alternative. All slab specimens exceeded the calculated failure load for a monolithic normal-strength concrete slab potentially due to the supplementary strength provided by the UHPC joint. The cracking loads for half-depth specimens were lower than those of full-depth specimens from previous research. In addition, the half-depth J3 specimens had smaller cracking loads compared to the Ductal® half-depth specimens. All half-depth specimens produced a comparable performance to full-depth specimens regarding flexural capacity. For cyclic testing, there was limited change in stiffness over time unless the maximum cyclic load was increased. The conclusions made from this study indicate that the non-proprietary UHPC alternative, J3, is a suitable repair material for bridge joints and can achieve similar performance to proprietary UHPC for certain applications.