Strength and Durability of Ultra-High Performance Concrete Materials and Structures.

Abstract

The need to address the aging of today’s infrastructures presents engineers and designers with a unique opportunity to redefine the methods and materials with which new civil projects are undertaken. Engineers must look to new innovations, taking into account resilience to natural hazards, efficiency in design, and sustainability of materials while cultivating new structural concepts. Ultra-high performance concrete (UHPC) is one such innovation. UHPC is a new class of cementitious materials that have exceptional mechanical and durability characteristics. While previous work on UHPC has focused on material characterization of strength, a comprehensive analysis of UHPC on a broader scale remains to be fully realized and is the focus of this seminar.

Through an extensive testing program, a low cost, non-proprietary UHPC mixture with excellent characteristics in compression and tension, as well as exceptional resistance to freeze-thaw and chloride ion penetration was developed. The proposed mix deviates from traditional UHPC mixtures in that it uses a 50:50 mix of Portland Type I and Ground Granulated Blast-Furnace Slag (GGBS) as a binder, lacks any silica powder (inert filler) and requires no post-placement treatment. The use of GGBS and removal of silica powder improves the material’s ‘greenness’ making it a more sustainable cementitious product. Following a complete material investigation of the new material, a comprehensive analysis of the developed bond between UHPC and deformed steel bars to facilitate and enable future structural applications was performed. Bond pull out tests showed the developed UHPC requires significantly reduced development lengths in order to attain steel bar yield compared to traditional concretes. A computational model to characterize the material was proposed and a UHPC joint consisting of two pre-cast bridge deck elements was developed and tested at full scale for accelerated bridge construction applications.