I-Corps: High-performance cementitious material

Texas State University - San Marcos, San Marcos TX

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project involves the development of a novel concrete mixture containing recycled steel fiber (RSF) as fiber reinforcement, and reclaimed asphalt pavement (RAP) as a virgin aggregate replacement. Rebar reinforcement makes conventional reinforced concrete structures less economical due to the material cost of the steel and the labor cost to install the rebar. The presence of rebar also makes concrete placement difficult and may lead to settlement cracking. Concrete blended with randomly-oriented RSF provides a solution for more affordable and versatile concrete structures by eliminating rebar reinforcement. Additionally, both RSF and RAP are underutilized in concrete. The existing applications of these materials, typically viewed as waste, have major limitations: RSF has been conventionally sold as scrap steel to make new steel, which is less economical and has higher environmental impact than direct reuse. RAP has been primarily used in new asphalt pavement but that usage is often restricted due to pavement cracking problems. By using RSF and RAP in concrete, significantly less energy and raw materials are consumed compared to to conventional concrete. This I-Corps project is based on the development of a cost-effective, high-performance, sustainable concrete. Unlike conventional concrete that is often brittle and rigid, this new concrete is semi-rigid. The new system uses recycled steel fiber (RSF) as fiber reinforcement, which markedly increases concrete toughness and ductility due to the fibers' ability to bridge cracks. Reclaimed asphalt pavement (RAP) is added as intermediate-sized coarse aggregate to achieve optimized aggregate gradation. Aggregate gradation optimization reduces paste content in concrete and this, in turn, results in better concrete performance and reduced shrinkage. Additionally, replacing virgin aggregate with RAP also produces more ductile and crack resistant concrete because of the viscoelastic nature of the asphalt in RAP that leads to high stress relaxation. The asphalt coating on RAP acts as a lubricant and increases the flowability and pumpability of the materials. Finally, the new concrete has better damping properties, which may more effectively reduce noise and vibration damage caused by wind and earthquakes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.