Production of ultra high performance concrete using recycled tire steel fiber: mechanical properties and life cycle assessment
Yanzhi Wang, Pizhong Qiao, Jing Sun, Hao Li, An Chen
Abstract
There is a lack of reliable carbon dioxide emissions factors (CDEFs) for recycled steel fiber (RSF) and quantitative studies assessing the carbon dioxide emissions (CDE) of ultra high performance concrete (UHPC) made with RSF (RSF-UHPC). Combined with experimental research and life cycle evaluation methods, the effects of key fiber parameters, strength, process, and material components on the mechanical properties and CDE of UHPC were studied. The results indicate that RSF-UHPC exhibited better flowability and comparable compressive strength and tensile strength to UHPC made with industrial steel fiber (ISF-UHPC) for the same fiber dosage. This is attributed to short fibers reducing the loss of flowability and the fibers helping to halt or slow the propagation of microcracks in RSF-UHPC. UHPC with 2% RSF is also more environmentally friendly, with calculated CDE of 929.64 kg CO2e /m 3 and a CDE intensity of 8.03 kg CO2e /(m 3 · MPa), which are, respectively, 23.91% and 18.1% lower than those of ISF-UHPC (for the same fiber dosage of 2%). Based on a life cycle assessment, the CDEF of RSF was determined to be 0.587 kg CO2e /kg. Furthermore, the CDE during the raw material acquisition stage are the primary contributors to the total CDE of UHPC, with cement and fibers being the main factors.