Modelling the compressive strength of non-proprietary ultra-high-performance fiber-reinforced concrete: A D-optimal mixture design approach

This study examines the compressive strength of an innovative non-proprietary ultra-high-performance fibre-reinforced concrete (UHPFRC) using an approach that combines experimental methods and mathematical modeling. The UHPFRC is developed using Portland limestone cement, river sand, rice husk ash, superplasticizer, recycled tire steel fibre, and water. This study aims to design, optimise, and develop prediction models that accurately predict the compressive strength of UHPFRC at 3, 7, 14, 28, 56, and 90 days, subjected to normal curing in water at 21 °C. A D-optimal mixture design approach was used to design the mixes. The laboratory test results of the mixes were studied, yielding prediction models that accurately predict the compressive strength of the UHPFRC with high values of the coefficient of multiple determinations (R ² ), insignificant lack of fit test results, low coefficient of variation and standard deviation indicate the precision, reliability and consistency of the models. Numerical optimisation revealed that UHPFRC can be designed with less amount of cement (36%), and recycled tire steel fibre (6.258%), yielding compressive strengths of 83.3 MPa, 91.84 MPa, 99.30 MPa, 105.44 MPa, 108.62 MPa, and 111.79 MPa at 3, 7, 14, 28, 56, and 90 days of curing, respectively. The research outcomes suggest that incorporating rice husk ash and recycled tire steel fibres in UHPFRC not only improves the compressive strength but also promotes sustainability in the construction industry, addresses the issue of standard construction material scarcity, reduces construction material costs, and supports local UHPFRC manufacturing.