Thermomechanical performance and RSM–ANN modeling of earth bricks reinforced with alkali-treated Syagrus romanzoffiana fibers and derived biochar

The construction sector faces urgent challenges to provide affordable, sustainable housing solutions amid rapid global population growth and climate change pressures. Developing earth-based construction materials with enhanced thermomechanical properties represents a strategic response to meet these global housing needs while reducing carbon emissions from traditional fired bricks. This study optimizes hybrid waste from Syagrus romanzoffiana palm trees (WSrP) and biochar (BC) produced by the pyrolysis of fruit waste from Syagrus romanzoffiana palm trees (FWSrP) for reinforced stabilized earth bricks (SEB). The SEB were reinforced with 1% WSrP fibers from the brick mixture, treated alkalinely at concentrations of 1–3% during immersion periods of 2–24 h with 1% by weight of BC. Statistical Response surface methodology (RSM) and machine learning (ANN) models were developed to predict compressive strength (CS), flexural strength (FS), and thermal conductivity (Tc) as functions of the two main variables: NaOH concentration and treatment duration. While experimentally optimal performance occurred at fibres treated with 2% NaOH for 8 h (FS = 0.76 MPa; CS = 3.51 MPa), while thermal conductivity decreases to 0.39 W/m K with WSrP/FWSrP + BC hybrid. Beyond this optimal threshold, FS and CS gradually decrease with increasing NaOH concentration and immersion time, with multi-objective optimization predicting 2.75% NaOH for 12.92 h as the ideal conditions for compressed earth bricks and may be suitable for building construction, especially as masonry bricks. These reinforced clay bricks offer an excellent thermomechanical compromise, enabling the construction of durable, affordable, and environmentally friendly structures, and are particularly well suited for masonry applications.