Modified mix design and statistical modelling of lightweight concrete with high volume micro fines waste additive via the Box-Behnken design approach

Abstract

The research paper presents a modified mix design to develop cellular foamed concrete (CFC) using hazardous micro fine in-situ stone sludge waste in the form of low grade dolomitic marble slurry (MS), as a replacement of fine river sand (FRS) and tap water. To utilize maximum amount of MS, optimization was done through the Box-Behnken design (BBD) of response surface methodology (RSM). The effects of three effective variable parameters i.e. temperature of water to be added into foaming agent solution (Tw), flow value (FV) and percentage replacement level of MS (%Rms) on the four responses i.e. oven dry density (ρOD), compressive strength at 28 days (fc.28d), strength performance factor at 28 days (PFc.28d) and thermal conductivity (λ-value) were stastically analyzed.ANOVA and multi-objective optimization was performed to finalize the mix having desirable hardened and functional properties. ρOD, fc.28d and λ-values of the CFC were varied in the range from 985 kg/m3 to 1268 kg/m3, from 3.89 MPa to 4.94 MPa and from 0.340 to 0.441 W/m.K, respectively. Advanced characterization techniques such as- field emission scanning electron microscopy (FE-SEM) and 3D morphological analysis were also performed to investigate the interaction of MS with CFC microstructure and cement paste matrix. The ρOD, compressive strength (CS), and λ-value of the CFC sample, mixed with 60.0 wt% MS; was 1046 kg/m3, 4.19 MPa, and 0.372 W/m⋅K, respectively.