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

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 (T-w) flow value (FV) and percentage replacement level of MS (%R-ms) on the four responses i.e. oven dry density (rho(OD)), compressive strength at 28 days (f(c.28d)), strength performance factor at 28 days (PFc.28d) and thermal conductivity (2-value) were stastically analyzed. ANOVA and multi-objective optimization was performed to finalize the mix having desirable hardened and functional properties. rho(OD), f(c.28d) and lambda-values of the CFC were varied in the range from 985 kg/m(3) to 1268 kg/m(3), 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 pop, compressive strength (CS), and lambda-value of the CFC sample, mixed with 60.0 wt% MS; was 1046 kg/m(3), 4.19 MPa, and 0.372 W/m.K, respectively.