Statistical analysis using the RSM approach of the physical behavior of green polymerized eco-mortar

In order to develop an innovative, environmentally friendly composite materials for the construction industry, this study aims to exploit three types of waste material to manufacture cement mortars for producing lightweight concretes, ecologically friendly paving slabs and pavers. For this purpose, the response surface methodology (RSM) was investigated to predict and optimize the physical properties of mortars made from dune sand (DS) combined with recycled sand (RS), which are abundant in the desert and considered as waste products, reinforced by polymerized polyethylene terephthalate (PET) fibers of two different lengths, 20mm and 30mm, respectively. This investigation was carried out to assess the material's capacity in terms of engineering criteria, including air content in the fresh state (Ac), shrinkage (Sh), flexural displacement (Yf), ultrasonic pulse velocity (UPV), and water absorption (WA). Further, the chemical composition and mineralogical transformations at high temperatures of the produced mortar were examined. The ANOVA analysis of variance and a desirability function (DF) test are developed based on the Box-Behnken Design to predict and optimize variables and output responses by maximizing the mechanical properties and minimizing the physical properties. The obtained results reveal a significant improvement in the physical properties of the mortars, 6.25% Sh, 43% Yf, 4.65% UPV, and 6.54% WA, confirming the beneficial effect of fiber-reinforced products compared with those without fibers. The proposed quadratic model proves the validity of the experimental results with a better accuracy of less than 4.5% error. The optimal formulation obtained in this protocol consisted of 50% DS, 50% RS, and 2% PET, with a length of 12.70 mm. This mix yielded 0.799% Ac, −95.28 μm/m Sh, 5.79 mm Yf, 3855.11 m/s UPV, and 11.91% WA, presenting an attractive option for applications in eco-construction sustainability. Therefore, The RSM model correlates well with the experimental data, which has contributed to an improvement in the physical-mechanical features. Consequently, this eco-mortar has several applications in buildings, roads, bridges, for bending elements (beams, slabs) and can also be used for repairing damaged structures.