Economic and Environmental Impact Assessments of Advanced Geopolymeric Materials - ENVISAGE

Geopolymers are a promising material with diverse applications in the construction industry, which offers an alternative to traditional cement-based materials. Inorganic-organic hybrid geopolymer, instead, offers more enhanced physical and chemical properties with the incorporation of the functional agents. Therefore, the aim of this PhD thesis is to propose an innovative and sustainable solution following the global pollution caused by the construction sector and aims to use local precursors to produce best performing green geopolymer and hybrid geopolymer materials. This thesis work was done in collaboration between University of Messina, ATHENA Green Solutions Srl in which raw materials and their characterization were done at Messina university while geopolymer and hybrid geopolymers materials was done at the Instituto de Ciencias de la Construcción ‘Eduardo Torroja’ (IETCC-CSIC) in Madrid (Spain). Firstly, a series of experiments were conducted, to synthesize, characterize and evaluate the performance and suitability of various geopolymeric materials to produce base geopolymers. Initially, the geopolymer was made of the combination of different local Sicilian raw materials including Electric Arc Furnace Slag (DS), clay, brick waste (BW), kaolin (K), and slag activated with NaOH solution in combination with alkaline activators liquid (A.A.L) and powder (A.A.P) under different conditions. Based on the different performance evaluation results through mechanical test, X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy, we had to further examine the properties of the calcined clay and electric arc furnace slag, and calcined clay and brick waste mixtures activated with (A.A.L) and (A.A.P) as a promising mixture for developing high-performance hybrid geopolymer. Secondly, through the sol-gel technique, we investigated the effect of incorporating four different organic functional agents: polydimethylsiloxane (PDMS), tetraethyl orthosilicate (TEOS), acrylic resin, and TP56 mixture, on the chemical-physical properties such as water resistance. In which, PDMS, TEOS, acrylic resin, and TP56 added separately the C-Clay and DSg mixture samples, thereafter only PDMS and TP56 added in the C-Clay and BW mixture samples. The results showed that the hybrid geopolymer based on C-Clay and DSg incorporated PDMS (H-GP @ PDMS), presented improved compressive strength properties, and surface water resistance. Hence, due to the improved performance, low cost, non-toxicity, and low volatility, we selected this consolidant for chemical-physical characterization with C-Clay @ DSg. The XRD analysis showed no change in phases with the addition of PDMS. The SEM analysis revealed microcracks in both types of alkaline activators. The porosity and water absorption results showed that the samples activated with A.A.L had increased compared to those activated with A.A.P due to the increased pores. The contact angle measurement indicated that GP-P is hydrophilic (rapid water absorption) while H-GP-P @ PDMS is highly hydrophobic (resistant to water absorption). Hybrid geopolymer made with A.A.L (H-GP-L @ PDMS) is less hydrophobic than hybrid geopolymer made with A.A.P (H-GP-P @ PDMS), which is consistent with contact angle results. Future research should be directed to conduct a life cycle assessment and life cycle cost to compare the environmental and economic impacts of geopolymers against traditional materials. The results are expected to contribute to demonstrating the feasibility of geopolymers as an alternative to conventional materials.