Abstract
The valorization of spent oil bleaching earths (SOBE) is crucial for the protection of the environment and the reuse of resources. In this research, alkali-activated binders were manufactured at room temperature using SOBE as a precursor by varying the mass ratio between the activating solutions of sodium silicate (Na2SiO3) and 6 M sodium hydroxide (NaOH) (activating solution modulus) (Na2SiO3/NaOH ratio = 1/1; 1/2; 1/3; 1/4) to investigate the influence on the technological properties of the materials. This process intends to evaluate the potential of SOBE, heat-treated at 550 °C (1 h), as a precursor of the reaction (source of aluminosilicates). Samples produced with higher amounts of sodium silicate developed a denser structure, with lower porosity and a higher amount of geopolymer gel. Maximum flexural (8.35 MPa) and compressive (28.4 MPa) strengths of samples cured at room temperature for 28 days were obtained with a Na2SiO3/NaOH mass ratio of 1/1. The study demonstrates that SOBE waste can be used as a precursor in the manufacture of geopolymer binders that show a good compromise between physical, mechanical and thermally insulating characteristics.
Highlights
IntroductionOrdinary Portland cement (OPC) is the most widely used binding material in construction, being one of the materials with the highest production worldwide, with a production in 2016 of 4174 Mt, corresponding to a growth of 2.3% compared to 2015 [1]
Introduction published maps and institutional affilOrdinary Portland cement (OPC) is the most widely used binding material in construction, being one of the materials with the highest production worldwide, with a production in 2016 of 4174 Mt, corresponding to a growth of 2.3% compared to 2015 [1].The global cement industry is one of the main greenhouse-gas (GHG)-emitting contributors as it generates 800 kg CO2 for each ton of Portland cement produced [2]
The reaction degree tends to increase in samples prepared with higher Na2 SiO3 /NaOH mass ratios, indicating the formation of a greater amount of N-A-S-H geopolymer gel
Summary
Ordinary Portland cement (OPC) is the most widely used binding material in construction, being one of the materials with the highest production worldwide, with a production in 2016 of 4174 Mt, corresponding to a growth of 2.3% compared to 2015 [1]. The global cement industry is one of the main greenhouse-gas (GHG)-emitting contributors as it generates 800 kg CO2 for each ton of Portland cement produced [2]. In order to meet environmental objectives, this industry is seeking alternative experimental ways to develop cements that require less energy to manufacture and emit less polluting gases into the atmosphere. Alkali-activated binders, or geopolymers, constitute an environmentally friendlier alternative, since CO2 emissions can be reduced by 20–50% in comparison to OPC [5,6,7].
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