Waste Glass Nanoparticles as an Alternative Supplementary Cementitious Material

摘要

Durability and sustainability of concrete infrastructures is becoming of critical importance for the construction industry. New cement and concrete materials with improved properties could be developed by using nanomaterials. For instance, utilizing spheroidized nanoparticles is one way that could stimulate the hydration reactivity and improve the rheological properties of concrete due to their fine size and spherical shape. In order to engineer a new nanometric SCM, micrometric waste glass powder, a high amorphous silica content material, can be vaporized and nucleated into nanoparticles using the technology of induction thermal plasma torch, a process comparable to electric arc process used in the production of SF. The resulting spheroidized glass powder (SGP) possesses a spherical and amorphous morphology with a bi-modal size range: composed of 85%-88% of 25-200 nm nanoparticles and the balance of 1-5 m microparticles. XRD and ~(29)Si MAS NMR were used to characterize the effect of a fraction of SGP in replacement of cement in hardened cement pastes. When compared to finely ball-mill ground glass powder (GP), this characterization indicates that SGP has a pozzolanic behavior at both early and late age. This increases both the consumption of hydrated lime generated during the hydration of ordinary Portland cement (OPC) and the polymerization of calcium silicate hydrate (C-S-H) gels. SGP enables a rapid control of the CH content in the paste and appears readily activated in the cement paste once the hydration has started. In cement mortars, the dispersion of SGP is investigated through the use of ultrasound waves and the chemistry of superplasticizer (SP) in order to increase the compressive strength at both early and late age. Compared to polynaphtalene (PNS) based SP, polycarboxylate (PCA) based SP use both their electrostatic and steric repulsion effects to improve the dispersion of the cement grains and SGP nanoparticles and yield higher compressive strengths. Scanning electron microscopy (SEM) observations show that SGP reduces amounts of portlandite (Ca(OH)2) and densifies the microstructure.