Waste glass as binder in alkali activated slag–fly ash mortars

Abstract

This paper illustrates the application of waste glass powder as part of the binder in slag-fly ash systems activated by NaOH and NaOH/Na 2 CO 3 activators. To evaluate the reaction kinetics, reaction products, mechanical properties, and durability performance of glass powder modified alkali activated slag-fly ash systems, calorimetry test, X-ray diffraction, FTIR, strength test, drying shrinkage tests, and carbonation test were conducted. From the isothermal calorimeter results, glass powder shows a higher reactivity compared to fly ash but still lower than slag. The reaction products of glass power modified samples exhibit an enhancement of polymerization degree of Si-O-T, observed in FTIR. As a consequence, higher drying shrinkage exists in glass modified mortars. The mechanical performance of different samples is mostly controlled by the Ca/Si of dry mixtures and activator type. After the slag-fly ash binder system was modified by the waste glass, a significant enhancement of resistance to carbonation was identified, especially for NaOH/Na 2 CO 3 activated mortars, which show an increase of 300% on the carbonation resistance ability compared to the reference sample. The Na/(Si ? Al) ratio of dry mixtures exhibits a positive correlation with carbonation resistance.

The role of recycled waste glass incorporation on the carbonation behaviour of sodium carbonate activated slag mortar

“…However, a significant shift from 953 cm À1 to 963 cm À1 , and from 953 cm À1 to 967 cm À1 are observed after incorporation of RGP in binders. This reveals that the addition of waste glass in binders increases the polymerization degree of SieO in C-A-S-H by providing more silicate, which is also observed in the previous study (G. Liu et al, 2019b). Furthermore, this observation is more significant in the NC5 series than in the NC3 series samples.…”

“…For sodium hydroxide/silicate blended activators, a high modulus of SiO 2 /Na 2 O was reported to present a high resistance to carbonation of alkali activated slag (Shi et al, 2018a). Similarly, in our previous investigation, superior resistance to carbonation was achieved in the waste glass containing GGBS/fly ash mortars activated by sodium carbonate/hydroxide, but the mechanism of improvement was not studied and discussed in details (G. Liu et al, 2019b). In addition, the report of durability evaluation of waste glass in sodium carbonate activated GGBS is still rare.…”

“…These carbonation products could fill the pores and reduce the volume of larger pores in gel, or even block the pore for CO 2 transportation. Therefore, a linear relationship can be observed between carbonation depth and the square root of carbonation duration G. Liu et al, 2019b).…”

The effect of glass waste as an aggregate on the compressive strength and durability of fly ash-based geopolymer mortar

“…Some studies [10,[16][17][18] reported improvement in strength development of geopolymer binders, in which glass-waste was used as a binder replacement. From the results compressive strength of fly ash geopolymers increases from 26 to 53 MPa, with an increase in glasswaste content from 5% to 30%, while some studies [8,19,20] reported the opposite. Most of the studies on the application of glass-waste as an aggregate replacement are in agreement that an increase in glass-waste content in geopolymer mixtures results in strength loss [15].…”

Chemical and Microstructural Properties of Fly Ash and Fly Ash/Slag Activated by Waste Glass-Derived Sodium Silicate

“…Due to its high content of amorphous silicates, waste glass is an ideal candidate for the production of low carbon binders from alumina silicates for alkali activated (sometimes referred to as geopolymer) concretes. To date, most of the studies that investigated the use of waste glass as a constituent of blended precursor for geopolymer concrete have shown that a substitution rate of 20% in binders reduces the shrinkage and improves the carbonation resistance [5][6][7][8]. A high-temperature process is, however, required for blended metakaolin-waste glass geopolymers [9].…”