Abstract
In this study, glass wool waste was utilized by means of alkali-activation with blast furnace slag. Reaction kinetics, workability, mechanical properties and autogenous shrinkage of alkali-activated slag and glass wool were comprehensively studied. Results indicated an optimal modulus (SiO2/Na2O) of the activator related to a long enough setting time and a high reaction degree of alkali-activated slag paste. The incorporation of glass wool as partial slag replacement did not necessarily lead to degradation in the performance of the pastes. While the compressive strength was always lower when glass wool was incorporated in the mixture, the flexural strength and workability could be improved with proper glass wool dosages. Autogenous shrinkage of blended pastes was always lower compared to the the mixture without glass wool. The results in this paper suggest that waste glass wool can be used as a precursor in slag-based alkali-activated system, resulting in improvements in the early-age properties of the paste such as a prolonged setting time and reduced shrinkage.
Highlights
An important part of demolition wastes is mineral wool waste, originated from insulation materials in buildings
Considering the high alkalinity of the activator, mineral wools may show higher reactivity in activated materials (AAMs) than in ordinary Portland cement (OPC). Both stone wool and glass wool contain Si, which is an important element for the production of the binding phases (C-A-S-H type gel and/or N-AS-H type gel) in AAMs
Several studies have been conducted on alkali-activated mineral wool [2,5,6,7], showing that the wool presents certain reactivity, the mechanical properties of alkali-activated stone wool (AASW) and alkaliactivated glass wool (AAGW) are low [2]
Summary
An important part of demolition wastes is mineral wool waste, originated from insulation materials in buildings. Considering the high alkalinity of the activator, mineral wools may show higher reactivity in AAMs than in OPC Both stone wool and glass wool contain Si, which is an important element for the production of the binding phases (C-A-S-H type gel and/or N-AS-H type gel) in AAMs. alkali-activation might be a feasible way to reuse the waste mineral wool. Ignition of wool waste to remove the organic resin is a potential strategy to increase the reactivity of the wool Another way to facilitate the development of mechanical properties is to use elevated temperature curing of the paste or concrete. The dissolution rate of wool and the reaction degree of the paste can both be improved [8] Both ignition of the raw materials and elevated-temperature curing impose high costs and energy consumption on the recycling process.
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