Abstract
An efficient solution to increase the sustainability of building materials is to replace Portland cement with alkali-activated materials (AAM). Precursors for those systems are often based on water-cooled ground granulated blast furnace slags (GGBFS). Quenching of blast furnace slag can be done also by air but in that case, the final product is crystalline and with a very low reactivity. The present study aimed to evaluate the cementitious properties of a mechanically activated (MCA) air-cooled blast furnace slag (ACBFS) used as a precursor in sodium silicate alkali-activated systems. The unreactive ACBFS was processed in a planetary ball mill and its cementing performances were compared with an alkali-activated water-cooled GGBFS. Mixes based on mechanically activated ACBFS reached the 7-days compressive strength of 35 MPa and the 28-days compressive strength 45 MPa. The GGBFS-based samples showed generally higher compressive strength values.
Highlights
The production of Portland cement uses processing temperatures exceeding 1400 ◦ C, leading to a large CO2 footprint [1]
The analysis showed a quite similar composition of the solidified binder matrixes in both tested slags
Main conclusions can be summarized as follow: The main conclusions can be summarized as follow: Inert and crystalline air-cooled slag can be amorphized and have enhanced reactivity by application
Summary
The production of Portland cement uses processing temperatures exceeding 1400 ◦ C, leading to a large CO2 footprint [1]. Environmental benefits can be achieved by the use of binders made of CO2 neutral alumina silicate rich industrial by-products or wastes. The GGBFS, which is in the focus of this research, can be utilized either as partial or full replacement of Portland cement. In the case of partial replacement, the GGBFS undergoes a secondary pozzolanic reaction due to the alkali activation process induced by the hydrating Portland cement [2]. The solidification is controlled by a combination of alkali activation processes and hydration. The chemical reactions are induced by strong alkalis such as sodium silicate or sodium hydroxide [3,4,5,6]
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