University of Oulu

Alternative alkali activator for blast furnace slag and stone wool

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Author: Ezu, Amarachi1
Organizations: 1University of Oulu, Faculty of Technology, Environmental Engineering
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.9 MB)
Pages: 89
Persistent link:
Language: English
Published: Oulu : A. Ezu, 2019
Publish Date: 2019-11-21
Thesis type: Master's thesis (tech)
Tutor: Kinnunen, Päivö
Adesanya, Elijah
Ohenoja, Katja
Reviewer: Kinnunen, Päivö
Adesanya, Elijah
Ohenoja, Katja


The utilization of desulphurization dust from the steel production as an alternative alkali activator for stone wool (SW) and blast furnace slag (BFS) was investigated in this thesis. These materials are industrial by-products considered as an alternative construction material for mitigating CO2 emissions associated with cementing materials, and to reduce their landfilling.

Previous literatures on alkali activated geopolymers were reviewed to establish the concept of utilizing industrial wastes or by-products in producing eco-friendly and sustainable alkali activated cementing materials equivalent to standard cementitious materials. The experimental procedure used in this study was the “one-part mix pathway” to achieve adequate paste workability and the highest mechanical strength via the various mix compositions which includes; constant water/binder (w/b) ratio, and varying ratios of silicon, calcium and sodium oxides. Also, addition of different percentages (0%, 0.05%, 0.10% and 0.15%) of Triisopropanolamine (TIPA) was used to aid in the dissolution of minerals. The amount of the desulphurization dust was kept constant in all mix compositions.

The different mix composition contained various percentages (0%, 5%, 10%, and 15%) of stone wool and were cured at 60 oC for 24 hours. Mechanical strength was tested at 7-day and 28-day. The highest compressive strength of 20.1 MPa was recorded at 28-day when 0.05% TIPA was added to 5% SW samples. A very good workability (96.2%) was observed when 0.1% TIPA was added to 5% SW samples.

In addition, characterization of the alkali activated geopolymer pastes was carried out using XRD, TGA and iso-thermal microscopy techniques to analyze the reaction products.

Overall result showed that desulphurization dust can effectively activate geopolymer precursors to produce desirable mortars, while SW is an appropriate co-binder to blast furnace slag, with an optimum amount observed to be 5% stone wool. Also, the effect of TIPA was significant in the workability and mechanical strength of the paste.

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