Production of bricks with fiber-reinforced alkali-activated desulfurization slag concretes containing carbonated BOF aggregates
1University of Oulu, Faculty of Technology, Environmental Engineering
|Online Access:||PDF Full Text (PDF, 15 MB)|
|Persistent link:|| http://urn.fi/URN:NBN:fi:oulu-201902081171
Oulu : K. Shaad,
|Publish Date:|| 2019-02-14
|Thesis type:||Master's thesis (tech)
This thesis investigates the efficiency of using carbonated Basic Oxygen Furnace (BOF) aggregates in different alkali-activated binders such as ladle slag and ground granulated blast furnace slag (GGBFS), and desulfurization (DS) slag. Sodium silicate and different molarities of sodium hydroxide were also used as alkali solution. BOF slag has high free CaO content, which leads to volume expansion problem under normal atmospheric condition. Additionally, free CaO and MgO are the reasons of volume expansion problem in desulfurization (DS) slag. To minimize and control this problem, BOF slags are exposed to CO₂ gas, which improves the volume stability.
The aim of the first chapter is to investigate using of carbonated BOF aggregates instead of normal aggregates with GGBFS and ladle slag precursors which activated by alkaline solution. The effects of using different precursor types and contents, aggregate types and contents, and different sodium hydroxide molarities (6M, 8M, and 10M) were determined by assessing the mechanical and mineralogical test.
After investigating the efficiency of carbonated BOF aggregates, the goal of the second chapter is to use carbonated BOF aggregate with different precursors types and content such as carbonated and non-carbonated desulfurization (DS) slag and different sodium hydroxide molarities (6M, 8M, 10M, and 12M). The effects of different parameters were carried out by evaluating mechanical, efflorescence, and pH experiments. Based on the results, mixture containing non-carbonated desulfurization (DS) slag with carbonated BOF aggregates and 8M NaOH provided excellent compressive strength compared to using carbonated DS. However, to minimize the efflorescence rate fiber reinforcement was introduced in the next chapter.
In the third chapter, the objective is to introduce fiber reinforcement to the selected mix composition, which containing alkali activated desulfurization slag with carbonated BOF aggregates and sodium hydroxide (8 M) to develop strength properties and limits the efflorescence rates. In the mix composition 4% fiber (in mass) was added. The selected four different fibers are basalt, PVA (8mm), Cellulose and Polypropylene (PP). Moreover, 4% and 8% combined PVA and basalt fibers are used. According to the results, it was noticed that basalt and cellulose fibers increased 15% (9 MPa) of the compressive strength compared to reference mixture and reduced the efflorescence compared to other used fibers.
In the last chapter, the main aim is to produce the bricks based on the mix compositions using carbonated BOF, desulfurization (DS) slag, and sodium hydroxide (8 M) with basalt and cellulose fibers. The effects of using selected fibers (basalt, cellulose) on the control mixture were conducted by mechanical strength, effects of carbonation, water absorption by capillarity, water absorption by immersion, efflorescence, ultrasonic pulse velocity, drying shrinkage, high temperature, and freeze-thaw test.
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