Influence of electric arc furnace slag on produced geopolymer composites

What is it about?

Effect of various doses of electric arc furnace slag (EAFS) – a by-product of steelmaking recovered after the oxidizing process – along with water cooled slag and cement kiln dust for the evaluation of optimum ratio of the added EAFS was studied. Results showed that the compressive strength of geopolymer specimens increases with EAFS up to 50% then decreases with further slag increase, giving an increased mechanical strength than the control by 7.94%, 23.9%, 80.8% and 17.8% at ages of 90 days and 9.49, 32.03, 89.68 and 37.6% at 120 days for replacement by 10, 25, 50 and 75% of EAFS, respectively. It is noticed that the enhancement in strength increases with EAFS and with curing time; even the full replacement by EAFS leads to further strength gain more than 10% replacement.

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Why is it important?

1-In the presence of Ca contained ingredients (slag) as a result of geopolymer coexistence and C–S–H phase and maximal geopolymer strength was reached. 2. Cement kiln dust has high alkalis content and free lime that can efficiently be utilized in the activation of industrial slag wastes results in the production of environmentally friendly cementing materials that can be applied in various building purposes. 3. Uses of electric arc furnace slag can be effectively used up to 50%, while further increase leads to increase in the iron content that will precipitate as hydroxide and lower the medium alkalinity. 4. Using 50% EAFS results in the growth of the amorphous content of N-A-S-H gel and the binding gels (C–(A)– S–H which has a positive effect on enhancement in the mechanical properties of the resulting structure. 5. The effect of combination of 50% EAFs in addition to 25% GGBFS in a mix as is likely to cause a higher strength values, also the Ca2+, Fe3+ are capable of acting as charge-balancing cations within the geopolymeric binder structure. 6. The compressive strength of geopolymer specimens increase with EAF slag up to 50% then decrease with further slag increase, giving an increased mechanical strength than the control by 7.94%, 23.9%, 80.8% and17.8% at ages of 90 days and 9.49, 32.03, 89.68 and 37, 6% at 120 days for replacement by 10, 25, 50 and 75% of EAFS, respectively. 7. It is noticed the enhancement in strength increase with EAFS with curing time; even the full replacement by EAF slag leads to further strength gain more than 10% replacement. 8. The efficiency factor of the geopolymer pastes increases gradually with the increase of the EAF slag content up to 50% giving an efficiency value of 2.88% after 120 days, while decreases with 75% EAFS reaching the value of 2.36%.