This paper summarized and reviewed the mechanism and macro-performance of alkali-activated metallurgical slag, including steel slag, copper slag, ferronickel slag, and lead-zinc slag. Better activated method and alkali-activator are still needed to be developed to improve the performance of the metallurgical slag with low reactivity. Besides, the chemical components’ variation of these metallurgical slags from different regions will lead to unpredictable performance, which needs further study.
Magnesium potassium phosphate cement (MKPC) is an excellent rapid repair material for concrete, and many mineral admixtures have been applied to promote its performance. This study focuses on the quantitative characterization of the physical and chemical contributions of granulated blast-furnace slag with various finenesses to the performance development of MKPC. It was found that the addition of slag could increase the setting time, which is mainly due to the dilution of cement. Fine slag tends to decrease the fluidity of MKPC mortar. The physical contributions of ordinary and ultrafine slag to the early performance of MKPC mortar are 23% and 30%, while the chemical contributions are only 6%~10%. At late ages, the physical contribution is less than 10% and the chemical contribution of slag is even slightly negative. The addition of slag is beneficial to the compact packing of MKPC, which is the main reason for the physical contribution. Slag could react in the MKPC system, and increasing the fineness significantly promotes the reaction kinetics.
Phosphorus slag (PS) and limestone (LS) composite (PLC) were prepared with a mass ratio of 1:1. The effects of the content of PLC and the water/binder ratio on the mechanical properties, durability and dry shrinkage of concrete were studied via compressive strength, electric flux, sulfate dry/wet cycle method, saturated drainage method, isothermal calorimeter, adiabatic temperature rise instrument and shrinkage deformation instrument. The results show that PLC can greatly reduce the adiabatic temperature rise of concrete. The adiabatic temperature rise is 55 °C with 33 wt.% PLC, 10 °C lower than that of the control sample. The addition in the content of PLC does not affect the long-term strength of concrete. When the water/binder ratio decreases by 0.1–0.15, the long-term strength of concrete with PLC increases by about 10%, compared with the control group. At the age of 360 days, the chloride permeability of L-11 (i.e., the content of PLC was 20%, the water/binder ratio was 0.418) and L-22 (i.e., the content of PLC was 33%, the water/binder ratio was 0.39) decrease to the “very low” grade. The strength loss rate of L-11 and L-22 after 150 sulfate dry/wet cycles is about 18.5% and 19%, respectively, which is 60% of the strength loss rate of the control sample. The drying shrinkage of L-11 and L-22 reduces by 4.7% and 9.5%, respectively, indicating that PLC can also reduce the drying shrinkage.
Blast furnace ferronickel slag (BFNS), currently an underutilized metallurgical residue, was investigated for use as a precursor for alkaline activation. Water glass solutions with various moduli (0.5, 1.0, 1.5 and 2.0) were used at the same water glass concentration of 10% to investigate the influence of the modulus on hydration and mechanical properties. The results show that the modulus has a certain impact on the hydration and mechanical strength development of alkali-activated BFNS. Increasing the modulus of water glass does not change the type of hydration product and the activity of the Mg-containing phases, but it decreases the amount of C2AS, the Ca/Si and Al/Si ratios of the (N,C)-A(M)-S-H gel. In addition, a high silicate modulus deteriorates the pore structure, which has an adverse effect on the development of compressive strength and splitting tensile strength.
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