The discarded mill tailings behind the dam will cause disasters at any time. A solution to this problem may be to utilize those wastes, e.g. mill tailings from magnetite, as the Manufactured Fine Aggregates (MFA) for preparation of concretes. The mill tailings from magnetite can be considered as new resources of sand. However, in production of MFA from mill tailings, the particles smaller than 75 μm were strictly eliminated. The degranulation results in not only lower utilization of the resources but also worse micro grading of MFA. The micro fines, i.e. powdery mill tailings from magnetite, supplements powder content in concrete systems in w/c>0.40 to modify the ratio of water to total powder (w/p). The perfect micro grading for good workability can be reached in the case of optimal w/p ratio. The filling effect owing to perfect micro grading of powdery mill tailings makes concretes more compact and the pozzolanic constituents in micro particles of the tailings contribute to the strength of concretes.

The magnesium slag is discarded from production of magnesium metal from dolomite. However the magnesium slag is slaked in some factories by means of sprinkling water to prevent from dust pollution. The possibility of slaked magnesium slag (SMS) to play a role of mineral admixture for concrete was investigated by experiments of mortars and concretes prepared with SMS. The results revealed that SMS was still reactive. When SMS is substituted for 30% of cement, its reactivity index is equivalent to that of grade I fly ash (FA). And when SMS is used as mineral admixture to prepare concrete, it contributes to strength of concrete no less than S95 ground granulated blast-furnace slag (GGBS). Better effect of binary or ternary blend can be obtained by combining SMS with GGBS and/or FA. Because the magnesium slag is slaked, SMS has no problem on soundness, so it can be applied in concrete as mineral admixture.

An anticorrosion conversion coating on metal magnesium surface was prepared using immersion method in an aqueous solution containing mainly phytic acid. The coating after the preparation could be dry in the air without a rinse process using water in the final stage. Hence there is no discharge of waste water and waste gas in the whole process. Influence of several factors on the anticorrosion performance of coating was tested. And optimal parameters in the coating formation process were obtained from orthogonal test. The results indicated that the coating had better corrosion resistance, when the solution contained 3% phytic acid, and the immersion time is 7 minutes and the PH value was 3.5. The surface conversion coating was characterized by SEM and EDS. The conversion coating is better than the traditional chromate passive film by testing corrosion speed of coatings using hydrogen evolution method. The technology of the environment-friendly conversion coating containing phytic acid has the potential to be a new anti-corrosion technology for magnesium surface.

In production of manufactured fine aggregate (MFA) from magnetite mill tailings (MT), the micro fines (particles smaller than 75 microns) was strictly eliminated. This results in lower utilization of the resources and worse micro grading of MFA. The mortar samples were prepared with MT at various micro fines contents to investigate the effects on their fluidities and strengths. In optimal water-to-powder ratio (w/p, all powders included), the fluidities of mortars reached maximum and the strengths of mortars could be improved at suitable content of micro fines in MFA. The application proves that MT can be used as MFA to prepare construction mortars up to standard and micro fines can be substituted for mineral admixture to prepare composite mortars for improving workability. So more MT can be utilized and micro fines in the tailings can take effect.