Electric Furnace Oxidizing slag (EOS) happens in the steelmaking process during refining process of pig iron. Based on literature reivew, no usage has been reported for the reason that EOS contains Free CaO, which causes expansiveness. Recently, application of technology on specification of EOS and Ladle Furnace slag led to establishment in Korean Standard (KS), so possibility of usage as aggregates for concretes has been proven. However, the fact that no standard about Free CaO has been listed on the KS causes no using as concrete aggregate and recycling in the form of low value such as road and roadbed. The standard and guideline on replacement with lack of aggregates and using as eco-friendly materials has been establishing in the foreign developed country.
EOS has high density with the value 3.0~3.8 ton/m3 and high unit volume when performing concrete mixing design. The concrete with high volume has been used for the heavy concrete and radiation shielding concrete, so a lot of researches has been carried out. However, these magnetite and barite are not being produced, and depend on imports. Recently, problems on imports of these materials from foreign countries causes replacement with plain concrete for radiation shielding concrete. Construction on thick concrete is being performed after formation with iron plate and lead plate, when pouring plain concrete.
Therefore, after the evaluation on the expansiveness of EOS is done and mechanical property for concrete aggregates is performed, the research on radiation shielding concrete with high value is needed.
On this study, possibility of development for radiation shielding concrete has been identified through performance of radiation shielding of EOS concrete after evaluation of safety against expansiveness of EOS.

(1) Suggestion of evaluation method on safety against expansiveness of EOS
To show the evaluation method on safety against expansiveness of EOS, KS standard is used for detailed analysis. For physical safety method, volumetric stability has been analyzed, and for chemical analysis method, method of CaO analysis has been investigated as followed KS.
For physical method, difference rate according to length change using sieve and mortar method with autoclave has been suggested. For chemical method, evaluation method of Free-CaO within EOS has been identified using Ethylene Glycol method, which is the method to figure out the amount of Free-CaO.

(2) Establishment of reliability on the evaluation method of safety against EOS''s expansiveness
① Through literature review, standard on change in amount of Free-CaO has been suggested according to change in temperature and time, and the amount of Free-CaO within cement and EOS has been evaluated using Ethylene Glycol method.
② Difference in contents of Free-CaO has been evaluated according to change in content of Free-CaO on each aging periods, and stockyard (1m depth difference between in and outside stocked slag).
③ The content evaluation of Free-CaO of EOS emitting EOS from 4 domestic steel companies (Hyundai steel, Dongkuk steel, Daehan steel, Kisco) has been done.

(3) Performance evaluation of mortar and concrete using EOS aggregate
The property of fresh concrete using EOS　aggregate has been evaluated, and then, the evaluation of change in compressive strength according to replacement rate of EOS and unit volume has been done. Furthermore, compressive strength and micro analysis of mortar according to replacement rate with EOS has been performed.

(4) Performance of radiation shielding of radiation shielding concrete with EOS
Radiation shielding performance of EOS concrete, plain and magnetite concrete has been done through transmission test of X-ray and gamma to figure out the possibility of development of radiation shielding concrete using EOS.