Experimental Study On Axial Compressive Properties Of Environmental Steel Slag Concrete

As steelmaking waste, steel slag (SS) is now not only occupying land, but also polluting environment. If the SS can be processed into steel slag powder (SSP), steel slag fine aggregate (SSFA) and steel slag coarse aggregate (SSCA) used in concrete production, it can help reducing environmental problems and giving economy benefits. For this purpose, an experimental study has been launched. In this study, axial compression test was carried out for normal strength concrete (NSC) and high-strength concrete (HSC) with different contents of SSP, SSFA and SSCA, and the effects of SSP, SSFA and SSCA on concrete failure mode, stress-strain curve, axial compressive strength, expansion coefficient, elastic modulus and ductility were investigated.Research work and results are summarized as below:(1) Steel slag powder:Axial compression test was carried out for NSC and HSC with 9 SSP contents (0%,5%,10%,15%,20%,25%,30%,35%,40%), the results showed that:1) For NSC, as SSP content increased, concrete failure cracks increased, stress-strain curves flattened, compression strength increased first then dropped down, expansion coefficient increased substantially, elastic modulus decreased substantially, ductility increased first then dropped down.2) For HSC, as SSP content increased, concrete failure cracks increased, stress-strain curves flattened, compression strength dropped down dramatically, expansion coefficient increased substantially, elastic modulus decreased substantially, ductility decreased gradually.3) The reasons for these phenomena may be that:SSP has some active ingredients for cement hydration, but it is not a cementitious material, adding too much SSP to reduce cement may impair cement hydration so as to affect axial mechanics behaviour of concrete; the hazardous substances in SSP may also affect concrete stability.4) Low content of SSP is feasible for NSC, but high content is not acceptable; SSP is not recommendable for HSC.(2) Steel slag fine aggregate:Axial compression test was carried out for NSC and HSC with 9 SSFA contents (0%,10%,20%,30%,40%,60%,80%,100%), the results showed that:1) For NSC, as SSFA content increased, concrete failure cracks increased, stress-strain curves flattened, elastic modulus decreased, compression strength, expansion coefficient and ductility of NSC with SSFA fluctuated, but not lower than that of NSC without SSFA.2) For HSC, as SSFA content increased, concrete failure cracks increased, stress-strain curves flattened first then steepened, ductility increased first then dropped down, compression strength, expansion coefficient and elastic modulus fluctuated, but the fluctuation range is acceptable.3) These phenomena may be caused by the combined effect of bleeding and hydration improvement as SSFA adding.4) From the view of economy and environmental protection, adding SSFA to replace natural fine aggregate for NSC and HSC is feasible and recommendable.(3) Steel slag coarse aggregate:Axial compression test was carried out for NSC and HSC with 9 SSCA contents (0%,10%,20%,30%,40%,60%,80%,100%), the results showed that:1) For NSC, as SSFA content increased, concrete failure cracks increased, stress-strain curves flattened, compression strength, expansion coefficient, elastic modulus decreased and ductility fluctuated.2) For HSC, as SSCA content increased, concrete failure cracks increased, stress-strain curves steepened first then flattened, compression strength dropped down undulately, expansion coefficient and elastic modulus increased undulately, ductility fluctuated drastically.3) These phenomena may be caused by the combined effect of bleeding and hydration improvement as SSFA adding; especially for HSC, the negative effect of bleeding is larger.4) From the view of economy and environmental protection, adding SSFA to replace natural coarse aggregate for NSC is feasible and recommendable; but SSCF is not suitable for HSC, unless the bleeding problem of SSCF is fixed.