Study On The Mechanical Properties Of Reactive Powder Concrete (RPC) With Activated Steel Slag Powder

Reactive Powder Concrete(RPC)is a new type of cement-based composite with high strength and toughness.However,the disadvantage is that the extensive use of cement and quartz materials leads to higher economic costs and significant environmental impacts.Steel slag materials contain mineral active ingredients,and can be used as a cementitious material instead of it after appropriate stimulation.Its large-scale utilization not only reduces the stacking of land resources and negative impacts on the surrounding environment,but also reduces the use of cement.It is an important direction for the development of future building materials.Based on RPC raw materials,cement and quartz sand were replaced by steel slag powder and steel slag sand at a ratio of more than 50% respectively,and chemical activators were added to activate the activity of steel slag powder.By removing quartz powder to further reduce costs and meet the target strength requirements,a green concept and low-cost activated steel slag powder RPC is obtained.The main work and important achievements include the following aspects.(1)On the basis of plain RPC100 mix proportion,50% steel slag powder and steel slag sand are used to replace cement and quartz sand respectively as the standard mix proportion of steel slag powder RPC with the compressive strength of 94.4MPa.It is used sodium sulfate,calcium sulfate,slag and sodium silicate activators to excite the standard mix proportion.The effects of the types and dosages of activators on the compressive strength and hydration performance of steel slag powder RPC with standard mix proportion were studied through cube compression tests and X-ray diffraction(XRD)patterns.Taking into account the above results,it is determined that sodium sulfate is the optimal activator.The compressive strength is 101.0MPa when a dosage of 1%.And with the help of scanning electron microscopy(SEM),the hydration products of steel slag powder RPC activated by sodium sulfate were observed and compared with that of standard mix proportion,in order to character the effect of the activator intuitively.(2)Based on the use of sodium sulfate and standard mix proportion,further improve the replacement ratio of steel slag powder(50%,60%,70%)and steel slag sand(50%,75%,100%),and add different volume amounts of steel fibers(0%,1%,2%,3%)to conduct compressive and flexural tests.The results indicate that as the replacement ratio of steel slag powder and steel slag sand increases,the compressive and flexural strength show a downward trend,with the steel slag powder showing a particularly significant downward trend.As the increase of volume amounts of steel fibers,the compressive strength first increases and then decreases,with a maximum value of 2%.The flexural strength shows an upward trend.The range analysis results indicate that steel slag powder has the greatest impact on compressive strength,while steel slag sand has the greatest impact on flexural strength.(3)By stimulating the prism compressive test,the compressive stress-strain curves of RPC with different amounts of steel slag powder and steel fiber were plotted.Obtain the variation pattern of peak stress,peak strain,elastic modulus,and Poisson’s ratio with different amounts of steel slag powder and steel fiber content.Normalize the stress-strain curve and use existing models for curve fitting.The results showed that the Wee model had the best fitting effect,and it was determined to stimulate the steel slag powder RPC model.The functional relationship between different replacement ratio of steel slag powder,volume amounts of steel fibers and the relevant parameters of the model was established,and the model was corrected.