Experimental Study On Steel Slag-Crushed Stone Pavement Base Materials Stabilized With Portland Cement

The pavement base, located under the surface of pavement, bears the vehicle load passed from the surface of pavement and spreads it to the soil base. Currently in China, crushed-stone stabilized with Portland cement or lime and coal fly ash, or gravel mixtures have been widely used as pavement base materials in highway construction, however, the acquaintance of these materials will do harm to the environment. To get double benefits of economic and environment protection, steel slag which is a waste from industry can replace them, and the application of steel slag will have great prospect for the application in semi-rigid pavement base.Steel slag is a byproduct stemmed from either the conversion of iron to steel in a basic oxygen furnace, or the melting of scrap to make steel in an electric furnace, and is liquid slag come from the reaction between fluxing medium （CaO、CaF2） and SiO₂ in iron. Steel slag is appropriate as pavement construction material, because of its excellent mechanical properties, such as high crushing value, abrasion resistance, etc. Additionally, active ingredients, such as C2S and C2S in steel slag, result in hydration, jellification and high alkalinity. However, f-CaO, f-MgO exsited in steel slag cause hydration swelling and thus is main reason of instability of steel slag. This paper is aimed at making full use of steel slag and avoiding its instability.First, steel slag of different grades is stabilized with Portland cement and the optimal grade of steel slag is determined by comparison of mechanical properties. And then crushed stones are added in the steel slag with various proportions to ensure the stability of steel slag. Next each fundamental mechanical property test is carried out, including compaction test, unconfined compressive strength test, indirect tensile test, compression modulus test of resilience, stability test, water erosion test and drying shrinkage test. And also the theoretical analysis on the mechanism of performance is proposed in depth. The experiment results are analyzed, providing reasonable information for application of steel slag in pavement base construction.It is indicated by experiments that the optimal grade of steel slag is medium grade. The unconfined compressive strengthen of steel slag-crushed stone stabilized with Portland cement is decreased with increase of crushed stone proportion and the order is 75:25>50:50>25:75. The order of water erosion resistance with different crushed-stone proportion is 75:25>50:50>25:75, superior to crushed stone. The more steel slag in the mixture, the less the average dry coefficient, and the order is steel slag <75:25<50:50<25:75<crushed stone. The more the crushed stone is, the less the immersion expansion rate, and the better the stability of the mixture. It can be known by analysis that it can satisfy the service performance requirement of pavement base completely if design is appropriate. Accordingly, steel slag, a waste residue of industry, can be applied in the pavement base successfully and efficiently, which not only can save the cost of exploring stone, but also can reduce its pollution to environment, so as to realize the double benefits of economic and environment protection.