**4. Conclusions**

In this study, we have conducted investigations on the recycling of carbon steel slag CSS to produce SCC. Our conclusions are as follows:


In this manner, we have shown that CSS can potentially be used as a cementitious material in self-consolidating concrete.

#### **5. References**

332 Material Recycling – Trends and Perspectives

(a) (b)

In this study, we have conducted investigations on the recycling of carbon steel slag CSS to

• The major chemical compositions of CSS are CaO, Al2O3 and SiO2, a composition similar to that of Portland cement and BFS. The PAI of CSS is 85% at 28 days. Hence, CSS can

• CSS can be designed as easily as SCC. In comparison with OPC, increasing the CSS

• Concrete using CSS has a higher compressive strength than that using OPC. If w/cm ratios of 0.32 or 0.40 are used, the percentage of compressive strength increases by more

• As the amount of CSS in concrete increases, the compressive strength decreases. The strength is similar to other concrete, however, when CSS of 5.0–7.5% is used, except at 7

• The SEM images show that the hydration rate of CSS is lower than that of OPC. Further, large amounts of Ca(OH)2 and AFm are present in CSS as a cementitious material. In this manner, we have shown that CSS can potentially be used as a cementitious material

Fig. 8. SEM micrograph of CSC32: (a) at 3 days; (b) at 28 days.

be expected to have good cementitious properties and effects.

produce SCC. Our conclusions are as follows:

content will increase the setting time.

than 21% at 90 days.

in self-consolidating concrete.

days.

**4. Conclusions** 


**14** 

*Italy* 

**Possible Uses of Steelmaking** 

Teresa Annunziata Branca and Valentina Colla *Scuola Superiore Sant'Anna - PERCRO - TeCIP Institute* 

**Slag in Agriculture: An Overview** 

Slags are the main by-products generated during iron and crude steel production and the

Over the past decades, the steel production has increased and, consequently, the higher volumes of by-products and residues generated have driven to the reuse of these materials in an increasingly efficient way. In recent years new technologies have been expanded, and some of them are still under developing, in order to improve the recovery rates of slags. On this subject material separation technologies and carbon sequestration could dramatically reduce CO2 emissions from steelmaking processes. On the other hand, the increase of slags recovery and use in different fields of application, such as in agriculture, allowed to reduce landfill slags and to preserve natural resources. In addition to the environmental achievements, these practices produced economic benefits, by providing sustainable solutions that can allow the steel industry to achieve its ambitious target of "zero-waste" in

1. the iron ore based steelmaking (Fig. 1), which represents about 60-70% of the world steel production. The main raw materials are: iron ore, coal, limestone and recycled steel scrap. The main production routes are: the ironmaking iron ore based on Blast Furnace (BF) followed by steelmaking in the Basic Oxygen Furnace (BOF), and the ironmaking based on Direct Reduction of Iron ore (DRI), followed by steelmaking in the Electric Arc Furnace (EAF). In the BF coke is the reducing agent of iron ore. Limestone or dolomite (fluxes) are added into the blast furnace where they react with iron ore impurities, such as silica. Steel is produced from pig iron, scrap and lime in the BOF,

2. the scrap-based steelmaking (Fig. 2), which represents about 30% of the world steel production. This way is based on the scrap recycling in the EAF, where the main input

In both BOF and EAF the reactions between oxygen, carbon (carbon as gaseous carbon monoxide), silicon, manganese, phosphorus and some iron as liquid oxides produce oxidized compounds that react with lime or dolomitic lime to form slag. At the end of the

are steel scrap and electrical energy that is needed to melt the scrap into steel.

steel industry is committed to increasing and improving their recycling.

**1. Introduction** 

the incoming years (worldsteel, 2008).

Steel is produced by mean two main ways:

where oxygen is blown to burn off the carbon.

