Kyoto Protocol

      No Comments on Kyoto Protocol

Nowadays, one of the primary objective in construction activity is to achieve sustainable development particularly after the Kyoto protocol which came into force in 2005 followed by Paris agreement in 2015 during which stress was laid to conserve natural resources and reduce waste [66].The problems attributed to utilization of natural materials are the enormous amount of extraction during production stage and long haul distances [63].

Cement manufacturing units generates about 1.6 billions of carbon dioxide annually throughout the globe [61].To lessen the demand on extraction industries and conserves natural resources, research has been considerably going to replace the natural material by alternative resources such as byproducts, new minerals and rocks in the construction [63].

The incorporation of industrial by product has two major advantages: one being the decrease in consumption rate of resources during concrete production and second being the less problems waste disposal [55,35]. In this regards, attention is paid to the slag coming from steel manufacturing units. The utilization of byproduct such as ground granulated blast furnace slag (GGBS) as a partial replacement of cement during concrete production has been going on from several decades [ ].

Currently, steel manufactured from basic oxygen furnace and other plants are replaced by electric arc furnace. Nowadays, more than 40% of the steel is generated from EAF steel furnace [65 ]. This has led to the development of new type of slag termed as electric arc furnace (EAF) slag or black slag [ ].Metallurgical slag, a byproduct in the form of steel slag can be used as cement or aggregate replacement and even for other application as it offers numerous environmental and economic benefits [35,43, 55]

Among various types of slag, the electric arc furnace slag has become a new promising construction material due to its chemical composition consisting of calcium oxide or lime and silica [59]. EAF slag is essentially a combination of various metal oxides among which iron oxide is most abundant. It occurs in the form of hematite (Fe2O3), magnetite (Fe3O4),goethite( FeOOH) and maghemite (ℽ-Fe2O3) [47]. Efficient management of EAF steel slag is hindered due to several factors. Firstly, slag essentially consists of oxides of calcium, magnesium and traces of heavy metals [42] that affects the environmental friendly disposal and causes soil pollution. Secondly, land filling leads to reduction in porosity of soil and reduces soil capacity [52].

Thirdly, recycling of slag requires large amount of energy to remove impurities [51]. Thus, utilizing EAF slag in construction industry can be considered as feasible and affordable alternative as it is treated as non hazardous and inert industrial waste [5,6, 47].EAF slag can be used for various types of concrete such as normal concrete, high strength concrete, roller compacted concrete, self compacting concrete, sprayed concrete [17,43,48].

The specific gravity of steel slag is approximately about 1.5 times as that of normal aggregate, thus making it suitable for heavy construction such as dams and retaining walls [59]. Further, it justifies the use as radio protection and gamma ray radiation for shielding concrete [2]. The main obstructions for this intended purpose are: low slump value in fresh state, enhanced density of hardened concrete and risk of low durability due to potential of expansion [18].

Blast furnace and steel slag are the major byproducts generated in steel mill. The physical characteristics of both slags are similar but differ in content of iron oxide. For steel slag, iron content varies between 16-23% while for blast furnace, 0.5% iron oxide is found [28]. The steel melting is carried out in batches and thus affects the chemical composition of steel slag, unlike granulated blast slag which is produced on continuous process [31]. Electric arc furnace generates about 150-180 kg of EAF slag per tonne of steel and in second stage, ladle furnace produces about 60-80 kg of ladle slag [10,37].

  • EAF slag has been used in the construction of road and railway embankments for preparing sub grade, sub base and treated slag as coarse aggregate in bituminous mixtures. High strength, angularity, low abrasion, high polished stone values make it favorable for such constructions [ 37,38, 40 ]
  • EAF mixture show high density characteristic and justify its use as radio protection and durable material. Design of shielding property of concrete against gamma-ray and neutrons is influenced by aggregate properties in two ways a) selection of aggregate capable of maintaining fixed water content during high temperature exposure and b) aggregates with high specific weight. [2].
  • Concrete structure made with EAF slag exhibits improvement in ductility behavior, enhances the strain capacity and increase energy dissipation. For the safety of structure against earthquake, weak beam and strong column mechanism is employed and EAF slag can be used as efficient material [11].
  • EAF slag can be effectively used as Fenton photocatalyst for both anionic and catonic dye because of good oxidation reduction property and producing highly active Oḣ radicals. The other benefits include cost effectiveness, easy separation, reduced land pollution problems [47].

Leave a Reply

Your email address will not be published. Required fields are marked *