One of the most important industries in the north of Spain, especially in the Basque

Country, is the steelmaking industry. The production of steel in electric arc furnaces,

prevalent in this small region generates huge amounts of industrial steelmaking waste

that have to be properly managed. For many years, the Electric Arc Furnace (EAF) slags

generated by the steelmaking industry have been dumped as waste material in landfill

sites. Nevertheless, many researchers have been investigating ways of standardizing

the use of EAF slag in construction and civil engineering, so that it can be used as aggregate in hydraulic and bituminous mixes. In this way, dumping sites will be relieved of this waste and the consumption of natural resources will be decreased.

In this PhD thesis, a step forward has been taken towards standardization of the re-use

of waste materials from the steelmaking industry as raw materials in the manufacture

of hydraulic mixes for their use in the construction industry. It has been demonstrated

that, with the correct mix design, EAF slag concrete of the desired workability may be

manufactured and that it can even perform well in real-scale structural elements.

Real-scale Reinforced Concrete (RC) beams with both pumpable and self-compacting

concretes have been manufactured to achieve this goal. Following the sustainability

approach, it was decided to manufacture the beams, not only with the standard Portland cement type I, but also with cement type IV with the addition of fly ash, in order to manufacture more sustainable concretes.

The decision to work firstly with small samples and to finish the work with real-scale

elements was taken to realize this objective. The experimental methods developed to

reach the final objective have been divided into three chapters in this PhD thesis. Each

chapter has introduced a different level of scale that has broadened the investigation.

The introductory chapters have presented the scope of the research and a full

description of the materials and methods used in the development of the thesis.

In the first part (Chapter 4), the work performed on mortar mixes has been presented.

Firstly, the interaction of the steel slags with cement type IV was analyzed by

manufacturing mixes with different dosages and developing mechanical and durability

tests. The mechanical properties displayed an excellent behavior.

Subsequently, the manufacture of self-compacting mortar mixes has been presented.

It is essential to obtain a good mortar paste, in order to manufacture self-compacting

concretes. Several mortar mixes were manufactured and their fresh properties

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analyzed. The hardened properties were also evaluated, achieving strengths of up to

100 MPa, and the mixtures manufactured with EAF slag aggregate displayed superior

behavior to mixtures manufactured with natural aggregates. This effect is a

consequence of a suitable mortar microstructure, as is evident from the MIP and CAT

analyses. Accelerated aging tests were also performed on the self-compacting mortar

mixes, demonstrating the innocuous effect of EAF slag.

In the second part (Chapter 5), the studies on pumpable and self-compacting concrete

mixes with EAF slag added as aggregate have been presented. An in-depth analysis of

the workability of self-compacting mixes has shown the essential need for careful

control of the fine fraction and selection of a compatible chemical admixture to attain

the required flowability. A numerical simulation of the viscous flux of these self-

compacting mixes has been proposed, reporting very acceptable results. The

mechanical properties of these concretes indicated good performance and the analysis

of some SEM observations of the fracture surfaces on the SCC-EAFS concrete revealed

significant features, which help us to understand their structure and mechanical

behavior.

An extensive testing regime to assess the durability of these concretes has also been

described. Some classical tests, such as freezing-thawing and drying-wetting, were

conducted until noteworthy deterioration was appreciated in the mixes. Singular tests,

such as immersion in sea water in the tidal zone, and a study on reinforcement

corrosion in marine environment, were also performed to evaluate the quality and

usefulness of this kind of concrete. The results have demonstrated that EAF slag

concretes behave in a satisfactory way in these environments.

In the last part (Chapter 6), the manufacture and performance of real-scale EAF slag

reinforced beams has been investigated. These beams were manufactured with

pumpable and self-compacting concretes and, for each consistency, cement type I and

cement type IV were used for manufacturing different mixes. All the mixes displayed

good fresh behavior during the casting period, producing beams without any

honeycomb. The flexural behavior of the beams was analyzed and yielded results

similar to analytical values calculated with the existing formulation. The long-term

deflection of the beams was evaluated and all the beams performed well over the full

duration of the test.

Analyzing the general conclusions drawn from this research, it can be stated that the

main objective of the thesis has been achieved.