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Modern society requires a large number of metal components manufactured by sand casting, which involves the generation of a waste product known as Used Foundry Sand (UFS), of which approximately 100 Mt are generated on an annual basis. Virtually all UFS is currently landfilled, despite the economic and environmental cost overruns that this entails. Here, the recovery of UFS as fine aggregates for the manufacture of concrete is proposed. Since the presence of UFS will mainly affect the mortar that binds the aggregates in the manufacture of concrete, it was decided to isolate this fraction and study only the effect of UFS in mortars. This study evaluated a total of 32 different mixes combining different W/C ratios varying between 0.5 and 0.7 with 5 replacement ratios of natural sand by UFS: 0, 25, 50, 75 and 100%, respectively. The combined effect was evaluated of the W/C ratio and the replacement ratio on the workability, physical properties, mechanical properties, mechanical durability, and microstructure of the mortars. The incorporation of UFS decreases the workability of the mortars due to the absorption of the residue. For the physical properties of the mortars, density decreased and porosity and absorption increased at all replacement percentages. Flexural and compressive strength decreased when the replacement percentage was higher than 25 wt.%. In terms of mechanical durability, the mortars with UFS showed abrasion marks within the limits of the EN-1338 standard. From the results obtained, it is possible to conclude that the mortars with UFS require a higher amount of water. Therefore, while small replacement levels lead to a slight improvement in the mechanical properties, this trend breaks down for high replacement levels due to the negative effect of the high W/C ratios required. The authors recommend that for replacements higher than 25 wt.% of UFS, the W/C ratio has to be taken into consideration to obtain the same workability as the control mortar, although this decreases the mechanical properties.

The use of concrete with aggregates with reduced environmental impact, as is the case of concrete with siderurgical aggregates (recovered slags), will inevitably increase in the future, as a result of policies promoting development of more sustainable construction materials. These concretes offer an excellent response to static loads, but their behaviour under dynamic loads has not yet been studied. The aim of this study is to characterize the fatigue behaviour, in terms of fatigue limit, of a concrete with siderurgical aggregates by comparing it with an analogous conventional limestone concrete. This characterization was carried out using the Locati method, which stands out for its convenience, speed and low cost, with the feature of being carried out at a high frequency corresponding to the resonance frequency. Performing high-frequency tests has drastically reduced test times and thus costs. Likewise, the results obtained show that, using various criteria found in the literature, concrete with siderurgical aggregates has a higher fatigue limit in absolute terms (MPa), but a lower one in relative terms (% fc).

The high consumption of natural resources in the industrial sector makes it necessary to implement measures that enable the reuse of the waste generated, seeking to achieve circular economy. This work assesses the viability of an alternative to the use of CEM III B 32.5 R cement in mortars for the internal coating of centrifugally spun cast iron pipes for water piping. The proposal is to reuse the slag generated in the casting process after being finely ground, as an addition mixed with CEM I 52.5 R cement, which is basically Portland clinker. In order to analyse this possibility, an extensive experimental campaign was carried out, including the analysis of the cupola slag (micro-structural and chemical composition, leachates, setting time, vitrification, puzzolanicity and resistance to sulphate) and regarding the mortars (workability and mechanical properties). The experimental programme has shown that the optimum substitution is achieved with a replacement percentage of 20% of the cement, with which similar workability, superior mechanical properties and guaranteed resistance to sulphate attack are obtained. In addition, both economic and environmental savings are achieved by not having to transport or landfill the waste. In addition, the new cement is cheaper than the cement currently used.

The main objective of this work is the study of the hillock and zinc whisker evolution of five different commercial zinc coatings applied on the same base steel wires of the patented EASYCONNECT system cable trays manufactured by VALDINOX Ltd.: white zinc alkaline electrolyte, yellow zinc trivalent electrolyte, acid zinc electrolyte, hot dip galvanized, and zinc nickel coating. The limited literature on the subject is summarized, and then the coating thickness, chemical composition, hardness and surface rugosity are characterized. The hillock and whisker density evolution are evaluated over a period of 12 months, considering the presence of compression bending stresses. It is concluded that the white alkaline and yellow trivalent coatings are the most affected, while the zinc-nickel shows the best behavior with no presence of whiskers; the acid zinc electrolyte also shows good results despite the delayed appearance of whiskers from the ninth month; the hot-dip galvanized coating does not show any presence of zinc whiskers or hillocks.

Obtaining new materials capable of meeting society’s demands motivates the search for new solutions that are capable of satisfying twofold requirements: respect for the environment and obtaining more durable and resistant materials. Cupola slag is a by-product generated in the process of obtaining ductile iron. When the slag undergoes rapid cooling, its vitrification is favored, leaving the silica in an amorphous structure and, thus, susceptible to reacting. Through reaction, the slag can develop cementing properties and cement can consequently be partially replaced with residue, providing savings in economic and environmental costs compared to traditional hydraulic binders. In this study, the physical and chemical properties of cupola slag and its recovery process are analyzed. Mortars that incorporate traditional admixtures (fly ash and limestone filler) have been manufactured and consistency and mechanical properties have been compared with mortars that incorporate cupola slag admixture. Mortars have also been manufactured with normalized sand and with Portland cement replacements (0, 10, 20, and 30% by weight) with cupola slag, and both the consistency and the mechanical properties have been compared at 7, 28, 60, and 90 days. The results obtained show the suitability of cupola slag as a binder and as an admixture, with respect to the traditional ones, and how the mechanical properties tend to converge for all of the replacement levels characterized, for ages close to 90 days of age.

Increasing amounts of sustainable concretes are being used as society becomes more aware of the environment. This paper attempts to evaluate the properties of precast concrete elements formed with recycled coarse aggregate and low clinker content cement using recycled additions. To this end, six different mix proportions were characterized: a reference concrete; 2 concretes with 25%wt. and 50%wt. substitution of coarse aggregate made using mixed construction and demolition wastes; and others with recycled cement with low clinker content. The compressive strength, the elastic modulus, and the durability indicator decrease with the proportions of recycled aggregate replacing aggregate, and it is accentuated with the incorporation of recycled cement. However, all the precast elements tested show good performance with slight reduction in the mechanical properties. To confirm the appropriate behaviour of New Jersey precast barriers, a test that simulated the impact of a vehicle was carried out.