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In recent years, the use of self-compacting concrete has been a great advantage and garnered undoubted interest in construction. Due to the environmental impact caused by the consumption of natural aggregates in the manufacture of concrete, a more sustainable approach is needed. An approach for more sustainable construction is to use industrial waste such as bottom ash from the combustion of biomass as a replacement for natural aggregates. This research aims to use biomass bottom ash as a replacement for natural sand (10%, 20% and 30% replacement); in addition, by utilizing a crushing process of the bottom ash, the ash has been used as a filler replacement (replacement 20%, 40% and 60%). The fresh and hardened properties have been evaluated according to the standard. The results show the feasibility of using biomass bottom ash in self-compacting concrete, providing a sustainable alternative in order to minimise environmental impacts related to the extraction and depletion of natural resources., FEDER/ Ministry of Science, Innovation and Universities—Agencia Estatal de Investigación (State Research Agency)/Valorisation of biomass bottom ash for sustainable construction applications (1264457-R)—BIOCEM

The valorization of residue from industrial processes for their use as components of other materials is seen as a highly effective solution for environmental problems associated with the bu...

Several studies have applied recycled aggregates (RA) in road layers and demonstrated appropriate results. In general, RA can be one of two types: recycled concrete aggregates (RCA) or mixed recycled aggregates (MRA), each of which has lower density, higher water absorption, and lower mechanical strength than natural aggregates (NA). Alumina waste (AW), obtained from the process of aluminum refinement, could be mixed with RA in order to improve its properties, such as compaction and bearing capacity, for application in road construction. Few studies have investigated the use of AW with RA in civil constructions. This paper presents the results of a laboratory study of different materials based on the addition of AW to RCA and MRA. In the experiment, the mechanical behaviors and microstructural properties of RCA, MRA, and mixes of RCA or MRA with AW were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties, and the formation of new cement hydrated particles was observed in these novel mixtures. The properties of the mixtures of RCA and MRA with AW suggest that these recycled materials can be used in unbound road layers to improve the long-term mechanical behavior.

Before being imbedded in concrete, rebars often contain rust layers. It is uncertain whether these layers may affect the stability required for the steel in reinforced concrete (RC) structures, as there is a lack of scientific consensus in the limited research dedicated to evaluating such an influence. The present paper therefore describes an experimental study aimed to clarify the consequences of rebar pre-rusting in the service life of RC structures. Samples of corroded reinforcement in construction works underway were collected and characterized, then embedded in concrete blocks. The evolution of their behavior was followed by measuring their corrosion rate. The results obtained show that the corrosion rates of the pre-rusted rebars were greater than those of the rebars that had not undergone any type of previous moisture-related corrosion. Under such circumstances the Tuutti “initiation period” would have disappeared, meaning its service life could be reduced to unacceptable values.

The management of different industrial by-products, such as recycled aggregates from construction and demolition waste and alumina by-products, as well as the reduction of landfill deposits by incorporating these products in a second life cycle, were the focus of this work. The aim of this study was to demonstrate the technical viability of using these waste and by-product as a material for road pavement base layers. For this purpose, a real-scale application was carried out, and the behavior of three types of materials, applied on a section of an experimental road under real vehicle traffic conditions, was studied and compared. Three materials were used in these sections applied in the road sub-bases. First, a control material composed of a type of artificial gravel was used to be compared with the rest of materials; the second material was composed of recycled aggregates, and the third was composed of a mix of recycled aggregates and alumina waste. The results concluded that the effectiveness of the sections built using recycled aggregates and alumina waste was very positive and similar those constructed using natural aggregates., Isolux-Corsan Construction

The application of mixed recycled aggregates (MRA) and recycled concrete aggregates (RCA) in road works has been studied intensively over the last two decades. One of the properties that has not been studied enough is the self-cementing capacity of recycled aggregates (RA), which favours improving the bearing capacity of compacted recycled aggregates. This research aims to analyse the variables that influence the self-cementing of recycled aggregates, both concrete and mixed. Elaborating recycled aggregate is carried out by crushing the material in a treatment plant which favours self-cementing. In this research part of the recycled material is crushed again in the laboratory in order to produce a better self-cementing process when the material is crushed and used in a short period of time. One of the causes for which the bearing capacity is improved is the appearance of old unhydrated cement particles, which can favour residual setting in the medium-term. In this work two series with different treatments, based on crushing and sieving part of the material, were studied to determine the influence of these changes on the bearing capacity: a series called All-in-one (AO) with a particle size of 0–20 mm, which includes coarse fraction (C) and fine fraction (F) and a second series, called Fine (F), which only include fine fraction with a particle size of 0–4 mm. In both series different samples of RA were processed by sieving, crushing and compaction in different ways. In addition, natural aggregate samples were studied to compare with recycled ones. The results show that the influence of the treatment in the material, mainly crushing and fresh compaction, as well as particle size, significantly improves the loading capacity of recycled aggregates.

The exposure to engineered nanomaterials (ENMs) is a new emerging risk at work due to an increase in the number of workers potentially exposed to them and the current lack of data on their health and safety risks. This paper reports the findings of a survey designed to study the safety practices employed by workers in Spanish research facilities performing tasks involving the use of ENMs at research level. A questionnaire pretested and validated by an expert panel was sent by e-mail to the target audience. The 425 surveys completed show that most of the respondents handled up to 5 different ENMs, in suspension, in small amounts during short periods of exposure. The implementation of common hygienic practices, such as the use of protection for hands and the implementation of fume hoods, is widely indicated. The selection of the preventive and protective measures does not depend on the characteristics of ENMs handled. Also, the risks posed by ENMs are widely ignored. Besides the performance of risk assessment, hygienic monitoring and the conducting of a specific health surveillance are practically non-existent although some accidents relating to ENMs were identified. In conclusion, workers’ exposure to ENMs seems to be low. Even though the best practices and preventive and protective measures reported were employed, most of the respondents could not be correctly protected. Moreover, workers do not associate the measures implemented with the nanorisks. Finally, there is a lack of proactive action underway to protect the workers, and concerns about safety are weakly evidenced.