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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.

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

Increased use of concrete in the construction industry worldwide, along with the negative impact of the use of nonrenewable materials such as aggregates and cement for making concrete, has led to a growing production of greener concrete. Excessive use of aggregates depletes natural resources, and inconsiderate quarrying and mining activities to extract these materials could lead to environmental issues such as damage to landscapes, disruption of the ecosystem, and contamination of water, soil, and air. There are various types of ecoefficient concrete, including concrete with partial to total replacement of ordinary Portland cement (OPC) as a binder, and/or concrete incorporating waste and recycled materials as aggregates. This chapter analyzes biomass used as aggregates in the manufacturing of cement based concrete. It presents an extended bibliometric analysis to highlight the importance of using biomass as a replacement for aggregates in production of cement based materials (CBM). Also included is an analysis of the incorporation of biomass residues for use in mortars and concrete.

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...

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 Pavement Quality Indicator (PQI) is a non-nuclear gauge used for the on-site density measurement of asphalt pavements without the need to extract core samples. Previous studies of hot asphalt mixes found that PQI density readings were very similar to laboratory density measurements of pavement cores. This paper describes the first stage of a research project whose objective is to analyze PQI density measurements of mixes manufactured with an asphalt emulsion binder. The PQI density variability for such mixes was verified and compared with the results obtained with other on-site methods for measuring pavement density.

This paper presents the results of a research study whose main objective was to analyze the environmental benefits derived from a cleaner production technology for manufacturing asphalt mixes. This study measured polluting emissions during the construction of two consecutive stretches of highway on which a hot mix and a half-warm mix were spread. Combustion gases (CO, NO x , O 2 , CO 2 ), total organic carbon (TOC), particles, volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs), were measured during the manufacturing of hot and half-warm asphalt in plant and also during the spreading and compaction processes. The results obtained in this research project show that for the same manufacturing and spreading conditions, the half-warm mix asphalt (manufactured at less than 100 °C) is a cleaner production technology and can be considered more environmentally friendly since it considerably reduced polluting emissions.

The cold in-place recycling (CIR) of asphalt pavements is a technique for pavement rehabilitation that uses 100% of the milled or reclaimed asphalt pavement (RAP) from a deteriorated road surface at ambient temperature, and which does not heat any of the mix components. Consequently, CIR has the advantage of reducing gas emissions into the atmosphere. It also cuts fuel consumption since there is no need to transport RAP to an asphalt plant or to convey the mix from the plant to the paving site for spreading and compaction. Nevertheless, one of the weaknesses of this technique is the design of the job mix formula since the densities of laboratory test specimens are generally higher than the densities of the samples obtained at the worksite. As a solution for this problem, we designed an in-laboratory compaction procedure capable of manufacturing test specimens, whose density closely approximated the density of the material at the worksite. For the purposes of our research, we selected three CIR roadwork projects carried out in 2009 in southern Spain. These sites provided the RAP and the emulsion for the laboratory work in our study. It was thus possible to validate the compaction method designed in our research by comparing the dynamic modulus values of pavement cores extracted at the worksite with the values of cores taken from the laboratory specimens. The results obtained validate the new compaction procedure designed in this study.

The use of crumb rubber from scrap tires in hot bituminous mixes in order to improve their performance has become a technique of great potential in recent years. The two techniques used to add crumb rubber to bituminous mixes are the wet process and the dry process. Of the two, the dry process is somewhat less popular because it initially produced poorer results. The objective of the research presented in this paper is to improve the application of this technique by analyzing the influence of the variables digestion time and percentage of crumb rubber on the mechanical performance of bituminous mixes. This research project had two phases. The first phase studied the influence of these variables on the mix design, whereas the second phase analyzed how the variables affected the mechanical performance of the mixes. This paper presents the results of the second phase which analyzed the mechanical performance of dry-process crumb rubber mixes, more specifically, their response to moisture sensitivity and plastic deformations. The results obtained indicated that the determining factor in mix performance was the amount of crumb rubber added. In contrast, the influence of digestion time was found to be negligible. The study showed that in reference to moisture sensitivity and plastic deformations, the best performances were achieved with a digestion time of 45 min and a crumb rubber percentage of 0.5% and 1.0% of the total weight of the mix.

The concept of sustainability has become crucial in today’s world. In fact, one of the major environmental priorities in scientific research is to discover innovative ways to recycle waste matter for its use in activities that benefit society. In the construction engineering sector, this trend has led to new techniques for recovering waste from industrial processes, and using it as a replacement for raw materials. The Construction Engineering Laboratory at the University of Granada carried out a research project to study the viability of using waste from the decorative quartz industry (sludge and chips from stone sheets) in the manufacture of bituminous mixes for road surfacing. This research study was performed in two phases. The first phase analyzed scraps and chips from stone sheets to see if they could be used to replace natural aggregate. The second phase focused on evaluating Silestone® sludge to see if it could be used as a substitute for the filler fraction in hot bituminous mixes. This paper presents the results obtained in this second phase in which different job-mix formulas were evaluated by varying their sludge content (0%, 60% and 100%). The properties of the various mixes were analyzed by subjecting them to a battery of mechanical tests that determined their susceptibility to moisture and resistance to rutting. The results obtained are eloquent proof of the viability of reusing Silestone® sludge as a replacement for conventional filler. This study showed that when performance of such mixes was tested, they amply fulfilled the standard technical requirements for roads in Spain. Furthermore, it was found that the job mixes with sludge had a significantly better performance than the standard F10 mix that did not contain it.

The use of crumb rubber modifier (CRM) in bituminous mixes made by the dry process is not as widely used as the wet process. Nonetheless, this process has advantages, such as the potential to consume larger quantities of crumb rubber, thus resulting in greater savings in energy and natural resources. This research study contributes to the further development and evolution of the dry process through the analysis of the effect of the digestion time (the contact time between the crumb rubber and the bitumen) and the quantity of crumb rubber on the mix design properties. The results of the study showed that the digestion time had no influence on the selection of the optimal binder content or on the compaction of the mixture. In contrast, the digestion time was found to have an impact on the mechanical performance of the mix. In this respect, an increase in the quantity of crumb rubber contributed to a corresponding increase in the amount of bitumen needed, and also caused the mix to become less compact. This study showed that a crumb rubber percentage of less than 1% of the total weight of the mix and a digestion time of 90 min produced the best results.

One of the most common road pavement pathologies is caused by water action. The presence of moisture causes a reduction in aggregate-binder adhesion in the mix as well as in the internal cohesion of the bitumen. This leads to problems such as pot holes, aggregate peeling, stripping, etc., which eventually lead to the structural failure of the pavement. Currently, there are numerous laboratory tests that analyze the susceptibility of bituminous mixes to moisture, providing a qualitative or quantitative evaluation. This study analyzes the performance of bituminous mixes in different experimental conditions. For this purpose, a comparative study of two laboratory tests was carried out. The tests differed in mix compaction method, the conditioning of the test specimens, and the type of load applied. The results obtained showed that in these tests the conditioning temperature had a greater impact on mix performance than the temporal duration of the conditioning process. Furthermore, the application of tensile stress was found to be more suitable for studying moisture susceptibility since mixes were found to be more sensitive to this type of load.