Replacing natural raw materials with industrial by-products can increase the sustainability of Self-Compacting Concrete (SCC), although its fresh and hardened behavior will usually worsen. The benefits of increased sustainability must therefore outweigh any reduction in concrete flowability and strength. These aspects can be analyzed through Multi-Criteria Decision-Making (MCDM) algorithms. In all, 19 SCC mixes were studied. One reproduced commercial SCC (limestone filler and conventional cement), the others were produced with more sustainable materials: 100% coarse Recycled Concrete Aggregate (RCA); 0%, 50% or 100% fine RCA; 45% Ground Granulated Blast-furnace Slag (GGBS); and sustainable aggregate powders such as limestone fines 0/0.5 mm and RCA powder 0/0.5 mm. Decreased flowability at 15 and at 60 min, compressive strength, modulus of elasticity, carbon footprint, and cost of mix were all studied. Both the carbon footprint and the cost were calculated considering only the composition of the SCC, without including aspects that depend on each particular case study, such as transport distances. These aspects constituted the decision-making criteria of the MCDM analysis, under which 14 scenarios were evaluated with different requirements for SCC, using 3 different algorithms (TOPSIS, AHP, and PROMETHEE). The results suggested that the ideal choice for fast concreting is a combination of GGBS, 100% coarse RCA and limestone fines, although if SCC has to be transported to the concreting point, then conventional cement should be used. Strength and stiffness can be maximized by limiting the fine RCA content to 50%. Finally, considering a versatile choice, only SCC with coarse RCA, limestone fines, GGBS and 0% fine RCA could compete with conventional SCC. Adapting the design to minimize the detrimental effects of by-products is therefore essential to promote sustainable SCC that is also commercially competitive., Spanish Ministry MCIU, AEI and ERDF [grant numbers PID 2020-113837RB-I00; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [grant number UIC-231, BU119P17]; Youth Employment Initiative (JCyL) and ESF [grant number UBU05B_1274]; and, finally, the University of Burgos [grant number SUCONS, Y135.GI].

Predicting the mechanical properties of Self-Compacting Concrete (SCC) containing Recycled Concrete Aggregate (RCA) generally depends, in great part, on the RCA fraction in use. In this study, predictive equations for estimating SCC mechanical properties are developed through SCC porosity indices, so they are applicable to any RCA fraction and amount that may be used. A total of ten SCC mixes were prepared, nine of which containing different proportions of coarse and/or fine RCA (0%, 50% or 100% for both fractions), and the tenth mixed with 100% coarse and fine RCA, and RCA powder 0–1 mm. The following properties were evaluated: compressive strength, modulus of elasticity, splitting tensile strength, flexural strength, and effective porosity as measured with the capillary-water-absorption test. Negative effects on the above properties were recorded for increasing contents of both RCA fractions. The application of simple regression models yielded porosity-based estimations of the mechanical properties of the SCC with an accuracy margin of ±20%, regardless of the RCA fraction and amount. The results of the multiple regression models with compressive strength as a secondary predictive variable presented even greater robustness with accuracy margins of ±10% and almost no significant effect of accidental porosity variations on prediction accuracy. Furthermore, porosity predictions using the 24-h effective water also yielded accurate estimations of all the above mechanical properties. Finally, comparisons with the results of other studies validated the reliability of the models and their accuracy, especially the minimum expected values at a 95% confidence level, at all times lower than the experimental results., Spanish Ministry of Universities within the framework of the State Program for the Promotion of Talent and its Employability in R + D + i, State Mobility Subprogram, of the State Plan for Scientific and Technical Research and Innovation 2017–2020 [PRX21/00007]; the Spanish Ministry MCI, AEI, EU and ERDF [grant numbers PID2020-113837RB-I00; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [grant numbers UIC-231; BU119P17]; Youth Employment Initiative (JCyL) and ESF [grant number UBU05B_1274]; and finally, the University of Burgos [grant numbers SUCONS, Y135.GI] and the University of Padova.

The high strength and durability of high-performance concrete (HPC) may be significantly reduced by shrinkage cracking. The use of reactive magnesium oxide (MgO) can reduce shrinkage of cement-based materials due to its expansive properties. This study intends to analyse the validity of MgO as shrinkage-reducing agent in recycled aggregate HPC. To do so, ten HPC mixes with 0%, 25%, and 100% of both early-age (7-days air curing) and matured (6-month air curing) RA were produced. In half of the mixes, 10% ordinary Portland cement was replaced with MgO. The use of MgO slightly worsened the mechanical behaviour of HPC, especially when combined with large amounts of RA. On the other hand, the expansion of MgO fully offset the autogenous shrinkage of HPC and reduced total shrinkage by around 20–40%. Water storage of RA, and its deferred release over time, produced a more efficient hydration of MgO, which in turn led to a further reduction of autogenous shrinkage. However, the increase of drying shrinkage caused by RA was greater than this decrease of autogenous shrinkage due to MgO, so the higher the RA content of HPC the lower the total shrinkage reduction when adding MgO. Thus, the decrease of total shrinkage caused by MgO was compensated by the shrinkage increase because of RA when adding amounts above 35% early-age RA and 42% matured RA. Therefore, despite the suitability of MgO as shrinkage-reducing agent in recycled aggregate HPC, its effectiveness was reduced with increasing amounts of RA., Spanish Ministry of Universities, MICINN, AEI and ERDF [grant numbers FPU17/03374; EST19/00263; PID2020-113837RB-I00; 10.13039/501100011033]. The authors also acknowledge the support of the Foundation for Science and Technology, CERIS Research Centre and Instituto Superior Técnico, the Junta de Castilla y León [grant number UIC231], and the University of Burgos [grant number Y135.GI].

The environmental conditions to which a concrete may be exposed will condition its real range of use. Thus, concrete behavior must, at all times, be verified under a wide variety of environmental conditions, in order to ensure its real applicability. In this study, the real strength development and durability behavior of a fiber-reinforced self-compacting concrete is analyzed. This particular concrete incorporates 100% coarse (4/12 mm) and fine (0/4 mm) Electric Arc Furnace Slag (EAFS) as aggregate, as well as limestone fines as aggregate powder (0/1.18 mm). Furthermore, Ground Granulated Blast Furnace Slag (GGBFS) was also added as binder. Four mixtures with and without either metallic or synthetic fibers, and different GGBFS contents were designed. Real strength development was evaluated in all the mixes by comparing the strength development of both cores extracted from full-scale beams and wet-cured laboratory specimens. The durability behavior was analyzed by Mercury Intrusion Porosimetry (MIP), freeze/thaw, moist/dry, sulfate-attack, chloride-penetration, carbonation, and SO2-attack tests. On the one hand, the long-term mechanical properties of the cores (real conditions) were similar to the properties of the specimens cured in a moist chamber for 90 days in all the mixes. On the other, the increase in water content when adding fibers to maintain flowability, as well as the addition of GGBFS, resulted in an increase in MIP porosity. Therefore, the use of fibers, both metallic and synthetic, slightly worsened the durability behavior of the concrete, facilitating the entry of aggressive external agents. Nevertheless, the increased flexibility of the cementitious matrix when adding GGBFS was beneficial against moist/dry and sulfate-attack phenomena, despite the increase in porosity. Overall, the mixes complied with the regulatory requirements for use in aggressive environments, although the amounts of fibers and GGBFS should be carefully studied., Spanish Ministry of Universities within the framework of the State Program for the Promotion of Talent and its Employability in R + D + i, State Mobility Subprogram, of the State Plan for Scientific and Technical Research and Innovation 2017-2020 [PRX21/00007]; the Spanish Ministry of Universities, MICINN, AEI, EU and ERDF [grant numbers PID2020-113837RB-I00; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [grant numbers UIC-231; BU119P17]; Youth Employment Initiative (JCyL) and ESF [grant number UBU05B_1274]; and finally, to the University of Burgos [grant numbers SUCONS, Y135.GI] and the University of Padova.

Electric Arc Furnace (EAF) slag can be reused as aggregate in Portland cement concrete mixes. The addition of EAFS and other waste co-products (fly ash, blast furnace slag) will modify the binding properties and will, importantly, enhance the global sustainability of such concretes. These mix designs offer acceptable pumpability and self-compaction in the fresh state and can be reinforced with fibers. In this study, eight different concrete mixes are designed within the range of medium-strength concretes (30–50 MPa) and are characterized in both the fresh and the hardened state. Large concrete volumes are used to pour reinforced beams, which are then subjected to small-span high-load tests to evaluate their resistance to shear stress, by analyzing two types of transversal (shear) reinforcement. The tests yielded promising results, contributing additional evidence on the viability of using recycled EAFS aggregate in structural applications. The mechanical behavior of these concretes was closely correlated with the strength predictions calculated with the formulas listed in various international standards., Spanish Ministry of Universities, MICINN, AEI, EU and ERDF [PID2020-113837RB-I00; RTI2018-097079-B-C31; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León and ERDF [UIC-231, BU119P17]; Youth Employment Initiative (JCyL) and ESF [UBU05B_1274]; the University of Burgos [grant number SUCONS, Y135.GI], and, finally, our thanks also go to the SAREN research group (IT1619-22, Basque Government).

The modulus of elasticity of a concrete depends on the elastic stifness of both the cementitious matrix and the aggregate–ITZ
system, which includes any slippage mechanisms under loading between the aggregate and the cementitious matrix within the
interfacial transition zone (ITZ). A procedure is presented in this paper to estimate the elastic stifness of an aggregate–ITZ
system within a cementitious matrix, by considering the relative volumes and the porosities of the concrete components.
The method was validated by determining the elastic stifness of both the limestone–ITZ and the electric arc furnace slag
(EAFS)–ITZ systems when embedded in a slag-based cementitious matrix. The greater stifness of the EAFS–ITZ system
in comparison with the natural aggregate system explained the higher strength and modulus of elasticity of the concrete
following additions of EAFS. Moreover, having determined those parameters, the elastic moduli of concretes with a similar
cementitious matrix could then be accurately estimated., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The authors wish to express their gratitude for funding this research work to the Spanish Ministry of Universities, MICINN, AEI, EU and ERDF [PID2020-113837RBI00; PID2021-124203OB-I00; RTI2018-097079-B-C31; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [UIC-231, BU119P17]; the Basque Regional Government through the consolidated research group SAREN [IT1619-22]; Youth Employment Initiative (JCyL) and ESF [UBU05B_1274]; and, fnally, the University of Burgos [Y135.GI].

The high fine-aggregate content of Self-Compacting Concrete (SCC) means that its deformational
behavior differs from that of vibrated concrete. SCC performance is further altered when industrial by-products are used as raw materials in those fractions. In this paper, the aim is to analyze
and to model the deformational behavior under compression and bending of SCC containing
100% coarse and 0%, 50%, and 100% fine Recycled Aggregate (RA), limestone and RA green
aggregate powders sized 0/0.5 mm, and Ground Granulated Blast-furnace Slag (GGBS) cement.
After the fresh and mechanical characterization of the 18 SCC mixes that were produced, their
compressive stress-strain and bending load-deflection curves were determined by continuously
recording the applied load and the strain/deflection values of the SCC test specimens. 100%
coarse RA yielded deformability levels in accordance with international standards, while higher
fine RA contents increased deformation under compression and reduced it under flexural stress.
SCC stiffness increased when GGBS was added, due to the adjustment of the proportion of
cementitious matrix, while the use of limestone powder and, especially, RA powder had the
opposite effect. Both compressive strain and flexural deflection were underestimated with
existing theoretical models. However, the incorporation in the models of both exponential
correction coefficients, dependent on the fine RA content, and partial adjustment coefficients,
dependent on the types of cement and aggregate powder, produced optimal fits with the experimental stress-strain and load-deflection curves. In view of the deformational behavior, which was
successfully modelled with maximum deviations of ±10%, fine RA may be used in combination
with GGBS and limestone powder, although it is recommended that fine RA should not exceed
proportions of 50%., The authors wish to express their gratitude for funding this research work to the Spanish Ministry of Universities, MICINN, AEI, EU, and ERDF [PID2020-113837RB-I00; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y Leon ´ (Regional Government) and ERDF [UIC-231]; and the University of Burgos [SUCONS, Y135. GI].

Numerous test results at laboratory scale confirm the utility of Recycled Aggregate (RA) for the development of
concrete that demonstrates durability and adequate in-fresh and mechanical behavior. However, feasibility
evaluations of the use of RA in real industrial applications are necessary, before any large-scale industrial
application of these products can begin. In this research, the feasibility of producing precast-concrete components containing large amounts of coarse RA at a precast-concrete plant is analyzed. Two Self-Compacting
Concretes (SCC) were produced incorporating 0% and 100% coarse RA, respectively, at both laboratory scale
(0.08 m3
) and industrial scale (2 m3
). Work took place at the industrial-scale facilities of a precast-concrete
company that was collaborating in this study. Flowability and mechanical behavior were maintained as concrete production volumes increased, and concrete strength even increased after adding coarse RA, due to a
careful mix design. However, the durability performance worsened by around 20% when produced at industrial
scale, being this worsening higher whether coarse RA was used. A Multi-Criteria Decision-Making (MCDM)
analysis, in which the criteria of the precast-concrete company defined the relative importance of each concrete
property, showed the feasibility of manufacturing precast-SCC components containing coarse RA for interior
usage, whose fundamental requirement is adequate mechanical strength. The results of the MCDM analysis also
underlined the lower cost of coarse RA, making its use in SCC components cast with large concrete volumes
advisable. Overall, the addition of coarse RA in the precast-concrete industry is recommended in the interests of a
greener construction sector., The authors wish to express their gratitude for funding this research work to the Spanish Ministry of Universities, MICINN, AEI, EU, ERDF and NextGenerationEU/PRTR [PID2020-113837RB-I00; 10.13039/ 501100011033; TED2021-129715B-I00; FPU17/03374]; the Junta de Castilla y Leon ´ (Regional Government) and ERDF [UIC-231]; and the University of Burgos [SUCONS, Y135.GI]. In addition, Priyadharshini Perumal acknowledges the financial support received from the project DeConcrete [grant # KO 4068: Eco-efficient Arctic technologies cooperation] funded by the Kolarctic CBC initiative of the European Union. Finally, the support and assistance of ARTEPREF S.A. for the development of this study is also highly appreciated.

Estimating the shrinkage of structural concrete is essential to calculate, at the design stage, the stresses that a
structure may experience due to this phenomenon. Nevertheless, changes in composition, as well as the use of
wastes as raw materials, alter the shrinkage behaviour of concrete and render invalid shrinkage-prediction
models from the standards. This paper shows a procedure to estimate the shrinkage of recycled aggregate
concrete made with alternative binders. This procedure is based on modifying the shrinkage estimated through
the Eurocode 2 or ACI 209.2R models by multiplying it by a partial correction coefficient for every change in
concrete composition. The application of this procedure to high-performance and self-compacting concretes
made with various contents of recycled aggregate of different maturity, reactive magnesium oxide and ground
granulated blast furnace slag showed that it is suitable for estimating long-term shrinkage with maximum deviations of ±10%. However, to obtain an adequate accuracy, it is necessary to bear in mind some tips, such as the
need to consider the prediction interactions between the factors, the usefulness of the natural logarithm of the
concrete age to improve the estimation accuracy or the convenience of introducing a concrete-age-dependent
coefficient to reach accurate shrinkage estimations at early ages. Finally, the partial correction coefficients are
found to be of a simpler nature for the ACI 209.2R model, so this model is recommended for predicting the
shrinkage of recycled aggregate concrete., This work was supported by the Spanish Ministry of Universities, MICINN, AEI, EU and ERDF [grant numbers PID2020-113837RB-I00; 10.13039/501100011033; FPU17/03374; EST19/00263]. Moreover, the authors acknowledge the support of the Junta de Castilla y León [grant number UIC231]; the University of Burgos [grant number Y135. GI]; and the Foundation for Science and Technology, CERIS Research Centre and Instituto Superior Técnico.

Recycled Aggregate (RA) usually increases porosity and weakens Interfacial Transition Zones (ITZs) of concrete,
which favors the appearance of internal thermal damage. Four Self-Compacting Concrete (SCC) mixes with
coarse and fine RA were subjected to positive and negative cyclic temperature variations to characterize their
thermal damage and quantify its effects. Two damage mechanisms were found. On the one hand, micro-cracks
appeared in the ITZs. On the other hand, micro-cracks arose from the micro-pores and propagated through the
cementitious matrix. Both damage mechanisms were promoted by the use of coarse and fine RA, respectively.
The damage was most notable at sub-zero temperatures and when adding coarse RA. Furthermore, it primarily
affected compressive strength, although ultrasonic pulse velocity and hardened density also decreased, which
served as non-destructive indicators to indirectly quantify the level of thermal internal damage of SCC., This work was funded by MICINN, AEI, EU, ERDF and NextGenerationEU/PRTR [PID2020-113837RB-I00; 10.13039/501100011033; TED2021-129715B-I00; FPU17/03374]; JCyL and ERDF [UIC-231]; and the University of Burgos [SUCONS, Y135.GI].

The hammer rebound index has traditionally been solely and exclusively used to estimate the compressive
strength of vibrated concrete. Its use has recently been extended to the prediction of the compressive strength of
Self-Compacting Concrete (SCC) and concrete produced with Recycled Concrete Aggregate (RCA). The conventional use of the hammer-rebound test is further developed in this paper, by demonstrating how it can be used
to estimate the overall mechanical behavior of SCC containing RCA. To do so, nine SCC mixes with different
contents and fractions (coarse, fine, and powder) of RCA are analyzed. Following a simple-linear-regression
validation and property standardization procedure, the hammer rebound index is then expressed as a linear
combination of four mechanical properties, adjusted through a multiple regression. The hammer rebound index
is therefore expressed as a weighting of both the mean value of compressive behavior (arithmetic mean of
compressive strength and modulus of elasticity) amounting to a weight of 72.8%, and the mean value of bendingtensile behavior (arithmetic mean of splitting tensile strength and flexural strength) amounting to a weight of
27.2%. The hammer rebound index can therefore be construed as an overall-mechanical-quality performance
indicator of the SCC containing RCA, which can also yield predictions of every mechanical property. In this way,
the application of the hammer rebound index could likewise be of use in rehabilitation, pathology, and healthmonitoring works where a full characterization of the mechanical performance of SCC with RCA is required,
facilitating the use of SCC with RCA in real structures., The authors wish to express their gratitude to the following government ministries, agencies, and universities for funding this research: the Spanish Ministry of Universities, MICIN, AEI, EU, ERDF and NextGenerationEU/ PRTR [PID2020-113837RB-I00; 10.13039/501100011033; TED2021- 129715B-I00; FPU17/03374; PRX21/00007]; the Junta de Castilla y León (Regional Government) and ERDF [UIC-231, BU119P17]; the University of Burgos [SUCONS, Y135.GI]; and, finally, the University of Padova.

Adding sustainable raw materials to Self-Compacting Concrete (SCC) modifies its flowability
behavior. Furthermore, the use of these raw materials may at the same time even improve one
fresh property while worsening another. An accurate flowability description of SCC containing
sustainable raw materials therefore requires a multi-parametric classification that simultaneously
covers all fresh properties (slump flow, viscosity, and blocking ratio) for an accurate description
of its potential applications. Existing classifications consider each fresh property independently.
In this paper, a multi-parametric flowability classification of SCC containing sustainable raw
materials is proposed. The effects of multiple sustainable raw materials on SCC flowability are
compiled in a dataset serving as a knowledge base with information on 663 SCC mixes containing
sustainable aggregates and binders. The statistical analysis of the dataset led to the definition of
three types of flowability zones. Firstly, the overall-flowability zones, in which SCC flowability is
described in absolute terms: the better the in-fresh properties, the better the overall-flowability
zone. Secondly, the flowability-balance zones reflect the balance between free flow (slump
flow and slump-flow viscosity) and flow around obstacles (V-funnel emptying time and L-box
blocking ratio). Finally, SCC is classified within flowability-predominance zones, which define the
main characteristic of SCC flowability, rate of flow (viscosity) or uniformity of flow (spreading).
The variability of the effect of each sustainable raw material on the flowability of SCC makes this
classification useful, in so far as it offers a complete picture of the fresh behavior of SCC in which
all fresh properties are simultaneously considered. Furthermore, based on the description in the
proposed classification of overall flowability and the balance between free flow and flow around
obstacles, the application fields are defined for which the use of each SCC mix with sustainable
raw materials is recommended., This research work was supported by the Spanish Ministry of Universities, MICINN, AEI, EU, ERDF and NextGenerationEU/PRTR [grant numbers PID2020-113837RB-I00; 10.13039/501100011033; TED2021-129715B–I00; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [grant number UIC-231]; and, finally, the University of Burgos [grant number SUCONS, Y135. GI].

Ultrasonic pulse velocity (UPV) is a non-destructive measurement technique with which
the quality of any concrete element can be evaluated. It provides information on concrete health
and for assessing the need for repair in a straightforward manner. In this paper, the relationship
is studied between UPV readings and the mechanical behavior of self-compacting concrete (SCC)
containing coarse, fine, and/or powdery RA. To do so, correlations and simple- and multipleregression relationships between compressive strength, modulus of elasticity, splitting tensile strength,
flexural strength, and UPV readings of nine SCC mixes were assessed. The correlations showed that
the relationship of UPV with any mechanical property was fundamentally monotonic. The inverse
square-root model was therefore the best-fitting simple-regression model for all the mechanical
properties, although for bending-tensile-behavior-related properties (splitting tensile strength and
flexural strength) the estimation accuracy was much lower than for compressive-behavior-related
properties (compressive strength and modulus of elasticity). Linear-combination multiple-regression
models showed that the properties related to bending-tensile behavior had a minimal influence on
the UPV value, and that their introduction resulted in a decreased estimation accuracy. Thus, the
multiple-regression models with the best fits were those that linked the compressive-behavior-related
properties to the UPV readings. This therefore enables the estimation of the modulus of elasticity
when the UPV and compressive strength are known with a deviation of less than ±20% in 87% of the
SCC mixes reported in other studies available in the literature., This research was funded by the Spanish Ministry of Universities, MICIN, AEI, EU, ERDF, and NextGenerationEU/PRTR, grant numbers PID2020-113837RB-I00, 10.13039/501100011033, and TED2021-129715B-I00; the Junta de Castilla y León (Regional Government) and ERDF, grant number UIC-231; and the University of Burgos, grant numbers SUCONS, Y135.GI.

An alternative experimental method for predicting the diagonal shear cracking resistance of steel-reinforced concrete beams is developed in this paper. Conventional extensometric strain-gauge rosettes are placed on the lateral surfaces of a set of four beams. As diagonal cracking propagates through the beams, the load–strain curves flatten out at a plateau and the mechanical property under consideration may be determined. The method is applied to four beams cast from pumpable and self-compacting concrete mixes with cement types I and IV containing electric arc furnace slag aggregates. The feasibility of applying standard design code formulas to the concretes containing these aggregates may therefore be studied and compared with other recent research works. Accurate experimental results were obtained with this method without having to interrupt the test for subjective visual appraisals of the test specimen., The authors wish to express their gratitude to: the Spanish Ministry MICINN, AEI and ERDF [RTI2018-097079-BC31; PID2020-113837RB-I00; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [UIC-231, BU119P17]; Youth Employment Initiative (JCyL) and ESF [UBU05B_1274]; and the University of the Basque Country [PPGA20/26] and University of Burgos [SUCONS, Y135.GI] for additional funding. Our thanks also go to the Basque Government research group [IT1314-19] and likewise to CHRYSO and HORMOR for supplying the materials used in this research.

This dataset contains the data generated during the execution of the project “Full-scale study of sustainable high performance hydraulic and bituminous concretes, manufactured with steelmaking and construction waste (FULLSCALE)”, code PID2020-113837RB-I00, corresponding to the 2020 Call of “Proyectos de I+D+i” of the State Research Agency (Agencia Estatal de Investigación, AEI) and the Ministry of Science and Innovation of the Government of Spain (Ministerio de Ciencia e Innovación del Gobierno de España)., The research work conducted within the framework of the FULLSCALE project (PID2020-113837RB-I00), which was funded by the Ministry of Science and Innovation of the Government of Spain (Ministerio de Ciencia e Innovación del Gobierno de España), the State Research Agency (Agencia Estatal de Investigación, AEI) and the European Regional Development Fund (Fondo Europeo de Desarollo Regional, FEDER) through the 2020 Call of "Proyectos de I+D+i".

Raw-crushed wind-turbine blade (RCWTB), a waste from the recycling of wind-turbine blades, is used as a raw material in concrete in this research. It contains not only fiberglass-composite fibers that bridge the cementitious matrix but also polyurethane and balsa-wood particles. Therefore, concrete containing RCWTB can be notably affected by moisture and temperature fluctuations and by exposure to high temperatures. In this research, the performance of five concrete mixes with 0.0%, 1.5%, 3.0%, 4.5%, and 6.0% RCWTB, respectively, is studied under moist/dry, alternating-sign-temperature-shock, and high-temperature-shock tests. Two damage mechanisms of RCWTB within concrete were found through these tests: on the one hand, micro-cracking of the cementitious matrix, which was verified by microscopic analyses and was dependent on concrete porosity; on the other, damage and degradation of the RCWTB components, as the polyurethane melted, and the balsa-wood particles burned. Both phenomena led to larger remaining-strain levels and reduced concrete compressive strength by up to 25% under temperature and humidity variations, although the bridging effect of the fiberglass-composite fibers was effective when adding RCWTB amounts higher than 3.0%. The compressive-strength loss after the high-temperature-shock test increased with the RCWTB content, reaching maximum values of 8% after an exposure time of 7 days. Statistical analyses revealed that effect of the RCA amount in the concrete was conditioned by the exposure times in all the tests. The accurate definition of those times is therefore key to set an RCWTB content in concrete that ensures its suitable behavior under the environmental conditions analyzed., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research work was funded by the Spanish Ministry of Universities, MICINN, AEI, EU, ERDF, and NextGenerationEU/PRTR [grant numbers PID2020-113837RB-I00, PID2023-146642OB-I00,https://doi.org/10.13039/501100011033, TED2021-129715B-I00, and FPU21/04364]; the Junta de Castilla y León (Regional Government) and ERDF [grant numbers UIC-231, BU033P, and3; BU066-22]; and, finally, the University of Burgos [grant number SUCONS, Y135.GI].

Recycled Concrete Aggregate (RCA) and Raw-Crushed Wind-Turbine Blade (RCWTB) are waste materials obtained from decommissioned wind turbines after crushing their foundations and blades, respectively. Their use as raw materials in concrete allows their recycling. RCA increases concrete sustainability, while the fibers of Glass Fiber-Reinforced Polymer (GFRP) in RCWTB (66.8 % wt.) improve its bending performance. Nevertheless, only balanced waste combinations provide an adequate concrete behavior. Following a characterization of concrete in terms of fresh and strength performance, Response Surface Method (RSM) was conducted based on the experimental results to define the optimum waste combinations to reach a concrete strength performance adequate for engineering applications. RSM highlighted the need to limit the RCWTB content to 3 % to reach a compressive strength higher than 45 MPa, while amounts below 3 % and above 7 % would allow obtaining a flexural strength over 5.5 MPa. In both cases, the maximum content of coarse RCA should be 80 %. 70 % coarse RCA and a RCWTB amount between 6 % and 10 % would enable to develop concrete mixes with conventional strengths of 30–40 MPa under compression and 5 MPa under bending. RSM results revealed that RCWTB and their GFRP fibers properly behave in concrete with coarse RCA., This research work was supported by the Spanish Ministry of Universities, MICINN, AEI, EU, ERDF and NextGenerationEU/PRTR [grant numbers PID2020-113837RB-I00; 10.13039/501100011033; TED2021-129715 B–I00; PID2023-146642OB-I00; FPU21/04364]; the Junta de Castilla y León (Regional Government) and ERDF [grant number UIC-231; BU033P23; BU066-22]; and, finally, the University of Burgos [grant number SUCONS, Y135. GI].

Nonselective crushing of wind turbine blades results in raw-crushed wind turbine blade (RCWTB), a material that can be used in concrete production. Wind farm decommissioning can also generate coarse recycled aggregate (CRA) from the demolition of wind turbine concrete footings. This paper proposes a first approach for the joint management of both wastes through their simultaneous use in low-strength concrete, with a target compressive strength of 25 MPa. Mixes with 50% and 100% CRA, and 0% and 10% RCWTB as a cement addition, were designed, with the effect of CRA content not being statistically significant, to analyze its interaction with RCWTB. The results showed that, on the one hand, RCWTB reduced strength and stiffness under compression by a maximum of 9%–15%, although the target strength was achieved in all mixes; the presence of balsa wood and polymer particles in RCWTB, with high flexibility, could explain these reductions. On the other hand, the stitching effect of the glass fiber–reinforced polymer fibers present in RCWTB largely improved the bending-tensile mechanical properties. For example, flexural strength was almost doubled (from 2.51 to 4.99 MPa) when RCWTB was combined with 50% CRA. Additionally, RCWTB reduced both the embodied carbon and cost of low-strength concrete, resulting in doubled flexural-strength efficiency (flexural strength per unit of embodied carbon and cost), regardless of the CRA content. Overall, the best interaction was observed with 10% RCWTB and 50% RCA. Therefore, this study opens the possibility of simultaneously using RCWTB and CRA in low-strength concrete for applications where bending stresses predominate., This research work was supported by the Ministerio de Ciencia, Innovación y Universidades (MICIU), Agencia Estatal de Investigación (AEI), European Union (EU), European Regional Development Fund (ERDF), and NextGenerationEU/PRTR (Grant Nos. PID2020-113837RB-I00, PID2023-146642OB-I00, 10.13039/501100011033, TED2021-129715B-I00, and FPU21/04364); the Junta de Castilla y León (Regional Government) and ERDF (Grant Nos. UIC-231, BU033P23, and BU066-22), and, finally, the University of Burgos (Grant No. SUCONS, Y135.GI). Authors Nerea Hurtado-Alonso and Javier Manso-Morato contributed equally to this paper.