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8 figures.-- Supplementary information available., The deterioration of monumental stones is a common event occurring to our historical and cultural heritage, threatening the preservation of our social identity and its legacy to future generations. The prolonged effect of inclement weather is very harmful for particular stone materials such as limestone and dolomite, to which a truly effective and durable protective agent has not yet been found. Herein, an unprecedented performance of graphene oxide (GO) for the shielding of carbonated ornamental stones against environmental aggressions, namely intense rainfall and extreme temperatures, is demonstrated. A simple additive-free aqueous suspension of GO serves as the perfect coating, exceedingly preventing from any kind of wear or erosion after different climatic simulations. Additionally, the stones’ original aesthetics is not altered (a critical issue in monuments), together with an improvement in their mechanical properties, reasserting the unique potential of GO for conserving exposed stone-based monuments in an affordable, accessible, and revolutionary way., This research received funding from the Univerisdad de León (ULE-PoC 2018) and “Fundación General de la ULE y de la Empresa (FGULEM)” under projects 2019/00149/001 and 2020. J.M.G.-D. is grateful to the Spanish Ministry of Science, Innovation and Universities for his “Juan de la Cierva-Incorporación” research grant and associated research funds (IJCI-2016-27789). In loving memory of Prof. Jose L. García-Fierro, whose support with the XPS characterization was helpful for the development of this work. The authors also thank Mr. Adrián Domínguez Gutiérrez for his assistance during the photogrammetric processing of some samples. Invaluable assistance from Dr. Rebeca Martínez García and Dr. Sagrario Fernández Raga is highly indebted. Further research will be funded through a recently granted MICINN project (PID2020-120439RA-I00).

One of the prime objectives of this review is to understand the role of design parameters on the mechanical properties (Compressive and split tensile strength) of Self-Compacting Concrete (SCC) with recycled aggregates (Recycled Coarse Aggregates (RCA) and Recycled Fine Aggregates (RFA)). The design parameters considered for review are Water to Cement (W/C) ratio, Water to Binder (W/B) ratio, Total Aggregates to Cement (TA/C) ratio, Fine Aggregate to Coarse Aggregate (FA/CA) ratio, Water to Solid (W/S) ratio in percentage, superplasticizer (SP) content (kg/cu.m), replacement percentage of RCA, and replacement percentage of RFA. It is observed that with respect to different grades of SCC, designed parameters affect the mechanical properties of SCC with recycled aggregates.

The concept of construction and demolition waste (CDW) embodies a vast amount of residues, among which the ceramic materials (mainly, bricks and tiles) are an important part as, in many countries of the European Union, they represent more than 50% of the total. Therefore, the reutilization of this type of waste is one of the most important challenges faced by the construction sector within the circular economy paradigm. This research work deals with a dual reutilization of the CDW ceramic fraction: firstly, as coarse recycled aggregates and, secondly, through the use of clay brick powder as a pozzolanic addition to the cement. Thus, two different recycled concrete mixtures were produced: (1) with a 50% partial substitution of the natural coarse aggregates (RC-RA) and (2) with a 50% substitution of the natural coarse aggregates and a 25% substitution of the ordinary Portland cement (RC-RAC). The mechanical performance (consistency, density and compressive strength) and microstructural properties such as porosity, elemental mapping analysis, hydration products and interfacial transition zones (ITZ) were assessed and compared with a control concrete (CC). It was revealed that the recycled concretes incorporating ceramic as secondary materials have a comparable performance level to the one exhibited by the conventional concrete at 28 days, in part due to their pozzolanic characteristics but also due to a lower effective w/c ratio, which demonstrates their potential for reuse and possible contribution to the circular economy.

The overconsumption of resources and the elevated generation of wastes are two of the most relevant environmental challenges of the 21st century. Traditionally, natural resources and wastes are found, respectively, at the start and end point of the linear model of production, i.e., the material life cycle, which encourages the take-use-dispose attitude responsible for the problems in the first place. Nonetheless, in the recent years, a new circular economy model has been supported by scientific efforts, political attempts, and social awareness to transform the production chains and consumption habits by means of turning waste into resources. In the path toward the sustainability in the construction sector, numerous studies have shown the feasibility of using recycled aggregates (RA) as replacement of natural aggregates (NA) for the manufacture of recycled concrete (Xuan et al., 2017; Thomas et al., 2018; Agrela et al., 2011; De Brito et al., 2005; Huda and Alam, 2014; Limbachiya et al., 2000; Poon et al., 2004a; Rahal, 2007; Rodriguez et al., 2016). However, to date, the higher water absorption (WA) of recycled aggregates is still regarded as a major barrier in the reuse of this secondary material and thus limiting its acceptance in the construction market (Sagoe-Crentsil et al., 2001; Evangelista and de Brito, 2007; Poon et al., 2004b; Tam et al., 2005). Thus, further research on the improvement of RA properties and the subsequent study of the feasibility to use them as a replacement of the conventional aggregate in the manufacture of concrete is still needed. Among the available techniques to palliate the drawback posed by the higher absorption of RA, it is worth mentioning the application of bacterially induced calcium carbonate precipitation as an eco-friendly technique to reduce the water uptake capacity of RA and thus to improve their quality to be reused in the concrete production. The biogenic CaCO3 acts as superficial treatment, covering the external micro-cracks of the RA and filling some superficial pores, as well as some of the deeper ones (Grabiec et al., 2012; Qiu et al., 2014; Garcia-Gonzalez et al., 2017). Furthermore, calcium carbonate precipitation has been proven to increase the RA density and strengthen their surface (Garcia-Gonzalez et al., 2017; Wang et al., 2017), which positively affects the mechanical and durability performance of the resulting recycled concrete.

The use of construction and demolition wastes (C&amp, DW) is a trending future option for the sustainability of construction. In this context, a number of works deal with the use of recycled concrete aggregates to produce concrete for structural and non-structural purposes. Nowadays, an important number of C&amp, DW management plants in the European Union (EU) and other countries have developed robust protocols to obtain high-quality coarse recycled aggregates that comply with different European standards in order to be used to produce new concrete. The development of self-compacting concrete (SCC) is another way to boost the sustainability of construction, due to the important reduction of energy employed. Using recycled aggregates is a relatively recent scientific area, however, studies on this material in the manufacture of self-compacting concrete have proven the feasibility thereof for conventional structural elements as well as high-performance and complex structural elements, densely reinforced structures, difficult-to-access formwork and difficult-to-vibrate elements. This paper presents an original study on the use of coarse recycled concrete aggregate (CRA) to obtain self-compacting concrete. Concrete with substitution ratios of 20%, 50% and 100% are compared with a control concrete. The purpose of this comparison is to check the influence of CRA on fresh SCC as well as its physical and mechanical properties. The parameters studied are material characterization, self-compactability, compressive strength, and tensile and flexural strength of the resulting concrete. The results conclude that it is feasible to use CRA for SCC production with minimal losses in the characteristics.

This research benefitted from an STSM grant awarded under COST Action CA15202 ( http://www.sarcos.enq.cam.ac.uk ). Funding was also provided by the Spanish Ministry of Economy, Industry and Competitiveness under project BIA2017-83526-R and by the Portuguese Foundation for Science and Technology (FCT/MCTES) by supporting the Civil Engineering Research and Innovation for Sustainability Unit-CERIS, Associate Laboratory for Green Chemistry-LAQV and Applied Molecular Biosciences Unit-UCIBIO (projects UIDB/50006/2020 , and UID/Multi/04378/2020 ). Paulo C. Lemos acknowledge the support by FCT / MCTES for contract IF/01054/2014/CP1224/CT0005 . Publisher Copyright: © 2021 The Authors Copyright: Copyright 2021 Elsevier B.V., All rights reserved. This study analyses the potential of a new eco-friendly bioproduct to construction sustainability and its contribution for improving the fresh and hardened properties of cement mortar. The bioproduct was obtained from biomass grown using crude glycerol (biodiesel production waste). With similar functionality than petrochemical-based additions, these bioproducts encourage the decrease on the use of fossil-based raw materials with the concomitant reduction in their carbon footprint. The effect of bioproduct's sonication and storage for 3 day at 4 °C were assessed. Properties such as consistence, porosity, density, compressive and flexural strength, water droplet absorption, capillary absorption, drying rate, thermal conductivity and ultrasonic pulse velocity of the bioformulated mortars were compared with a control cement mortar. The findings show that the bioproducts can be used as renewable and eco-friendly alternative to petrochemical-based polymer admixtures to lengthen mortar service life, even after storage. Sonicated bioproduct improved the water related mortar properties, while non-sonicated bioproduct developed higher mechanical properties. Contributing for a cleaner production of cementitious products, an original waste from chemical industry was transformed into a valuable raw material for use in the construction industry. publishersversion published

This research focuses on improving the quality of mixed and ceramic recycled aggregates by microbially induced carbonate precipitation ( Bacillus sphaericus ). The precipitation contributed to a weight increase and unleashed a waterproofing response. The roughness of the ceramic particles created a more uniform layer compared to natural or concrete particles. For the concrete fraction, which had a higher macroporosity, the consolidation effect was more pronounced. High ceramic content aggregates profited from a greater biodeposition, leading to a remaining amount of precipitates after sonication which was still greater than in cementitious materials. Pore-filling effect was detected by SEM, supporting the waterproofing result.

[ES] El impacto medioambiental ocasionado durante las últimas décadas por el sector de la construcción, ha fomentado su interés por el conocimiento y uso de los materiales reciclados. En el presente estudio se muestran las diferencias de comportamiento existentes entre un hormigón convencional y un hormigón reciclado (50% del árido grueso natural se ha sustituido por árido reciclado mixto) cuando estos son utilizados en el sector agroganadero. Este tipo de ambientes son muy exigentes con los materiales constructivos, ya que la presencia de ácidos orgánicos generados por los efluentes del material ensilado y las excreciones de los animales junto con la abrasión mecánica ejercida por la maquinaria y los propios animales, ocasionan un alto nivel de degradación. Empleando un equipo de ensayo de degradación acelerada implementado en la Universidad de Gante (Bélgica), se han sometido las probetas de hormigón a ciclos de degradación ácida en una mezcla de base acuosa donde se incorporan ácido láctico y ácido acético, con una concentración de 30g/l. Los resultados muestran como el hormigón reciclado presenta una mayor resistencia a los ataques ácidos y mecánicos que pueden darse en un ambiente ganadero, debido al efecto que ejerce el material cerámico sobre la red porosa del hormigón., Este artículo ha sido desarrollado gracias a la financiación del Ministerio de Economía y Competitividad a través del proyecto BIA2013-48876-C3-3-R, así como de la ayuda FPI BES-2011-047159 asociada al proyecto BIA2010-21194-C03-02. También a la financiación del Ministerio de Educación, Cultura y Deporte por la ayuda FPU AP2010- 0613. Finalmente, los autores agradecen la desinteresada participación de las empresas TEC-REC desde Madrid; ARD desde Amberes; y Bierzo Recicla desde Castilla y León.

The use of construction and demolition waste in concrete manufacture allows the concept of sustainability to be included in the construction industry and helps to alleviate both the large consumption of natural resources and the high generation of waste. The present research assesses first the suitability of two different mixed recycled aggregates as coarse aggregates for concrete according to the code on structural concrete (EHE-08), and subsequently evaluates the effect of their use as a partial (50%) replacement of natural coarse aggregate (gravel) on the mechanical properties (compressive strength, splitting-tensile strength, flexural strength, stress–strain curves and modulus of elasticity) in concrete mixes of 25 MPa strength grade. The secondary material characterisation shows that, although presenting promising properties in terms of granulometry, particle size, density and shape, the recycled aggregates should be pretreated in order to comply with the quality of fines and water absorption, and their resistance to fragmentation limits their application in concrete mixes with a strength grade below 30 MPa. Regarding the results of the tests performed on the hardened concrete, the values obtained suggest that the use of mixed recycled aggregates is feasible, but at the expense of minor losses of the mechanical characteristics.

The manufacture of any kind of product inevitably entails the production of waste. The quantity of waste generated by the ceramic industry, a very important sector in Spain, is between 5% and 8% of the final output and it is therefore necessary to find an effective waste recovery method. The aim of the study reported in the present article was to seek a sustainable means of managing waste from the ceramic industry through the incorporation of this type of waste in the total replacement of conventional aggregate (gravel) used in structural concrete. Having verified that the recycled ceramic aggregates met all the technical requirements imposed by current Spanish legislation, established in the Code on Structural Concrete (EHE-08), then it is prepared a control concrete mix and the recycled concrete mix using 100% recycled ceramic aggregate instead of coarse natural aggregate. The concretes obtained were subjected to the appropriate tests in order to conduct a comparison of their mechanical properties. The results show that the concretes made using ceramic sanitary ware aggregate possessed the same mechanical properties as those made with conventional aggregate. It is therefore possible to conclude that the reuse of recycled ceramic aggregate to produce recycled concrete is a feasible alternative for the sustainable management of this waste.

The replacement of natural aggregates by recycled aggregates in the concrete manufacturing has been spreading worldwide as a recycling method to counteract the large amount of construction and demolition waste. Although legislation in this field is still not well developed, many investigations demonstrate the possibilities of success of this trend given that concrete with satisfactory mechanical and durability properties could be achieved. However, recycled aggregates present a low quality compared to natural aggregates, the water absorption being their main drawback. When used untreated in concrete mix, the recycled aggregate absorb part of the water initially calculated for the cement hydration, which will adversely affect some characteristics of the recycled concrete. This article seeks to demonstrate that the technique of pre-saturation is able to solve the aforementioned problem. In order to do so, the water absorption of the aggregates was tested to determine the necessary period of soaking to bring the recycled aggregates into a state of suitable humidity for their incorporation into the mixture. Moreover, several concrete mixes were made with different replacement percentages of natural aggregate and various periods of pre-saturation. The consistency and compressive strength of the concrete mixes were tested to verify the feasibility of the proposed technique.

The use of recycled aggregate to produce new concretes has become increasingly widespread, and numerous studies have demonstrated that the final product performs similarly to traditional concrete. However, construction and demolition waste (CDW) presents certain characteristics which could limit its acceptance in the construction sector due to worse performance than natural aggregates. One example of this is water absorption, which in recycled aggregates reaches such high values that the amount of free water calculated for mixing the concrete is affected, consequently impacting on the concrete's properties, especially consistency. This paper reports the possibility of solving this problem with a simple and inexpensive method; pre-saturation of recycled aggregates prior to adding them to the mix. The results of two different pre-treatments are compared; one consisted of immersing the aggregates in water for 10 minutes and the other, in addition to the above procedure, included a brief period of air drying and subsequent elimination of surface water from the aggregate. Both pre-treatments were found to solve the problem of consistency.

When recycled aggregates are used appropriately, it is possible to obtain good quality, economic and environmentally friendly building materials. The emergence in recent years of the use of recycled materials in the construction industry, specifically in the production of concrete, has met with varying degrees of success due to the barriers that the market for recycled products has still to overcome. Scientific studies have focused on the good properties presented by the coarse fraction of construction and demolition waste (CDW), leading to the formulation of various international recommendations which, although still insufficient, provide a stimulus to the use of recycled aggregates in concrete.

The construction sector comprises a number of activities that may result in environmental impacts of considerable magnitude, waste generation being one of the major negative effects of this industry due to the large streams generated. Proper knowledge of the environmental problem caused by the sector is of great importance in order to achieve an effective waste management. Thus, this paper analyse the Spanish situation regarding construction and demolition waste (CDW) compared with other European Union countries; which sets out the current figures of the CDW scenario (legislation, generation, composition, treatment and market) as well as the difficulties encountered when handling this residue.