Improving properties of recycled concrete aggregates by accelerated carbonation

peer reviewedDesign of concrete with recycled concrete aggregates by means of Packing Density Metho

Rapport scientifique et technique final - Partenaire ULiège-GeMMe

Dans ce rapport final, nous avons choisi de présenter les résultats en fonction des produits testés (et non des tâches). Les travaux de recherche présentés dans ce rapport sont exposés en trois chapitres : 1. le premier chapitre traite des cendres volantes de charbon et des cendres volantes de biomasse ; 2. le deuxième chapitre décrit les travaux de recherche réalisés sur les granulats recyclés de béton, notamment en combinaison avec des fillers calcaires pour la formulation de bétons ; 3. le troisième chapitre porte sur la caractérisation des granulats recyclés de mâchefers d’incinérateur d’ordures ménagères (MIOM) et sur la formulation de bétons

Une nouvelle méthode de caractérisation des granulats recyclés industriels: application aux mortiers et bétons

editorial reviewedUne méthode permettant de quantifier la teneur en pâte de ciment durcie dans les granulats recyclés (GR) est présentée. Cette méthode est basée sur la mesure de la fraction soluble des GR dans l’acide salicylique (FSAS). La FSAS est mesurée pour quatre classes granulaires croissantes sur des sables recyclés produits dans différentes plateformes de concassage. Pour les granulats recyclés testés, la FSAS varie de manière quasi linéaire en fonction de la classe granulaire. Une méthode basée sur l’utilisation de la relation FSAS/absorption d’eau est proposée, permettant de déterminer précisément le coefficient d’absorption d’eau de la fraction 0/0,63mm des granulats recyclés. Ensuite, deux séries de mortiers sont réalisées avec l’un des granulats recyclés étudiés précédemment. La série A est utilisée pour étudier l'influence des proportions de sable recyclé sur les propriétés des mortiers. La série B permet d'étudier l'influence de chaque fraction granulaire de sable recyclé sur les propriétés des mortiers. Dans toutes les séries étudiées, le sable naturel calcaire est partiellement ou totalement remplacé par le même volume de sable recyclé. Les résultats montrent que la résistance à la compression des mortiers diminue quasi linéairement quand le pourcentage de remplacement du sable recyclé augmente. En outre, il est démontré que la fraction la plus fine du sable recyclé (0/0,63mm) a l’effet le plus pénalisant sur les propriétés mécaniques des mortiers

State of the art on recycling techniques for the production of recycled sands and aggregates from construction and demolition wastes

Construction and demolition wastes (C&DW) are estimated at one third of total wastes generated in the European Union (EU) and represent the main flux in volume. These wastes can be recycled in suitable recycling facilities which include a series of techniques able to crush and sort materials to finally produce recycled sands and aggregates with required properties. Common sorting techniques consist in ferrous metal sorting, hand-picking sorting and washing or air shifting sorting. Crushing is usually carried out by an impact or a jaw crusher and less frequently by a cone crusher. A combination of different crushers is also common for stationary recycling plants. In order to continuously improve the quality of the produced recycled materials, results obtained from innovative recycling techniques are also increasingly documented in literature. Some of the main innovative techniques related to C&DW recycling purposes are introduced in the study

Performance and durability of self-compacting mortar with recycled sand from crushed brick

peer reviewedThe demolition of brick masonry structures and the rejected non-conform bricks are generating a great volume of brick residues. The use of recycled sand from brick residues in the production of mortar could decrease the amount of waste going into landfills and reduce the consumption of natural resources. This paper investigated the feasibility of using recycled sand from crushed brick (RBS) in the self-compacting mortar (SCM). The crushed limestone sand was partially replaced with RBS at different levels (0, 5, 10, 25 and 50%). The properties at fresh state, mechanical behavoir, drying shrinkage and durability of SCM were discussed. As the substitution of limestone sand by RBS increased, the compressive strength of mortars slightly reduced at the age of 28 days (3.3% and 16.9% lower than the reference mortar, respectively for 25% RBS and 50% RBS content); however, which is within the compressive strength requirement in European standard EN 998-2 for masonry mortars. The incorporation of RBS in SCM showed better resistance to chloride diffusion, whereas more attention should be paid to carbonation and sulphate attack. The results indicate that it is possible to manufacture SCM by partially replacing the crushed limestone sand with RBS up to 25% replacement level.ECOLISER - ÉCOliants pour traitement de Sols, Etanchéité et Routes

SeRaMCo Final Conference : Influence of the wet process on the quality of recycled aggregates

SeRaMCo : Secondary Raw Materials for Concrete Precast Product

Recycling fine particles from construction and demolition wastes: characterization and effects on concrete perfromances

Recycling construction and demolition wastes induce the production of coarse aggregates, quite easily valorized in road foundations and concretes but also fine and very fine particles which are characterized by high water absorption level. The fine particles are very often rejected as they are containing polluting materials or because of their fineness and shape. This paper tends to show different ways of using Recycled Fine Aggregates (RFA).Integrative solutions for the valorization of CDW for transborder circular economy - Design and manufacture of customized 3D printed urban furniture using recycled sand - Secondary Raw Materials for Concrete Precast Products (introducing new products, applying the circular economy

Report of RILEM TC 281-CCC: outcomes of a round robin on the resistance to accelerated carbonation of Portland, Portland-fly ash and blast-furnace blended cements

Many (inter)national standards exist to evaluate the resistance of mortar and concrete to carbonation. When a carbonation coefficient is used for performance comparison of mixtures or service life prediction, the applied boundary conditions during curing, preconditioning and carbonation play a crucial role, specifically when using latent hydraulic or pozzolanic supplementary cementitious materials (SCMs). An extensive interlaboratory test (ILT) with twenty two participating laboratories was set up in the framework of RILEM TC 281-CCC ‘Carbonation of Concrete with SCMs’. The carbonation depths and coefficients determined by following several (inter)national standards for three cement types (CEM I, CEM II/B-V, CEM III/B) both on mortar and concrete scale were statistically compared. The outcomes of this study showed that the carbonation rate based on the carbonation depths after 91 days exposure, compared to 56 days or less exposure duration, best approximates the slope of the linear regression and those 91 days carbonation depths can therefore be considered as a good estimate of the potential resistance to carbonation. All standards evaluated in this study ranked the three cement types in the same order of carbonation resistance. Unfortunately, large variations within and between laboratories complicate to draw clear conclusions regarding the effect of sample pre-conditioning and carbonation exposure conditions on the carbonation performance of the specimens tested. Nevertheless, it was identified that fresh and hardened state properties alone cannot be used to infer carbonation resistance of the mortars or concretes tested. It was also found that sealed curing results in larger carbonation depths compared to water curing. However, when water curing was reduced from 28 to 3 or 7 days, higher carbonation depths compared to sealed curing were observed. This increase is more pronounced for CEM I compared to CEM III mixes. The variation between laboratories is larger than the potential effect of raising the CO concentration from 1 to 4%. Finally, concrete, for which the aggregate-to-cement factor was increased by 1.79 in comparison with mortar, had a carbonation coefficient 1.18 times the one of mortar

Valorisation des sables de béton recyclé pour la fabrication de mortiers

Very large quantities of construction and demolition wastes and especially concrete wastes are produced yearly. At the same time, high amounts of natural aggregates are needed for construction industry. Up to now, only a small fraction of these concrete wastes is re-used as recycled concrete aggregates (RCA) for the manufacture of concrete. RCA are composed of an intimate mix between aggregates and hardened cement paste (HCP). Hardened cement paste is much more porous than the natural aggregates and the properties and proportions of HCP largely influence the properties of RCA. As a consequence, the fine fraction of RCA (FRCA), essentially composed of mortar and cement paste, possesses a large water demand which makes it harder to recycle into concrete. The objective of this research was to better understand the role played by HCP on the properties of RCA in relation with the improvement of the characterization methods of these materials and their reuse in the manufacture of mortar or concrete. Firstly, an experimental method based on salicylic acid attack of RCA allowed us to determine a soluble fraction in salicylic acid (SFSA) that is related to the HCP content. FRCA properties were then studied as a function of SFSA, particle sizes and properties/composition of the original concrete. From the obtained relationship between water absorption and SFSA, the water absorption coefficient of the smaller fraction (0/0.63mm) was estimated as it is not accurately measured with the standard methods. Secondly, different industrial RCA were characterized which allowed us to expand the preceding conclusions to “real RCA”, meanwhile, the influence of carbonation on the properties of FRCA was also carried out. Finally, the influence of the saturation state of FRCA on the properties of fresh and hardened mortars and on their microstructure was explored. The recycled mortars with dried FRCA had better compressive strength than that made with saturated FRCA, which was confirmed by the study of ITZ properties. The mechanical properties of mortars with different RCA content and replacement fraction were determined. The finer fraction of RCA had a worse influence on the mechanical properties of RAC than the coarser fraction