The foundry industry generates large amounts of spent foundry sands, which are stored, available for recovery in other industrial sectors but unfortunately poorly exploited. Different authors have studied the possibility of recovering them in concretes, which would also allow production of more sustainable cementitious materials. The variability of their results highlights the importance of a better understanding of the potential influential parameters of the by-products. Unfortunately, exhaustive characterizations of the materials are rarely performed, especially for chemically bound foundry sands. This article presents a case study for the recovery of a spent chemical foundry sand with an exhaustive physicochemical characterization of the by-product and an analysis of its influence on the workability and mechanical strengths of cementitious materials. The tests recommended by the European standard for aggregates for concrete confirmed the suitability of the by-product. Associated with additional chemical tests (scanning electron microscopy, X-ray fluorescence, X-ray diffraction, etc.) as well as metallic particles characterization, they highlighted possible influential parameters. The workability and mechanical resistance tests carried out on mortars and concretes confirmed the influence of the fineness of the by-product associated with other parameters. Its use at a substitution rate of 30% results in a strength class C 30/37 concrete.

Matériaux & Techniques, la revue des matériaux industriels et de leurs techniques de mise en oeuvre

In this paper, supplementary cementitious materials are used as a substitute for cement to decrease carbon dioxide emissions. A by-product of the iron manufacturing industry, ground granulated blast-furnace slag (GGBS), known to improve some performance characteristics of concrete, is used as an effective cement replacement to manufacture mortar samples. Here, the influence of curing conditions on the durability of samples including various amounts of GGBS is investigated experimentally and numerically. Twelve high-strength Portland cement CEM I 52.5 N samples were prepared, in which 0%, 45%, 60%, and 80% of cement were substituted by GGBS. In addition, three curing conditions (standard, dry, and cold curing) were applied to the samples. Durability aspects were studied through porosity, permeability, and water absorption. Experimental results indicate that samples cured in standard conditions gave the best performance in comparison to other curing conditions. Furthermore, samples incorporating $45\%$ of GGBS have superior durability properties. Permeability and water absorption were improved by $17\%$ and $18\%$, respectively, compared to the reference sample. Thereafter, data from capillary suction experiments were used to numerically determine the hydraulic properties based on a Bayesian inversion approach, namely the Markov Chain Monte Carlo method. Finally, the developed numerical model accurately estimates the hydraulic characteristics of mortar samples and greatly matches the measured water inflow over time through the samples.

This study will investigate the effect of non-woven PET plastic tissue on the fresh, physical, mechanical, acoustic, thermal, and microstructural behaviors of concrete. Including reference specimens, non-woven fabrics were considered in two ways: (a) as a layer with four various configurations of 1-layer, 2-sides, 3-sides, and full wrapping (4-sides) to strengthen specimens, and (b) as (10 × 10) mm cut pieces with three different incorporated percentages of 0.25%, 0.50%, and 0.75%. Based on the experimental results, mechanical properties (compressive, split tensile, and flexural strengths) were remarkably improved by applying non-woven sheets as a layer. For instance, the cylindrical compressive and split tensile strengths were improved by 13.40% and 15.12% for the strengthened specimens compared to the reference specimens, respectively. Moreover, control specimens were damaged to many fragments after mechanical testing, but the samples strengthened by such fabrics or containing cut pieces were maintained and not separated into many small parts. The acoustic behavior and thermal conductivity declined by 9.83% and 19.67% with the attachment of tissue on one side and 2-sides, respectively. Acoustic behaviors decreased by 10.0%, 17.60%, and 26.30% and thermal conductivity decreased by 6.60%, 12.10%, and 15.50%, with the incorporation of 0.25%, 0.50%, and 0.75% of cut pieces, respectively. Finally, it was discovered that non-woven tissue is advised to enhance particular properties of concrete.

La corrosion des armatures est une pathologie fréquente des ouvrages du génie civil pour laquelle les moyens de lutte ne sont généralement pas satisfaisants sur le plan environnemental. L’objectif de cette étude est d’évaluer un adjuvant inhibiteur de corrosion dont le principe actif est un biopolymère écorespectueux aux propriétés inhibitrices de corrosion des aciers. Des échantillons ont été réalisés à partir de deux nuances cimentaires, le traditionnel CEM I et un CEM V, plus écorespectueux car contenant des résidus et sous-produits industriels. Des essais d’imbibition capillaire et de porosité totale à l’eau ont montré la faible influence de l’adjuvant aux biopolymères sur la structure poreuse des mortiers. Après immersion en eau de mer naturelle de pâtes de ciment renforcées d’une armature en acier C15, des mesures électrochimiques ont montré que ce biopolymère n’influence pas le potentiel libre de corrosion des armatures ni la composition de leur couche passive mais inhibe la réaction cathodique de réduction de l’oxygène. Rebars corrosion is a common pathology of civil engineering works for which the protective and curative solutions are generally not in agreement with environmental considerations. This study aims to evaluate a corrosion inhibitor admixture whose active component is an ecofriendly biopolymer having corrosion inhibiting properties. The samples were manufactured using 2 cement bases including a CEM V that is more ecofriendly than traditional CEM I because containing industrial residues and byproducts. Capillary imbibition tests and water total porosity showed the low influence of the admixture on the pore structure of mortars. After immersion in natural seawater of cement pastes reinforced with steel C15 rebars, electrochemical measurements showed that the biopolymer does not affect the free corrosion potential of reinforcement nor the composition of passive layer but inhibits the cathodic reaction of oxygen reduction.