Giacomo Moriconi

Recycling of rubble from building demolition for low-shrinkage concretes

In this project concrete mixtures were prepared that were characterized by low ductility due to desiccation by using debris from building demolition, which after a suitable treatment was used as aggregate for partial replacement of natural aggregates. The recycled aggregate used came from a recycling plant, in which rubble from building demolition was selected, crushed, cleaned, sieved, and graded. Such aggregates are known to be more porous as indicated by the Saturated Surface Dry (SSD) moisture content. The recycled concrete used as aggregates were added to the concrete mixture in order to study their influence on the fresh and hardened concrete properties. They were added either after water pre-soaking or in dry condition, in order to evaluate the influence of moisture in aggregates on the performance of concrete containing recycled aggregate. In particular, the effect of internal curing, due to the use of such aggregates, was studied. Concrete behavior due to desiccation under dehydration was studied by means of both drying shrinkage test and German angle test, through which shrinkage under the restrained condition of early age concrete can be evaluated.

Use of rubble from building demolition in mortars.

Because of increasing waste production and public concerns about the environment, it is desirable to recycle materials from building demolition. If suitably selected, ground, cleaned and sieved in appropriate industrial crushing plants, these materials can be profitably used in concrete. Nevertheless, the presence of masonry instead of concrete rubble is particularly detrimental to the mechanical performance and durability of recycled-aggregate concrete and the same negative effect is detectable when natural sand is replaced by fine recycled aggregate fraction. An alternative use of both masonry rubble and fine recycled material fraction could be in mortars. These could contain either recycled instead of natural sand or powder obtained by bricks crushing as partial cement substitution. In particular, attention is focused on the modification that takes place when either polypropylene or stainless steel fibers are added to these mortars. Polypropylene fibers are added in order to reduce shrinkage of mortars, stainless steel fibers for improving their flexural strength. The combined use of polypropylene fibers and fine recycled material from building demolition could allow the preparation of mortars showing good performance, in particular when coupled with bricks. Furthermore, the combined use of stainless steel fibers and mortars containing brick powder seems to be an effective way to guarantee a high flexural strength.

Environmentally-friendly mortars: a way to improve bond between mortar and brick

In order to find new application fields for either fine materials coming from building demolition or industrial byproducts, some mortars, in which fine recycled materials, obtained from a plant where rubble from building demolition are ground, are substituted to natural sand, were tested.Moreover, mortars containing either fly ash or ground brick powder as partial cement replacement were studied.Based on characterization results and performance evaluations, recycled-aggregate mortar seems to be superior in terms of mortar-brick bond strength, mainly because of its rheological properties.In addition, the use of fine recycled aggregate instead of natural sand is in accordance with the sustainable development concept, with recycling and reuse of building rubble playing a key role in meeting the need to complete the building life cycle.RésuméEn vue de trouver de nouveaux domaines d’application pour les déchets de démolition ou pour quelques sous-produits industriels, des mortiers ont été produits. C’est dans ceux-ci que, par rapport à un mortier traditionnel à base de ciment, on a étudié le remplacement du sable naturel par la fraction fine recyclée obtenue d’une installation de recyclage, dans laquelle les déchets de démolition sont concassés.En outre, on a étudié des mortiers contenant soit des cendres volantes, soit de la poudre de briques concassées au lieu du ciment. En les comparant selon les résultats de la caractérisation et selon l’évaluation des performances, les mortiers avec granulats recyclés semblent les meilleurs aux termes de la tension d’adhérence entre le mortier et la brique, due à ses propriétés rhéologiques.De plus, l’usage de la fraction fine des granulats recyclés au lieu du sable naturel correspond à la notion du développement soutenable et le recyclage et le réemploi des déchets de démolition jouent un rôle clé dans la fermeture du cycle de vie des bâtiments.

Tetracalcium aluminoferrite hydration in the presence of lime and gypsum

Abstract The influence of lime and/or gypsum on the C4AF hydration was examined and the results were compared with those obtained for the C3A hydration. Gypsum is more effective than CH in retarding the hydration of C4AF. Ettringite produced in the C4AF hydration in the presence of C S ·H2 seems to be more stable than that produced in the C3AC S ·H2H2 system. The consumption of gypsum, the transformation of ettringite into monosulfate and the hydration of C4AF in the C4AFC S ·H2H2O system are much slower than those in the C3AC S ·H2H2O system. The retardation of hydration of C4AF or C3A in the presence of C S ·H2 is further increased by the add i tion of CH.

Influence of gluconate, lignosulfonate or glucose on the C3A hydration in the presence of gypsum with or without lime

Abstract The influence of gluconate, lignosulfonate or glucose at 0.1–0.3% dosages on the C3A hydration in the presence of gypsum with or without lime has been examined. In the presence of lime all the admixtures at 0.3% dosage stabilize ettringite and retard its conversion to monosulfate; only 0.3% glucose retards gypsum consumption and ettringite production. In the absence of lime stabilization of ettringite by admixtures at 0.3% addition appears to be much less effective; no admixture is able to retard the ettringite production or gypsum disappearance. At 0.1% addition, the influence of admixtures seems to be negligible except when glucose is used in the presence of lime: in this case, the conversion of ettringite into monosulfate is retarded.

Thaumasite: evidence for incorrect intervention in masonry restoration

Abstract Thaumasite, as well as ettringite, are compounds which are increasingly found as deterioration products of cementitious materials subjected to sulfate attack. Thaumasite, and especially ettringite, have been abundantly reported in relation to concrete deterioration as well as, more recently, to the deterioration of cementitious mortars for masonry and for plasters. In particular, the problem appears serious in the field of repair of historical buildings, where the cementitious mortar can easily deteriorate just because of the formation of ettringite and thaumasite. However, although thaumasite is responsible for deterioration, in most cases, it may not be detected since it can be partially or almost completely removed by atmospheric agents. Many causes can be responsible for the presence of sulfates in masonry. At the same time, mortar and plaster are, in most cases, sources of calcium carbonate. Moreover, masonry is typically a porous material, which can be easily permeated by water, either rising groundwater or falling rainwater. Therefore, when cement based materials, which are in turn sources of calcium aluminates and calcium silicates, are used as binders, all of the ingredients necessary to cause thaumasite formation are present. Consequently, a compatibility issue emerges, which if not kept into proper account, will lead sooner or later to ineffective intervention.

Influence of lignosulphonate, glucose and gluconate on the C3A hydration

Abstract The influence of desugarized sodium lignosulphonate, glucose and sodium gluconate on the C 3 A hydration has been examined using DTG analysis. At relatively low concentration levels of admixtures in the aqueous phase (1 to 3 g/l), such as those practically used for concrete mixes, lignosulphonate and glucose retard only slightly the C 3 A hydration. Sodium gluconate is significantly more efficient in retarding C 3 A hydration than lignosulphonate and glucose.

Combined effect of lignosulfonate and carbonate on pure portland clinker compounds hydration. III. Hydration of tricalcium silicate alone and in the presence of tricalcium aluminate

Abstract The effect of sodium carbonate and/or sodium lignosulfonate on the hydration of C2S alone and in the presence of C3A has been examinated by DTG and TG curves and by zeta potential measurements. The combined addition of sodium carbonate and lignosulfonate retards the C2S hydration to a lower extent than that observed for the C3S hydration. The retarding effect on the C2S hydration is significantly lower in the presence of 20% C3A. On the other hand, the early C3A hydration is completely blocked by admixtures simultaneously added. Addition of 0.9% sodium carbonate without lignosulfonate blocks the early hydration of both C3A and C2S. This effect was not found in the C3SC3A system.

Particle size, size distribution and morphological evaluation of glass fiber reinforced plastic (GRP) industrial by-product

The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management.

DSP cement composites for electromagnetic shielding: practice and experimental analysis

In this work, the shielding effectiveness (SE) of a densified-small-particles (DSP) cement composite, with different loading particles embedded in, has been investigated through the nested reverberation chamber facility. Particular effort has been spent in characterizing the SE behavior with the increasing drying and in improving the experimental practice to solve out previously faced measurement troubles. Findings are of interest in architectural shielding, microwave spectroscopy and investigation of physical-chemical properties of DSP materials.