Extrusion-based additive manufacturing of concrete products. Revolutionizing and remodeling the construction industry

Additive manufacturing is one of the main topics of the fourth industrial revolution; defined as Industry 4.0. This technology offers several advantages related to the construction and architectural sectors; such as economic; environmental; social; and engineering benefits. The usage of concrete in additive technologies allows the development of innovative applications and complexity design in the world of construction such as buildings; housing modules; bridges; and urban and domestic furniture elements. The aim of this review was to show in detail a general panoramic of extrusion-based additive processes in the construction sector; the main advantages of using additive manufacturing with the respect to traditional manufacturing; the fundamental requirements of 3D printable material (fresh and hardened properties), and state-of-the-art aesthetic and architectural projects with functional properties

La triste parabola dell'autonomia contabile degli enti territoriali. Se la Corte costituzionale decide sugli stanziamenti di bilancio

Prendendo spunto dalla importante produzione legislativa che negli ultimi anni ha inciso profondamente il sistema finanziario, con l’introduzione di principi generali di forte impatto - ad esempio, la formalizzazione costituzionale del principio di equilibrio di bilancio, con la riforma dell’art. 81 e la modifica dell’art. 97 Cost. - ma anche con la disciplina minuziosa, da parte del legislatore statale, della contabilità degli enti autonomi (regioni ed enti locali), il lavoro di approfondimento scientifico, da un lato, evidenzia la valorizzazione ordinamentale degli istituti della finanza e della contabilità pubblica, i quali trovano evoluzione fino a vedere riconosciuta la centralità del bilancio (dei documenti di bilancio, attraverso cui si realizza la decisione di economia e finanza) quale strumento fondamentale dell’azione di finanza pubblica e dell’amministrazione finanziaria, quale strumento di raccordo tra la finanza statale e la finanza europea, quale elemento essenziale e finanche condizionante il principio di buon andamento della pubblica amministrazione (di cui all’art. 97 Cost.). Sotto altro aspetto, lo studio osserva criticamente l’azione del legislatore statale volta – sulla base di una interpretazione eccessivamente estensiva, e non sempre convincente, dei valori costituzionali di armonizzazione dei bilanci pubblici e di coordinamento della finanza pubblica - a disciplinare in modo pervasivo (ultra regolamentare) il sistema contabile delle regioni e degli enti locali, e ne evidenzia: da un lato, la difficile compatibilità con i principi autonomistici stabiliti in Costituzione; e, da altro lato, la problematica congruenza con l’impostazione generale, come detto, valorizzativa del bilancio e degli strumenti di decisione finanziaria. I quali, negli enti territoriali, subiscono ridimensione nella disciplina legislativa stabilita dallo Stato e conoscono (segnatamente, i bilanci delle regioni) interventi anche profondamente incisivi da parte della Corte costituzionale, la quale, in particolare sulle questioni che investono profili finanziari, si mostra incline ad assecondare la tendenza espansiva del legislatore statale. La ricerca analizza, inoltre, le elaborazioni della giurisprudenza costituzionale, rimarcandone i profili di carattere evolutivo (pur rilevando gli aspetti non sempre condivisibili delle ricostruzioni giurisprudenziali); e, comunque, evidenzia il ruolo della Corte costituzionale quale organo di “controllo” e di garanzia degli equilibri di bilancio

Coordinamento finanziario e autonomie. I problemi che la riforma costituzionale non risolveva

Il lavoro approfondisce l'impatto della proposta di riforma costituzionale (respinta in seguito all'esito negativo del referendum del dicembre 2016) sugli assetti finanziari pubblici definiti in Costituzione. Richiamati i più recenti momenti di evoluzione legislativa che hanno riguardato il sistema di finanza pubblica, e, in particolare, l'assetto contabile pubblico, l'approfondimento scientifico si concentra sulla interpretazione del principio costituzionale di coordinamento della finanza pubblica, alla luce delle disposizioni legislative e delle posizioni della giurisprudenza costituzionale; e si sofferma sull'impatto della impostazione interpretativa prevalente nell'ordinamento sul sistema delle autonomie definito in Costituzione

Influence of Waste Tire Rubber Particles Size on the Microstructural, Mechanical, and Acoustic Insulation Properties of 3D-Printable Cement Mortars

3D printing technologies of construction materials are gaining ground in the building industry. As well documented in the literature, these advanced manufacturing methodologies aim to reduce work-related injuries and materials waste, enhancing architectural flexibility which would enable more sophisticated designs for engineering and aesthetic purposes. In this framework, the development of functional and eco-sustainable printable materials represents an extremely attractive challenge for research, promoting digital fabrication to reach its maximum cost-effective and technological potentials. The use of recycled tire rubber particles in 3D printable Portland-based compounds is an exclusive contribution in this field. This line of research aims to integrate the well-known engineering performances of rubber-cement materials with the advanced peculiarities of additive manufacturing methodologies. As an innovative contribution, the authors propose here a detailed study on the possible relationship between rubber particle size and technological properties of the 3D printable mix. Specifically, two groups of continuous size grading polymer aggregates (0-1 mm rubber powder and 1-3 mm rubber granules as fine and coarse fractions, respectively) were analyzed in terms of impact on rheology, print quality, microstructure, mechanical properties, and acoustic insulation performance. Concerning the print quality, rubber aggregates altered the fluidity of the fresh mix, improving the adhesion between the printed layers and therefore enhancing the mechanical isotropy in the post-hardening sample. A remarkable influence of the rubber gradation on the compounds’ behaviour was found in hardened properties. By comparing the rubberized compounds, the fine polymer fraction shows greater interfacial cohesion with the cement paste. However, more significant mechanical strength loss was found due to a greater reduction in density and increased porosity degree. On the other hand, mortars doped with larger rubber particles tend to have a higher unit weight, finest pore distribution, minor mechanical strength drop, and higher ductility but worse interface binding with the matrix. Regarding the acoustic insulation properties, a proper balance between rubber powder and granules in the mixes allows to obtain comparable/superior performance compared to plain mortar but the effect of the aggregate size is strongly dependent on the sound frequency range investigated. Future findings revolve around applicability studies of these formulations in civil and architectural fields, benefiting from the design flexibility of 3D printing. Doi: 10.28991/cej-2021-03091701 Full Text: PD

Thermal insulation performance optimization of hollow bricks made up of 3D printable rubber-cement mortars. Material properties and FEM-based modelling

Sustainable construction is attracting more attention lately. It involves the design of eco-friendly building structures, the reduction of energy consumption and waste, the use of renewable and recyclable resources, and the enhancement of low-impact manufacturing methods. This paper addresses some of these sustainability questions, in the context of the use of tire recycled rubber particles as aggregates of cement mortars suitable for Additive Manufacturing (AM) processes. Specifically, the effect of rubber aggregates on physical and thermal properties was investigated, to evaluate the heat-insulating performance of the compounds. The lightweight and non-polar nature of rubber improve the thermal insulation and physical-structural properties of the material, in terms of thermal conductivity, unit weight, and porosity respectively. However, these effects are closely related to the particle size and their adhesion with the cement matrix. In the second part of the manuscript, applicability study of rubber-cement compounds based on the design and finite element method (FEM)-based thermal analysis of innovative hollow bricks is presented. Fractal cavities were investigated as a functional inner architecture to improve the thermal behavior of the component. FEM results show an increase of more than 30% in thermal resistance (RT) for fractal-based brick compared to conventional designs, demonstrating that the holes' geometric irregularity is a key feature in the thermal flow attenuation

Aerogel technology for thermal insulation of cryogenic tanks. Numerical analysis for comparison with traditional insulating materials

The traditional choice of insulation material for liquefied natural gas (LNG) transportation with cryogenic tankers is the back-filled perlite-based system. However, aiming to further cut down the insulation cost, spare additional arrangement space, and provide safety in installation and maintenance, the requirement of looking for alternative materials still exists. Fiber-reinforced aerogel blankets (FRABs) could represent good candidates in designing insulation layers for LNG cryogenic storage because of their ability to ensure adequate thermal performance without the need to create deep vacuum conditions in the annular space of the tank. In this work, a finite element method (FEM) model was developed to study the thermal insulation performance of a commercial FRAB (Cryogel ® Z) for application in cryogenic storage/transport LNG tanks, comparing it with the performance of traditional perlite-based systems. Within the reliability limits of the computational model, the analysis proved that FRAB insulation technology gave encouraging results and might be potentially scalable for transporting cryogenic liquid. In addition to demonstrating superior performance in terms of thermal insulating efficiency and boil-off rate over the perlite-based system, as far as a perspective of cost savings and space gain, FRAB technology allows for higher levels of insulation without vacuum and with lower thickness of the outer shell, which is therefore beneficial for storing more material and lightening the weight of the LNG transportation semitrailer

Zeolite-Clinoptilolite conditioning for improved heavy metals ions removal: a preliminary assessment

The emerging problem of nickel allergy is increasingly widespread due to the increase in nickel content in everyday foods. The physicochemical structure of the zeolites makes it possible to adsorb nickel ions in solution. The properties of molecular sieves, together with those of a size and a chemical composition compatible with the human gastrointestinal tract, are present in a particular zeolite called clinoptilolite. In this work, a type of natural clinoptilolite was characterized before and after being subjected to two different conditioning processes with NaCl to increase its adsorption efficiency and specificity against nickel. The three forms of clinoptilolite, natural, conditioned, and biconditioned, were compared based on analysis of absolute density, X-ray diffraction pattern, granulometry, porosity, chemical composition, and grain morphology. Finally, nickel ion removal tests were performed in an aqueous solution that simulates the conditions of the gastrointestinal tract. The Ni2+ removal efficiency of natural clinoptilolite is 73.2%, while after conditioning it reaches 96.6%. Double conditioning with Na does not generate a considerable increase in removal efficiency which remains at 96.8

Tire recycled rubber for more eco-sustainable advanced cementitious aggregate

This research focused on using ground tire rubber (GTR) with different grain sizes as a replacement for the mineral aggregates used in a cement-based mixture suitable for extrusion-based Additive Manufacturing. The use of two types of GTR particles and the possibility to apply rubberized mixtures in advanced manufacturing technologies are the innovative aspects of this work. At the base of this strategy is the possibility of achieving cementitious aggregates, which would potentially be improved regarding some technological-engineering requirements (lightness, thermal-acoustic insulation, energy dissipation capacity, durability) and environmentally sustainable. The integration of waste tires into cement-based materials is a promising solution for the reuse and recycling of such industrial waste. In addition, this approach may involve a considerable reduction in the use of natural resources (sand, water, coarse mineral aggregates) needed for the building materials production. The purpose of the research was to investigate the effect of sand-GTR replacement on certain chemical-physical properties of mixtures (permeable porosity, surface wetness, and water sorptivity), closely related to material durability. Besides, the role of rubber on the printability properties of the fresh material was evaluated. GTR fillers do not alter the rheological properties of the cement material, which was properly extruded with better print quality than the reference mixture. Concerning chemical-physical characterization, the GTR powder-granules synergy promotes good compaction of the mixture, hinders the cracks propagation in the cement matrix, decreases the permeable porosity, improves the surface hydrophobicity and preserves optimal water permeabilit

Recent advances in Geopolymer technology. A potential eco-friendly solution in the construction materials industry. A review

In the last ten years, the Portland cement industry has received wide criticism due to its related high embodied energy and carbon dioxide footprint. Recently, numerous “clean” strategies and solutions were developed. Among these, geopolymer technology is gaining growing interest as a functional way to design more eco-friendly construction materials and for waste management issues suffered by various industries. Previous research has highlighted the attractive engineering properties of geopolymeric materials, especially in terms of mechanical properties and durability, resulting in even higher performance than ordinary concrete. This review provides a comprehensive analysis of current state-of-the-art and implementations on geopolymer concrete materials, investigating how the key process factors (such as raw materials, synthesis regime, alkali concentration, water dosage, and reinforcement fillers) affect the rheological, microstructural, durability, and mechanical properties. Finally, the paper elucidates some noteworthy aspects for future research development: innovative geopolymer-based formulations (including alkali-activated blends for additive manufacturing and thermo-acoustic insulating cellular compounds), concrete applications successfully scaled in the civil-architectural fields, and the perspective directions of geopolymer technology in terms of commercialization and large-scale diffusion

Corte cost. (ord.) 8 febbraio 2019, n. 17: il difficile equilibrio tra esigenze di tempestività della decisione di bilancio e garanzia delle attribuzioni parlamentari

Il lavoro analizza le statuizioni di Corte cost. (ord.) 8 febbraio 2019, n. 17 ed il loro impatto sul sistema di bilancio e sul procedimento legislativo della legge di bilancio; rilevando alcuni profili di criticità della decisione e soffermandosi, tra l'altro, sull'esercizio provvisorio del bilancio quale rimedio (a carattere eccezionale) apprestato in Costituzione