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

Abstract

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: PDF

Finite Element Multi-Physics Analysis and Experimental Testing for Hollow Brick Solutions with Lightweight and Eco-Sustainable Cement Mix

“…Specifically, the mix design incorporated fine and coarse polymer aggregates in equal proportion (50% v/v RP-50% v/v RG). Such selected GWTR dosage was determined as "optimum" in previous research works conducted by the authors, where the influence of the tire aggregate size on the physical, mechanical, and microstructural performances of 3D printable cement [29,30] mixes and rubberized alkali-activated composites [31] was investigated in detail.…”

Novel cement-based sandwich composites engineered with ground waste tire rubber: design, production, and preliminary results

“…The acoustic insulation performance was evaluated experimentally by means of a custom-made impedance tube [8,27], following the test configuration illustrated in Fig. 6.…”

“…8d). The influence of the GWTR size gradation on the interface properties in cementitious composites was extensively addressed in many studies [23,27,33]. According to them, the finer the polymeric fraction the better the rubber-cement interfacial adhesion, resulting from the rough micromorphology and greater specific surface area exhibited by the fine rubber particles which promotes a more efficient mechanical gripping.…”

Prospect and barrier of 3D concrete: a systematic review

“…Sambucci and Valente [57] reported improvement in the print quality of the mixes containing tyre rubber particles as coarse and fine aggregate over the plain mortar in terms of inter-layer adhesion and mechanical isotropy of the hardened material. The particle size of rubber particles influenced in modulating the physical-mechanical behaviour of the printer materials.…”