Contribuição para a dosagem de argamassas sustentáveis para impressão 3D : uso de fíler calcário

Abstract

3D printing with cementitious materials has emerged as a promising technology in the construction industry, particularly due to its potential to reduce waste, streamline processes, and expand geometric design freedom. However, it still faces challenges related to the development of mortars that simultaneously achieve extrudability, dimensional stability, mechanical performance, and sustainability—especially given the high cement consumption involved. In this context, this study aimed to contribute to the mix design of sustainable mortars for 3D printing through the incorporation of limestone filler as a fine plasticizing material, with the goal of reducing cement consumption without compromising technical performance. Specifically, the study sought to: experimentally validate a mix design method for extrudable mortars; evaluate the influence of limestone filler content and sand fraction on volumetric structure and properties in both fresh and hardened states; compare the performance and differences resulting from the use of calcitic and dolomitic fillers; investigate the effects of progressively increasing filler content in optimized compositions; and finally, refine technically viable mixtures for 3D printing applications. The methodology was structured into four sequential experimental programs. In Program 1, initial formulations were developed based on Selmo’s (1989) mix design method, adapted to the requirements of additive manufacturing. In Program 2, the compositions were validated through mechanical testing and dimensional stability analysis. In Program 3, the influence of limestone filler content on mixture properties was investigated. In Program 4, mixture optimization was carried out, with integrated evaluation in both fresh and hardened states. The results demonstrated that the mixtures exhibited suitable behavior for extrusion and geometric stability compatible with the successive deposition of layers. In terms of mechanical performance, a significant increase in strength over time was observed, reaching flexural tensile strengths of up to 11.74 MPa and compressive strengths of up to 39.2 MPa at 28 days in the optimized compositions. Increasing the limestone filler content improved the behavior and cohesion of the mixtures, contributing to layer stability and reducing defects such as segregation and bleeding. On the other hand, a reduction in mechanical strength was observed with increasing filler content, varying according to the type of limestone and aggregate fraction. Overall, the incorporation of fine materials enhanced particle packing and water retention, improving the overall performance of the mortars. It can be concluded that the proposed methodology is effective for developing mortars for 3D printing, allowing control over properties in both fresh and hardened states. The use of limestone filler proved to be technically viable, contributing to mixture performance and reducing cement consumption, thus representing a promising alternative for additive manufacturing applications in the construction industry.