Caracterização de massa de terra crua para extrusão em impressora 3D

Abstract

3D printing by raw earth extrusion for the construction industry is emerging as a technology with the potential to reduce environmental impacts by using natural materials and decreasing the consumption of industrialized inputs. Therefore, this study aims to characterize natural soils for the formulation of raw earth mixtures suitable for application in extrusion-based 3D printing processes. The soils were collected in the city of Crateús, Ceará, Brazil, and analyzed individually and in combination at different proportions. Granulometric characterization tests and plasticity analyses were performed. The results revealed distinct behaviors between the analyzed soils. Soil A exhibited a clayey character, with approximately 29.9% clay and 12.4% silt, a liquid limit of 42%, and a plasticity index of 16%. Soil B showed predominantly sandy behavior, with 48.7% sand, low fines content (8.4% clay and 7.6% silt), a liquid limit of 16%, and no plasticity. The combination of the two materials resulted in a mixture composed of 35% clayey soil and 65% sandy soil. The final mixture presented 45.3% sand, 18% clay, and 11.8% silt, with a liquid limit of 25% and a plasticity index of 9%, values within the ranges recommended in the literature and compatible with extrusion process requirements. The consistency test of the mixture showed a spread diameter of 17.96 cm, placing the material within an intermediate consistency range and indicating a balance between deformability and dimensional stability. In the extrusion test, the material enabled the formation of continuous filaments, with the best geometric performance observed using the 24 mm nozzle. Compressive strength tests yielded values of 1.62 MPa at 7 days and 1.83 MPa at 28 days, which is characteristic of raw earth-based materials that exhibit limited mechanical strength. The study contributes to the understanding of the use of natural soils in additive manufacturing, highlighting the potential of raw earth as a sustainable construction alternative and providing technical support for the development of mixtures suitable for this technology.