Investigating the Influence of Superplasticizer and Umbrella Grass (Cyperus alternifolius) Fiber on the Fresh and Hardened Properties of 3D-Printable Mortar
Benedictus Sonny Yoedono (a*), Dionysius Joseph Djoko Herry Santjojo (b), Istiroyah (b), Masruroh (b)

a) Doctoral Program in the Department of Physics, Faculty of Mathematics and Natural Science, Brawijaya University, Malang, Indonesia
*sonny_yoedono[at]student.ub.ac.id

b) Department of Physics, Faculty of Mathematics and Natural Science, Brawijaya University, Malang, Indonesia

Abstract

Three-dimensional printable concrete (3DPC) is a revolutionary digital construction technology that enables complex geometries to be fabricated without formwork in an automated process. This significantly reduces labor, material waste, and construction time while further enhancing precision and sustainability [1, 2]. Among the key challenges in 3DPC is balancing rheological parameters: flowability, extrudability, and buildability for achieving an optimum between print quality and structural integrity [3]. The addition of various synthetic and natural fibers to concrete improves its tensile strength, flexural strength, and durability. Moreover, incorporating fibers helps reduce shrinkage cracking in concrete [4]. Among the numerous natural fibers, umbrella grass (Cyperus alternifolius) fiber displays a promising profile considering renewability, low cost, and high cellulose content that enhances fiber-matrix bonding, thus potentially enhancing post-cracking performance. The potential of using umbrella grass fiber in 3D printable mortar has rarely been explored. This paper therefore discusses the influence of superplasticizer dosage and umbrella grass fiber content on fresh and hardened properties in 3D printing mortar. The targeted properties - flowability and compressive strength - were tested at four levels of SP (0, 0.15, 0.30, and 0.45) combined with four levels of fiber content (0, 0.1, 0.3, and 0.5). The combined influence of superplasticizer (SP) and umbrella grass fiber plays a critical role in governing the flowability and compressive performance of 3D-printable mortar. An optimal balance is achieved with an SP dosage of 0.15 and fiber content of 0.1-0.3%, yielding a flowability of 65-75% and a compressive strength of approximately 38 MPa-conditions that support both smooth extrusion and adequate structural capacity. The relationship between flowability and strength is distinctly nonlinear: moderate SP enhances workability, whereas excessive amounts (>0.30) lead to instability and segregation- similarly, fiber addition improves strength only up to a threshold, beyond which it increases mixture stiffness. At the material level, SP promotes particle dispersion and lubrication, while fibers provide crack-bridging and tensile reinforcement. When either component exceeds its effective range, the cohesion-flow equilibrium is disrupted, underscoring the importance of precise mix proportioning.

Keywords: 3D Printable Concrete (3DPC)- Umbrella Grass Fiber (Cyperus Alternifolius)- Superplasticizer- Flowability- Compressive Strength- Fresh and Hardened Properties

Topic: Material Physics