Influence of Curing Methods on Mechanical Properties of Concrete Beams Produced Through Additive Construction Methods

The integration of advanced additive manufacturing technologies, particularly 3D printing (3DP), also known as Additive Construction (AC), could influence a shift in the construction industry towards improved efficiency and automation. This research evaluated the effect on hardened properties of two different concrete mixes for use in 3DP based on the presence or absence of alkaline-resistant (AR) glass fibers. Furthermore, three different curing methods were evaluated: air-curing, plastic-covered curing, and spray-curing. Concrete beams were printed for flexural testing, and cores were taken from other depositions to evaluate compressive strength and split-tensile strength. An analysis of the size and location of cracks on the beams after curing was performed for the different mixes and curing methods. For beams without fibers, plastic-covered curing produced the highest flexural modulus values, and air-curing produced the lowest flexural modulus values. Plastic-cured beams with fibers had higher flexural modulus values than the air-cured beams with fibers. However, the spray-cured beams with fibers produced somewhat anomalous results, with one flexural modulus value being larger than those of the plastic-cured beams, and the other flexural modulus value being less than those of the air-cured beams. All 28-day compressive strengths and split-tensile strengths across mixes and curing conditions fell within a small band ranging between ~19.3–22.1 MPa and ~1.7–2.0 MPa (~2800–3200 psi, and 240–290 psi), respectively. There was a large amount of scatter in some of the tests. It appears that neither the presence of the AR-glass fibers, nor the type of curing had a large influence on compressive strength or split-tensile strength. Results showed that the addition of fibers and the use of the plastic during curing significantly reduced the occurrence, the width, and the depth of cracks as a result resulting from the curing process. Plastic-curing was the most effective curing method for minimizing the occurrence of cracks. Any cracks that formed during plastic-curing were extremely fine and had little or no effect on mechanical properties.