Additive Manufacturing using Cellular Concrete: Development of an Optimized Low-Cost Foam Generator and Aspects Related to Surfactants Efficiency

This paper presents a study on the development and optimization of a simple and low-cost foam generator device designed as a system component to produce lightweight mortar suitable for use in additive manufacturing. The project guidelines are the repeatability of the foam characteristics, continuous production, low cost to build the equipment, and targeting the surfactant´s maximum efficiency. After an introduction about air incorporation in cementitious materials, addressing the main methods and equipment for foam production present in literature, the details of the project, its calibration process and the obtained results are presented. The quality criteria attributed to the foam that measure the efficiency of the device are quantified and discussed. For each device configuration, the variation in the produced foam volume, target density and bubble stability were documented. The results show a relation on the foam quality linked to the outlet nozzle diameter variation as well as the amount of foaming agent employed in the water solution. The foam obtained with the highest quality had a production rate of 70ml/s, density of 43.43kg/m³ and a drainage amount of 4ml for 500ml of foam at rest for 5 minutes. The study demonstrates that despite the use of a low and constant air pressure of 5.80psi, obtained through a small electromagnetic air compressor, the target foam quality was successfully achieved. As a result, a methodology could be established to obtain the best foam regardless of the surfactant used. Because it is a small, low-cost and easy-to-build device, since many components are made by 3D printing, it can be useful in research for the development of lightweight cementitious materials on the bench that require smaller amounts of foam.