Simplified assessment for one-part 3D-printable geopolymer concrete based on slump and slump flow measurements

A combination of three-dimensional (3D) printing and one-part geopolymer concrete is an innovative and sustainable construction method to prevent environmental degradation. To perform well in a 3D printing application, one-part geopolymer concrete requires rheological specifications that will generate concrete that is printable. However, measuring rheological properties and interpreting the rheological results is time-consuming. It needs to have a standardized field-friendly method to assess the printability of one-part geopolymer concrete before printing. This study introduces a simplified way of predicting the printability of one-part geopolymer concrete for 3D printing with the use of a slump and slump flow diagram. Nineteen (19) mixtures of one-part geopolymer concrete with various water/binder ratios and different content of sodium tetraborate pentahydrate (borax) added were studied. The slump and the corresponding slump flow of these concrete mixtures were measured. Then, the actual printings were carried on to assess the printability of these mixtures. The open time of concrete was also determined. After 3 days of curing, the compressive strength of the concrete was evaluated. The investigation indicated that the mixtures with a slump in a range of between 15 mm and 30 mm accompanied by a slump flow of between 210 mm and 240 mm were found to be well-suited for 3D printing. Furthermore, the results figured out that to achieve a desirable open time for successful 3D printing, the borax content of 2–4% should be added while the appropriate water/binder ratio of higher than 0.34 should be used.