Dimensional Stability of SBR-Modified Cementitious Mixtures for Use in 3D Additive Construction

Abstract

This study experimentally investigated the dimensional stability of SBR (styrene butadiene rubber)-modified cementitious mixtures in order to determine whether their properties are sustainable as a 3D additive construction material. Dimensional stability refers to resistance to material deformation caused by changes in internal relative humidity and temperature. Hence, drying and thermal shrinkage, which are the primary factors affecting dimensional stability, were tested. The mixing ratio of SBR-modified cementitious mixtures was determined based on a predetermined optimal flow of 70% +/- 1% applicable for 3D additive construction applications. The results of this study showed that the elastic modulus, and drying shrinkage strain, excluding the coefficient of thermal expansion, all significantly improved as the SBR/cement ratio increased. In particular, drying shrinkage can be a disadvantage in 3D additive construction because drying in the printed mixtures is rapid due to the large specific exposure area of moldless construction. Consequently, mitigating drying shrinkage is very important. The elastic modulus, drying shrinkage, and coefficient of thermal expansion were all found to be associated with the dimensional stability obtained in this study. It was concluded that using SBR-modified cementitious mixtures was advantageous in terms of dimensional stability.