Investigation of limestone-calcined clay-based cementitious materials for sustainable 3d concrete printing

Abstract

Extrusion-based 3D concrete printing (3DCP), as one of the emerging techniques, has received considerable attention from both academia and industry, due to its numerous benefits for concrete construction, through enhancing the freedom of architectural design, eliminating formwork, optimizing material use, and decreasing wastes, labors and costs. However, in most of proposed 3D printable cementitious materials, ordinary Portland cement (PC) still occupies a relatively high content, which partially neutralizes the sustainable benefits of 3DCP in aspects of formwork free and material-efficient designs. To date, considerable attempts have been made to develop sustainable cementitious materials in the context of 3DCP. Common supplementary cementitious materials (SCMs), i.e., fly ash, silica fume, and slag, are utilized as an ingredient of the binder in 3D printable cementitious materials, which is the most generic and applicable strategy for reducing the use of PC. Nevertheless, these common SCMs, which belong to industrial by-products, are gradually being depleted. For longer-term development, limestone and calcined clay appear to be suitable alternatives to SCMs, considered the worldwide abundance of raw materials and low CO2 footprint in the material production. The main goal of this thesis is to develop limestone-calcined clay-based cementitious materials for 3DCP. In order to develop such printable mixtures, investigations about the effect of different material and printing parameters on fresh and hardened properties were conducted. In Chapter 1, the subject of this research,