**1. Introduction**

Cement production has become very energy-intensive, consuming more than 5% of the world's total energy demand, and a large portion of CO2 emissions is associated with the cement industry [1]. However, cement concrete is widely used as a construction material due to its low cost and long service life. Although this material has high compressive strength and durability, its structural use is limited by the low tensile strength of the material and its susceptibility to crack expansion. In addition, the cement production process has a significant influence on global warming [2,3]. Presently, global production of Portland cement is approximately 4.6 billion tons per year. It is expected to reach a capacity of more than 6 billion tons by 2050 [4]. For countries around the world to achieve the goal of net-zero CO2 emissions by 2050, there is an urgent need to find suitable substitutes for cement materials and significantly reduce cement usage [5], or to use alternative fuels, such as natural gas, biomass and agriculture-related secondary wastes (e.g., tires, sewage sludge, and municipal solid waste). This could significantly reduce indirect carbon emissions from burning fossil fuels or coal mines in heating rotary kilns [6]. Other strategies aim to use blended cement (such as ground granulated blast-furnace slag (ggbs), fly ash and other supplementary cementitious materials to replace cement) through the addition of cementitious materials; other chemical additives or aggregate types and grading optimization strategies may change the characteristics of concrete proportions and their environmental impact [5,7]. These strategies represent a significant research

**Citation:** Chang, Y.-H.; Fiala, L.; Záleská, M.; Ko ˇnáková, D.; Lin, W.-T.; Cheng, A. Study on the Blending Characteristics of Ternary Cementless Materials. *Mater. Proc.* **2023**, *13*, 9. https://doi.org/10.3390/ materproc2023013009

Academic Editors: Katarzyna Mróz, Tomasz Tracz, Tomasz Zdeb and Izabela Hager

Published: 14 February 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

area focused on developing methods to achieve the same material design parameters as those found in concrete structures using pure cement concrete but with a lower demand for Portland cement. The most effective approach is to completely replace cement with appropriate industrial wastes to achieve net-zero carbon emissions. This would significantly contribute to reducing emissions.

In this study, three industrial by-products were blended to completely replace cementitious materials without adding alkali activators to produce ternary cementless composites. After demolding, the test specimens were tested for cross-comparison of the compressive strength between air and water curing. The ternary cementless composites were tested using the flowability, setting time, X-ray fluorescence (XRF), and scanning electron microscopy (SEM) to verify their applicability and feasibility.
