Introduction

 

From December 13 to 16, 2023, the Innovative Valorization of Alternative Materials and Waste towards Circular Constructionthe International Conference (WASCON-202) took place in Hong Kong, China, organized by the department of civil and environmental engineering at the Hong Kong Polytechnic University and Hunan University, etc. The conference, held every three years since 1991, serves as a platform for the exchange of ideas and current research on waste, industrial by-products, and the utilization of construction materials. Ms. Luo Shuang, Ph.D student of the NEXCEL 2023 Ph.D project, titled "Beneficial Use of Desulfurized Petrol Coke Residue to Prepare CO2-Ready-Mix Cement-Based Materials", attended the conference and delivered a presentation entitled "First 60 min behavior of fresh properties and reaction mechanisms of cement pastes intermixed with CO2."

 

 

The study involved injecting CO2 gas into the cement paste during the mixing process to explore the reaction mechanisms of CO2-intermixed cement paste, focusing on pH evolution, carbonation mechanisms and microstructure change during the initial 60 minutes of hydration.

The experimental results indicated significant increases in calcium hydroxide formation and heat release in the CO2-intermixed group compared to the control paste at 0 and 5 minutes, respectively. Furthermore, all CO2-intermixed pastes maintained reasonable pH values within 60 minutes, while gypsum content in these pastes was detectable compare to pure cement paste, possibly due to preferential reactions of C3A and amorphous calcium carbonate in CO2-intermixed cement paste.

During the conference, Shuang Luo provided a detailed presentation on the physical changes of CO2-intermixed cement paste within the first 60 minutes, along with a thorough explanation of the reaction mechanisms. His presentation garnered unanimous recognition from the attending researchers.