Mechanical and Microstructural Characteristics of Calcium Sulfoaluminate Cement Exposed to Early-Age Carbonation Curing.

Weikang Wang,Bokang Li,Xinhua Cai,Hongyang Deng,Xuanchun Wei

doi:10.3390/ma14133515

Abstract

The early-age carbonation curing technique is an effective way to improve the performance of cement-based materials and reduce their carbon footprint. This work investigates the early mechanical properties and microstructure of calcium sulfoaluminate (CSA) cement specimens under early-age carbonation curing, considering five factors: briquetting pressure, water–binder (w/b) ratio, starting point of carbonation curing, carbonation curing time, and carbonation curing pressure. The carbonization process and performance enhancement mechanism of CSA cement are analyzed by mercury intrusion porosimetry (MIP), thermogravimetry and derivative thermogravimetry (TG-DTG) analysis, X-ray diffraction (XRD), and scanning electron microscope (SEM). The results show that early-age carbonation curing can accelerate the hardening speed of CSA cement paste, reduce the cumulative porosity of the cement paste, refine the pore diameter distribution, and make the pore diameter distribution more uniform, thus greatly improving the early compressive strength of the paste. The most favorable w/b ratio for the carbonization reaction of CSA cement paste is between 0.15 and 0.2; the most suitable carbonation curing starting time point is 4 h after initial hydration; the carbonation curing pressure should be between 3 and 4 bar; and the most appropriate time for carbonation curing is between 6 and 12 h.

Highlights

Since the beginning of the 21st century, infrastructure construction projects in various fields have been rapidly developing and improving in China
This research advances our understanding of the early-age carbonation of calcium sulfoaluminate (CSA) cement-based materials
The current results of carbonation experiments conducted by mercury intrusion porosimetry (MIP), thermogravimetry and derivative thermogravimetry (TG-DTG), X-ray diffraction (XRD), and scanning electron microscope (SEM) lead to the following conclusions

Summary

Introduction

Since the beginning of the 21st century, infrastructure construction projects in various fields have been rapidly developing and improving in China. The production of cement is accompanied by high energy consumption, high emissions, and serious pollution, and the production of 1 ton of cement in China produces more than 900 tons of CO2 , which is a great challenge for the country’s low-carbon, green sustainable development strategy [2,3]. The cement industry produces a mass of CO2 gas that accounts for approximately 5% of the global CO2 emissions, which has become a major environmental problem [5]. In order to address the issue of global warming and reduce the carbon footprint of the building materials industry, experts and scholars proposed the idea of carbonation curing technology as early as the 1970s. It has been estimated that approximately 1.5 million metric tons of CO2 can be sequestered annually by carbonation curing of concrete masonry units, which will lead to a reduction of nearly

Methods

Results

Conclusion