Effect of Blast-Furnace Slag Replacement Ratio and Curing Method on Pore Structure Change after Carbonation on Cement Paste

Abstract

The frost damage resistance of blast-furnace slag (BFS) cement is affected by carbonation. Hence, this study investigates the carbonation properties of pastes incorporating BFS with different replacement ratios, such as 15%, 45%, and 65% by weight, and different curing conditions, including air and carbonation. The BFS replacement ratio properties, determined by the Ca/Si ratio of calcium silicate hydrate in the cement paste sample, were experimentally investigated using mercury intrusion porosimetry, X-ray diffraction, and thermal analysis. The experimental investigation of the pore structure revealed that total porosity decreased after carbonation. In addition, the porosity decreased at a higher rate as the BFS replacement rate increased. Results obtained from this study show that the chemical change led to the higher replacement rate of BFS, which produced a higher amount of vaterite. In addition, the lower the Ca/Si ratio, the higher the amount of calcium carbonate originating from calcium silicate hydrate rather than from calcium hydroxide. As a result of the pore structure change, the number of ink-bottle pores was remarkably reduced by carbonation. Comparing the pore structure change in air-cured and carbonation test specimens, it was found that as the replacement rate of BFS increased, the number of pores with a diameter of 100 nm or more also increased. The higher the replacement rate of BFS, the higher the amount of calcium carbonate produced compared with the amount of calcium hydroxide produced during water curing. Due to the generation of calcium carbonate and the change in pores, the overall number of pores decreased as the amount of calcium carbonate increased.

Performance Assessment of Carbon Dioxide Sequestration in Cement Composites with a Granulation Technique

“…Like the trends reported in [ 32 , 33 , 34 ], the porosity results showed that S g series and F g series showed less porosity than C g series. In addition, CCHG also brought about a minimal filler effect, as confirmed by Figure 9 .…”

“…Of course, those existing studies treated the materials to meet the aim of their studies. However, the usual cases use the FA or BFS as a supplementary material to the cement, therefore, the packing effect of FA and BFS [ 32 , 33 , 34 ] had a negative effect on the CO 2 sequestration in this study. The packing effect was confirmed by the MIP results, which showed that the porosity was significantly reduced than C-G0 and C-G5 before CO 2 -ppm.…”

“…It was considered that the filler effect from BFS and FA disturbed the improvement in CO 2 sequestration performance. As is well known, BFS and FA make cement composites denser [ 32 , 33 ]. This means that the porosity is reduced, in other words, the path of airflow is also reduced.…”

Influence of Accelerators on Cement Mortars Using Fluid Catalytic Cracking Catalyst Residue (FCC): Enhanced Mechanical Properties at Early Curing Ages

“…For decades, studies into supplementary cementitious materials (SCMs) have demonstrated their viability as partial replacements of PC, and for providing technological and environmental benefits [ 2 ]. The most widely used SCMs are fly ash (FA) [ 3 , 4 , 5 ], silica fume (SF) [ 6 , 7 ], or blast furnace slag (BFS) [ 8 , 9 ]. Fluid catalytic cracking catalyst residue (FCC) use has been studied since the late 1990s by various research groups worldwide [ 10 , 11 , 12 , 13 ].…”