Harirchi Peyman, Yang Mijia
Department of Civil, Construction and Environmental Engineering, North Dakota State University, Fargo, ND 58104, USA.
Materials (Basel). 2022 May 7;15(9):3357. doi: 10.3390/ma15093357.
In this paper, the effect of carbon curing procedure on low reactive fly ash alkali-activated pastes was investigated. Specimens were cured with pure carbon dioxide (CO) gas for different curing times under 4 bar pressure. Chemical and physical characteristics of the geopolymer pastes were obtained from mass monitoring, titration test, XRD, FTIR and TGA-DTG analyses. Regarding the test results, after three days of CO curing, the highest was obtained at 4.8 wt% of fly ash precursor, with carbon sequestration efficiency at 22.6%. The ratio of carbon dioxide absorbed as efflorescence to the total absorbed CO was measured. The results show that at early age, almost 50% of carbonated products appeared as efflorescence; however, by increasing the curing time, and after 3 days of curing, about 80% of carbon dioxide was stored in the matrix. It was found that, in all cases, carbonation curing was detrimental to the geopolymerization process due to a high amount of efflorescence and led to a reduction in the compressive strength. At 24 h and 3 days, the specimens showed a lower reduction in compressive strength in comparison to CO samples cured at 3 h, 6 h and 12 h. Regarding the XRD results, calcite was detected in the 24 h and 3 days specimens, which contributes to lower pore sizes due to a higher molar volume and production of silica gel that might participate in the polymerization processes and results in densified microstructures.
本文研究了碳化养护工艺对低活性粉煤灰碱激发浆体的影响。试样在4巴压力下用纯二氧化碳（CO）气体养护不同时间。通过质量监测、滴定试验、XRD、FTIR和TGA-DTG分析获得了地质聚合物浆体的化学和物理特性。根据试验结果，二氧化碳养护三天后，当粉煤灰前驱体含量为4.8 wt%时，获得了最高值，固碳效率为22.6%。测量了以风化形式吸收的二氧化碳与总吸收二氧化碳的比例。结果表明，在早期，几乎50%的碳酸化产物以风化形式出现；然而，随着养护时间的增加，养护三天后，约80%的二氧化碳储存在基体中。研究发现，在所有情况下，碳化养护由于大量的风化现象对地质聚合过程不利，并导致抗压强度降低。与在3小时、6小时和12小时养护的二氧化碳试样相比，在24小时和三天时，试样的抗压强度降低较小。根据XRD结果，在24小时和三天的试样中检测到方解石，由于较高的摩尔体积和可能参与聚合过程的硅胶的产生，方解石有助于减小孔径，从而形成致密的微观结构。
