Effects and Mechanism Research of Different Chemical Activators on Activity of Recycled Fine Powder

Abstract

Abstract: Recycled fine powder (RFP) is difficult to be effectively utilized due to its low activity, resulting in a great waste of resources. To stimulate the activity of RFP, the effects of traditional alkali activators (sodium hydroxide, calcium hydroxide, magnesium hydroxide, sodium silicate), alcohol amine activators (polyisomeric alcoholic amine, triethanolamine) and nanocrystalline nuclear activator on the compressive strength of mortars mixed with RFP were investigated. Meanwhile, the effects of chemical activators on the hydration heat release, hydration products and microstructure of RFP-cement pastes were analyzed to reveal their promotion mechanism. The results show that sodium hydroxide and sodium silicate can further reduce the compressive strength of mortars mixed with RFP, and the relationships are linear inverse with their dosage. Calcium hydroxide, magnesium hydroxide,triethanolamine and nanocrystalline nuclear activator can improve the early strength under certain dosage conditions, but can not improve the later strength. Polyisomeric alcoholic amine can significantly improve the compressive strength of each age through promoting the hydration of mineral phases tricalcium aluminate (C₃A) and tetracalcium aluminoferrite (C₄AF), accelerating the hydration process of RFP-cement pastes, improving the compactness of the interfacial bond between cement matrix and sand. The activity index of RFP increases from 62.8% to 74.8% at the optimal dosage of 0.2% (mass fraction). The research results can provide reference for improving the utilization rate of RFP and achieving the goal of energy conservation and emission reduction in the construction industry.

Key words: recycled fine powder, chemical activator, activity index, hydration of cement, interfacial bond

CLC Number:

TU528

CHEN Junsong, QIAO Min, WU Qingyong, LI Zhen, ZHAO Shuang. Effects and Mechanism Research of Different Chemical Activators on Activity of Recycled Fine Powder[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(4): 1409-1417.

References

[1] TANG Q, MA Z M, WU H X, et al. The utilization of eco-friendly recycled powder from concrete and brick waste in new concrete: a critical review[J]. Cement and Concrete Composites, 2020, 114: 103807.
[2] 李贞, 刘加平, 乔敏, 等. 基于减水剂吸附行为的再生微粉-水泥浆体黏度调控机理研究[J/OL]. 材料导报, 2023, 37(8): 21090090 [2022-12-22]. https://kns.cnki.net/kcms/detail/50.1078.TB.20220928.1027.002.html.
LI Z, LIU J P, QIAO M, et al. Mechanism of viscosity for recycled powder-cement paste based on the adsorption of superplasticizer[J/OL]. Materials Reports, 2023, 37(8): 21090090 [2022-12-22]. https://kns.cnki.net/kcms/detail/50.1078.TB.20220928.1027.002.html (in Chinese).
[3] 刘超, 胡天峰, 刘化威, 等. 再生复合微粉对混凝土力学性能及微观结构的影响[J]. 建筑材料学报, 2021, 24(4): 726-735.
LIU C, HU T F, LIU H W, et al. Effect of recycled composite micro-powder on mechanical properties and microstructure of concrete[J]. Journal of Building Materials, 2021, 24(4): 726-735 (in Chinese).
[4] YUAN C F, WANG D, SETIAWAN H, et al. Effect and mechanism of different excitation modes on the activities of the recycled brick micropowder[J]. Science and Engineering of Composite Materials, 2021, 28(1): 676-688.
[5] 康晓明, 李滢, 樊耀虎. 不同激发方式对再生微粉性能的影响研究[J]. 硅酸盐通报, 2019, 38(4): 1135-1139.
KANG X M, LI Y, FAN Y H. Effect of different excitation methods on the properties of recycled concrete powder[J]. Bulletin of the Chinese Ceramic Society, 2019, 38(4): 1135-1139 (in Chinese).
[6] 屈孟娇. 化学-热处理耦合激发废弃混凝土再生微粉研究[D]. 开封: 河南大学, 2022.
QU M J. Research on the activation of recycled powder from waste concrete under chemical-thermal coupling[D]. Kaifeng: Henan University, 2022 (in Chinese).
[7] XU J, KANG A H, WU Z G, et al. The effect of mechanical-thermal synergistic activation on the mechanical properties and microstructure of recycled powder geopolymer[J]. Journal of Cleaner Production, 2021, 327: 129477.
[8] LU B, SHI C J, ZHANG J K, et al. Effects of carbonated hardened cement paste powder on hydration and microstructure of Portland cement[J]. Construction and Building Materials, 2018, 186: 699-708.
[9] QIN L, GAO X J. Recycling of waste autoclaved aerated concrete powder in Portland cement by accelerated carbonation[J]. Waste Management, 2019, 89: 254-264.
[10] ZHANG D S, ZHANG S X, HUANG B W, et al. Comparison of mechanical, chemical, and thermal activation methods on the utilisation of recycled concrete powder from construction and demolition waste[J]. Journal of Building Engineering, 2022, 61: 105295.
[11] 周长顺, 吉红波, 赵丽颖. 再生微粉在水泥基材料中的应用与研究进展[J]. 硅酸盐通报, 2019, 38(8): 2456-2463.
ZHOU C S, JI H B, ZHAO L Y. Application and research progress of recycled micro-powders in cement-based materials[J]. Bulletin of the Chinese Ceramic Society, 2019, 38(8): 2456-2463 (in Chinese).
[12] 田青, 屈孟娇, 张苗, 等. 废弃混凝土再生微粉激活方式研究进展[J]. 硅酸盐通报, 2020, 39(8): 2476-2485.
TIAN Q, QU M J, ZHANG M, et al. Research progress on activation way of recycled powder of waste concrete[J]. Bulletin of the Chinese Ceramic Society, 2020, 39(8): 2476-2485 (in Chinese).
[13] 庞超明, 唐志远, 杨志远, 等. 水泥基材料中的早强剂及其作用机理综述[J/OL]. 材料导报, 2023, 37(9): 21110247 [2022-12-22]. https://kns.cnki.net/kcms/detail/50.1078.tb.20220707.1048.006.html.
PANG C M, TANG Z Y, YANG Z Y, et al. Review of early strengthening agent and its mechanism in cementitious composites[J/OL]. Materials Reports, 2023, 37(9): 21110247 [2022-12-22]. https://kns.cnki.net/kcms/detail/50.1078.tb.20220707.1048.006.html (in Chinese).
[14] 李琴, 张春红, 孙可伟. 不同激发剂激发建筑垃圾再生微粉活性研究[J]. 硅酸盐通报, 2016, 35(7): 2187-2192+2197.
LI Q, ZHANG C H, SUN K W. Preliminary study on micronized active regeneration experiment with different activator excitation construction waste[J]. Bulletin of the Chinese Ceramic Society, 2016, 35(7): 2187-2192+2197 (in Chinese).
[15] 董自修. 碱激发制备废弃混凝土地聚物基再生材料[D]. 大连: 大连理工大学, 2018.
DONG Z X. Production of geopolymer-based recycled materials from waste concrete by alkalia-activation[D]. Dalian: Dalian University of Technology, 2018 (in Chinese).
[16] 李兰. 有机无机纳米杂化材料对水泥水化的影响及机理研究[D]. 重庆: 重庆大学, 2020.
LI L. Study on the influence and mechanism of nano organic and inorganic hybrid materials on cement hydration[D]. Chongqing: Chongqing University, 2020 (in Chinese).
[17] 田培, 刘加平, 王玲, 等. 混凝土外加剂手册[M]. 北京: 化学工业出版社, 2009: 109.
TIAN P, LIU J P, WANG L, et al. Handbook of concrete admixtures[M]. Beijing: Chemical Industry Press, 2009: 109 (in Chinese).
[18] 孔祥明, 卢子臣, 张朝阳. 水泥水化机理及聚合物外加剂对水泥水化影响的研究进展[J]. 硅酸盐学报, 2017, 45(2): 274-281.
KONG X M, LU Z C, ZHANG C Y. Recent development on understanding cement hydration mechanism and effects of chemical admixtures on cement hydration[J]. Journal of the Chinese Ceramic Society, 2017, 45(2): 274-281 (in Chinese).
[19] 安明喆, 张戈, 韩松. 速凝剂主要组成对水泥水化影响机理研究[J]. 铁道工程学报, 2019, 36(11): 74-81.
AN M Z, ZHANG G, HAN S. Research on the influence mechanism of accelerator main components on cement hydration[J]. Journal of Railway Engineering Society, 2019, 36(11): 74-81 (in Chinese).