{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T10:19:11Z","timestamp":1787566751695,"version":"build-2736575974"},"reference-count":46,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2026,8,23]],"date-time":"2026-08-23T00:00:00Z","timestamp":1787443200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100012905","name":"Natural Science Foundation of Shandong Province","doi-asserted-by":"publisher","award":["ZR2023ME044"],"award-info":[{"award-number":["ZR2023ME044"]}],"id":[{"id":"10.13039\/100012905","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>In this study, rapid-hardening sulfoaluminate cement (SAC) was used as cementitious material, and recycled fine aggregates (RFAs) were surface pretreated by immersion in nano-SiO2 (NS) suspensions. NS-modified SAC recycled fine aggregate mortars were prepared at three cement\u2013sand ratios (1:1, 1:2 and 1:3) to systematically investigate the regulatory effects of NS concentrations (0%, 1%, 2% and 3%) on macroscopic performance, hydration products and interfacial microstructure. Multi-scale characterizations, including XRD, TG-DTG, SEM-EDS and microhardness tests, were carried out. The testing results show that appropriate NS can optimize SAC hydration by heterogeneous nucleation and the pozzolanic reaction. At a cement\u2013sand ratio of 1:1, the compressive and flexural strengths gradually increase as the NS concentration rises from 0% to 2%. Compared with the control group, the 28 d compressive and flexural strength are enhanced by 19.5% and 16.6%, respectively, the drying shrinkage decreases by 8.0%, and carbonation resistance is obviously improved. Meanwhile, the formation of AFt is promoted, amorphous C-S-H gel accumulates continuously, and the content of Ca(OH)2 is gradually consumed by the pozzolanic reaction of NS. For specimens modified with 2% NS, the maximum microhardness reaches 1326 HV, which greatly benefits the mechanical properties of mortar. However, further increasing the NS concentration to 3% triggers nanoparticle agglomeration and reduces effective reactive silica, leading to a decline in hydration products, deteriorated interfacial compactness and reduced mechanical performance. Therefore, 2% can be determined as the optimal NS concentration which can provide a theoretical basis for high-value resource recycling of recycled fine aggregates in SAC mortar.<\/jats:p>","DOI":"10.3390\/nano16171051","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T08:03:41Z","timestamp":1787558621000},"page":"1051","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Performance Evolution and Microstructure Optimization of Recycled Fine Aggregate Rapid-Hardening Sulfoaluminate Cement Mortar by Nano-SiO2 Surface Modification"],"prefix":"10.3390","volume":"16","author":[{"given":"Meinan","family":"Wang","sequence":"first","affiliation":[{"name":"College of Civil Engineering & Architecture, Qingdao Agricultural University, Qingdao 266109, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shuo","family":"Liu","sequence":"additional","affiliation":[{"name":"Qingdao Branch of Tongyuan Design Group Co., Ltd., Qingdao 266001, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cong","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Civil Engineering & Architecture, Qingdao Agricultural University, Qingdao 266109, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yaning","family":"Wu","sequence":"additional","affiliation":[{"name":"College of Civil Engineering & Architecture, Qingdao Agricultural University, Qingdao 266109, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Liang","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Civil Engineering & Architecture, Qingdao Agricultural University, Qingdao 266109, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tieming","family":"Guo","sequence":"additional","affiliation":[{"name":"College of Civil Engineering & Architecture, Qingdao Agricultural University, Qingdao 266109, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"146354","DOI":"10.1016\/j.conbuildmat.2026.146354","article-title":"Influence of nanoparticles on the hydration and salt-freeze resistance of concrete made from all-solid-waste cementitious materials","volume":"524","author":"Zhang","year":"2026","journal-title":"Constr. 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