| Title |
A Study on the Bleeding Behavior and Fire Resistance of Blast-Furnace Slag Cement Paste Incorporated with Sodium Aluminate |
| Authors |
강경신(Kang, Kyeong-Sin) ; 김지홍(Kim, Ji-Hong) ; 이재승(Lee, Jae-Sung) |
| DOI |
https://doi.org/10.5659/JAIK.2026.42.9.395 |
| Keywords |
Blast Furnace Slag Cement; DLVO Thoery; Bleeding; Microstructure; Fire Resistance |
| Abstract |
Blast-furnace slag cement (BFC) paste has been largely confined to structural applications due to delayed early hydration. This study
examines whether a high water-to-cement (w/c) ratio with 4 wt.% sodium aluminate (SA) can yield a porous BFC paste suitable for
fire-resistant use. Bleeding tests on pastes with w/c of 0.6?2.0 were interpreted using a water-film-thickness (WFT) model based on
body-centered cubic packing and DLVO theory. SA addition extended the bleeding-free range to w/c ? 1.4, attributed to an enlarged WFT
threshold from enhanced ionic dissociation under high alkalinity. Microstructure transitioned from a crystalline-dominant heterogeneous
structure at low w/c, through a gel-dominant structure at intermediate w/c, to an open cellular pore network at high w/c. Fire resistance was
assessed via the KS F 2257-1 heating curve on 60 × 60 × 100 mm specimens cured for 14 days; results serve as a comparative
material-level index, not a direct measure of structural member performance. The time to reach 538°C at the specimen center increased from
77 min (w/c = 0.6) to 97 min (w/c = 1.4), and the average heat absorption rate decreased from 3.12 to 2.22 kJ/min, indicating that greater
pore volume at high w/c prolongs evaporative heat absorption and delays internal temperature rise. These results demonstrate that a high w/c
ratio can be controlled as a microstructural design parameter to enhance the fire resistance of BFC paste. |