(과제확인)숏크리트용 산업부산물 기반 무시멘트 콘크리트의 기초특성에 관한 연구

초록

This study aims to evaluate the feasibility of cementless concrete using industrial byproducts as an eco-friendly alternative to conventional cement concrete. Ground-granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF) were employed as binder materials, and the mechanical performance, plastic shrinkage behavior, and microstructural characteristics of cementless concrete were investigated to verify its applicability as a structural and shotcrete material capable of reducing CO₂ emissions. Cementless concrete mixtures were prepared using GGBFS, FA, and SF as binders, activated by sodium hydroxide and sodium silicate with water-to-binder (W/B) ratios of 0.40, 0.45, and 0.50. Conventional cement concrete with equivalent water ratios was used for comparison. Compressive strength tests were conducted at curing ages of 1, 3, 7, 14, and 28 days. Plastic shrinkage cracking was evaluated according to the ASTM C1579 standard. Microstructural development and reaction products were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Cementless concrete with W/B ratios of 0.45 and 0.50 exhibited compressive strength comparable to or higher than that of cement concrete from early ages and demonstrated superior 28-day strength performance. No plastic shrinkage cracking was observed for any mixture, indicating excellent early-age crack resistance. SEM analysis revealed progressive densification of the microstructure owing to the formation of C-(A)-S-H and N-A-S-H gel phases with increasing curing age. XRD results showed limited portlandite formation in cementless concrete, accompanied by an increased development of aluminosilicate reaction products after 7 days, resulting in reduced porosity and enhanced structural compactness. Experimental results confirmed that cementless concrete incorporating industrial byproducts can achieve mechanical performance and durability characteristics comparable to or exceeding those of conventional cement concrete when an appropriate W/B ratio is applied. Reduced portlandite formation and dominant alkali-activated reaction products contributed to the improved chemical stability and resistance to deterioration. Therefore, cementless concrete has a strong potential as a sustainable construction material capable of reducing CO₂ emissions while maintaining its structural performance, particularly for shotcrete applications.

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