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Title |
Effect of Crumb Rubber Content on the Ductility and Extrudability of 3D Printable Cement-Free SHCC
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Authors |
현창진(Chang-Jin Hyun) ; 방성현(Sung-hyun Bang) ; 이방연(Bang-Yeon Lee) ; 김윤용(Yun-Yong Kim) |
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DOI |
https://doi.org/10.11112/jksmi.2026.30.4.221 |
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Keywords |
SHCC; 고무분말; 인장 변형률 능력; 다중 미세균열; 압출성; 알칼리 활성 슬래그 SHCC; Crumb rubber; Tensile strain capacity; Multiple cracking; Extrudability; Alkali-activated slag |
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Abstract |
Crumb rubber (CR) was incorporated as an external addition into polyethylene (PE) fiber-reinforced, alkali-activated slag (AAS)-based strain-hardening cementitious composites in which the fiber volume fraction was reduced to 1.0 vol.% to secure extrudability. The CR content was varied as a single variable at 0, 1, 3, 5, and 10 % by binder mass. Compressive strength, direct tensile behavior, and surface cracking were evaluated, and extrusion behavior was assessed using a manual caulking-gun extrusion test with a 12 mm nozzle. As the CR content increased, the 28-day compressive strength decreased by up to 33 % relative to the CR1 mixture and the tensile strength by about 19 %, whereas the tensile strain capacity increased from 4.73 % to 9.46 % and the number of surface cracks counted within an 80 mm gauge length increased from about 10 to 40. The increased strain capacity was associated with a more distributed multiple-cracking pattern rather than localized crack opening. The first-cracking stress did not decrease with CR content, indicating that the improvement is not explained by a simple reduction in matrix cracking strength alone. All mixtures could be extruded manually, but the required pressing force increased and CR10 showed repeated flow discontinuity and surface tearing. Under the tested conditions, a CR content of 3?5 % by binder mass provided the best balance between mechanical performance and extrusion behavior.
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