Pengembangan Alkali-Activated Materials Berbasis Slag-Class F Fly Ash sebagai Alternatif Material Perbaikan Perkerasan Beton secara Cepat

Oleh :
Muhamad Aditya Pratama - S942408018 - Fak. Teknik

Rapid repair of concrete pavements requires materials capable of achieving high early-age strength within a few hours without compromising workability and bond performance with the existing concrete substrate. Alkali-activated materials (AAMs), especially those based on slag and Class F fly ash, have emerged as a promising alternative; however, their optimal formulations, the reliability of maturity methods for predicting early-age compressive strength, and their interfacial bond performance have not yet been comprehensively investigated. This study aims to (1) identify the optimal mixture proportions that provide a balance between workability and early-age compressive strength, (2) evaluate the reliability of standardized maturity methods (Nurse–Saul and Arrhenius) in predicting early-age strength, and (3) assess the early-age interfacial bond performance between AAMs and existing concrete.A full factorial experimental design (3×3×3) was employed by varying the slag content (65%, 75%, and 85%), Na2O dosage (4%, 6%, and 8%), and silicate modulus (Ms = 0.75, 1.00, and 1.25). All mixtures were initially screened through fresh-state testing at both paste and mortar scales, including setting time and flowability measurements. The responses to Na2O dosage and Ms then served as the basis for selecting the most promising formulations for early-age compressive strength evaluation. The selected mixtures were subsequently used to calibrate and validate the Nurse–Saul and Arrhenius maturity models, as well as to evaluate interfacial bond performance through slant shear, splitting tensile, and push-off tests.The results demonstrated that mixtures containing 65–85% slag, 6% Na2O, and an Ms ≈1.00 provided the optimal balance between workability and early-age strength development. These mixtures exhibited initial setting times of 22.4–28.1 min, final setting times of 35–50 min, flow values of 20.25–55.25%, and compressive strengths of 12.7–18.9 MPa within 6 h, satisfying the operational requirements for both partial- and full-depth repair scenarios. The kinetic parameters governing the maturity method were strongly influenced by the precursor proportion; specifically, increasing the slag content decreased T0 from 3.70 °C to −7.10 °C and the Ea from 29.27 to 22.28 kJ/mol. The Arrhenius-based maturity model consistently outperformed the Nurse–Saul approach, achieving an R2 of up to 0.958, an RMSE as low as 3.52 MPa, and a bias of only 0.18 MPa. All mixtures also satisfied the requirements of ASTM C928 in the slant shear test from 1 day onward and met the BS EN 1504-3 Class R4 bond strength requirement based on the splitting tensile test at 28 days. The push-off test could not be used for quantitative evaluation due to an up-lift phenomenon during loading, which prevented the specimen from maintaining a pure shear condition.This study demonstrates that slag–Class F fly ash AAMs with an optimized formulation not only satisfy the performance requirements for rapid concrete pavement repair but can also be reliably predicted using maturity methods and exhibits robust interfacial bond performance with existing concrete.