The Analysis of Fly Ash Content Variation, GGBFS and RCA on Mechanical Properties of Roller Compacted Concrete

Mochamad Solikin (Universitas Muhammadiyah Surakarta)
Hafid Nurrohman (Civil Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Surakarta)
Yenny Nurchasanah (Civil Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Surakarta)
Budi Setiawan (Civil Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Surakarta)
Nur Aklis (Mechanical Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Surakarta)
Arruna Rodhi Prasetya (Civil Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Surakarta)
Erwin Suspatriya (Civil Engineering Department, Faculty of Engineering, Universitas Muhammadiyah Surakarta)

Reka Buana : Jurnal Ilmiah Teknik Sipil dan Teknik Kimia
Vol. 11 No. 2 (2026): EDISI SEPTEMBER 2026

Rigid pavement based on Roller-Compacted Concrete (RCC), which has zero slump, a low water-cement ratio, and is compacted using rollers, is now widely developed. However, studies that simultaneously evaluate fly ash content variations, Ground Granulated Blast Furnace Slag (GGBFS), and Recycled Concrete Aggregate (RCA) in RCC mixtures remain limited. This study investigated the use of fly ash content variations of 20%, 30%, and 40% combined with 20% GGBFS as a partial cement replacement and 25% RCA as a partial coarse aggregate replacement, with the addition of 0.8% superplasticizer, in roller-compacted concrete mixtures. The research used an experimental method with RCC mix designs based on ACI 211.3R-02 and a target compressive strength of 30 MPa. Testing programs included initial setting time, Vebe time, compressive strength, flexural strength, and modulus of elasticity tests at 28 days; specimens were compacted using a vibrating hammer. XRF analysis showed that the fly ash was Class C and the GGBFS had good hydraulic reactivity. The results showed that higher fly ash content prolonged the initial setting time. All mixtures satisfied the target Vebe time of 30–40 seconds, with the best workability achieved at 40% fly ash + 20% GGBFS, giving a Vebe time of 30.13 seconds. Mechanically, the mixture with 20% fly ash + 20% GGBFS (RG-F20) showed the most optimal results, increasing compressive strength by 1.54% (33.10 MPa), flexural strength by 4.01% (3.74 MPa), and elastic modulus by 0.77% (27,013 MPa) compared with normal concrete. A strong linear correlation was found between compressive and flexural strength (R² = 0.9384). All variations met the ACI 325.10R requirements. These findings indicate that the combination of fly ash, GGBFS, and RCA is viable for sustainable rigid pavement construction, with the 20% fly ash + 20% GGBFS mixture providing the best mechanical performance. Future research should examine long-term durability, environmental cycle resistance, and chemical attack resilience.