The National Road Section Demak - Kudus is one of the most populous road sections connecting East Java province with West Java province through the city of Semarang. Repeated damage conditions raise the suspicion that the subgrade under the road body has special criteria that need further handling before repairs are made to the pavement. In addition, based on the soft soil distribution map and soil data with the results of existing laboratory testing, categorized as soft soil. For this reason, it is necessary to handle the subgrade to improve soil parameters, which is physical and mechanical. Therefore, chemical stabilization was chosen to obtain a chemical reaction from the soil. The selected chemicals to induce these reactions is coal combustion waste which are fly ash and bottom ash. Exhibiting pozzolanic properties that can react and cause flocculation in the soil. The research involves mixing the soil with stabilizing materials in three different combinations: first, soil mixed by fly ash (FA); second, soil mixed by bottom ash (BA); and third, soil mixed by both fly ash with bottom ash (FABA), optimum stabilizing mixture material at 20%. The initial soil, which is highly plastic clay with a classification of CH/A-7-6, having a plasticity index (PI) of 43.23% and California Bearing Ratio (CBR) of 0.92%, undergoes improvement with adding FA stabilizer, resulting in MH/A-7-5 with a PI of 27.07% and CBR of 12.39%. The mixture of soil with FABA is MH/A-7-5 with a PI of 28.87% and CBR of 9.60%. However, the improvement in the mixture of soil with BA is not as significant, remaining in the CH/A-7-6 category with a PI of 31.83% and CBR of 3.00%.

Babo, Frans de Jesus and Suprayitno, H. (2019) “Road Network Connectivity Quality Assesment for Timor Leste National Road Network”. Journal of Infrastructure and Facility Asset Management - JIFAM 1(2) September 2019.

Bina Marga (2018) “Spesifikasi Umum 2018 untuk Pekerjaan Konstruksi Jalan dan Jembatan (Revisi 2)” Kementrian Pekerjaan Umum Dan Perumahan Rakyat, Direktorat Jendral Bina Marga.

Budi, G. S., Cristanto A., and Setiawan E. (2003) “Pengaruh Fly Ash Terhadap Sifat Pengembangan Tanah Ekspansif” Civil Engineering Dimension, Vol. 5, No. 1, 20–24, March 2003 http://puslit.petra.ac.id/journals/civil.

Cadersa, A.S., Seeborun A.K. and Yuk A.C.C. (2014) “Use of Coal Bottom Ash as Mechanical Stabiliser in Subgrade Soil” Journal of Engineering, Hindawi Publishing Corporation Volume 2014, Article ID 184607, 6 pages http://dx.doi.org/10.1155/2014/184607.

Dissanayake, T. B. C. H., S.M.C.U. Senanayake and M.C.M. Nasvi (2017) “Comparison of the Stabilization Behavior of Fly Ash and Bottom Ash Treated Expansive Soil” Journal of the Institution of Engineers, Sri Lanka, Engineer Vol. L, No. 01, pp. [11 - 19].

Jimoh, Richard, et al. (2021) “Influence of Sustainable Construction Practice Awareness Level on Extend of Usage in Abuja-Nigeria” Journal of Infrastructure and Facility Asset Management - JIFAM 3(3) Desember 2021.

Leliana, A., and Nur Andajani (2015) “Pengaruh Penambahan Fly Ash Terhadap Nilai Kuat Tekan Bebas pada Tanah Lempung Ekspansif di Daerah Magetan Jawa Timur” Teknik Sipil Vol 1 Nomer 1/rekat/15 (2015), 1 – 8.

Navagire, O. P., Shashi Kant Sharma, and Dadi Rambabu (2022) “Stabilization of Black Cotton Soil with Coal Bottom Ash” Materials Today: Proceedings, 53, 979-985 https://doi.org/10.1016/j.matpr.2021.10.447.

Onyelowe, Kennedy C., Michael E. Onyia, Duc Bui Van, Haci Baykara, and Hyginus U. Ugwu (2021). “Review Article, Pozzolanic Reaction in Clayey Soils for Stabilization Purposes: A Classical Overview of Sustainable Transport Geotechnics” Advances in Materials Science and Engineering Volume 2021, Article ID 6632171 https://doi.org/10.1155/2021/6632171.

PT. Morang Rekayasa Geoteknik (2022). “Laporan Penyelidikan Tanah Kajian Kerusakan Jalan Nasional Demak-Kudus”

Purnama, Yuda and Machfud Ridwan (2008) “Pengaruh Penambahan Bottom Ash pada Tanah Lempung Ekspansif di Daerah Lakarsantri Surabaya Terhadap Nilai Daya Dukung Pondasi Dangkal”. Vol 2 No 2/REKAT/18 (2018): Wisuda ke-92 Periode 2 Tahun 2018.

Sharma, V., and Sandeep Singh (2019) “Modeling for The Use of Waste Materials (Bottom Ash and Fly Ash) in Soil Stabilization”. Materials Today: Proceedings, 33, 1610–1614 https://doi.org/10.1016/j.matpr.2020.05.569.

Suprayitno, Hitapriya, et al. (2020). “Preliminary Reflection on Basic Principle of Operation Management for Public Work Infrastructure Asset Management”. Journal of Infrastructure and Facility Asset Management - JIFAM 2(Sup1) December 2020.

Suprayitno, H. & Soemitro, R.A.A (2018). ”Preliminary Reflexion on Basic Principle Infrastructure Asset Management”. Jurnal Manajemen Aset Infrastructur & Facilitas – JMAIF 2(1) Maret 2018.

Wahyuni, N. D., Andius D. Putra, Aminudin Syah, and Iswan (2021) “Kinerja Fly Ash Terhadap Stabilisasi Tanah Lunak sebagai Material Perbaikan Tanah Dasar (Subgrade)”. JRSDD, September 2021, Vol.9, No.3, Page:547-558.

Widayanti, Ari, et al. (2019). ”Gradation Analysis of Reclaimed Asphalt Pavement from National Road as Asphalt Concreate Layer”. Journal of Infrastructure and Facility Asset Management - JIFAM 1(1) March 2019.