Efek Penambahan Limbah Marmer Pada Mortar Geopolimer Berbasis Fly Ash dan Rice Husk Ash dengan NaOH 10M

Effect Of Marble Waste Addition On Fly Ash and Rice Husk Ash Based Geopolymer Mortar Using 10M NaOH

Mortar menggunakan semen Portland sebagai bahan pengikat dalam produksinya. Dalam proses produksi semen Portland, jumlah karbon dioksida menjadi salah satu penyebab pemanasan global. Alternatif pengganti semen yang populer adalah geopolimer. Beberapa penelitian menunjukkan bahwa kandungan CaO dalam fly ash dapat meningkatkan sifat mekanik geopolimer. Material lain yang memiliki kadar CaO tinggi adalah limbah marmer, yaitu sebesar 98,85%. Penelitian ini dilakukan untuk mengetahui efek penambahan limbah marmer terhadap nilai kuat tekan, porositas dan waktu pengikatan pada mortar geopolimer berbahan fly ash, rice husk ash dengan larutan aktivator NaOH 10M. Benda uji mortar berbentuk kubus berukuran 50x50x50 mm3 dengan variasi penambahan sebesar 0%, 2,5%, 5%, 7,5%, 10%, 12,5%, 15%, 17,5%, 20%. Hasil menunjukkan bahwa penambahan limbah marmer dapat meningkatkan kuat tekan hingga rasio 12,5%, lalu menurun. Sebaliknya, porositas justru meningkat setelah 12,5%. Hal ini disebabkan ketidakseimbangan reaksi akibat kelebihan CaO terhadap SiO2 dan Al2O3, sehingga kuat tekan tertinggi tercapai sebesar 24,35 MPa dengan porositas 7,57%. Waktu ikat akhir menghasilkan kurva polinomial dengan persamaan y = -0,1947x3 + 7,084x2 - 92,493x + 961,21, dimana x adalah penambahan marmer dan y adalah waktu.

Kata kunci: Fly ash, Kuat tekan, Limbah marmer, Porositas, Rice husk ash, Waktu ikat

Mortar is a widely used construction material, with conventional types relying heavily on Portland cement as the primary binder. However, the production of Portland cement releases significant amounts of carbon dioxide, contributing to global warming. A prominent alternative to cement is geopolymer mortar. Several studies have shown that geopolymer mortar has the potential to produce better mechanical properties of the conventional one with the presence of CaO contained in fly ash. Marble waste has the potential to be used as a binding material in geopolymer mortar mixtures because it has a CaO content of 98.85%. This study was conducted to determine the behavior of marble waste addition on the compressive strength, porosity and setting time of geopolymer mortar made from fly ash, rice husk ash and activator solution in 10M NaOH. The mortar specimens were in the form of cubes masuring 50x50x50 mm3 with variations in the percentage of marble waste addition are 0%, 2,5%, 5%, 7,5%, 10%, 12,5%, 15%, 17,5%, 20%. Results showed that the addition of marble waste increased the compressive strength up to a 12,5%, the decreased. Conversely, porosity increased after 12,5%. This was due to reaction imbalance from excess CaO against SiO2 and Al2O3. The highest compressive strength was 24,35 MPa with 7,57% porosity. Final setting time followed a polynomial curve with equation y = - 0,1947x3 + 7,084x2 - 92,493x + 961,21, where x is marble addition and y is time.

Keywords: Compressive strength, Fly ash, Marble waste, porosity, rice husk ash, setting time