Physical and Mechanical Properties of Green Cementless Mortar Incorporating Waste Paper Sludge Ash
Authors: Jamaluddin Aida Nabila , Saad Siti Asmahani , Masjuki Siti Aliyyah , Wan Hassan Wan Nur Firdaus , Che Deraman Siti Noratikah , Md Husain Nadiah 
Published: January 2025

As an alternative to conventional construction material such as normal concrete, waste paper sludge ash (WPSA) based geopolymer is seen as a promising and viable option in construction material selection due to its high amount of aluminum (Al) and silicon (Si) content. This research aims to determine the microstructure and mechanical characteristics of WPSA in geopolymers. The alkaline solution that contains 6 M of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used to activate the geopolymer. The hardened 50 mm-sized mortars were prepared and underwent a heat-cured process for 1 day at various temperatures at 24 ?, 60 ?, and 90 ?, respectively. Then, the mortar cubes were placed in the laboratory until the testing days. A compression test was conducted to identify the strength development of the WPSA-based geopolymer mortar at 7, 14, and 28 days, respectively. Chemical composition was analyzed using X-ray fluorescence (XRF). Furthermore, Fourier-transformed infrared spectroscopy (FTIR) was conducted to ascertain the structural elucidation and scanning electron microscope (SEM) analysis was done to provide microstructural observations of the geopolymer. Based on the XRF analysis, the WPSA has the highest amount of calcium oxide (CaO) instead of aluminum oxide (Al2O3) and silicon dioxide (SiO2), and it reduces the performance of WPSA as a cement replacement material. The ratio of SiO2 and Al2O3 is recorded as 1.1:1. Therefore, it is suitable for bricks and ceramics production instead of concrete production. As for the curing process, the heat-cured method is evident in accelerating strength development in the WPSA-based geopolymer mortar compared to the ambient curing method due to the rapid polymerization process in the geopolymer system. It is proven that 60 ? is the optimum temperature for the curing process for geopolymer mortar.
ABSTRAK: Sebagai salah satu alternatif kepada bahan binaan konvensional seperti konkrit biasa, geopolimer berasaskan abu enap cemar kertas (WPSA) adalah dilihat sebagai pilihan yang baik kerana bahan ini mempunyai kandungan aluminium (Al) and silika (Si) yang tinggi. Penyelidikan ini bertujuan untuk menentukan struktur mikro dan ciri mekanikal WPSA dalam geopolimer. Larutan alkali yang mengandungi 6 M natrium hidroksida (NaOH) dan natrium silikat (Na2SiO3) digunakan untuk mengaktifkan geopolimer. Mortar yang bersaiz 50 mm telah disediakn dan ia melalui proses pengawetan haba selama 1 hari pada suhu yang berza-beza, iaitu 24 ?, 60 ?, and 90 ?.  Kemudian, kiub mortar tersebut diletakkan di dalam makmal sehingga hari ujian. Ujian mampatan dijalankan untuk mengenal pasti perkembangan kekuatan mortar geopolimer apabila mencapai 7, 14, dan 28 hari. Komposisi kimia dalam sampel telah dianalisa menggunakan pendarfluor sinar-X (XRF). Tambahan pula, Spektroskopi inframerah fourier transformasi (FTIR) untuk memastikan sifat bahan dan analisis pengimbasan mikroskop elektron (SEM) untuk menyediakan pemerhatian struktur mikro geopolimer. Berdasarkan data dari analisa XRF, WPSA mempunyai jumlah kalsium oksida (CaO) tertinggi berbanding aluminium oksida (Al2O3) dan silikon dioksida (SiO2), dan ia mengurangkan prestasi WPSA sebagai bahan gantian simen. Nisbah SiO2 dan Al2O3 direkodkan sebagai 1.1:1. Oleh itu, ia sesuai digunakan untuk pengeluaran batu bata dan seramik berbanding pengeluaran konkrit. Bagi proses pengawetan, kaedah pengawetan haba terbukti mempercepat perkembangan kekuatan geopolimer berasaskan WPSA berbanding pengawetan pada suhu ambien disebabkan  berlakunya proses pempolimeran yang sangat pantas dalam sistem geopolimer tersebut. Telah terbukti bahawa suhu 60 ? adalah suhu optimum bagi proses pengawetan mortar geopolimer berasaskan WPSA ini.