Effects on cement after partial replacement with burned joss paper ash

Abstract

In the last ten years, as international environmental protection consciousness has increased, the study and applications of green building, green construction materials and energy savings as well as reduction of carbon dioxide have become urgent issues for governments. In Taiwan, joss papers are burned in more than 11,731 registered shrines or temples in traditional Chinese deity or ancestor worship ceremonies during special holidays or occasions. Instead of placing this large amount of burned joss paper ash (BJPA) in landfills, this study proposes recycling BJPA by replacing some cement with calcined BJPA (CBJPA) in mortar specimens. After BJPA samples were calcined at a high kiln temperature, mortar samples were created using CBJPA to replace cement at seven different levels: 0%, 5%, 10%, 15%, 20%, 25% and 30%. Tests like setting time and compressive strength were performed for macro-analyses; scanning electron microscopy–energy dispersive spectroscopy, X-ray diffraction and thermal gravimetric analysis/differential thermal analysis were carried out for the microstructure and chemical composition analyses. The test results showed that the compressive strengths of specimens with different levels of CBJPA replacement were apparently less than those of the control group (0% CBJPA) at all curing times. The compressive strength and setting time both decreased as the fraction of CBJPA in the mortar increased. Furthermore, because the hydration product did not cement and the mortar specimen structure was loose, the expected strength improvement from the pozzolanic reaction provided by the CBJPA was not clearly observed.