Potential of municipal woody biomass waste ash in the production of cold-bonded lightweight aggregates

Abstract

Nowadays, increasing biomass wastes are incinerated and then transported to landfills for disposal, which occupies many land resources and causes health problems due to lack of any form of control. Therefore, a novel and green recycling method is urgently needed. In this study, a type of municipal woody biomass waste ash (MWBA) was granulated into a new type of artificial lightweight aggregates by the cold-bonded method. The effects of different water content (20–33%), rotation speed (30, 40, 50, 60 rpm) and rotation angle (30–60°) on the granulation efficiency and particle size fraction (4 mm–10 mm, 10 mm–16 mm, 16 mm–20 mm) of the municipal woody biomass waste ash aggregate (MWBAA) as well as the impact of varying cement content (5, 10, 15, 20%) and curing time (3, 7, 14, 28 days) on the performance of MWBAA were investigated. The MWBAA met the bulk density requirement of lightweight aggregate in EN13055 with bulk density between 841 and 1058 kg/m3. It was also found that 27–29% is the optimum water content for MWBAA manufacturing. The highest granulation efficiency (97.84%), as well as better gradation of MWBAA, could be achieved at a rotation angle of 55° and a rotation speed of 60 rpm. After 28 days of curing, the highest compressive strength of 2.6 MPa was achieved by the MWBAA with 20% cement content. Nevertheless, the porous and irregular shape of the unburned wood ash resulted in higher water absorption (25%), but had negligible effect on the bulk density and strength performance of MWBAA. This study thus provides an alternative solution to effectively recycle MWBA and potentially granulate MWBA into lightweight aggregate that can be utilized in concrete.