Fabrication of a non-cement binder using slag, palm oil fuel ash and rice husk ash with sodium hydroxide

The aim of the study is to fabricate a new non-cement binder (NCB) using slag, palm oil fuel ash (POFA) and rice husk ash (RHA). To activate these materials, sodium hydroxide (NaOH) was used at 2.5%, 5.0% and 7.5% by weight of NCB. Four different mix ratios of the slag, POFA and RHA were designed to fabricate the NCB. Mortar-prisms of NCB were cast using water-to-binder ratio of 0.5 and 0.6 with required superplasticizer. Mortar specimens were immersed in a water bath at 25 ± 2 °C for curing. NCB was tested for its consistency, setting time, flow, flexural and compressive strengths. XRD, SEM and FTIR analyses of NCB-mortars were also obtained. The results revealed that the consistency, setting time, flow and strength of NCB-paste/mortars are greatly influenced by the mix proportion and fineness of constituent materials of NCB, and NaOH doses. NCB-mortar containing 42% slag, 28% POFA and 30% RHA with 5% NaOH achieves the highest compressive strength of 40.68 MPa and a flexural strength of 6.57 MPa at 28 days. From the FTIR analysis, NCB-mortars are observed to have silica–hydrate bond with sodium or other inorganic metals (i.e., sodium–silica–hydrate–alumina gel). Therefore, NCB could be fabricated from the aforementioned materials.