Effect of nano alumina on geopolymer mortar developed from untreated and treated palm oil waste ashes / Ng Connie

Ng, Connie (2019) Effect of nano alumina on geopolymer mortar developed from untreated and treated palm oil waste ashes / Ng Connie. Masters thesis, University Malaya.

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Abstract

Malaysia is known as the world’s second largest producer of palm oil, which in turn has been generating huge amount of palm oil waste as the demand of palm oil products increases. Both ashes of palm oil fuel ash (POFA) and palm oil clinker powder (POCP) could be produced by burning the palm oil waste and fibres. POFA and POCP possess pozzolanic characteristics as these materials have silica content. Also, further processing the POFA and POCP at 500°C will produce treated POFA (TPOFA) and treated POCP (TPOCP). Geopolymerization of pozzolanic materials was adapted in this study in order to use the POFA, POCP, TPOFA and TPOCP as a whole replacement for conventional Ordinary Portland Cement (OPC). This research aims to study the effect of nano alumina on geopolymer mortar using treated and untreated palm oil waste ashes. Dry mixing method is employed in this study to ensure well dispersion of nanoparticles, binders and sands. The alkaline activator solution (AAS) was prepared by using 10 molarity of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). After casting, the geopolymer specimens were cured in oven at 65°C for 24 hours. After demoulding, all the specimens were kept at room temperature until the day of testing. Compressive strength tests, ultrasonic pulse velocity (UPV) and setting time were carried out to study the trend of strength gain of the palm oil waste ashes based geopolymer mortar with and without nano alumina incorporated. Scanning Electron Microscope (SEM), Energy Dispersive X-Ray (EDX) and X-ray diffraction (XRD) analyses were conducted to study the effect of nano alumina and POFA, POCP, TPOFA and TPOCP particles in geopolymerization. The addition of nano alumina in the palm oil waste ashes based geopolymer mortar was done to reduce the mole ratio of SiO2/Al2O3 and enhance the compression strength and subsequent change in the microstructure arrangement. The optimized POFA-based geopolymer mortar with 5% nano- alumina produced 28-day compressive strength of 35 MPa; on the contrary, POCP-based geopolymer mortar with 7% nano-alumina has only about 12 MPa after 28 days and this could possibly be attributed to higher water content as reflected in the SEM image. XRD analysis hinted the presence of amorphous geopolymer product as the wide hump of POFA and POCP have shifted after the geopolymerization process. Phases of quartz, albite and corundum were observed in all the samples. However, peaks of albite for TPOCP is dissolving as it approached 28 days of curing. In conclusion, 5% of nano alumina in POFA-based geopolymer mortar performed better than other binders.

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