Engineering properties of ternary blended geopolymer concrete and role of oxide composition on mortar / Afia Sharmin

Afia, Sharmin (2016) Engineering properties of ternary blended geopolymer concrete and role of oxide composition on mortar / Afia Sharmin. Masters thesis, University of Malaya.

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Abstract

The use of mineral admixtures has had positive effect in reducing carbon-di-oxide (CO2) emission. However, the quantity of mineral admixtures being used in the cement or concrete production is small compared to the mineral admixtures or pozzolanic materials produced. Recent advances in concrete that include geopolymer concrete utilize more amount of mineral admixture. This has resulted in cement free concrete and effective use of more quantities of suitable mineral admixtures and pozzolanic materials. This research investigates the contribution of different oxides present in the rice husk ash (RHA), ground granulated blast furnace slag (GGBS) and metakaolin (MK) on the performance of geopolymer mortars. Twenty-six mixes were designed with combined base materials and varied NaOHaq concentration used as one of the activators. RHA, GGBS and MK were varied between 15% and 70%, 0% and 75%, and 0% and 40%, respectively. The binder/fine aggregate, water/binder and alkaline activator/binder ratios were constant and the values were 0.5, 0.25 and 0.5 while all the samples were cured at 65oC for 24 h. The mixture (ternary) that contained 25% RHA, 25% MK and 50% GGBS (M25R25G50) gave the maximum compressive strength of 48 MPa, in addition to better flow rate and density than any binary combinations. Among the twenty six mixes, four mixes with NaOHaq concentration 14M were tested with scanning electron microscope (SEM) and energy dispersive X-ray spectroscopic analysis (EDS) and X-ray diffractometer to investigate the effect of oxide composition on mortar. The findings through microstructural and characterization tools show that regardless of the source, SiO2 and CaO present in the base materials contributed to the strength, while Al2O3 influenced the amorphorsity of the products. The SiO2 present in MK and GGBS were more reactive compared to the SiO2 based RHA. The use of oil palm shell (OPS) and palm oil clinker (POC) in construction material industry would enable the disposal of huge amount of wastes from palm oil industry and also reduce the negative effect of construction on the environment. Five concrete mixtures were prepared with POC as fine aggregate with manufacture sand (M-sand) and rice husk ash (RHA), ground granulated blast furnace slag (GGBS), metakaolin (MK) as pozzolan or whole cement replacement materials. The mechanical properties of OPS light weight geopolymer concrete including compressive strength, flexural strength, ultrasonic pulse velocity and splitting tensile test were investigated and reported. OPS and granite (9 mm) were used in different percentages as coarse aggregates in five different mixes. As the volume of OPS increased, the resulting compressive strength decreased because the increase of OPS content reduced the density of concrete significantly due to more pores in this concrete. An increase in the replacement of OPS by granite led to an increase in UPV values. The test results showed that 20% OPS and 80% granite containing POC sand up to 50% with M-sand, a grade 35 OPS lightweight geopolymer concrete can be produced with 14% lighter than normal weight concrete. The effect of micro-steel fiber on the fracture energy and toughness was also investigated; fracture test has been conducted on five mortar specimens prepared by using steel microfiber up to 3%, in addition to the control specimen. Fracture energy was increased up to 10 times due to the incorporation of microfiber at 3% compared to control specimen. In addition to the fracture energy, fracture toughness was also calculated using RILEM TC 50-FMC and it was found that the highest fracture toughness was achieved for the specimen with 1.5% steel microfiber.

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