| Summary: | 博士 === 國立臺灣科技大學 === 營建工程系 === 101 === The possibility of using residual rice husk ash, a by-product of power boilers, containing high carbon content in concrete was investigated in this study. The residual rice husk ash or so-call black rice husk ash used in this study was mostly amorphous silica and partially crystalline silica and mean particle size of 12 μm. The black rice husk ash was used in conventional concrete and self-consolidating concrete as cement substitute up to 30% replacement in weight. The proposed mix design method using the combination of Fuller's grading curve and coating paste thickness theories was also investigated and used to design self-consolidating concrete mixtures containing black rice husk ash. More specifically, the black rice husk ash was incorporated in high volume fly ash self consolidating concrete. The concretes produced were tested for compressive strength and durability properties, i.e. electrical resistivity, ultrasonic pulse velocity, chloride ion penetration, sulfate attack, length change, porosity and water absorption. The results show that up to 30% black rice husk ash replacement 28-day compressive strengths in the ranges of 47−66 MPa and 51−62 MPa were attainable on conventional concrete and self-consolidating concrete, respectively. Up to 20% of black rice husk ash could be advantageously blended with cement without adversely affecting the strength and durability properties of both conventional and self-consolidating concretes. The conventional black rice husk ash concrete showed the good resistance to the chloride penetrability and the sulfate attack in the long-term. Self-consolidating concrete containing black rice husk ash designed by the proposed method attained high flow ability without bleeding or segregation, cost effectiveness, and durable features as expected. Over 50% in consumption of cement could be saved from the use of the proposal method when comparing to the conventional mix design method at the same compressive strength. The high volume fly ash self consolidating concrete having 28-day compressive strength level of 28.47−44.98 MPa could be obtained with cement content of as low as 152−203 kg/m3 and the amount of fly ash and black rice husk ash of 60% in weight of binder amount. The results on durability properties evidenced the concretes could be consider to be durable and good corrosion endurance. In summary, the above results definitively proved many possible applications of the black rice husk in concretes.
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