| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程技術研究所 === 86 === This study is based on results of past studies, a comparison on the microstructure and mechanical properties of various pozzolans will be conducted to select a relatively ideal proportioning technology of HPCs with fly ash,blast refurnace slag and silica fume.It will also study models of various mixtures of HPC with pozzolans.To control high fluidity and high strength requirements of HPC, slump will be set at 25±2℃, and 28 days compressive strength at above 560kg/cm2 to serve as basis for mix design for concrete. First material factors such as method of replacing pozzolans and rate of fine aggregate shall be considered before adopting the ACI mix design method and minimum void mix design method to produce HPC that meet requirements.
After which, mechanical tests such as compressive strength, flexural strength, shear strength and fracture toughness and micro-analysis technology shall be conducted to observe and explain its mechanical theory as well as study related models of mechanical behaviors. Results of study showed that under revised ACI mix design method and minimum void mix design metnhod,if appropriate factors were considered, compressive strength and workability can be adjusted to meet requirements of high performance concrete,Under revised ACI mix design method, fluidity of HPC with non-unitary pozzolans is relatively small compared with fluidity obtained in minimum void mix design method. Likewise, slump and flow values are also relatively small. Pozzolans such, as blast furnace slag fly ash silica fume have a positive impact in areas relating to slump and fluidity of HPC. In terms of workability benefits under equivalent ratios blast furnace slag > fly ash > silica fume. Under similar water cement ratio ,similar workability and materials ratio,HPCs with blast furnace slag and fly ash has a reducing effect on the strength of HPC at the early stage.
On the other hand,HPC with silica fume has an absolutely positive, slag or fly ash and silica fume were gathered and replaced with cement or fine aggregate,it will have a mutually offsetting effect.As such, in terms of strength benefits at the early stage under equivalent ratio, silica fume > blast furnace slag> fly ash.HPC with blast furnace slag, fly ash and silica fume has a positive effect on the long term strength of HPC.Under equivalent mixtures,silica fume > blast furnace slag >fly ash.
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