中低強度稻殼灰飛灰高性能混凝土之工程性質研究

Abstract

本研究的目的是採用稻殼灰,飛灰取代部分水泥,產製目前土木工程常用之中低強度稻殼灰 -飛灰高性能混凝土(Rice husk-Fly ash High Performance concrete, R-F HPC).在膠結 料固定為450kg/m3情況下,藉由改變不同配比與拌合方法,達到要求的工作度(坍度>=20cm, 流度>=50cm),且不可骨料析離或泌水.希望由本實驗瞭解稻殼灰,飛灰取代方式對高性能混 凝土工程性質的影響.試驗結果顯示:稻殼灰,飛灰取代量越高則工作度越差,可利用二次加 劑法減少水及強塑劑量,但前後加加劑的濃度必須適當.稻殼灰可使混凝土發揮早強效果, 用量以15kg/m3最佳.劈裂抗張強度主要還是取決於抗壓強度的大小,稻殼灰飛灰對劈裂抗 張強度的影響並不明顯.稻殼灰飛灰取代量越高,乾縮及重量損失率就越大.而以大量飛灰 取代波特蘭水泥對改善混凝土抗硫酸鹽侵蝕是有效的.適當的養護對稻殼灰飛灰高性能混 凝土的強度發展和耐久性更是特別重要.稻殼灰飛灰高性能混凝土在200'C時,剩餘強度百 分比大約是100+-10%左右,在400'C時剩餘強度百分比大約是80+-10%左右,在600'C時剩餘 強度百分比大約是40+-5%左右,至於稻殼灰及飛灰對混凝土的耐火性能並無明顯改善. The objective of this study is using rice husk (R) and fly ash (F) to replace some coment, to produce middle/low strength rice husk-fly ash high performance concrete (R-F HPC). With the fixed binder content of 450 kg/m3, by adjusting d ifferent propertions and mixing method, the fresh concrete with the demanded w orkability (slump >= 20cm, flow >= 50cm), without aggregate segregation or ble eding was achieved. In this study, the influence of rice husk and fly ash upon the engineering properties of R-F HPC is investigated. Experimental results i ndicted that the workability of the fresh concrete decreases with increasing r ice husk and fly ash content. It is found that use of secondary-adding method can reduce the amount of water and superplasticizer needed, however the concen tration of first and second add solution must be appropriate. The adding of ri ce husk can increase the early strength of concrete and the optimal amount is 15 kg/m3. The splitting tensile strength of R-F HPC specimen is not related to the rice husk and fly ash content. The dry shrinkage and weight loss ratio of concrete increase with the increasing replacement of rice husk and fly ash. H igh fly ash content can effectively improve the sulfate resistance of concrete . Proper curing is very important to the strength development and durability o f R-F HPC. After concrete suffer the high temperature of 200'C, 400'C and 600' C, the residual strength ratio is 100+-10%, 80+-10% and 40+-5% respectively. T he adding of rice husk and fly ash does not effectively improve the refractory characteristic of the R-F HPC.