添加稻殼灰飛灰高性能混凝土拌合效能之研究

Abstract

本研究主要在，以經濟性為觀點探討以相同配比之稻穀灰-飛灰高性能混凝土(Rice Husk Ash-Fly Ash High Performance Concrete ，R-F HPC)，膠結料固定在450 kg/m3 之情況下，改變其各種組成材料之添加方式，時機及骨材之級配，並模擬預拌廠之配料方 式，以期R-F HPC 在實際量產及澆注時能以較經濟之方式得到良好的工作性，及所需之強 度或性質． 試驗結果顯示：拌合時強塑劑要與水分開，且要在水的後面加入，則可獲得 較佳之拌合效能．新拌時如產生泌水，仍可藉由預拌車在輸送往工地途中繼續拌合，則可 消除泌水；且泌水量越大可輸送的時間越長．低水膠比或低強塑劑量時飛灰要放在強塑劑 的前面，高水膠比或高強塑劑量時飛灰要放在強塑劑的後面，以改善泌水．強塑劑留到混 凝土輸送到工地時再一次添加，比分成兩次添加的效果好．用水量加到一定程度時（最大 約為原用水量的35%），坍流度即不再增加；且每增加1 kg/m3之用水量約降低55psi之抗 壓強度．R-F HPC在低水膠比時，骨材細度模數大，則有較佳之拌合效能，但在高水膠比 時則對拌合效能影響不大．提高細骨材之細度模數及縮小30-100號篩的範圍可使水膠比降 低．R-F HPC之劈裂強度與彈性模數都有隨抗壓強度之增高而增高之趨勢． This study is made from the economical point of view on how to obtain t he good workability and the required strength or property of Rice Husk Ash-Fly Ash High Performance Concrete，(R-F HPC) when it is fixed under the conditio n of 450 kg/m3 by binder in order to change the way and timing for adding the component materials and graded aggregate，to simulate the manner of mixing the materials in a patching plant in order that the desired purpose may be achiev ed when R-F HPC is actually produced and poured． The test report shows t hat superplasticizer and water should be separated and water should be added a little bit later．Under this condition，a better mixing effect may be obtai ned． When the phenomenon of bleeding is noted in the mixing operation，it ma y be eliminated by continued mixing action which may be done by a mixing tran sportation truck in the course of shipping the premixed concrete from the pat ching plant to the job site．The larger quantity of bleeding ，the longer time may be spent to send the premixed concrete to the job site．When water-binder ratio or superplasticizer is low，fly ash should be added ahead of superplas ticizer．On the contrary，fly ash should be added after superplasticizer in or der to improve the bleeding condition when water-binder ratio and the quantity of superplasticizer is high．All superplasticizer should be added into concre tein once when the premixed concrete has been sent to the job site then this w ay shall be better than adding it in two times.When the amouconcrete is added to certain degree (The maximum is 35% of the original amount of water needed) ，the slop flow shall stop ．With the increase in water amount of 1 kg/m3，the anti-pressure strength shall decrease 55 psi．When water-binder ratio of R-F HPC is low， and when fineness modulus of aggregate is high，better mixing eff ect may be obtained．However，the mixing effect shall not be affected whenwate r-binder ratio is high． Water-binder ratio may be lowered by increasing finen ess modulus of aggregate and by reducing the range of the sieve number from 30 to 100．The splitting tensile strength and elastic modulus of R-F HPC may be increased with the increase of anti-pressure strength．