大坍流混凝土應用於一般營建工程之研究

台灣營建產業對於坍度15公分左右的傳統混凝土，常因工作性不佳、施工不確實而導致工程品質不良。目前最常見施工人員在混凝土澆置過程中，為了便於澆置而加水，提高工作坍度至22公分左右，反而使得混凝土強度及品質與原設計有很大的偏差；而如果採用HPC或是SCC混凝土，又因其低水比與高流動性使得一般泵送車無法順利澆置甚至爆模，而且費用增加不少。為了改善前述缺點，因而研發適當的配比設計及摻料，以不增加總灰量下，減少拌合用水，並將坍度提升至22cm~26cm之大坍流混凝土（Hight Flow Concrete，簡稱HFC）。為了能夠普及使用HFC，必須對於HFC的特性有更深入的了解，因此研究內容包含：第一階段試驗以規劃相同水膠比配比，僅以不同摻料比來進行新拌以及硬固性質的試驗並研究及決定最佳摻料比。第二階段試驗以相同之總灰量及坍度控制在24±2公分內，調製HFC、SCC及一般混凝土，據以比較其新拌以及硬固性質。第三階段試驗以相同摻料比及坍度，來調製不同強度之HFC，據以比較其坍流度、泌水及抗壓強度之性質。第一階段試驗之結果顯示以摻料比0.9%之配比最能達到HFC之坍流度及相關品質要求；第二階段之結果顯示證明HFC具有良好之坍流度、低坍損、泌水較一般混凝土少、後期強度較高、乾縮量較一般混凝土及SCC為佳；而第三階段不同強度之HFC均能達到設計目標，代表品質無虞。本研究發展之HFC之配比，是以最專業及最經濟方式，提昇現有混凝土之施工品質與工作性，並驗證其合理性與實用性，可供工程之配比設計參考與應用。

關鍵字

工作坍度；大坍流混凝土；摻料比； SCC

並列摘要

Taiwan construct industry deems the traditional 15cm-slump concrete could not match current requirements. It could cause bad quality even if pouring reluctantly under the unwell-workability and pouring uncorrected situation. Mostly it happens when workers pour and add water into the concrete, in order to increase good workability, to slump up to 22cm. It could get possible variation between concrete strength/quality and design strength. However, if we use HPC or SCC, the low-cement ratio and high fluidity might cause pump truck not send concrete smoothly even formwork breakdown. And the cost is higher than normal concrete. In order to improve above defects, people research and develop the slump between 22cm ~ 26cm (High Flow Concrete, called HFC). In order to apply HFC widely, it’s necessary to recognize and to research deeply the characteristic of HFC. The contents are, the 1st step – using same water-to-binder ratios, but different admixture ratio to fresh property and harden property testing and then research and decide the best admixture ratio. The 2nd step – using same fly ash volume and control the slump within 24±2 cm, then mix HFC, SCC and normal concrete to compare with fresh and harden property. The 3rd step – using same mixture ratio and slump to mix different strength HFC, and then comparing flowing-slump, bleeding and compressive strength. The testing result of 1st step is using 0.9 % mixture ratio could reach the flowing-slump and related quality requirement of HFC. Furthermore, the testing result of 2st step is HFC has good flowing-slump, low-slump and less water than normal concrete. The later strength and shrinkage is better than normal concrete and SCC. The testing result of the third step shows different strength of HFC may reach designer’s requirement which represents good quality. This researching development of HFC ratio is based on the professional and most-economic manner to improve the existing concrete quality and workability. And it has been tested and approved the rationality and practicability. It may be referred and applied widely by construction engineering for design ratio.