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.