抄録
Water reducing admixtures are usually added to concrete mix in order to improve workability of fresh concrete, and to improve physical properties of hardened concrete. Customarily, these admixtures are dissolved in mixing water, and then mixed with other concrete materials. It was found that the effectiveness of the admixtures can be greatly enhanced by changing purposely the timing of admixture addition to concrete mix.
Ready mixed concrete
Method A: Add an admixture to concrete mix at the end of the ordinary mixing period. The concrete mix is then agitated during the transportation period.
Method B: Add an admixture at a job site. The concrete mix is then agitated vigorously in a truck mixer.
Method C: Combination of methods A and B.
Job site mixing
Method D: Add an admixture to concrete mix at the delayed time, and then complete the mixing.
The following advantages can be expected when a suitable admixture is used combined with an appropriate choice of methods described above:
(1) Retempering by admixtures, (2) to produce flowing concrete and (3) to improve the water reducing action of admixtures. These advantages can be achieved economically without any deteriorating effects on the final products.
