To achieve good strength gain, especially at an early age, the unit water content was controlled to be less than 150 kg/[m.sup.3], and a polycarboxylate-based water-reducing agent was added after being specially modified through the adjustment of the amount of polyethylene glycol alkyl ether and the addition of an amine.
The state of moisture in aggregates was measured before the mix of concrete, and the surface water on aggregates was then reflected through the correction of the unit water content.
Admixtures, unit water content, unit cement content, and designed compressive strength are as follows:
Under the conditions of this experiment (W/C: 50%; unit water content: 175 kg/[m.sup.3]; unit cement content: 350 kg/[m.sup.3]; acquired compressive strength: 33 to 34 MPa; and S/a: 42%, 47%, and 52%), the compressive strength of RAC did not change when the amount of AE admixture added to the RAC was between 5 g and 10 g.
Figure 1 shows the fine aggregate ratio as well as the unit water contents
according to the change of FMC.