Development of an Admixture for Self-Leveling Concrete
Sebastien Rols, Jean Ambroise and Jean Pera
Appears on pages(s):
Accelerating agents; admixtures; bleeding (concrete); compressive
In the past decade, many efforts have been undertaken to develop highly-workable concrete which consolidates under its own weight without any vibration, specially in Japan. The admixtures used in such concrete are mainly composed of high water reducing superplasticizers, fine limestone dust and viscosity agents to maintain not only high flowability but high segregation resistance of the concrete. The water to cement ratio is generally lower than 0.55. A new admixture is proposed in the present study. It is a mixture of a super-plasticizer and an accelerator with plasticizing properties which also acts as a viscosity agent. The compsition o f the self-levelling concrete is as follows. The total amount of fine materials (cement + fly ash or cement + ground limestone) is 370 kg/m3, while the cement content (normal portland cement CEMI 52.5) is 260 kg/m3. The water to cement ratio is 0.73. The mechanical performancess of the hardened concrete is better than those of a usual French building concrete. The compressive strengths at 16 hrs, 7 days, and 28 days are 8, 30, and 35 MPa, respectively. The unrestrained drying shrinkage reaches 600 to 700 pm/m, at 90 days as predicted from the 28 day results.