Title: Fast Track Construction with High-Strength Concrete Mixes Containing Ground Granulated Blast Furnace Slag

Author(s): M.N. Soutsos, S.J. Barnett, J.H. Bungey, and S.G. Millard

Publication: Symposium Paper

Volume: 228

Issue:

Appears on pages(s): 255-270

Keywords: activation energy; adiabatic temperature rise; blast furnaceslag; concrete compressive strength; early age strength development;fast track construction; ground granulated heat of hydration;maturity

DOI: 10.14359/14474

Date: 6/1/2005

Abstract:
The early age strength development of concretes containing ground granulated blast furnace slag (ggbs) at cement replacement levels of 20, 35, 50 and 70% have been investigated to give guidance for their use in fast track construction. 28-day target mean strengths for all concretes was 100 MPa. Although supplementary cementitious materials like ggbs are economical, their use has not gained popularity in fast track construction because of their slower strength development at early ages and at standard cube curing temperatures. There are however indications that supplementary cementitious materials are heavily penalised by the standard cube curing regimes. Measurements of temperature rise under adiabatic conditions have shown that high levels of cement replacement by ggbs, e.g. 70% are required to obtain a significant reduction in the peak temperature rise. However, despite that these temperature rises are lower than those of portland cement mixtures they are still sufficient to provide the activation energy needed for the reaction of ggbs to “kick-in” earlier. The early-age strength under adiabatic conditions of ggbs mixtures can be as high as 250% of the strength of companion cubes cured at 200C. The high early age temperatures are shown to be especially beneficial to ggbs concretes. Maturity measurements will be needed in order to take advantage of the enhanced in-situ early age strength development of ggbs concretes. The contractor needs to be able to confirm that the actual strength of the concrete in the structure at the time of formwork removal exceeds a certain compressive strength. Maturity functions like the Nurse-Saul and the Arrhenius equation have been examined for their applicability to ggbs concretes. Activation energies, required as input for the Arrhenius equation, have been determined according to ASTM C1074-98.