Title:
Mechanical Properties, Creep, and Resistance to Diffusion of Chloride Ions of Concretes Incorporating High Volumes of ASTM Class F Fly Ashes from Seven Different Sources
Author(s):
V. Sivasundaram, G. G. Carette, V. M. Malhotra
Publication:
Materials Journal
Volume:
88
Issue:
4
Appears on pages(s):
407-416
Keywords:
chlorides; compressive strength; concretes; creep properties; fineness; fly ash; mechanical properties; modulus of elasticity; plasticizers; setting (hardening); water-cementitious ratio; Materials Research
DOI:
10.14359/1930
Date:
7/1/1991
Abstract:
Reports an investigation in which the performance of seven low-calcium (ASTM Class F) fly ashes in the high-volume fly ash concrete system was studied. The cement content and the water-cementitious materials ratio (w/c + f) of the concretes were kept at two levels: 155 kg/m3 of portland cement and a w/c + f of 0.31; and 225 kg/m3 of portland cement and a w/c + f of 0.22. The concretes were made incorporating fly ash at 58 percent of the total cementitious material content. Large dosages of a superplasticizer were used to obtain the required workability. Concrete specimens were tested for compressive strength, Young's modulus of elasticity, creep strain, and resistance to chloride ion diffusion at various ages up to 1 year. The fly ash concretes did not perform similarly either in the plastic or hardened condition. In the instances in which an excessive dosage of superplasticizer had to be used to obtain the workability, delay in setting was observed. However, the setting delays did not affect the strength development of the concretes. The concretes incorporating fly ashes with higher fineness and higher pozzolanic index achieved higher compressive strength and modulus of elasticity, although there were some exceptions. Further, most of the fly ashes performed relatively better in concretes with 155 kg/m3 of cement than in concretes with 225 kg/m3 of cement. Overall, the fly ash from Atlantic Canada performed better than the other fly ashes in the high-volume fly ash concrete, yielding 1-year strengths of 52 MPa and 83 MPa with 155 kg/m3 and 225 kg/m3 of cement, respectively. The creep strain at 1 year was found to be low in both series of concretes, ranging from 156 x 10-6 to 352 x 10-6 in concretes with 155 kg/m3 of cement and from 211 x 10-6 to 501 x 10-6 in concretes with 225 kg/m3 of cement. The rapid chloride ion diffusion tests performed on specimens of concretes with 155 kg/m3 of cement indicated very low chloride ion diffusion at 91 days, ranging from 197 to 973 coulombs.