Frost Resistance of Roller-Compacted High-Volume Fly Ash Concrete

Abstract

Laboratory investigations were performed to design four high-volume fly ash roller-compacted concrete mixtures. The amount of fly ash was fixed at 63% of the total cementitious material. Two mixtures (one air-entrained and one non-air-entrained) had a cementitious material content of 12% (as a proportion of the total mass of dry materials), and two mixtures (one air-entrained and one non-air-entrained) had a cementitious material content of 15%. The apparatus used to prepare the cylindrical specimens required for the tests was specifically designed for this purpose. In this apparatus, the concrete is placed in a cylindrical mold that is vibrated laterally while a longitudinal compressive force is applied to the concrete. Each mixture was tested for strength, absorption, permeability, determination of the air-void characteristics, and frost resistance. The frost resistance of air-entrained concretes (tested according to Procedure A of ASTM Standard C 666) was found to be very good, irrespective of the cementitious material content. These concretes contained only a small number of irregularly shaped compaction air voids. The value of the air-void spacing factor was 250 ± 5 μm for the air-entrained concretes, and only slightly higher at 309 μm and 393 μm for the non-air-entrained concretes. The latter concretes also showed adequate frost resistance. Notwithstanding these conditions, the use of air entrainment is recommended for roller-compacted, high-volume fly ash concretes.