Mechanisms of high frost scaling resistance of SHCC

Abstract

This study aimed at evaluating the scaling resistance of strain-hardening cement-based composite (SHCC) exposed to freezing and thawing cycles. RILEM-CDF test was conducted to clarify which parameters of the composition of SHCC have an impact on the scaling resistance.The investigation was made to determine the influence of the following parameters on the scaling: water cement ratio of the mortar matrix, fiber volume, air volume, and the mixing ratio of non-binding materials, namely limestone powder, quartz sand, and sand. The water cement ratio was set to 0.3, 0.4, and 0.55. The volumetric ratio of fiber and air ranged from 0 to 1.2% and 0.8 to 11.0%, respectively. The CDF test was conducted on trowel-finished surfaces for 60 cycles, and the scaling mass was measured every 6 cycles. The specimen surfaces were observed after the test. Samples were taken out from the center part of the test specimens and pore size distributions were measured.The results indicated a generally high scaling resistance of SHCC, its scaling mass being lower than that of ordinary mortar with the same water cement ratio. Even an SHCC mortar matrix without fiber suffered less scaling than the ordinary mortar having the same water cement ratio. The scaling amount reduced proportionally to the particle size of the non-binding materials, i.e., the finer the non-binding material, the lower the scaling amount, presumably because finer particles make the microstructure denser. The fiber apparently also improved the resistance against the progress of scaling by bridging cracks.