Transport Properties of Engineered Cementitious Composites under Chloride Exposure

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Title: Transport Properties of Engineered Cementitious Composites under Chloride Exposure

Author(s): Mustafa Sahmaran, Mo Li, and Victor C. Li

Publication: Materials Journal

Volume: 104

Issue: 6

Appears on pages(s): 604-611

Keywords: chloride diffusivity; cracking; engineered cementitious composites

Date: 11/1/2007

Abstract:
This paper presents the results of an experimental investigation on the chloride transport properties of engineered cementitious composites (ECC) under combined mechanical and environmental loads. ECC is a newly developed, high-performance, fiber-reinforced cementitious composite with substantial benefit in both high ductility and improved durability due to tight crack width. By employing micromechanics-based material design, maximum ductility in excess of 3% under uniaxial tensile loading can be attained with only 2% fiber content by volume, and the typical single crack fracture behavior commonly observed in normal concrete or mortar is converted to multiple microcracking in ECC. In this study, immersion and salt ponding tests were conducted to determine chloride ion transport properties. Under high imposed bending deformation, the preloaded ECC beam specimens reveal microcracks less than 50 mm and an effective diffusion coefficient significantly lower than that of the similarly preloaded reinforced mortar beam because of the tight crack width control in ECC. In contrast, cracks larger than 150 mm are easily produced under the same imposed deformation and have significant effects on effective diffusion coefficient of reinforced mortar. Moreover, through the formation of microcracks, a significant amount of self-healing was observed within the ECC cracks subjected to NaCl solution exposure.