Title: Forced Bleeding Test to Assess Stability of Flowable Concrete

Author(s): Yannick Vanhove and Kamal Henri Khayat

Publication: Materials Journal

Volume: 113

Issue: 6

Appears on pages(s): 753-758

Keywords: bleeding; fluid concrete; forced bleeding; pumpability; segregation; stability

DOI: 10.14359/51689240

Date: 11/1/2016

Abstract:
Ensuring adequate stability is critical in flowable and lean concrete prone to bleeding and segregation. This paper proposes a forced bleeding test method that can be used to determine the ability of fresh concrete to retain some of its mixing water under a pressure gradient across a drainage surface. The investigated concrete was proportioned with a water-cement ratio (w/c) of 0.55 to 0.65 with slump values varying between 70 and 240 mm (2.75 and 9.45 in.). The proposed forced bleeding test has an overhead pressure of 138 kPa (20 psi) with the pressure maintained for 1 minute. This short test duration and relatively low overhead pressure yielded better results than higher testing pressure gradients or longer test durations. Forced bleeding test results showed good correlations between the rate of forced bleeding at 1 minute and physical tests to evaluate stability. Physical tests included the determination of external bleeding for 2 hours, the measurement of coarse aggregate distribution along hardened concrete samples, as well as the variation in electrical conductivity along concrete sample height during the dormant period of cement hydration to evaluate homogeneity.