Evaluation of internal bleeding in concrete foundation from the Terzaghi's effective stress postulate

When it is necessary to ensure a function of retaining wall, load-bearing or waterproofing, diaphragm walls are used as the definitive structure to fulfill these requirements. Despite compliance with the normative rules for the preparation of concrete, as the latter are poured over great heights, a migration of water from the concrete takes place that can lead serious concerns about the durability of the diaphragm wall as well as the impairment to the strength and stiffness. The water retention capacity of a foundation concrete is determined from specific tests such as static bleeding testing according to standard ASTM C232 or even according to standard NBN EN 480-4 or also according to the 'Bauer' test of pressure filtration. These tests make it possible to quantify the rate of bleeding but do not provide sufficient understanding of the levels of the physical mechanisms responsible for the migration of water in concrete. For that, an approach is proposed here, resulting from soil mechanics, starting from the theory of one-dimensional primary consolidation of Terzaghi. The investigated concrete was proportioned with different water-cement ratio to promote bleeding. Oedometric tests made it possible to assess the ability of water to move in the concrete (coefficient of permeability) as a function of time for different load cases (self-weight of the concrete at different depths). The results show, whatever the stress applied, a good correlation between the values measured by the pore pressure sensor and the excess pore pressure values determined from the solution of the differential equation for one-dimensional consolidation proposed by Terzaghi.

Automated summary

This study investigates the movement of water in concrete using soil mechanics theory, different water-cement ratios, and oedometric tests. The results show a good correlation between water movement in concrete and time, depth, and stress levels.