X10 Concept to Improve Quality and Durability of Diaphragm Walls-Paper

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The paper presents X10, a concrete mix developed to improve the quality and durability of diaphragm walls. Conventional mixes can have limited flowability and stability, leading to bentonite inclusions, poor reinforcement coverage, cavities and porous concrete—defects that are especially concerning in aggressive environments.<br /><br />X10 uses a stabilizing admixture to achieve self-compacting-concrete-level flow while retaining fresh-concrete stability and water under pressure. Laboratory tests found substantially less water loss than with conventional mixes, along with better flow retention and ability to pass through reinforcement. The tested X10 mixes also showed higher compressive strength and resistance to chloride penetration.<br /><br />A full-scale trial compared X10 with a reference mix in 22-metre-deep panels. Core investigations showed better reinforcement enclosure with X10 (94% versus 83%), no continuous cavities along outer reinforcement bars in X10 samples, and a denser, less defective concrete cover. Core compressive strengths were similar for both mixes. The improved cover quality was observed even where concrete had to flow farther from the tremie pipe.<br /><br />X10 has been used in a river-embankment project and is being applied to the heavily reinforced walls of the new IJmuiden sea lock, designed for a 100-year service life. Although the mix does not meet the standard minimum binder-content requirement for diaphragm walls, the authors argue that its demonstrated performance may justify its use under the Equivalent Concrete Performance concept in EN 206.<br /><br />The study concludes that X10 can reduce placement risks and improve durability, particularly for walls exposed to salts, chemicals, changing water levels or dense reinforcement.

Keywords

X10 concrete mix

diaphragm walls

self-compacting concrete

stabilizing admixture

flowability

reinforcement coverage

chloride penetration resistance

compressive strength

durability

Equivalent Concrete Performance