This paper describes a series of tests carried out to
determine a suitable mortar mix design to fill slender steel hollow
sections. The strength, compaction and
shrinkage properties of such a mix are important if the concrete infill is to
contribute to the resistance and ductility of the filled composite member. Four different types of tests addressing
compressive and tensile strength, compaction and shrinkage were used to
evaluate the merits of six mix designs.
These mixes varied by water/cement ratio, and by the inclusion of two
different admixtures: one to improve compaction and one to reduce
shrinkage. The test results clearly
identify the optimum mix, and this has been employed in a wider range of
structural tests on composite bracing members.
The superior performance of specimens filled with the optimum mix over
hollow specimens is illustrated.