Properties of mortar for self-compacting concrete
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The effect of types and amount of powder materials, admixtures, sand and water
content on the properties of self-compacting concrete (SCC) have been investigated
by tests on the mortar fraction. Tests on concrete have also been a carried out to
confirm the most important effects.
The component materials used were
* eight types of powder- PC and SRC, GGBS, PFA, CSF and three types of LSP,
* six superplasticizers -a naphthelene (Conplast 430) and melamine type, two copolymers,
one polycarboxylic ether (Glenium 51) and one formulated for S CC,
* two viscosity agents - Welan gum and a cellulose product ,
* one fine and coarse aggregate, generally at volumetric proportions of 40-47.5% of
the mortar and 31.7% of the concrete respectively.
Testing has concentrated on workability and workability retention of mixes with a
single powder, binary and ternary powder combinations, with and without a viscosity
agent. Tests have included spread/slump flow, V-funnel flow time, and two-point
workability tests for mortar and concrete, a U-box test for concrete, and some
strength tests on concrete.
The most important outcomes include:
* Glenium 51, the most efficient superplasticizer, was selected for most of the
programme, added at 1 minute after the start of mixing.
* Excellent workability and workability retention was obtained in binary and
ternary mixes containing CSF, and in SRC single powder mixes.
* Yield stress and plastic viscosity are two distinct and independent properties.
* Welan gum has better compatibility with Conplast 430 than Glenium 5l; its use
improved workability retention but slightly decreased strength.
* There are strong relations between the properties of concrete and its mortar component, and the rheological constants and single point test results for mortar and concrete.
* The rheology of some mortar mixes may be better described by the Herschel-
Bulkley model than by the Bingham model.