Chemical admixtures - Concrete Mix Design, Quality Control and Specification - page 68

Table 4.1 (Continued) Admixtures, their characteristics, and usage
Admixture type Effects and benefits Materials

Flocculating Increase interparticle

attraction to allow paste to
behave as one large flock.

Vinyl acetate-maleic
anhydride copolymer.

Fungicidal, cermicidal,
insecticidal

Inhibit or control bacterial,
fungal, and insecticidal
growth.

Polyhalogenated phenols,
emulsion, and copper
compounds.

Rheology/viscosity
modifying

Modify the rheological
properties of plastic
concrete.

Polyethylene oxides,
cellulose ethers (HEC,
HPMC), alginates (from
seaweed), natural and
synthetic gums, and
polyacrylamides or
polyvinyl alcohol.

Air detraining Tributyl phosphate, dibutyl

phosphate,
dibutylphthalate,
polydimethylsiloxane,
dodecyl (lauryl) alcohol,
octyl alcohol,
polypropylene glycols,
water-soluble esters of
carbonic and boric acids,
and lower sulfonate oils.
Source : American Concrete Institute (ACI) Committee 212, ACI 212.3R-10, Report on Chemical
Admixtures for Concrete, 2010.

Reduce air in concrete
mixtures, cement slurries,
and other cementing
applications.

as “especially suitable for use with fly ash mixes” without any warning
as to type and proportion of the latter. The admixture in question was
Grace WRDA, but it is emphasised that this admixture is a very normal
lignosulphonate that has been in wide use in many countries for many
years. It seems that the same effect might have occurred with other similar
competing products. The point in relating this incident is that, until its
occurrence, Day had for many years been happy to design concrete mixes
over the telephone in many countries, and recommended that the first trial
mix be a full size delivery to the actual structure, without encountering any
problem. He has also recommended readers to find and rely on the techni-
cal representative of a reputable admixture supplier. Clearly this advice
must now change, and concrete producers, while still listening to advice,
must satisfy themselves through trial mixes before believing it.
The authors have seen trial mixes undertaken with the “same” admixture,
which had profoundly different performance in concrete with otherwise the
same mix composition. This was clearly due to a different chemistry where
the supplier was using the project as a product development laboratory. This
sometimes cavalier attitude to modifying admixtures does involve some