Antiwashout

Fig. 6.8 Ready-to-use water-soluble packages of antiwashout admixture (courtesy Fritz Admixtures, Texas, USA).

LMC is used in underwater concrete for both new construction and repair. The important requirements to obtain antiwashout capability, such as segregation resistance, flowability, self-leveling characteristics and lower bleeding are provided by the addition of viscosity-enhancing polymeric admixtures at polymer-cement ratios of 0.2-2.0%. These admixtures are water-soluble polymers, and classified under two groups, viz., cellulose types such as methyl cellulose and hydroxy ethyl cellulose and polyacrylamide types such as polyacrylamide and polyacrylamide-sodium acrylate [101]. 

Underwater concreting can be done by three methods the pumping of antiwashout concrete produced by the combined use of water reducing admixtures, superplasticizers and VEAs the use of tremies also using antiwashout concrete and the preplaced aggregate method discussed above. 

Figure 8.7 Mechanism of antiwashoutability development by water-soluble polymer in antiwashout underwater concrete. ( 1991, JSCE, reprinted with permission.)... 

Property Type of Antiwashout Admixture Cellulose Type (MC) Hydroxyethyl Cellulose Type (HEC) Polyacrylamide Type... 

Tanaka S, Kishi T, Shimogoryo R, Matsuya S, Ishikawa K. Biopex acquires antiwashout properties by adding sodium alginate into its liquid phase. Dent Mater J. 2003 Sep 22(3) 301-12. 

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