Inclusion of polymeric substances into hydraulic cement concrete has made a tremendous impact towards
improving its performance properties. However, polymers to be included into concrete should neither cause
damage to its mechanical capacities nor to its durability characteristics. This article reports experimental
findings regarding influence of non-hydrocarbon substances present in natural rubber latex (NRL) on the
compressive strength of NRL-modified concrete. Six selected clonal latexes were chemically analyzed for
thirteen compositional parameters each. The latexes are used in making modified concretes and specimens
obtained from these concretes were given both moisture and dry curing treatments for effective cementhydration
and latex-film formations respectively. Eventually, concretes modified with latexes containing
higher non-hydrocarbon substances especially volatile fatty acids (VFA) and zinc were observed to suffer
significant compressive strength losses. Indeed, 12.4% loss in compressive strength was recorded against
concrete modified with the latex having the highest contents of VFA and zinc. However, 2% and 4% increase
in the strength over normal concrete were observed in relation to two of the latexes investigated.