Another factor which might contribute to the low performance
of modified phases especially MC-5% and MC-10% could be attack
on the hydrocarbon particles by the H2SO4. In fact, at the end of
the last two curing regimes a layer of latex was found on the surface
of specimens. Close observations revealed that the peripheral
latex especially at the top horizontal surface has been transformed
into jelly like form with substantial increase in volume. This was
believed to be caused by the action of the H2SO4. Previous reports
regarding acidic substances coming into contact with polymer substances
suggested that harm can occur on the polymeric Si–O–Al
bonds with consequence strength weakening through ejection of
tetrahedral alumina from the aluminosilicate [24,25].