英译中,求译文,It is well known that in early ordinary Portland cem

英译中,求译文,
It is well known that in early ordinary Portland cement (OPC)
concrete,before setting,the region close to the aggregate surface
has on average less cement grains and is instead filled to a
significant extent with water.This water-rich region is approximately
50 μm thick,similar to the thickness of the interfacial
transition zone (ITZ) in mature OPC mortars and concretes.
Dissolved ions therefore must diffuse from the nearby cement
particles to this region if the aggregate is chemically inert.
According to some investigators,the differential diffusion ofCa2+
relative to Si4+ in a hydrating Portland cement system is responsible
for the higher calcium hydroxide concentration
observed in the ITZ than in the bulk cement gel.
There is,however,increasing evidence suggesting that
mineral aggregates do chemically interact with the cement
pore solution.Tasong et al.[12] reported that siliceous rocks
such as basalt and quartzite,and silica sand,could absorb
‘significant’ amounts of OH− and Ca2+ from an artificial cement
solution (∼70 mM of OH−,∼6 mM of Na+,∼36 mM of K+,
and ∼4 mM of Ca2+).Si4+ was found to dissolve from the
aggregates initially and then start to precipitate after a period of
time.These results suggest that heterogeneous nucleation of
calcium hydroxide could originate at the aggregate surface,as
has also been reported by other investigators [10,13].Calcium
silicate hydrates (C–S–H) could then form at or near this
calcium hydroxide layer at the aggregate surface after the
solubility limit with respect to C–S–H is reached.This implies
that the C–S–H within the ITZ,and to some degree in the bulk
cement paste as well,could be comprised in part of the Si4+
dissolved from both the cement and the siliceous aggregates.
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