Pore Structure Analysis of Cement Samples

These cement
samples cured under different conditions were treated by vacuum-saturated
water. Then the Carr–Purcell–Meiboom–Gill method
and LFNMR (MicroMR, Niumag Instrument Corporation) were utilized to
analyze the pore structure of these cement samples cured under CETS,
ETS, and HCC conditions, by testing the transverse relaxation time
(T₂) of hydrogen protons in the pores
of cement samples.^{1 (link),48 (link),49 (link)} The relation between T₂ and pore size
of the cement paste is expressed as where γ is the relaxivity. Zhou et al.^{50 (link)} reported that the relaxivity of the cement paste
is 1.88 nm/ms. R is the pore radius in the cement
paste.^{51 (link),52 (link)}Through the further calculation of
LFNMR data, the porosity, ϕ_NMR, can be obtained using where m_i is the T₂ increment, M_b is the total T₂ amplitude
of the standard sample, S_b is the scanning
time of the standard sample, s is the scanning time
of the cement paste, G_b is the receiver
gain of the standard sample, g is the receiver gain
of the cement paste, V_b is the total water
volume of the standard sample, and ϑ is the volume of the cement
paste.