  This PhD thesis (defended in 2014) is focused on the estimation of the CMB
polarised anisotropies power spectra on a masked sky and on forecasts of
constraints set on the primordial universe physics thanks to these
anisotropies. After an introduction on the light polarisation, the standard
model of cosmology and the CMB properties, I show the results obtained on the
use and efficiency of pseudospectrum methods to correct for the so-called
E-to-B leakage. Afterwards, I present the forecasts obtained on the detection
of the tensor-to-scalar ratio r and on the detection of chiral gravity, using
the pure pseudospectrum method. The study of forecasts of a primordial magnetic
field detection using the CMB polarised anisotropies is finally briefly
tackled.

Cosmology and Nongalactic Astrophysics