  We present K-band imaging and photometry of a sample of 52 radio loud quasars
(RQs) selected from the B3 survey with flux densities above 0.5 Jy at 408 MHz.
The optical completeness of the sample is 90% and the quasars cover the
redshift range 0.4 - 2.3. For ~57% of the sources for which the quality of the
images allowed a detailed morphological study (16/28) resolved extended
emission was detected around the QSO, and its K flux was measured. Interpreting
this ``fuzz'' as starlight emission from the host galaxy, its location on the
K-z plane at z<1 is consistent with radio quasars being hosted by galaxies
similar to radio galaxies (RGs) or giant ellipticals (gEs). At higher redshifts
the detected host galaxies of RQs are more luminous than typical RGs and gEs,
although some weak detections or upper limits are consistent with a similar
fraction of RQs being hosted by galaxies with the expected luminosities for RGs
or gEs. We found a significant correlation between radio power and nuclear
infrared luminosity indicating a direct link between the radio synchrotron
emission and the nuclear emission in K. This correlation is more tight for the
steep-spectrum sources (99.97% significance). In addition, a trend is found
between radio power and infrared luminosity of the host galaxy (or mass), in
the sense that the most powerful quasars inhabit the most luminous galaxies.
