Photocatalytic activity of white Portland cement paste samples, added with 0.5, 1.0 and 3.0% wt of titanium dioxide nanoparticles, was evaluated trough the degradation of Rhodamine B. The degradation was measured by the change of the color coordinates CIE L*a*b* of samples exposed to a UV source and a photocatalytic efficiency coefficient, ξ, was calculated for two times of curing (65h and 28d). Three ratios of anatase:rutile were used (100:0, 85:15, 50,50) for each percentage of addition. Results showed that samples with the highest photocatalytic activity correspond to 3.0% of anatase at early ages, and 3.0% of anatase:rutile (50:50) at late ages.