depending on the stain, a poultice from kitty litter or diatomaceous earth mixed w/xylene as a poultice will generally pull them out of conc,,, you may need to apply several times,,, don't use heat as that'll just drive the stain deeper into the conc,,, mix up into a poultice & cover the stain(s) - then cover the poultice w/cardboard weighed down to prevent wind from blowing it out of position
|