Imperfections in vertical architectural concrete surfaces (bugholes, honeycomb, sand streaks, discoloration and dusting) can result from a variety of circumstances. This article discusses some ways to avoid these troubles. SAND STREAKS Sand streaking is a condition in which some of the Portland cement has been washed out of the fines in the concrete next to the forms leaving exposed fine aggregate in the surface. These streaks usually occur at vertical form joints or where forms join at corners. The following measures will prevent sand streaks: form joints should be tight to prevent any leakage of mortar or bleed water; always use concrete that contains an adequate amount of entrained air; and use a mix with a slump of no more than 4 inches that does not bleed excessively. If the sand is deficient in fines passing the Number 30, 50 or 100 sieves, a better graded sand should be substituted if possible. Otherwise it may be necessary to increase the sand content slightly and reduce the amount of coarse aggregate correspondingly.