The coarse aggregate particles in a lightweight-aggregate mix are giving trouble by floating to the top of the lift during vibration. This shows up as a difference in surface texture along horizontal lift lines after the forms are stripped. The aggregate is one we have not encountered before so we think it may be the aggregate itself that is causing the trouble rather than something that we are doing wrong. Can you pinpoint the trouble?
You may be right that it is the aggregate causing the trouble. The coarse particles in lightweight-aggregate concrete have a specific gravity lower than that of the mortar and consequently they tend to rise during vibration. The first thing to do, if not already done, is to introduce normalweight sand into the mix in place of lightweight sand. This sand is quite effective in resisting the upward movement of the coarse lightweight particles. Experimental adjustments in grading or a decrease in slump may also be helpful.