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This research assessed the shrinkage behavior of mortar containing recycled sand generated from aerated blocks and clay bricks by replacing natural sand with a volume ratio of 30%. Five mix proportions were prepared to cast mortar plate specimens. They were named as the control, ABs1, ABs2, CBs1 and CBs2. Among them, ABs1 and CBs1, containing recycled sand from aerated blocks and clay bricks respectively, have the same water/cement ratio as the control. ABs2 and CBs2 had the same workability as the control by adjusting the required amount of water. Digital image correlation (DIC) was adopted to determine the strain distribution during the plastic shrinking period. The results showed that, when no extra water was added, the mortar containing the aerated blocks sand had a lower risk of cracking, because of the internal curing effects brought by the low–weight fine aggregates. However, when the extra water was added to ensure the same fluidity with the control, there were obvious visible cracks in group ABs2, and the average distance between cracks reached 25 mm. On the contrary, the brick sand has no obviously higher water requirement, as a result, it did not lead to higher risk of cracking. The aerated block sand particles contain 2–50 μm pores, which is the reason why aerated block sand tremendously reduced the fluidity of the mortar.