If a recently placed concrete slab develops hairline cracks or the surface is dusting, what is the likely cause?
Excessive troweling after the placement and screeding of the concrete will bring excess fines and water to the surface, weakening the surface. Hairline cracks and dusting can result. Over-troweling the surface during finishing can produce the same problems. Additionally, the rapid of loss of water from the surface of the concrete will cause the slab to cure at an uneven rate. This can happen during periods of high temperature or wind. If the top portion of the slab dries before the lower portion, the concrete will cure at different rates, causing the slab to develop cracks.
