We recently placed a slab and topped it with a mixture of one part cement and three parts sand. The slab was given a broom finish before the topping was applied. No bonding agent was used between the slab and the topping. After the topping had been placed we were caught in a heavy rainstorm and the surface is now sandy and loose. What do you suggest as a way to repair it?
If the topping you applied is loose it should be removed. After the old base has been roughened and cleaned, prepare a grout of one part cement and one part fine sand by weight and enough water to produce a creamy consistency. Brush it into the base just before placing the new topping. Be sure that the base concrete is damp so that it will not absorD too much water from the grout and topping mix. The new topping should be at least one-inch thick. Use a mix consisting of one part cement, 1'/2 parts sand and two parts 3/5-inch gravel or stone. Avoid an overly wet mix and excessive troweling. Troweling a wet mix will bring fine material to the top and this will result in a dusting surface after the concrete has hardened. Finally, cure it thoroughly for example, seven days at 70 deg rees F.