We built a swimmingpool using concrete without waterproofing. what should we do?
You should clean the concrete of dirt and dust, then wash it with clean water.
Then fix a reinforcing fabric by dowels. A wire is about 1-2 mm thick, a cell is from 50х50 to 100х100 mm.
Make a waterproof mixture using sand, cement and the D-5 admixture. For 1 portion you need: Portland cement 500 without admixture or Portland cement 500 with 20% admixture = 1 bag (50 kg); the D-5 admixture = 1 package (1 kg); medium sand = 7 buckets of 12 liters (120 kg) and water of about 20 liters. All components should be thoroughly mixed. Fill the D-5 admixture in the mixer after cement. It is recommended to pour water in 2 stages: first pour about half of the expected amount of water, until the required fluidity is obtained. It is important not to use too much water here! After all the components are added, the mixing time must be at least 3 minutes.
It is recommended to plaster walls in 2 stages: first the outline, then, after the first layer is fixed on the wall, the outline of the second layer and the trowel finish. The plaster layer on the walls must be not thicker than 2-3 cm. A mixture of medium and coarse sand in about equal proportions should be applied on the bottom. The bottom concrete should have minimal fluidity. The concrete must be compacted while laying. Put it in one layer to the required thickness at once. The layer should be from 3 to 5 cm thick.
The “cold” joints between the wall plaster and the bottom concrete must be cleaned with a metal brush to eliminate the film from laitance and baring of the concrete. After that the dust must be washed out with clean water. In this case, maximum adhesion and splicing of the fresh concrete with the previously laid and solidified concrete and high waterproofness of the “cold” joint will be ensured.
If the work is carried out in summer and under open air, it is necessary to prevent rapid evaporation of water from the plaster layer in order to avoid formation of cracks: pour water and cover walls and bottom with film. It is recommended to wet walls and bottoms 2 times a day (in the morning and in the evening) during the first 7 days. After 7 days of hardening under such conditions high waterproofness and strength of plaster layer with the D-5 admixture will be ensured. So it is possible to pour water into the pool to the full depth and check it for waterproofness.