![]() Section 7.6.1.1 of the NPC 8 th Edition Technical Manual explains in detail what an “aggressive chemical attack” is and what it means for your plaster's health.Ĭementitious surface coatings are susceptible to chemically aggressive swimming pool water or to any chemical that is capable of deteriorating the cementitious materials of a surface coating. You can calculate how to keep your water chemistry in proper balance using the Langelier Saturation Index (LSI), as seen on the NPC Start-Up Procedures Card, which is offered here. One of the most common issues in pool plaster is etching deterioration, or 'spot etching.' This can result from aggressive water chemistry: low carbonate alkalinity and elevated cyanuric acid are the main contributors to spot etching. Structural movement cracks, tensile stress cracks, and all other cracks, that develop throughout the life of the coating, subsequent to the first twenty-four hours after application. Open shrinkage cracks that develop during application or within the first twenty-four hours after final set. Cracks can be classified into one of these three types:Ĭlosed Shrinkage Cracks that develop during application or within the first twenty-four hours after final set. The following types of cracking are generally in need of some type of repair.Ĭracks in cementitious surface coatings should be classified as to their type, prior to determining the optimum method of repair. However, any cracks that remain open 24-hours after the pool has been filled should be reported to the Pool Builder or Plastering Company. They are common to all cement and concrete products, and are generally nothing to worry about. These cracks are known as 'check cracks' (or closed shrinkage cracks). In fact, these micro-cracks actually seal themselves shut with cement hydration material after the pool is full. ![]() Once the water evaporates, or once the pool is filled with water, they are no longer visible. The cracks (having the appearance of a road map) appear to be 'highlighted' by the water absorbing into them. This results in these micro-cracks becoming visible. Microscopic shrinkage cracks (micro cracks are present in all hardened plaster, precast, shotcrete, and concrete products) absorb water faster than the overall surface. New installations and drained pools: A common appearance of cracking can occur when a cementitious interior finish is wetted prior to being filled. (Some sections that deal with cracking are given below) Each type of cracking is defined in the NPC 9th Edition Technical Manual. Closed shrinkage cracks, open shrinkage cracks, and structural movement cracks are each unique, in terms of the cause and remedy. First, you need to diagnose which type of cracking has occurred. There is more than one reason why an interior finish could be cracking.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |