NASCLA Accredited Commercial General ContractorFinishesMedium
A contractor is applying a skim coat of plaster to a lath substrate. To achieve optimal adhesion and prevent cracking, which component is typically added to the plaster mix to improve its workability and plasticity?
- AAccelerator
- BFiberglass mesh
- CLime
- DRetarder
Show answer & explanationAnswer & explanation
Correct answer: C. Lime
Lime is a traditional and essential component added to gypsum or cement plasters. It improves workability, plasticity, and elasticity, allowing the plaster to be spread more easily and reducing the risk of cracking as it cures.
Why the other options are wrong
- A. Accelerators speed up the setting time, which can reduce workability.
- B. Fiberglass mesh is used as reinforcement within the plaster layers, not as an additive to the mix for workability.
- D. Retarders slow down the setting time, but their primary purpose isn't to improve plasticity.
Plaster Workability Additive
A material, typically lime, added to plaster mixes to enhance their plasticity, workability, and elasticity, thereby improving application and reducing cracking.
- Increases plasticity
- Improves workability
- Reduces cracking
Memory trick: To make plaster 'workable' and 'smooth', add 'Lime' like a dash of 'magic'.