The correct grout proportions are ______ part Portland cement to ______ parts sand by volume?

The correct grout proportions of 1 part Portland cement to 3 parts sand by volume are optimal for creating a stable and workable mix. This ratio ensures that the grout is sufficiently strong while maintaining the necessary workability to fill joints effectively. The Portland cement acts as the binder, providing strength, while the sand helps to bulk up the mix and improve its flow characteristics, making it easier to apply in a variety of applications, including tile setting and pool surrounds.

Using this specific ratio results in a grout that has good adhesion properties and minimizes shrinkage as it cures, which is crucial in maintaining the integrity of the joints in a pool setting. Additionally, the 1:3 ratio balances the stiffness and flexibility of the mixture, providing durability against the movement and settling that can occur over time in a pool environment.

Other proportions, while they might lead to different characteristics and uses, do not offer the same combination of strength, workability, and durability that you achieve with the 1 part to 3 parts ratio. Therefore, this particular mix is widely recognized as the standard for grout used in various settings, especially in commercial pool applications.