What type of ties are used to maintain spacing of form walls during concrete placement?

Snap ties are specifically designed to maintain spacing between form walls during the pouring of concrete. They allow the formwork to stay secure and stable, ensuring that the concrete sets properly in the correct position and shape. Snap ties are effective because they create a firm connection between the inner and outer forms while also being easy to remove afterward, which is crucial for the construction process. This functionality is critical in achieving the desired wall thickness and ensures that the forms are not pushed apart under the weight of the wet concrete.

While the other types of ties, like cross ties or bracket ties, can serve different functions in formwork systems, snap ties are particularly suited for this specific purpose, making them the correct choice for maintaining proper spacing during concrete placement. Chain ties might be used in different structural applications but do not maintain spacing in the same way as snap ties do.