What is the relationship between extra water and concrete strength?

Using extra water in the concrete mix decreases the strength of the final product. This relationship is primarily due to the effect of water on the cement-paste bonding process. When additional water is introduced beyond the specified water-to-cement ratio, it leads to an increase in the porosity of the concrete once it sets.

Higher porosity results in more voids within the concrete matrix, weakening the overall structural integrity. As the concrete dries and cures, these voids cannot contribute to the load-bearing capabilities of the concrete, thereby leading to decreased compressive strength. Therefore, adhering to the correct water-to-cement ratio is essential for ensuring optimal strength and durability in concrete mixes.

While it may seem intuitive to think that increasing the amount of water could make the mixing process easier or enhance certain characteristics, it ultimately compromises the concrete's strength. The other options suggest that extra water improves strength or has no effect, both of which are inconsistent with established principles of concrete technology. Additionally, the option indicating that extra water makes concrete lighter overlooks the implications of increased porosity, as the overall density of concrete is more accurately described by the volume of solids and voids combined.