What effect does a high water-cement ratio have on concrete?

A high water-cement ratio in concrete primarily leads to lower strength and durability. This occurs because the excess water in the mixture results in a higher porosity and less dense concrete. When the water evaporates, it leaves behind voids or air pockets within the hardened concrete, which can compromise the material's strength and overall structural integrity.

Additionally, with a higher water-cement ratio, the hydration process is affected, resulting in less complete bonding between the cement particles and the aggregates. This unfinished bonding can further weaken the overall concrete structure. As a consequence, the concrete becomes more susceptible to environmental conditions, such as freeze-thaw cycles and chemical attacks, ultimately reducing its durability.

While it is true that a higher water-cement ratio can enhance the workability of the mixture initially, the trade-off in terms of strength and durability makes it a less desirable choice in structural applications where performance and longevity are critical. Therefore, the most significant consequence of a high water-cement ratio is indeed the reduction in the concrete's strength and durability.