The water-to-cement ratio is the weight of water divided by the weight of cement in a concrete mix, the single biggest factor in how strong and durable the finished slab will be.
In depth
Lower ratios, around 0.40 to 0.50, produce dense, strong concrete. Higher ratios make the mix easier to pour but leave excess water behind, creating a porous, weaker slab that shrinks more as it cures. That extra shrinkage is a common source of early cracking.
Contractors sometimes add water on site to make concrete easier to work, a shortcut that permanently reduces strength. Like aggregate quality, the water-to-cement ratio is locked in on pour day.
How Acme applies it. When we inspect cracked or deteriorating slabs, mix quality is part of the picture. A slab weakened by a high water-to-cement ratio may still be liftable, but we will be honest with you if the concrete is too far gone for raising to make sense.
Related terms: Compressive Strength, Concrete Cracking, Curling, Scaling
Frequently asked questions
Can a bad water-to-cement ratio cause my slab to sink?
No, sinking is a soil problem. But a watery mix cracks and deteriorates faster, which can turn a simple settlement issue into a replacement issue.
What is a good water-to-cement ratio for a driveway?
Roughly 0.45 to 0.50 for exterior flatwork in a freeze-thaw climate, combined with air-entrainment for winter durability.