When the summer heats up, we often begin looking for methods of keeping things cool while outdoors. Whether we are trying to cool our gardens, our structures, or ourselves, water is considered one of the most effective tools in this regard. But not all things will benefit from added water, even on a hot summer day.
Concrete is the most widely-used building material in the world. It is celebrated for its compressive strength, which is produced by a combination of the chemical reaction between cement and water, and the presence of aggregate within the mix. The ratio between these materials within a concrete mix can have great effects on the strength of the hardened product. In particular, excessive water can have extended adverse effects on the strength of new concrete as it hardens and cures, and therefore can compromise the integrity of the resulting concrete structure.
Because of the impact that water can have on concrete strength gain, engineers have closely studied and observed the relationship between water content and concrete compressive strength. The figure below (https://www.engineeringintro.com/concrete/concrete-strength/water-to-cement-ratio/) is a graph representing that relationship, which shows the reduction of fully-cured compressive strength as the water-cement ratio is increased. The water-cement (w/c) ratio is the value of weight of water divided by weight of cement in a concrete mix. During concrete placement, the w/c ratio increases when water is added to the mix without also adding more cement. As we can see from the graph, the proportion of water within a concrete mix plays an important role in allowing the hardened concrete to reach its design strength.
Each year, the hottest months of the summer bring plenty of concerns for new concrete, one of the primary items involving high temperatures (see our blog post, August 13, 2012). In an effort to keep a concrete mix temperature down, it is no real surprise that someone’s first instinct might be to add water. But there are other effective ways to cool concrete without compromising strength- so that we can save some water and help build stronger structures.