The loss of slump in concrete is usually due to which of the following?

The loss of slump in concrete is primarily associated with low water content. Slump is a measure of the workability or consistency of fresh concrete; it indicates how much the concrete will flow or spread when placed. When there is insufficient water in the concrete mix, it can lead to a more rigid and less workable mass. This reduces the slump, making the concrete difficult to work with and form into desired shapes.

In contrast, other factors like excessive aggregate, high temperature, and excessive mixing can affect the overall properties and behavior of the concrete but do not directly cause a loss of slump in the same way that low water content does. Excess aggregate could lead to a denser mix, but that wouldn't necessarily correlate to a decrease in slump by itself. Similarly, high temperatures might accelerate hydration and could impact workability in different contexts, but it's the lack of water that fundamentally limits slump the most. Finally, while excessive mixing could lead to segregation, it typically does not lead to greater loss of slump than what would occur with inadequate water. Understanding the role of water in concrete mixtures is crucial for achieving the desired workability and performance in concrete applications.