Increasing the mixing time and temperature generally has what effect on concrete?

Increasing the mixing time and temperature tends to enhance the workability of concrete. When the temperature is raised, the viscosity of the concrete mix decreases, which allows for easier placement and more effective compaction. Additionally, longer mixing times lead to a more uniform distribution of materials, thus improving the overall flow characteristics of the concrete. This improved workability is especially beneficial for complex pours or when using stiff mixes that would otherwise be challenging to handle.

In contrast, higher temperatures can increase the rate of hydration in concrete, leading to a faster setting time. While this can be advantageous in terms of workability at first, it may also pose risks of cold joints if the mix sets too quickly. However, the focus here is on the overall increase in workability due to the factors mentioned.

While options like reducing strength, decreasing hydration, and increasing air voids focus on other aspects of concrete properties, they do not correlate with the direct effects of increased mixing time and temperature that enhance workability.