Which factor does NOT contribute to the effectiveness of freshly mixed concrete?

Excessive water content does not contribute positively to the effectiveness of freshly mixed concrete. While water is a crucial ingredient in the concrete mix, providing too much can lead to problems such as decreased strength and durability in the cured concrete. An excess of water can cause the mixture to become overly fluid, which may lead to segregation of the aggregate and cement particles. This results in a weaker final product that is more susceptible to cracking and other structural issues over time.

Conversely, factors like high temperature, low humidity, and wind speed can adversely affect the curing process of concrete. High temperatures can accelerate the setting time, making it difficult to properly finish the surface. Low humidity and high wind speed can lead to moisture loss, which can also impair the curing process and negatively impact the strength and integrity of the concrete. Therefore, managing water content is crucial to obtaining concrete with the desired properties, making excessive water content the correct answer in this context.