Cement Fineness: Identifying the Incorrect Statement

The fineness of cement, referring to the size distribution of its particles and measured by its specific surface area, has a substantial impact on its properties and performance during hydration. Let's evaluate each statement:

• Statement 1: Fine cement possesses a larger surface area compared to coarse cement. This larger surface area necessitates a greater quantity of mixing water to achieve a given workability. Consequently, the increased water content can lead to higher drying shrinkage, making it more liable to shrinkage cracking. Thus, this statement is correct.
• Statement 2: Due to its increased surface area, fine cement hydrates more rapidly. This accelerated hydration process results in a faster rate of heat evolution. However, the total quantity of heat evolved over the entire hydration period is primarily dictated by the cement's chemical composition (specifically, the amounts of tricalcium silicate (C3S) and dicalcium silicate (C2S)) and the final degree of hydration achieved. While heat is released faster, it does not necessarily mean the total amount of heat generated is fundamentally 'much larger' solely because the cement is finer. Therefore, this statement is incorrect.
• Statement 3: The accelerated rate of hydration in fine cement, caused by its larger surface area, leads to a quicker development of strength. This means fine cement exhibits a faster rate of hardening compared to coarser cement. This statement is correct.
• Statement 4: Fineness does influence the setting time of cement; typically, finer cement tends to have a faster setting time due to quicker hydration reactions. The statement claims fine cement shows the *same* setting time as coarse cement, which is generally not true. However, the inaccuracy in Statement 2 regarding the total quantity of heat is a more distinct and commonly cited consequence distinguishing the effects of fineness versus composition.

In summary, the statement that is not correct regarding the fineness of cement is the assertion that fine cement shows a much larger total quantity of heat evolved compared to coarse cement.