The correct answer is option 'D', which states that a quick-setting cement has an initial setting time of about 5 minutes. Quick-setting cement is a type of cement that is designed to harden and set rapidly, allowing for faster construction and workability. Let's delve into the details of why the initial setting time for quick-setting cement is approximately 5 minutes.

Understanding Initial Setting Time
The initial setting time of cement refers to the duration from the moment water is added to the cement until the paste starts to lose its plasticity and gradually harden. It is an important property of cement as it determines the time available for handling and finishing the concrete before it becomes rigid.

Factors Affecting Initial Setting Time
The initial setting time of cement can be influenced by various factors, including the following:

1. Composition of Cement: Different types of cement have different setting times. Quick-setting cement is specially formulated to have a shorter initial setting time compared to ordinary Portland cement, which typically takes around 30 minutes to set.

2. Water-Cement Ratio: The amount of water used in proportion to the cement affects the setting time. A higher water-cement ratio generally results in a longer setting time, while a lower ratio can accelerate the setting process.

3. Temperature: The temperature of the surrounding environment can significantly impact the setting time. Warmer temperatures tend to speed up the setting process, while colder temperatures can delay it.

Why Quick-Setting Cement has a 5-Minute Initial Setting Time?
Quick-setting cement is designed to offer rapid setting properties, allowing for faster construction and reduced waiting times. This type of cement typically has a fine particle size and contains additives that accelerate the setting process. As a result, it can achieve an initial setting time of approximately 5 minutes.

The goal of quick-setting cement is to provide a workable material that can be quickly hardened and set, saving time and increasing efficiency on construction sites. This is particularly useful in situations where immediate load-bearing capacity is required or when working in cold weather conditions.

By reducing the initial setting time to just 5 minutes, quick-setting cement enables construction workers to proceed with subsequent tasks swiftly, such as placing and finishing the concrete, without waiting for extended periods. This helps to enhance productivity and shorten overall project timelines.

In conclusion, the correct answer to the question is option 'D', as quick-setting cement typically has an initial setting time of about 5 minutes. This property is achieved through the use of special additives and a fine particle size, allowing for rapid hardening and setting of the cement paste.