After concrete is mixed, approximately how long does it take to begin to harden? 15 minutes 60 minutes 2 hours 3 hours

The correct answer is 2 hours.<br /><br />After concrete is mixed, it typically takes about 2 hours for it to begin to harden. This process is known as the initial setting time, during which the concrete starts to harden and gain strength. It is important to note that the exact time may vary depending on factors such as the type of cement, the water-cement ratio, and the ambient temperature.