What are the primary purposes and benefits of concrete grinding as a surface preparation technique, and how does it contribute to achieving a smooth, level, and visually appealing concrete grinding minneapolis surface prior to the application of coatings or finishes? Furthermore, what are the key factors that determine the appropriate grinding method and equipment to use, considering variables such as concrete hardness, thickness, and desired surface textue? Lastly, how does the use of advanced dust extraction systems during concrete grinding enhance the safety and efficiency of the process while minimizing airborne dust particles?