Consider the following statements about 3D printing technology in Construction:

1. It is a method for manufacturing construction elements or entire buildings by means of a 3D printer printing concrete, polymer, metal, or other materials, layer-by-layer. 

2. 3D printing in construction has increased productivity but is less sustainable than normal manufacturing.

3. Spray, Powder Bonding and Extrusion are methods of Construction 3D printing.

Which of the above statements is/are correct?