when did 'stacked art' sculptures first became accepted as a form of 'art'?

[Laura Elle]

I am talking about sculptures that are made from stacking and compiling everyday objects like Tony Cragg's eroded land scape (1990), and Doris Salcedo's 1600 chairs ??. When did this type of scultpure first become accepted as Art? I need an approximate year and who really pioneered it and made it 'art' first?