By using a platier or more acicular or fibrous granulated filler, you can decrease the amount of binder needed, although at some point you start having the stuff stick together without any binder at all. Using smoother surfaces and larger particles also decreases the amount of binder needed as well as the tendency to stick together without binder.
This has implications for powder-bed 3-D printing: a small amount of binder can bind a large amount of powder into a continuous solid network, although the bound powder may be porous and weak.
Promising fillers that come to mind include talc, mica, milled clays such as kaolin, acicular hydroxyapatite, asbestos, jade, graphite, mullite, rockwool, glass fiber, carbon fiber, acicular wollastonite (CaSiO3, the calcium analogue of enstatite, which has a totally different crystal structure), ceramic fiber, steel fiber, acicular boehmite (AlOOH, which more typically crystallizes in a massive habit),