Sticky Mortar?

1,500 years ago, Chinese construction workers developed what was probably the world's first composite mortar, a mortar made from both organic and inorganic materials. The mortar was made by combining sticky rice soup with slaked lime, limestone which has been heated to high temperatures then exposed to water. This "sticky rice" mortar was stronger and more resistant than pure lime mortar.

Scientists have recently discovered that amylopectin, a type of polysaccharide, is the ingredient in the sticky rice that is responsible for the strength of this ancient mortar. The amylopectin in the mortar acts as inhibitor, controlling the growth of the calcium carbonate crystals, resulting in a compact microstructure which leads to greater mechanical strength.

Reference:
Fuwei Yang, Bingjian Zhang, Qinglin Ma. Study of Sticky Rice-Lime Mortar Technology for the Restoration of Historical Masonry Construction. Accounts of Chemical Research, 2010; : 100510131945076 DOI: 10.1021/ar9001944