Several trivia bits.
First of all, in the US, we know sticky rice as “short grain rice”, which is uncommon, compared to the “long grain rice” we typically eat. Short grain rice is favored by the better Oriental restaurants because of its sticky texture and moistness compared to long grain.
Second, the purpose of mortar is primarily to provide as flat a surface as possible for the stone, block or brick. This distributes the weight, and any bulge or gap in the mortar that causes uneven distribution acts as a force multiplier to damage the stone, block or brick.
Third, mortar determines the strength of the wall or building. The better the mortar, the longer it will last, and the easier ti will be to be repaired.
The most common mortars used in construction are types M, S and N. This ancient mortar must have been type R (rice).