Why were eggs and rice water added to the masonry mortar in ancient times?

During my school years, I remember information about the construction of fortresses. The teacher said that raw eggs were added to the solution to increase the strength of the clutch. Then this information seemed unusual or something like a legend. In our time, this information is confirmed by many on the forums on the Internet, but no one can name a clear answer for what exactly.

Yes, almost all of the comments say that the egg white added strength to the solution. But by what means? Where is the crystallization of the binder and where is the protein! How are inorganic minerals related to organic matter? I do not think that ancient references are fictions or myths. Let's figure it out.

I read that in addition to eggs, milk was added to the masonry mortar, and in China, rice water. There is even a legend about the Charles Bridge in Prague. That for its construction eggs and milk were collected from all around. And which of the peasants did not understand why - brought boiled eggs and cottage cheese with cheese.

First, a brief information on binders for the solution. Portland cement is now used in the solution. It is known that Portland cement was received only in 1824. D. Aspdin from the breed on the island. Portland in England. It's burnt kninker and plaster. True, it was known before him roman cement, known since the 18th century. (burnt marls and gypsum). And before that he was known Roman concrete (lost recipe) and just mortar.

Brick buildings are much older than the period of application of Roman cement. Basically, lime mortars were used in their masonry. As it was found out, in order to impart greater plasticity to the solution, eggs were added to it and thereby the water-lime ratio decreased (as when using modern plasticizers).

The solution compacted better and its strength characteristics increased. In our time, there are also organic plasticizers. Although lime itself has good plasticity, in contrast to modern cement-based mortars. The addition of additional plasticizer to lime raises the question.

It also turned out that the protein is an inhibitor of the growth of calcium carbonate crystals (which is released during the hardening of a mortar based on calcium hydroxide - slaked lime). Even a recipe for such solutions has been preserved, which someone translated from old books:

Approximate ratio: approximately 1 egg per 1 kg lime mortar. There is also an opinion that protein was added to the solution in order to prolong or maximize the reaction of slaking quicklime. If the solution was based on it. There was a better roasting of limestone with a large formation of calcium carbonates. The modern method is the autoclaving of concrete at high temperatures as an analogue.

Eggs were also added to the mortar for plastering in churches - to give more strength to the plaster. Lime was an antiseptic and, despite the fact that organics like mushrooms, mold did not form.

It was possible to find a study by European scientists who established the optimal ratio of protein in masonry mortar. This value turned out to be 6%. Lower or higher - the solution had a lower strength:

On 10 l lime mortar you need 0.6 l egg white.

But what was it for rice water in solution in China? Rice contains almost all carbohydrates! It turned out that this broth contains a lot of amylopectin (a carbohydrate from starch). And it also acts as an inhibitor of the growth of calcium carbonate crystals.

In China, they conducted a scientific study of mortar from the ancient masonry of the wall and similar samples of mortar without and with rice water. Here's what the scientists saw under an electron microscope:

1 - sample from the wall. 2 - lime mortar without amylopectin. 3, 4 and 5 - with rice water. Crystals are smaller and they are linked more strongly. Samples 3, 4 and 5 were added 1%, 3% and 5% rice broth to the volume of the solution. A source: https://www.gazeta.ru/science/2010/05/31_a_3377254.shtml

Those. there are quite scientific rationales for the ancient use of such recipes with organic fillers. But then the question is - where did the ancients have such knowledge in chemistry, materials science? Was everything empirically obtained? Or was the alchemy of that time not such a pseudoscience with delusions? And some medieval recipes on this topic can be quite working? After all, who in our time in their right mind would like to add rice water to lime plaster? But it turns out - it makes sense and this is pure science!

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