In order for concrete stairs and paths to serve as long as possible, you need to control the amount of water in the solution, and add some unusual "ingredients" there.
You must have heard the story that in ancient times chicken eggs were added to concrete, and it was as if they provided incredible stability of the structures? In particular, allegedly thanks to the eggs, Charles Bridge in Prague has been indestructible for more than six centuries.
However, the solution holding the stones of this bridge together is not at all the material that builders use today! Portland cement - an astringent that is now used in all concrete and mortar, was invented only at the beginning of the twentieth century.
And before, lime and clay were mainly mixed with sand. These are very unstable substances that soften under the influence of water, so the structures often had to be repaired and rebuilt.
And the mentioned Charles Bridge is no exception. People were looking for a way to make buildings stand for at least a century. And that they did not have at least some understanding of how the hardening process takes place, and he himself seemed to them a miracle, they acted on the basis of their understanding of miracles management. A miracle requires sacrifice, our ancestors thought. And they chose eggs, milk and blood for this. Interestingly, under certain conditions, these substances could indeed strengthen the solution.
How exactly? In general, the main reason for the decrease in the strength of any solution is the abundance of water that is needed to form a mixture. Water then does not enter into chemical reactions, just evaporating, and pores are formed in the mortar, which hardens. These voids reduce the strength of the material. But the addition of a number of substances, such as fats, makes the components of the mixture quite slippery without excess water. Therefore, if, by adding eggs, milk and even blood, at the same time, reduce the amount of water in the solution - it really will become stronger. Substances acting on this principle are called plasticizers.
True, organic products have a disadvantage - they contain a large amount of acids. And acids actively destroy concrete. Therefore, chemists have developed special synthetic substances that can ensure the strength of concrete or mortar, while reducing cement consumption by 10%.
What then should be added to concrete for strengthening? The easiest option is soapy water. Fats in soap can also act as plasticizers. Of course, the effect will be if you add less soapy water than usual. This is much cheaper and more effective than mixing eggs or milk!
Washing powder is also an excellent plasticizer. Indeed, in its composition there are lignosulfonates - substances that are used as chemical additives to concrete. The introduction of washing powder with a small amount of clay can also be effective. Often sand, which is used in construction, stained with clay, this gives it a dark yellow or brown color. Builders know that mortar mixed in such sand becomes “greasy”. Clay gives concrete density, but draws water onto itself, which makes it difficult to mix. However, using clay and washing powder at the same time can significantly increase the strength of masonry and pouring.
