Chapter 189 Brick And Cement Kilns

Alexander had given the schematics of brick and cement-making kilns to the stonemasons during the first week of this landing.

And they had been at it for a week, entering the city far before Alexander had decided to move in himself.

Now. with seven days past, Alexander was eager to know about their progress.

"We have finished building twenty of the two brick-making kilns and can start production any time," Jazum reported.

"And we are using the blacksmith forge to make the cement kiln. It should be done within the week." He assured.

"Good, good, keep up the good work," Alexander was very pleased by the reported progress, evidenced by his saying the word 'good' three times in a sentence.

The task set to them was no easy feat.

They were instructed to make three types of kilns and make as many as they could.

The first two were brickmaking kilns, with one being used to dry the raw, wet, brick-shaped clay, which operated at around 100 degrees Celsius, and the other was used for the actual firing of the bricks which could reach as much as 1000 degrees Celsius.

These kilns made been designed by Alexander while on the ship and from the outside looked like rectangular houses on raised platforms.

The first kiln used for drying the bricks looked like a house having only its sides and roof with both the front and back open.

Green bricks would be put into his 'house' carpeted with hay and various kindling like sawdust, logs, crushed and chipped wood, then be lit alight, slowly cooking the bricks.

This burning would continue for a day or two depending on the clay and moisture content. with the temperature being between one hundred (100) to two hundred (200) degrees Celsius.

Alexander had intentionally made the kiln very open and prone to heat loss to achieve this low temperature, as too high a temperature would crack the raw bricks.

This would happen because, at too high a temperature, the water around the surface of the bricks would evaporate too quickly and cause the surface layer to shrink, while the inner layer would remain the same volume, and will resist the shrinkage, thus cracking the outer surface and disintegrating the brick.

The second brick kiln, to be used for firing, was like a huge dome, standing on a raised platform.

The platforms were hollowed in the middle and top and thus allowed air to pass in and out of the chamber above it through small porous holes in the floor.

The bricks would be put into the kiln from the top along with all the necessary kindling, like the previous kiln, and then closed with a heavy bronze top to reduce heat loss.

Periodically the top would be opened to add more kindling.

This firing process would also continue for one to two days at around a thousand degrees (1000) and once firing was complete, the bricks would be further allowed to cool inside the kiln for at least a day.

In this way, a batch of bricks, numbering around a hundred could be made in three-five days.

The third kiln was a bit more special as it need to reach fifteen hundred degree celsius to achieve its purpose.

It was to be used to make cement and the chemical reaction that produces concrete would occur only at around temperature.

But the problem was that the temperature using firewood and normal kindling could only achieve around a thousand degrees.

To overcome this, a blower or a bellow had to be used, which blew fresh oxygen into the fuel and increased the burning rate enough to reach those temperatures.

And so Alexander had to design a brand new kind of kiln to do this, a design he came up with in his head after years.

His first innovation was the material to be used.

Usually, kilns were made of mud and earth, which were fantastic refractory materials and highly resistant to high temperatures.

But they had two very big drawbacks.

First, they lacked the structural integrity to reach large heights, usually capping out at six to seven meters.

The way to overcome this would be to use a reinforcing material, but there was no appropriate material to be found.

Such long iron rods existed only in the realms of fantasy and wood would decompose and break down in the extreme heat of the kiln.

The second drawback was it took very long to make a mud kiln.

A simple brick took Alexander five days to make, and so the time needed to dry, fire, and cool a ten-meter kiln could be imagined.

So, here Alexander decided to use his first innovation, making the kiln out of stone.

And astonishingly, the mortar that he used to bind the stone was cement, the very thing he was trying to make, which he got using the blacksmith's forge.

He did this by getting sand, crushed limestone, and clay and mixing them into appropriate proportions (around 1:3:1 respectively).

Then he put this slurry inside the forge, heating the raw materials using the blowers for twenty to thirty minutes.

This made an intermediate product called clinkers which looked like small pebbles, which was then mixed with three-four percent gypsum, which was a white, naturally occurring mineral, and ground into a fine powder.

And thus, the world's first portland cement was manufactured.

The only drawback to this manufacturing was the very small scale of it and thus the need for a large-scale kiln.

Alexander's second innovation regarding the cement kiln was the design of the kiln itself.

Unlike the usual dome shape, it was conical, with a vertical height of twelve meters and a diameter of four meters at the base and one meter at the top, with the charge (raw materials) coming from the top.

The reason for this design change was due to his third innovation, the position of the firing chamber.

While conventional wisdom dictated that the fire should be placed at the bottom, he placed the heart of the kiln at the sides, as it beat furiously with fire and flame, as if wanting to devour the whole structure.

The fuel chamber was six meters high and protruded one meter into the kiln, thus the necessity of making the structure conical as otherwise the raw materials might fall directly into the fire and extinguish it.

Alexander's fourth innovation was the design of the fuel chamber.

The fuel chambers had an upper opening through which firewood and kindling would be constantly fed into the burning inferno.

But they also had three large concrete pipes protruding out of them and each of them was vital to the kiln's function.

Two pipes growing off the sides were the air vents.

They had huge blowers, about the size of a man attached to them that would constantly throw fresh oxygen into the fiery flame, spurring it to burn even brighter.

The last pipe was situated at the bottom of the chamber and this was the waste pipe, through which the ash that would accumulate at the feet of the fuel chamber could be easily removed.

And Alexander's last innovation was the design of the lower floor.

Instead of being flat, it was curved, almost spherical in shape, causing anything on it to slide off it.

This was done to facilitate the exit of the finished product as the kiln was designed like that.

The way it would work was that it would be first fully filled up with the charge and the fires would be lit, allowing the gases to slowly rise up through the charge, depositing their heat to the raw materials and allowing a number of reactions to occur at different temperatures.

In this way, the raw material would change from a slurry-like mixture into small chucks in a step-by-step process and then would smoothly roll off the curved surface, exiting the kiln through the large holes at back and front of the kiln and into the waiting horse cart outside.

Once outside, these clinkers would be taken to a different location, mixed with gypsum, and then manually crushed by large hammers to make the all-elusive concrete.

And the main bottleneck that was preventing Alexander from getting his hands on this magical powder, according to Jazum, was the manufacturing of the blowers.

They had never made such huge blowers, which were to be made out of bronze and leather, and it was taking some time to process the necessary amount of leather to make them.

"I truly apologize for the delay," This was said by Krishok, who as the lead tanner was mainly responsible for processing the hide.

"It's okay, I don't mind," Alexander lightly smiled and reassured the flustered bald man, adding, "Take your time and make sure the thing is sturdy. It will be a pain to replace it frequently."

"Yes, lord Pasha. I'm confident that the finished product will please you," Krishok was eager to please Alexander and snatch a noble title for himself.

All in all, Alexander was very pleased that his trump card would soon be ready.