Roland stood in the backyard of the firing room waiting for the first batch of cement to come out.

The brick house, which he designed specifically for cement production, is about fifteen meters long and four meters wide. There is a door at the front and back, the difference is that the front door is as wide as possible for people to carry materials. The back door was only one person wide, allowing Anna to sneak into the firing room.

To this end, he also built a fence halfway up the house to enclose the back half of the firing room, and arranged for the entrance and exit to be guarded by knights, all of whom were Carter's subordinates, and their loyalty was unquestionable.

The production process of cement is very simple, the limestone is crushed into powder, mixed with clay and iron powder, calcined by dry or wet process, and then ground with gypsum. The raw materials are very ordinary, and it is difficult to make a large amount of iron powder without putting it, and the key is the calcination temperature of the clinker.

Roland didn't remember the exact temperature needed to make cement, and even if he did, he couldn't measure and control it – neither an infrared thermometer nor a thermocouple thermometer was countless times more complicated than cement. All he knew was that the temperature was almost similar to the melting point of iron, and that the calcination process was also a difficult part of the cement production.

In the era when smelting technology was underdeveloped, maintaining blast furnace temperature has always been a problem that bothered everyone. The heat loss of ordinary open furnaces is extremely large, and it is difficult to keep the furnace temperature above 1200 degrees. And the reverberatory furnace needs a high-temperature resistant liner, and he can't think of how to make refractory bricks for a while. The traditional blast furnace of ironmaking is even worse, the temperature may be up to standard, but relying on the narrow furnace cavity alone to calcine the cement is afraid that it will not be able to burn enough when the demon moon has passed.

Therefore, Roland designed the firing room without any heating measures at all, and he relied on Anna.

The small grains of limestone that have been crushed by hand are mixed with clay and mixed with water to form a slurry, which is evenly spread in the firing room. Then the knight locked the gate and removed the handyman. Anna entered through the back door and let the flames bake the slurry on the floor until the iron rods that had been placed in the room melted.

Roland was a little restless, and this was his first step in garrisoning the border town. If concrete cannot be made, the plan to build a wall in three months is just talk. There is no city wall to stop it, but I'm afraid that no one wants to die in this hellish place. Whether it is real history or fictional literature, if you want to farm well, a stable base area is essential.

"Your Highness, what you mean by this thing can really stick all the stones together?" asked Carter Lannis, who was guarding the fourth prince's side. Although the prince told him that this was the latest research result of the Alchemy Workshop of the Grey Keep, he would still be skeptical. After all, those people have never made any truly reliable alchemy products.

"Who knows? that's what they say," Roland said, spreading his hands.

Alchemy and astrology in this world are known as the art of the sages, and they are very popular in mainland countries. The royal family generally trained its own alchemists and astrologers for the refining of secret elixirs and the prediction of fate. For ordinary people, these studies are so lofty that they give rise to the psychology of blind faith. With this in mind, Roland naturally led the question of the origin of the cement formula to the alchemy workshop. As for the chief knight believe it or not, it doesn't matter at all.

The flames from the window gradually extinguished, and it looked like it was fired.

Roland stood up with a suffocation, drove Carter out of the yard, and waited alone in front of the back door of the brick house.

The iron door creaked open, and Anna **** walked out. Roland put his robe on her for the first time, and brought her a glass of water, "How is it?"

The witch's face was dusty, and although the wet cement was low-dust, the scorching air still carried dust with it when calcined. For her, who can't wear a mask, it is obviously not too comfortable to stay in it for dozens of minutes. She coughed twice and nodded, "The mud has turned to dust." ”

Unable to wait for the temperature in the firing room to cool down enough, Roland wrapped the wet towel around his head, grabbed a shovel and slipped through the back door.

The hot air instantly surrounded him, and he felt a little difficult to breathe for a while, and the skin on his hands was burned painfully. Fortunately, it doesn't take much time to shovel a handful of ash, otherwise staying in this environment for a few minutes will only cause heat shock.

"Is this what you want?" asked Anna, as she put on the witch's suit, as she reached over her head.

"It looks like it," Roland flattened the powder, feeling its warmth with his fingers, "We'll have to try it to find out." ”

"What's the use of it?"

"There are so many places where you can build houses, bridges, and roads. If it succeeds, the people's dwellings will be able to withstand the wind and cold, and the torrential rain and snow will not be able to destroy it. He patted the little girl on the head with his other hand, "You made it." ”

Anna bowed her head. I don't know if it's an illusion, but he felt the girl's breathing become faster.

Theoretically, the fired clinker should be ground with gypsum to adjust its hardening time. But there was no need to think about it so much at this time, Roland took a short break and shoveled out two more handfuls, and then called Carter, who was standing outside the courtyard, and asked him to prepare cement mortar according to the ratio of three parts of ash powder mixed with one part of river sand.

The Chief Knight didn't mind doing some menial work at all, and it was much better for him to do this kind of thing than to fight for His Highness or hook up with a noble lady when he was in Grey Keep.

Because no iron powder is added to the raw materials, the cement slurry is light in color and grayish-white. Roland poured them down on one stone brick and snapped the other onto it. The cement set in about four hours, and considering the instability of the prototype, he planned to wait until tomorrow to see the results.

Early the next morning, Roland hurried to the backyard of the firing room with Carter and Anna. Pushing open the door, he noticed that the cement was solidified on the outside, tightly joined by the two stone bricks. The consolidated surface looks uneven, with hoarfrost in some places.

Roland squatted down, scraped off the hoarfrost produced by the alkalizing reaction, and pressed the hardened cement with his fingers, and the touch made him happy - the surface of the cement was firm and handy, completely different from the touch of the soil after tamping, even if he used his fingernails to buckle hard, he could not leave a trace on it.

After receiving the signal from the fourth prince, Carter first tried to lift the stone bricks, but was unsuccessful. He kicked hard from the side several times until the junction between the cement and the ground was broken, and the two stone bricks were still firmly bonded together. Finally, he swung the hilt of his sword and struck them hard, but he could only knock down a small corner of the corner.

"Is this the effect of cement," Carter immediately realized what it did, "it's incredible." Yesterday it flowed like a molten candle, and it was as solid as a rock after just one night. With this kind of thing, the walls can be built as fast as they want. With enough stones, we can even build a wall around the border in five years!"

"What's the use of that?" Roland said disapprovingly, "no amount of the tall walls can stop the enemy from within. I'd rather turn the dilapidated wooden houses in the border towns into sturdy concrete houses, so that my people no longer have to worry about being left homeless after a natural disaster. ”

"......" The chief knight was stunned, he really didn't expect the fourth prince, who had all kinds of aristocratic bad habits, to say such a thing.

"You'll see later," Roland reaffirmed the path he was going to take—for many travelers, technology was the primary productive force. And here, witches are the primary productive force.