Roland stood in the backyard of the kiln, waiting for the first batch of cement to be produced.

The brick house was specially designed by him for cement production, about fifteen meters long and four meters wide. There was a door at the front and back, but the front door was as wide as possible for people to carry materials. The back door was only wide enough for one person, allowing Anna to secretly enter the kiln.

To this end, he also built a circle of walls around the middle of the house, surrounding the back half of the kiln, with knights guarding the entrance and exit – they were all subordinates of Carter, and their loyalty was beyond doubt.

The production process of cement is simple: crush the limestone into powder, mix it with clay and iron powder, calcine it into clinker by dry or wet method, and then grind it with gypsum for use. The raw materials are very common. If it is difficult to obtain a large amount of iron powder, it can be omitted. The key lies in the calcination temperature of the clinker.

Roland didn't remember the specific temperature required for cement calcination, and even if he did, he had no way to measure and control the temperature - both infrared thermometers and thermocouple temperature guns were countless times more complex than cement. He only knew that this temperature was almost close to the melting point of iron, and the calcination process was also a difficult task in cement production.

In the era of underdeveloped smelting technology, maintaining the furnace temperature had always been a problem that plagued everyone. The heat loss of ordinary open hearth furnaces was extremely large, making it difficult to maintain the furnace temperature above 1200 degrees. The reverberatory furnace also required a high-temperature resistant liner, and he couldn't think of how to make refractory bricks for the time being. Traditional iron-smelting blast furnaces were even more unsuitable. The temperature might meet the standard, but relying on that narrow furnace chamber to calcine cement, he was afraid that not enough would be produced even after the Months of Demons were over.

Therefore, the kiln designed by Roland had no heating measures at all. He relied on Anna.

The artificially crushed small particles of limestone were mixed with clay, stirred with water into a slurry, and evenly spread in the kiln. Then the knights locked the gate and cleared the handymen. Anna entered from the back door and let the flames bake the slurry on the ground until the iron rods placed indoors melted.

Roland was a little restless. This was the first step for him to garrison Border Town. If cement could not be produced, the plan to build a city wall in three months would be just empty talk. Without a city wall to block them, he was afraid that no one would be willing to defend this godforsaken place. Whether in real history or fictional literature, a stable base was essential for good farming.

"Your Highness, can this thing you mentioned really stick stones together?" Carter Lannis, who was guarding the Fourth Prince, asked. Although the prince told him that this was the latest research result of the Graycastle Alchemist Workshop, he was still skeptical. After all, those people had never made any truly reliable alchemical products.

"Who knows? That's what they said anyway," Roland spread his hands.

In this world, alchemy and astrology were collectively known as the arts of the wise, and were very popular in continental countries. The royal family would generally cultivate their own alchemists and astrologers for secret medicine refining and predicting fate. For ordinary people, these studies were too lofty, resulting in a psychology of blind faith. Considering this, Roland naturally attributed the source of the cement formula to the Alchemist Workshop. As for whether the Chief Knight believed it or not, it didn't matter at all.

The flames emerging from the window gradually died down, indicating that the calcination was complete.

Roland stood up with a whoosh, drove Carter out of the courtyard, and waited alone at the back door of the brick house.

The iron door creaked open, and Anna walked out naked. Roland immediately draped his robe over her and brought her a glass of water, "How is it?"

The witch's face was covered in gray dust. Although wet-process cement produced less dust, the hot air during calcination would still stir up dust. For her, who couldn't wear a mask, it was obviously not very comfortable to stay inside for dozens of minutes. She coughed twice and nodded, "The slurry has turned into gray powder."

Roland couldn't wait for the kiln temperature to drop low enough. He wrapped a wet towel around his head, grabbed a shovel, and entered the back door.

The hot air instantly surrounded him, and he felt a little difficulty in breathing. The skin on his hands was burning. Fortunately, shoveling a handful of ash didn't take too long, otherwise staying in this environment for a few minutes would probably cause heat stroke.

"Is this what you want?" Anna asked, sticking her head in after putting on her witch suit.

"Looks like it," Roland flattened the powder and felt its residual heat with his fingers, "We'll have to try it to know if it works."

"What's it for?"

"Building houses, building bridges, repairing roads, there are too many places where it can be used. If it succeeds, people's homes will no longer be afraid of wind and cold, and heavy rain and snow will not be able to destroy them." He patted the little girl's head with his other hand, "It was made thanks to you."

Anna lowered her head. Maybe it was an illusion, but he felt that the girl's breathing quickened.

In theory, the calcined clinker should be ground with gypsum to adjust its hardening time. But there was no need to consider so much at this time. Roland rested for a while and shoveled out two more handfuls, then called Carter, who was standing outside the courtyard, and asked him to prepare cement mortar in a ratio of three parts ash powder to one part river sand.

The Chief Knight didn't mind doing rough work at all. For him, doing this kind of thing was much better than fighting or hooking up with noble ladies for the prince when he was in Graycastle.

Since no iron powder was added to the raw materials, the color of the mixed cement slurry was light, appearing grayish-white. Roland poured them all onto a brick, and then placed another one on top. The cement hardening time was about four hours. Considering the instability of the prototype, he decided to simply wait until tomorrow to see the results.

Early the next morning, Roland hurriedly led Carter and Anna to the backyard of the kiln. Pushing open the door, he noticed that the cement surface was already in a solidified state, tightly bonded to the two bricks. The solidified surface looked uneven, and white frost appeared in some places.

Roland squatted down, scraped off the white frost produced by the alkalization reaction, and pressed the hardened cement with his fingers. The touch made his heart rejoice – the cement surface was firm and rough to the touch, completely different from the touch after compacting the soil. Even if he tried to scratch it hard with his fingernails, he couldn't leave a trace on it.

After receiving a signal from the Fourth Prince, Carter first tried to lift the brick, but failed. He kicked it hard several times from the side until the junction between the cement and the ground broke, but the two bricks were still firmly bonded together. Finally, he waved the hilt of his sword and hammered them hard, but could only knock off a small piece of the edges and corners.

"Is this the effect of 'cement'?" Carter immediately realized its role, "It's incredible. Yesterday it could still flow like melted wax, and it's as hard as rock in just one night. With this thing, the city wall can be built as fast as possible. As long as there are enough stones, we can even build a wall around the border within five years!"

"What's the use of that?" Roland said dismissively, "No matter how high the wall is, it can't stop enemies from within. I would rather turn the dilapidated wooden houses in Border Town into solid cement houses, so that my people will never have to worry about being homeless after a natural disaster."

"..." The Chief Knight was stunned. He really didn't expect the Fourth Prince, who was full of aristocratic habits, to say such a thing.

"You'll see in the future," Roland reaffirmed the path he wanted to take - for many transmigrators, technology was the primary productive force. But here, the witch was the primary productive force.