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Chen Chuangu teased, "I have never seen Qin Ke be so considerate toward anyone."

Rong Xi's heart gave a jolt, but his smile remained gentle. "It is Xi's good fortune."

The two said no more. Chen Chuangu took his leave and headed north through the wind and snow.

Several days later, after the raw materials had been fired by the kiln workers into clinker, Rong Xi mixed it with gypsum, thus producing cement.

Rong Xi piled up earth into a three-dimensional rectangular mold and set steel bars vertically within it.

The steel bars had been forged by Jiang Weiping according to the method Rong Xi had taught him.

He then mixed the cement with sand and gravel, added water and stirred it evenly, then poured it into the rectangular frame, forming blocks of concrete.

Once it had hardened, the earth was stripped away. After the moisture dried, its shape was neat and even.

When Cheng Hao saw it, astonishment filled his eyes. He had someone strike it with a hammer, yet it suffered scarcely any damage. It was exceedingly sturdy.

"Uncle Cheng, if this were used to build city walls, it should be sturdier than yellow mud, should it not?" Rong Xi asked with a smile.

Though border city walls were built more solidly, mostly with rammed earth and faced with brick and stone, they still fell somewhat short of concrete in strength.

In truth, lime mixed with glutinous rice slurry made an even sturdier material, but glutinous rice was limited. Great Wei had countless cities and houses, and gathering such materials was no easy task.

Mengshan County's city wall was piled from loess, easy to attack and difficult to defend.

Though this was not a strategic stronghold, Mengshan County now housed a Military Equipment Bureau workshop. Its strategic importance