As long as you are an elderly person in the countryside, you will definitely know this question. chengcuiyuan1's answer is absolutely correct. The loess bricks you mentioned are the adobe bricks used by the elders. We call this kind of bricks "Ji", which are made with wooden molds. There are usually two types, one is the flat-shaped "Ji". They are used in pits in rural areas; the other type is the loess bricks you mentioned, which are called "xiaoji" in rural areas and are used for building walls. In our north, they are mixed with wheat straw, which is equivalent to the bricks in reinforced concrete today. The steel bars use the tensile properties of the fibers inside the wheat straw to enhance the tensile strength of the loess bricks. It is nonsense to talk about insulation. When making it, we use high-quality clay soil. After pouring water on it, we take off our shoes and use our feet to step on the wheat straw and clay and mix them evenly. I wonder if this is the origin of the word "mud legs"! Then find a flat ground, use wooden molds to "take off" one by one (this is another dialect), dry them and put them away for later use. Of course, this kind of loess bricks cannot be compared with today's red bricks or reinforced concrete, but in those poor years, how could you have the money to buy these building materials? In our rural areas, before the 1980s, generations of ancestors used this material to build houses.