Glutinous rice mortar is one of the most widely used building cementing materials in ancient China. At least not later than the Southern and Northern Dynasties (386-589 AD), glutinous rice mortar has become a relatively mature technology. Adding glutinous rice to cooked lime paste can increase the bonding strength, surface hardness, toughness and impermeability of mortar and obviously improve the firmness and durability of masonry. Today, many ancient buildings using glutinous rice mortar, such as the ancient city walls of Nanjing, Xi 'an, Jingzhou and Kaifeng, and the fish scale stone pond of Qiantang River in Ming and Qing Dynasties, are still very strong despite hundreds of years of wind and rain. Facts have proved that glutinous rice mortar is an excellent building cementing material.

Traditional mortar is a building mortar with lime as the main cementing component, which is generally composed of lime, sand, clay, additives and other materials, and is mainly used for building masonry, jointing and plastering. It has played an important role in the development history of human architecture. It was not until the middle of19th century that mortar was gradually replaced by portland cement. Lime is one of the earliest artificial cementitious materials invented by human beings. Lime aggregate ground discovered in Israel and the Levant before this year is considered as the earliest artificial lime material discovered at present.

According to archaeological data, China was able to burn and use lime in the Yangshao culture period of the Neolithic Age. At that time, natural ginger stone was calcined in the central plains in the north, and oyster shells were calcined in the south and coastal areas to obtain lime raw materials. For example, the "white flour" material often found in prehistoric and ancient archaeological sites was proved to be made of ginger stone by analysis and testing, and mortar digested by calcined limestone was widely used in buildings in the Western Zhou Dynasty. The application of this mortar reached a high level in the Eastern Han Dynasty. In the Southern and Northern Dynasties, the ancients began to add organic materials such as glutinous rice to the mortar to improve its performance. The Ming Dynasty's Tiangong Wu Kai described in detail the mortar made of organic materials: ash was used to fix ship seams, tung oil and fish oil were used to thicken wires and filaments, etc ... And the walls used for chalk were clearly separated by paper ribs. If it is used in tombs and reservoirs, it is divided into two parts, namely ash, river sand, loess, mixed glutinous rice and walnut juice. This building is strong and will never collapse. Modern research shows that the organic matter in these organic mortars plays a role in regulating biological templates and can effectively improve some mechanical properties of mortars.

Answer: When I was a student, I participated in the protection project of Gao Tai site unearthed from Shu Ya site in old Gu Lou, Chongqing, and did a simple analysis of jointing materials at Gao Tai site. Combining the existing protective materials with ancient literature records, we have obtained a mortar material with excellent performance, which can resist both compression and tension. The formula and process are as follows:

Formula and technology of glutinous rice mortar material

1 formula

Sample: Mortar for ancient buildings, taken from the former site of Shu Ya, Gulou, Chongqing, was collected on the spot, and 9 groups of samples were collected in different areas.

Experimental materials: glutinous rice (purchased from shopping malls), calcium hydroxide powder and sand (all purchased from construction shops), red soil (collected from Shu Ya site of Chongqing Old Drum Tower) and iodophor.

When making simulated mortar, the proportion of samples is 600g of lime, 300g of sand, 70g of red soil and 30g of glutinous rice.

2 process

Based on the knowledge of some ancient mortar manufacturing technical data, the simulation sample technology has made the following experimental preparations:

(1) Soak hydrated lime in water for more than 24 hours, during which the water level is always higher than that of hydrated lime, and let it stand. Prevent hydrated lime from contacting carbon dioxide in the air and converting it into calcium carbonate.

(2) The sand can be kept in a natural air-dried state.

(3) Take a small amount of glutinous rice, put it into a mortar and grind it until it has no graininess. Weigh 30g glutinous rice on the electronic balance, put it into a beaker, add part of deionized water (until the glutinous rice flour is submerged), put it into an electric furnace, heat and stir until it becomes sol, and stop heating.

Mix the weighed sand, hydrated lime, red soil and cooked glutinous rice sol together, add water and stir until uniform, put them into a 5*5*2cm mold, and dry them in the shade for later use. The number of samples is 8. There is no glutinous rice sol in the blank group, and the rest parts are the same, with 8 samples.

For the materials without glutinous rice pulp, we tested them together and concluded that glutinous rice pulp can significantly improve the tensile properties of mortar.

Therefore, at present, the application of glutinous rice mortar does exist in cultural relics protection projects.

Glutinous rice pulp not only plays a role in regulating the crystallization process and microstructure of calcium carbonate, but also closely combines with the generated calcium carbonate to form a composite structure with matching organic/inorganic materials and dense filling, which should be the micro-foundation of glutinous rice pulp's excellent mechanical properties such as high strength and toughness.