High-strength concrete and preparation method thereof

A concrete comprising lignin, recycled fine powder, P.042.5 grade cement, water, sand, gravels with a particle size of 6 mm to 10 mm, and a polycarboxylic acid water reducing agent;

• wherein
• a weight ratio of the cement, water, sand, gravels and the polycarboxylic acid water reducing agent in the concrete is 1:0.3:1.2:2.8:0.01;
• a weight ratio of the lignin to the cement in the concrete is 0.1-0.3:20;
• a weight ratio of the lignin to the recycled fine powder in the concrete is 0.1:5-10;
• the recycled fine powder is recycled powder of discarded concrete, and is prepared by:
• separating solid waste of discarded buildings, removing impurity and crushing, and grinding into dust with a particle size of less than 0.16 mm by a ball mill;
• the lignin is discarded wood lignin, which is extracted by:
• crushing wood, stirring and extracting with a sodium hydroxide aqueous solution with a mass concentration of 5% for 1 to 2 hours at 80° C. to obtain a black lignin alkali solution, adding a hydrochloric acid solution with a mass concentration of 30% into the black lignin alkali solution while stirring, reducing pH to 7.0, and obtaining the lignin by standing and layer separation;
• and the concrete is made by a method comprising the following steps:
• (1) pouring the lignin and the recycled fine powder into a portion of water to obtain a first uniformly mixed mixture,
• (2) pouring the cement into the remaining water with a cement mixer to obtain a second uniformly mixed mixture,
• (3) pouring the first uniformly mixed mixture into the second uniformly mixed mixture to obtain a third mixture, and then adding the polycarboxylic water reducing agent to the third mixture to obtain a uniformed mixed mixture A, and
• (4) pouring the gravels and sand into the uniformly mixed mixture A for thoroughly stirring to obtain the concrete.