Concrete, as an important material in the field of modern architecture, its fundamental knowledge is crucial for personnel engaged in related work. Through the introduction of this article, I believe everyone can have a more comprehensive and in-depth understanding of concrete, laying a solid foundation for future learning and practice.

What is pre mixed concrete?

Answer: Pre mixed concrete is a concrete mixture that measures and mixes components such as cement, water, sand, gravel, admixtures, and mineral admixtures in a certain proportion at a mixing plant, and then delivers them to the delivery location of the purchaser within a specified time. The meaning of concrete is artificial stone, representing concrete.

What are the grades of concrete strength?

Answer: According to the standard curing strength of concrete test blocks after 28 days, they can be divided into 13 levels: C10, C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C70, and C80. C is the first capital letter of an English word for concrete, which represents concrete, with corner numbers indicating strength grade.

What are the commonly used cement in mixing plants and what are the items for re inspection?

Answer: Commonly used cement in mixing plants includes: Portland cement, ordinary Portland cement, and composite cement. Portland cement is further divided into P · I and P · II types. Ordinary Portland cement is divided into ordinary type and early strength type, with the code name P · O. The items that need to be retested for cement include setting time, stability, strength, and fineness (specific surface area).

What are the quality requirements for good sand?

Answer: There are the following items:

(1) The particle size distribution meets the requirements of medium sand;

(2) The particle size is medium sand, and the content of particles larger than 10mm is relatively small, with a maximum of no more than 10%;

(3) Mud free eggs, large mud lumps, with a mud content not exceeding 3%;

(4) No tree roots, grass roots, mud, plastic bags or other debris. 

Why is medium sand preferred for pumping concrete?

Answer: Sand is divided into coarse sand (3.1-3.7), medium sand (2.3-3.0), and fine sand (1.6-2.2) according to its fineness modulus. The grading of medium sand is reasonable, and the particle content below 0.3mm can reach about 15%, which is beneficial for pumping. Coarse sand has high frictional resistance, which is not conducive to pumping. The surface area of fine sand is large, and using more cement at the same strength increases the probability of cracking