Performance and causes of insufficient concrete strength
Performance of insufficient strength: insufficient concrete strength will be accompanied by reduced impermeability and durability, and more importantly, it will affect the bearing capacity of the structure. It is mainly manifested in three aspects:
1. Reduce structural strength and rigidity.
2. Poor crack resistance and a large number of wide cracks.
3. The component is deformed, and the deformation is large enough to affect the normal use.
Reasons for insufficient strength:
I. poor quality of raw materials:
（1） Poor quality of cement: 1. Low actual activity of cement; 2. The cement stability is unqualified;
（2） Poor quality of aggregate (sand and stone): 1. Low strength of stone; 2. Poor stability of stone volume; 3. The shape and surface state of stones are poor; 4. The content of organic impurities and dust in sand and stone is high, and the content of mica in sand is high;
（3） Unqualified mixing water quality:
（4） The quality of admixture is unqualified or the composition ratio is improper
II. Improper concrete mix proportion:
Concrete mix proportion is one of the important factors to determine the strength. The size of water cement ratio directly affects the concrete strength. Other factors such as water consumption, sand rate and bone cement ratio also affect various properties of concrete, resulting in the accident of insufficient strength.
（1） Increased water consumption: the more common are the inaccurate measurement of the water adding device on the twin shaft mixer
（2） Random application of mix proportion;
（3） The amount of admixture is not allowed
（4） Improper use of admixtures;
（5） Inaccurate measurement of sand and gravel and insufficient cement consumption.
III. incorrect construction process
（1） Poor mixing, too short or too long, resulting in unevenness.
（2） Serious cement slurry leakage during pouring; False setting and initial setting of concrete; The vibration is not solid.
（3） Improper maintenance; Such as early water shortage, dryness, freezing, etc.
IV. the test block is not cured according to the standard or not manufactured according to the regulations
For the remedy and treatment of insufficient concrete strength, the actual strength is generally measured, the later strength is used to reduce the structural load, structural reinforcement, analysis and checking calculation, demolition and reconstruction, etc. Use high quality Macpex concrete batching plant can produce high quality concrete that can meet high standard.
