Post Date:19,Jun,2023

三. Non coagulation phenomenon

Phenomenon: After adding a water reducing agent, the concrete has not solidified for a long time, even for a day and night, or the surface exudes slurry and turns yellow brown.

Reason analysis:

(1) Excessive dosage of water reducing agent;

(2) Excessive use of retarders.

Terms of settlement:

(1) Not exceeding 2-3 times the recommended dosage, although the strength has slightly decreased, the 28 day strength reduction is less, and the long-term strength reduction is even less;

(2) After final setting, appropriately increase the curing temperature and strengthen watering and curing;

(3) Remove the formed part and pour it again.

四. Low intensity phenomenon

Phenomenon: The strength is much lower than the test results of the same age, or although the concrete has set, the strength is extremely low.

Reason analysis:

(1) Excessive addition of air entraining water reducing agent results in excessive air content in concrete;

(2) Insufficient vibration after mixing with air entraining water reducing agent;

(3) Not reducing water or increasing water cement ratio instead;

(4) Increase the amount of triethanol added.

Terms of settlement:

(1) Adopting other reinforcement measures or re pouring;

(2) Strengthen post pouring vibration;

(3) Take measures to address the aforementioned reasons.

五. Rapid loss of slump

Phenomenon: Concrete quickly loses its workability, and with every 2-3 minutes of extension after being discharged from the tank, the slump decreases by 1-50 mm, and there is a significant bottom sinking phenomenon. High slump concrete is more prone to this phenomenon.

Reason analysis:

(1) Water reducing agents have poor adaptability to the cement used;

(2) The bubbles introduced into the concrete continuously overflow, causing water evaporation, especially when using air entraining water reducing agents;

(3) High concrete mixing temperature or environmental temperature;

(4) The slump of concrete is very high.

Terms of settlement:

(1) Find the cause and take measures to address it;

(2) Using the post mixing method, the water reducing agent is added 1-3 minutes after mixing the concrete or even before pouring, and then re mixed;

(3) Be careful not to add water.

六. Settlement joint

After pouring, there will be several short, straight, wide, and shallow cracks in the concrete before and after initial setting.

Reason analysis:

After adding water reducing agents, the concrete is more viscous, does not bleed and is not easy to completely settle, often appearing above the steel bars;

Terms of settlement:

Apply pressure to the cracks before and after the initial setting of the concrete until they disappear.