Causes of slump loss

1. Influence of raw materials

Whether the cement and pumping agent used is matched and adapted, must be derived through the adaptability test, pumping agent mixing to determine the optimal mixing through the adaptability test with cement cementitious materials. Pumping agent in the air-entraining, retarding the number of ingredients, the slump loss of concrete has a greater impact, air-entraining, retarding more ingredients, the slump loss of concrete is slow, otherwise the loss of fast. Naphthalene high efficient water reducing agent formulated concrete slump loss is fast, in the low positive temperature +5 ℃ below, the loss is slower.

If the mixing agent in cement is hard gypsum, it will cause the slump loss of concrete to accelerate, and the content of C3A in cement is more than the early-strength component, the use of "R" type cement, the fineness of cement is very fine, and the setting time of cement is fast, etc. All of these will cause the slump loss of concrete to accelerate, and the slump loss of concrete will be related to the quality of mixing materials and the amount of mixing materials in cement. The slump loss of concrete is related to the quality of mixed materials in cement and the amount of mixing. The content of C3A in cement should be within 4% to 6%, when the content is lower than 4%, the air-entraining and retarder components should be reduced, otherwise it will cause the concrete not to solidify for a long time, and when the content of C3A is higher than 7%, the air-entraining and retarder components should be increased, otherwise it will cause the loss of concrete slump soon or the phenomenon of false coagulation.

The mud content and mud content of coarse and fine aggregates used in concrete exceeds the standard, and the content of crushed stone needle-like particles exceeds the standard, etc. will cause the slump loss of concrete to accelerate. If the coarse aggregate water absorption rate is large, especially the crushed stone, in the summer high temperature season after high temperature exposure, once put into the mixer it will be a large amount of water in a short period of time, resulting in a short period of time (30min) slump loss of concrete accelerated.

2. Mixing process impact

Concrete mixing process also has an impact on the loss of concrete slump, mixer models and mixing efficiency are related, therefore, the requirements of the mixer should be regularly overhauled, mixing blades should be regularly replaced. Concrete mixing time can not be less than 30s, such as less than 30s concrete slump instability, resulting in relatively faster slump loss.