Technical Issues In The Application Of Polycarboxylate Superplasticizer Water Reducers

Sensitivity of polycarboxylic acid superplasticizer to mud content

The mud content of concrete raw material sand and gravel will have an irreversible effect on the performance of concrete and reduce the performance of polycarboxylic acid superplasticizer. The fundamental reason is that after polycarboxylic acid superplasticizer is absorbed by clay, the part used for dispersing cement particles is reduced, and the dispersibility becomes worse. When the mud content of sand and stone is high, the water reduction rate of polycarboxylic acid water reducer will decrease obviously, the slump loss of concrete will increase, the fluidity will decrease, the concrete will crack easily, the strength will decrease, and the durability will become worse.

There are several conventional solutions to the current mud content problem:

(1) Increase the amount or add slow-release anti-collapsing agent in a certain proportion, but control the amount to prevent concrete yellowing, bleeding, segregation, bottom grabbing and setting time is too long;

(2) Adjust the sand production ratio or increase the amount of air inducer. On the premise of ensuring good workability and strength, reduce the sand mixing ratio or increase the amount of air entrainment agent to increase the free water content and paste volume of concrete system, so as to adjust the performance of concrete;

(3) Appropriate addition or replacement of parts to solve the problem. The experiment shows that adding proper amount of sodium metabisulfite, sodium thiosulfate, sodium hempetaphosphate and sodium sulfate in water reducer can reduce the influence of mud content on concrete to a certain extent. Of course, the above methods do not solve all the mud content problems. In addition, the impact of mud content on concrete durability needs further study, so reducing the mud content of raw materials is the fundamental solution.

Calcium Lignosulfonate (CF-4)

Calcium Lignosulfonate (CF-2)

Redispersible Polymer Powder (RDP JF2)