The influence of polycarboxylate water reducer on the performance of concrete

Now with the continuous requirements for the quality of housing construction, the strength of concrete is constantly improving. The problem of shrinkage and cracking has become a hot spot in the field of concrete research at home and abroad, and it is also one of the severe problems faced by the construction engineering community. Today we will discuss the impact of concrete shrinkage.

A. The dry shrinkage of PCE concrete is lower than that of concrete mixed with naphthalene and sulfamate water-reducing agent under the same conditions.

B. In the range of 0.28-0.34, the plastic shrinkage and cracking degree of PCE concrete increases with the increase of the water-binder ratio.

C. Kingsun PCE concrete admixture has a good synergistic effect with expansion agents, fibers, and shrinkage reducing agents, and has a good inhibitory effect on the shrinkage and cracking of the concrete, and it has the best effect when mixed with shrinkage reducing agents.

D. The 24h shrinkage of PCE-mixed high-strength concrete decreases with the increase of ambient temperature, and increases with the increase of airflow rate; moisture-maintaining and secondary plastering processes have a better inhibitory effect on the plastic cracking of PCE-mixed concrete.

E. PCE obviously delays cement setting, the saturated adsorption capacity and zeta potential in the cement system are lower than naphthalene and sulfamate water reducers.

Polycarboxylic acid water reducing agent can greatly improve the construction performance of concrete, but improper use will cause concrete bleeding. The following is a brief understanding of the causes of concrete bleeding caused by polycarboxylic acid water-reducing agents:

1. Aggregate mass fluctuates. In the process of concrete production, it is often encountered that the quality of sand and gravel aggregate fluctuates, such as the increase or decrease of mud content, the fluctuation of water content, the change of aggregate gradation, the change of sand fineness modulus, and so on, which may increase the possibility of concrete bleeding.
2. Compared with other water-reducing agents, the water reducing and slump protecting properties of polycarboxylic acid water-reducing agents are greatly affected by temperature. When the temperature is high in summer, the polycarboxylic acid water reducer with good slump protection performance may appear when the temperature suddenly decreases, the slump "down" phenomenon may occur.
3. The use of polycarboxylic acid superplasticizer secondary add adjustment, sometimes can not reasonably grasp the amount of use, more than the theoretical requirements of the amount of superplasticizer, too much superplasticizer in the concrete after pouring still play a role, so that part of the concrete moisture precipitation.

4. In order to obtain good slump protection performance of concrete, a certain amount of retarder component is often added when compound polycarboxylic acid superplasticizer. When the dosage of retarding component is too large, or when the temperature of the polycarboxylic acid superplasticizer is relatively good, the excessive retarding component will slow down the hydration of cement and cause concrete bleeding.

5. The uncoordinated chemical changes among the complex components of concrete, especially the compatibility between cement and polycarboxylic acid superplasticizer, are particularly prominent. If the cement and polycarboxylic acid superplasticizer compatibility is poor, it will increase the saturated content of the superplasticizer, superplasticizer will extend the initial setting time of concrete while making the free water precipitation in concrete. In addition, when the soluble alkali in cement is low, the hydration rate of cement is slow, and the phenomenon of delayed bleeding often occurs.

Kingsun is a professional concrete admixtures manufacturer and supplier.