Self Leveling Screeding System Construction Admixtures Materials

In the whole dry powder mortar system, self leveling /screeding is undoubtedly the most complex product. The formula design and the selection of raw materials have great influence on the final quality. From the perspective of formula and raw materials, the common factors causing bleeding sedimentation mainly include the following aspects:


1. Ratio of silt to river sand


If the amount of cementitious material and fine filler is low and the amount of river sand is high, the slurry dispersed by superplasticizer can not fully wrap the river sand, which is easy to cause the settlement and bleeding of heavier particles.


2. Gradation of river sand


When the overall gradation of river sand is coarse and the particles are heavy, the river sand particles are more likely to sink to the bottom of the mortar due to its own gravity. When the grading and mud content of river sand vary greatly between batches, the flow state of products will be greatly different, which will easily cause bleeding settlement.


3. Water reducing agent


If the efficiency of superplasticizer in self leveling mortar is not high and the cementitious materials can not be effectively dispersed, workers will often add excessive water to improve the fluidity of the slurry during construction, which is prone to bleeding and settlement.


4. Cellulose ether


Cellulose ether mainly improves the viscosity and suspension of slurry. If the suspension property of the system is poor, the separation of slurry and water will occur, resulting in bleeding sedimentation.


In addition, the operation of workers is not standard, excessive water can easily exceed the tolerance of the system, which will damage the balance of the system, resulting in bleeding and settlement of mortar.


It can be seen from the above analysis that, on the one hand, the proportion of fine powder and river sand should be optimized to control the quality of river sand; on the other hand, water reducer and cellulose ether with excellent performance should be selected and used.


The amount of water reducer and cellulose ether is also important. If the dosage of superplasticizer is too low, the fluidity of slurry is not enough, and the loss of fluidity is fast; if the dosage of superplasticizer is too high, the fluidity is too large, which is easy to cause bleeding. If the content of cellulose ether is too low, the suspension performance of the system is poor, which is easy to cause bleeding sedimentation; if the content is too high, the slurry is viscous and the fluidity is reduced. Therefore, in addition to the quality of water reducing agent and cellulose ether to meet the demand, it is also very important to master the mixture ratio of the two.


In addition, the sedimentation of self leveling slurry can be effectively improved by adding stabilizer and other materials.

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