Foam concrete exudation rate concepts and how to avoid the measures

Foam concrete exudation rate concepts and how to avoid the measures
Foam concrete in the process of transportation, vibrating, pumping appear coarse aggregate sinking, exudation water floating phenomenon known as concrete.Bleeding is an important aspect and fresh concrete properties.Usually, describe the concrete secrete water feature indicators have secrete water (i.e., concrete mixing content per unit area of average secrete water) and exudation rate (i.e., secrete the ratio of the water on the ratio of water content of concrete mixing).Bleeding can lead to some adverse consequences, such as can cause pitting surface, plastic cracking, surface problems such as the decrease of strength of concrete.Bleeding will make concrete uneven, and secrete water itself is uneven in the concrete, must have certain unfavorable effects on the concrete.Bleeding parts will have defects in concrete, bleeding site water-cement ratio decreased at the same time, in the region left defects, lead to the intensity of each part of the body.Secrete water also decreases the permeability resistance of concrete, clothing and freezing-thawing resisting ability.
To avoid "qinshui" phenomenon in a concrete surface, first of all, foam concrete concrete itself has good water retention, to prevent serious water secretion lead to concrete surface water cement ratio is too large.Starting from the choice and composition of materials, shoulds not be too great attention should be paid to control the water cement ratio, admixture don't mix, and the setting time is appropriate.Sand and stone aggregates to meet the national quality requirements, especially pay attention to below 0.315 mm particle content in the sand.The cement setting time not too long, specific surface area shoulds not be too small, grading shoulds not be too concentrated;
Secondly, the construction process to prevent excessive vibration caused by serious segregation and bleeding of concrete;Again, after construction should pay attention to timely maintenance, both to prevent concrete surface hardening before was caused by the rains washed out concrete water-cement ratio is too large, and to prevent moisture from the concrete loss before surface to build strength, especially the concrete mixed with fly ash or slag, due to its low early strength, hydration product surface is not enough to seal the surface of wool stoma, if do not pay attention to the early full wet curing, concrete surface moisture lost faster is more, the surface of cement can not get adequate hydration, also can cause the surface strength of concrete is low, loose structure.
Usually, in the final set near the end of the foam concrete concrete, to secondary coating on concrete surface (or pressure), the concrete surface structure more compact.