There are many factors that influence the slump of concrete. The slump loss of concrete directly affects the constructability of concrete, brings difficulties to construction, may cause construction accidents, and affects the quality of hardened concrete. The main manifestations of the loss of concrete slump caused by the loss of water-reducing agent are:
1. Increased drying shrinkage value of concrete leading to early cracks
Commonly used naphthalene-based water-reducing agents can reduce Concrete water consumption, but usually does not reduce the drying shrinkage of concrete. The water present in the concrete will still evaporate after the concrete curing is completed, and the concrete will still dry out. Moreover, the smaller the water-cement ratio, the greater the increase in the drying shrinkage value. The bigger.
Factors affecting concrete slump loss – mineral admixtures
In order to improve the performance of concrete and reduce the cost of concrete, mineral admixtures are often added during the concrete preparation process. Add to concrete. Mineral admixtures improve the particle gradation of cement, thereby reducing water demand and helping to improve the fluidity of concrete. At the same time, the reaction of mineral admixtures is potential hydration reaction and volcanic ash effect, which reduces the water consumption of cement in the early stage of hydration and is also beneficial to improving the fluidity of concrete. However, when the carbon content of fly ash exceeds 5%, due to the adsorption of water and admixtures by carbon, the concrete slump decreases and the concrete slump loss also increases.
2. The naphthalene-based water-reducing agent is not compatible with the cement used, which will accelerate the occurrence of early cracks in concrete.
When the water-reducing agent is not compatible with the cement used, it will This causes poor fluidity of concrete, rapid slump loss of pumped concrete, and affects the hardening degree of concrete. The reason may be that the components of the cement itself and the water-reducing agent are not fused, causing problems in the reconciliation of the two. Construction workers at the construction site often add water to the concrete at will, which reduces the cohesion of the concrete mixture and causes segregation of the slurry and aggregates, thereby accelerating the occurrence of early cracks in the concrete.
3. The loss of the function of the water-reducing agent causes the loss of concrete slump
The use of naphthalene series water-reducing agent can effectively increase the slump of concrete and maintain the strength of concrete, but its Once the function is weakened or lost, the slump of the concrete will also be lost, making construction difficult and causing cracks in the concrete.
4. The proportion of naphthalene-based water-reducing agent is not appropriate, which will destroy the original stability and uniformity of the concrete.
The solid content of the water-reducing agent will affect the cohesion of the concrete mixture and reduce the water content. The retardant component in the agent affects the fluidity of the concrete mixture. When pumping concrete is configured, when the fluidity and cohesion of the concrete mixture are out of balance and the cohesion is low, the coarse and fine aggregates of the concrete will separate from the pure slurry under the action of its own gravity or other external forces, destroying the homogeneity of the material composition. properties and stability, causing segregation of concrete, which may cause cracks.
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