Influence of water consumption of self-levelling mortar on construction quality
Cement self-levelling and gypsum self-levelling two kinds of inorganic self-levelling mortar are the two most common types in the world. The amount of water used in self-levelling mortar, i.e. ‘water-cement ratio’, is a key parameter, which directly affects the performance of the mortar, and in turn affects the delivery quality of the ground project.
Self-levelling mortar as a new type of ground levelling material, in the construction project has been widely used. Cement self-levelling and gypsum self-levelling two kinds of inorganic self-levelling mortar are the two most common types in the world. The amount of water used in self-levelling mortar, i.e. ‘water-cement ratio’, is a key parameter, which directly affects the performance of the mortar, and in turn affects the delivery quality of the ground project.
1. Fluidity performance
- When the water consumption is lower than the formula design water consumption, the consistency of self-levelling mortar is larger, and the fluidity is poor. This will lead to the mortar in the construction process is difficult to achieve self-levelling characteristics, easy to appear local unevenness, surface puddling phenomenon.
- With the increase of water consumption, the fluidity of the mortar can be improved. However, if the water consumption exceeds the designed water consumption, water segregation will occur, resulting in floating slurry on the surface of the mortar, prolonging the setting time, sinking of aggregates, lowering the strength and other quality problems, affecting the quality of ground delivery and shortening the service life.
- Gypsum self-levelling is more sensitive to water consumption than cement self-levelling. Once the water consumption is too much, in addition to the above quality problems, it will be accompanied by particularly serious loss of strength, and it is possible to lose more than half of the strength, or even not dry for a long time, and then there will be siltation phenomenon, complete loss of strength, and gypsum self-levelling will be directly dried and scrapped.
2. Hardening performance
- Suitable water consumption is the necessary condition for cement and gypsum and other cementitious materials to be fully hydrated. Insufficient water, cementitious materials hydration is incomplete, hardened mortar strength will be reduced, affecting the hardness of the ground and abrasion resistance, at the same time there may be an increase in the internal pores, the structure of the situation is not uniform.
- Too much water will dilute the cement or gypsum slurry, and the crystal growth of cementitious materials will be interfered, resulting in increased porosity of the hardened mortar, reducing its compactness and strength and affecting its durability.
3. Shrinkage deformation
- Improper water consumption will affect the shrinkage deformation of self-levelling. Too little water, due to incomplete hydration of cement, mortar in the hardening process may produce a large self-shrinkage.
- Too much water, the excess water in the evaporation process will lead to greater drying shrinkage, easy to cause ground cracking.
In practical application, according to the specific project requirements, material properties and construction environment and other factors, choose the self-levelling materials to meet the requirements, precise control of self-levelling mortar scientific water consumption, in order to ensure that a good construction effect and ground quality. For cement self-levelling, it is necessary to take into account the requirements of its high strength and durability, reasonable control of water consumption to balance the strength and shrinkage and deformation; for gypsum self-levelling, it is necessary to take into account the characteristics of its fast-setting fast hardening and high horizontal accuracy, optimise the water consumption to ensure the surface quality and strength development. Only in this way, can give full play to the advantages of self-levelling mortar in the construction of ground engineering. Lastly, under the condition of guaranteeing the performance of the product, the lower the water consumption, the better the quality of the product.