Mechanical Properties of Modified Plastering Mortar Based on the Mesh Number of Manufactured Quartz Sand and Additives

Plastering mortar plays a protective role for building surface. Its mechanical properties are influenced by different factors. To improve the mechanical properties and solve the problems of mortar cracking and falling, this study proposed a method of studying the change in mechanical properties in accordance with the mesh number of quartz sand. The optimal mesh number of quartz sand was selected by measuring the water–cement ratio and consistency of fresh mortar, the compressive and flexural strength, and the water absorption rate of specimen. On the basis of the mesh number, an orthogonal test was designed using silica fume, calcium sulphoaluminate expansion agent, and polycarboxylate superplasticizer. The performance changes caused by the mesh number of quartz sand and the dosage of additives were analyzed, and plastering mortar with good mechanical properties was determined. Results demonstrate that the key to modification is to strengthen hydration reaction and compactness because cement mortar is porous and brittle. The mechanical properties of plastering mortar decrease with the increase in quartz sand mesh, and the effect is the best when 60–80 mesh quartz sand is used. When the additives are used for modification, the best effect can be obtained when mixing 3% silica fume, 5% calcium sulphoaluminate expansion agent, and 0.5% polycarboxylate superplasticizer. In this case, the compressive strength of the plastering mortar increases by about 22.8% and the water absorption decreases by about 2.4% compared with that before modification. The conclusions obtained in this study can provide an important reference for the modified application of plastering mortar. © 2022. School of Science, IHU. All rights reserved.