The Research On The Properties Of Mortar For Autoclaved Aerated Concrete Block

In recent years, with the continuous reduction of arable land and the growing of the environmental consciousness and awareness of building energy efficiency, ordinary clay brick as a traditional wall material is gradually restricted or prohibited, and autoclaved aerated concrete block as one of new wall materials is more common in the construction industry applications. Autoclaved aerated concrete block is superior to ordinary clay brick with light weight, good insulation properties and machinability and other advantages, so it can be widely used in non-bearing wall of multi-story buildings. The autoclaved aerated concrete block wall causes easily crack and local hollowing in plaster layer because of its water absorption and big drying shrinkage which will not only affect the appearance of the building but also affect its thermal insulating properties, and finally limit its function to play. Therefore, the problem that autoclaved aerated concrete block wall is easy to produce cracks limits autoclaved aerated concrete block further development.Based on the mechanism of the autoclaved aerated concrete block wall cracks, this paper analyses the reasons why the wall is easy to crack. Combined with the material properties of the autoclaved aerated concrete block, the shrinkage performance and compressive strength of three mortars including ordinary mortar, mortar with mortar admixture and modified mortar with polypropylene fiber and fly ash for autoclaved aerated concrete block are tested and compared in this experiment. The test aims to improve the performance of the special mortar through adding fly ash, compound admixture for mortar and polypropylene fiber into mortar, and make its properties matching the performance of autoclaved aerated concrete block in purpose to reduce the uncoordinated deformation because of shrinkage and can prevent the cracks of wall.The result shows that under the condition of meeting the requirements in the mortar, the shrinkage of the modified mortar with polypropylene fiber and fly ash for autoclaved aerated concrete block of 60 days is 0.7002mm/m under nature conditions. The shrinkage of mortar with mortar admixture is reduced by 36.8% compared with ordinary cement mortar, and the shrinkage of modified mortar with fly ash for autoclaved aerated concrete block is reduced by 23.7% compared with ordinary cement mortar, and the strength of modified mortar with fly ash is also close to that of autoclaved aerated concrete block. Therefore, the use of modified mortar with polypropylene fiber and fly ash in the autoclaved aerated concrete block wall can reduce the mismatch deformation, which aims to reduce cracks in the wall.Based on the measured shrinkage values, this paper draw estimated formulae for the shrinkage of modified mortar with polypropylene fiber and fly ash under both curing room conditions and nature conditions which consider temperature and humidity, and the measured values are in good agreement with the calculated values by comparison.