Research On Preparation And Performance Of Recycled Brick-Concrete Powder Based Geopolymer

The low strength,long setting time,poor workability,high drying shrinkage and serious efflorescence of recycled Brick-Concrete powder based geopolymer under ambient curing condition seriously limit the resource utization of recycled Brick-Concrete powder.In order to improve the performance of recycled Brick-Concrete powder based geopolymer.In this paper,appropriate activators were selected to prepare the recycled Brick-Concrete powder based geopolymer,and systematically studied influences of activator parameters and curing conditions on its compressive strength,workability and setting time.In addition,the improvement on strength,working performance,setting time and durability of recycled Brick-Concrete powder based geopolymer by adding highly active admixtures was studied.The main conclusions are as follows:(1)The modified sodium silicate solution promote the dissolution of aluminosilicate minerals of recycled Brick-Concrete powder,make it to Low polymerization and formed a new structure form of hydration gel,make geopolymer paste’s compressive(modulus 0.9,alkali equivalent 6%,high temperature curing at 90 ℃ for 24 hours)strength reaches 28.74 MPa in 28 days.At the same time,the addition of slag can further accelerate the dissolution of active silicoaluminate,promote the densification of the specimen matrix,and make the bond between the Brick-Concrete powder particles closer.The maximum compressive strength of geopolymer(with slag content of 45%)reaches 77.56 MPa at room temperature curing for 28 days,which is 14.13 times of geopolymer without slag.(2)The addition of slag can increase the contents of hydration gel CASH and hydroxyl in slurry,shorten the setting time of slurry,and improve the flow performance of slurry.When the alkali equivalent is more than 6% or the modulus of sodium silicate solution is less than 1.1,the leaching of active calcium ions in the slurry can be inhibited and the setting time of the slurry can be prolonged.(3)The combination of reclaimed brick powder and slag improves the resistance of matrix to drying shrinkage deformation,and the two have a synergistic effect on the improvement of drying shrinkage performance of the gelling system,which reduces the drying shrinkage rate of the gelling system by 76.3%(slag content is 45%).At the same time,the addition of slag reduced the porosity and capillary water absorption rate of the specimen,effectively hindered the migration of water and sodium ions in the pore solution of the specimen,reduced the degree of alkali-spreading of the specimen,and reduced the mass loss of the specimen by 97.9%.56 Figures,9Tables,96References...