Abstract:

Paishanlou gold mine uses crushed stone and cement slurry spray cementation filling technology，and the cement consumption accounts for more than 15%.Due to the poor water absorption of the crushed stone，the gaps between the particles are large and interconnected，a considerable part of the cement slurry is lost，which not only causes waste of materials，but also seriously pollutes the underground environment.In order to solve the problem of the lack of filling materials，the Paishanlou gold mine investigated the conditions of the source of aggregates near the gold mine.Then construction waste piled up on the southern edge of Fuxin City was processed and crushed into underground paste filling material aggregates.Portland cement was used as a cementing material，and a scientific and reasonable material ratio was designed to fill the goaf.By using construction waste，while solving the problem of insufficient sources of underground filling materials，it reduces various hazards caused by a large amount of construction waste.Not only can it bring significant economic benefits to the enterprise，but also make full use of bulk solid waste，resulting in huge environmental and social benefits.Using the method of geotechnical test，the universal hardness of the concrete block was measured to be 3.74，which is a medium firm rock，and the difficulty of breaking is moderately small.The universal hardness of the brick is 1.17，which is a relatively soft rock and easy to break.The apparent density of the material is 2.137，which is less than 2.6~2.8 of general rocks.The natural moisture content is 3.56% and it is in a relatively dry state.The water absorption rate is 9.3%.In view of the lack of intermediate particle size of construction waste in primary crushing，a new crushing process was proposed：1/3 of the coarse aggregate after primary crushing is crushed to less than 15 mm and backmixed to obtain a well-graded aggregate.Good gradation is beneficial to the workability，water requirement and fluidity of the slurry.Aiming at the strength and fluidity of paste filling materials，construction waste is used to prepare aggregates，ordinary cement is used as cementing material，and fly ash is used as additives to prepare paste materials that meet fluidity and strength requirements.Uniaxial compressive strength tests and slurry slump test were conducted.The results show that when preparing aggregates from construction waste， 15% fly ash，10% cement，and 78% slurry mass concentration are the optimal mix ratios.The uniaxial compressive strength of the filling body is 1.15 MPa at 3 d and 3.5 MPa at 28 d.The moisture content is 27%~28%， and the slump is 21.5 cm to 24.0 cm.It can meet the requirements of the strength and fluidity of the paste material.

Key words: gradation optimization, crushing process, construction waste, paste material, uniaxial compressive strength, slump