| With the rapid development of China’s industry,the output of solid waste is increasing rapidly year by year,which is in urgent need of resource utilization.At the same time,the demand for building materials in China’s development is increasing,thus the preparation of building materials from industrial solid waste has become one of the hot topics.At present,the aggregate prepared from industrial solid waste has some defects,such as high content of cement,low strength and serious environmental pollution.Based on previous research,the non-sintering high-strength solid waste aggregates（SWAs）was prepared with dredged soil,ground-granulated blast-furnace slag（GGBFS）,steel slag,phosphogypsum and municipal solid waste incineration（MSWI）fly ash as raw materials in this study,and the extremely low content of cement（1.5%）and high strength of SWAs（20.35 MPa）were achieved.The environmental solid waste aggregate permeable brick（SWAPB）was made with SWAs as raw materials,which provided reference and inspiration for effectively solving the existing problems of industry,dredging,environmental protection and construction in China.The research contents and conclusions of this study are as follows:（1）The particle size distribution,phase composition and microscopic morphology of solid waste raw materials were tested by laser particle size analyzer,X-ray diffraction（XRD）and scanning electron microscope（SEM）,respectively.The analysis showed that dredged soil,GGBFS,steel slag and phosphogypsum were used as the core layer of SWAs,and cement,GGBFS,phosphogypsum and MSWI fly ash were used as the shell layer of SWAs,can realize the complementary advantages of solid waste raw materials.（2）The optimal raw material ratio of SWAs was determined.When curing age was 28d,the formula of core layer for SWAs was as follows:dredged soil:GGBFS:steel slag:phosphogypsum=40:24:18:18,and the optimal formula of shell layer for SWAs was as follows:cement:GGBFS:phosphogypsum:MSWI fly ash=5:60:25:10,and solid waste consumption was up to 98.5%,while cement content was only 1.5%of the total weight of SWAs（core layer+shell layer）.Na2SO4 with a mass concentration of 2%was determined as an early activator to stimulate the early activity of solid waste and then improve the early strength of SWAs.Silicone waterproofing agent with a mass concentration of 0.08%was selected for waterproofing treatment of SWAs shell to improve the softening coefficient of SWAs.（3）The properties of SWAs prepared with the optimum formula were studied.The results showed that for SWAs,the cylinder compressive strength was 20.35 MPa,the softening coefficient was 0.84,and the 1 h water absorption rate was 8.73%,all of which met the requirements of GB/T 17431.1-2010.The leaching of SWAs in the actual application environment was simulated,and the relevant indicators in the leaching solution were all within the safe range.XRD showed that calcium silicate hydrate（C-S-H）,a substance that contributes to the strength development of SWAs,was formed in the SWAs shell,and the same conclusion was obtained by thermal gravity-differential thermal gravity（TG-DTG）.SEM observation showed that the shell layer of SWAs presented a laminar distribution with dense structure and foil-like hydration products（C-S-H）.（4）The properties test of SWAPB prepared with SWAs as aggregate showed that for SWAPB,the compressive strength was 16.7 MPa,the water permeability coefficient was0.022 cm·s-1,the flexural strength was 3.78 MPa,and the strength loss rate after 25freeze-thaw cycles was 10.4%,and the mass loss rate was 0.95%.SEM was used to observe the section of SWAPB after freezing and thawing,and it was found that there was no obvious crack in the SWAPB after freezing and thawing,instead of a few micro-pores. |
