The Strength And Microstructure Of Soda Residue-Slag-Carbide Slag-Flyash Based Binding Materials

Soda residue and carbide slag,which were solid wastes produced in the processes of soda production by ammonia-alkali method and acetylene production by hydrolysis of calcium carbide,have caused serious environment problem due to its stockpiling and discharge.Therefore,the quantitative and large-scale reuse of soda residue and carbide slag has become the focus of scholars at home and abroad.On the basis of the existing soda residue-slag binding material,a kind of quaternary binding material based on soda residue,slag,carbide slag and fly ash was developed in this paper.The 40 mm×40 mm×160 mm mortar specimens prepared based on the quaternary binding material were tested for mechanical and working properties.The chemical bond rate of chloride ion of mortar specimens with the optimal mixing ratio curing for 28 days was tested.Microstructure and composition of hardened paste of soda residue-slag-carbide slag-fly ash binding material curing for 28 days were analyzed by means of scanning electron microscope?SEM?,energy spectroscopy?EDS?and X-ray diffraction?XRD?.With the water-binder ratio was 0.5,sand-binder was 3:1,and soda residue,slag,carbide slag and fly ash were mixed according to the mass percentage of 1:3:0.5:0.5,the compressive strength of the specimen based on quaternary binding material was 34.1 MPa and the flexural strength was 5.0 MPa after curing for 7 days;the compressive strength of the specimen based on quaternary binding material was 51.8 MPa and the flexural strength was 6.4 MPa after curing for 28 days;and there was no downward trend in the strength of the specimens at the age of 90 days.The quaternary binding material have high compressive and flexural strength at all ages which could meet the strength requirements of P.O 42.5 portland cement.The fluidity of mortar paste reached 153 mm.The mass fraction of water-soluble chloride ion in the mortar specimen was 0.462%,and the chemical binding ratio of chloride ion was 80.38%.After curing for 28 days,the the slurry structure of the quaternary binding material was basically formed which was observed by means of scanning electron microscope.Meanwhile,the needle,irregular flaky-shaped crystals with overlapping and filling functions combined with amorphous gel hydration products constituted the strength source of the quaternary binding material mainly.The hydration products of binding material after curing for 28 days were mainly C-S-H gel,NaCl crystal?3CaO·Al₂O₃·CaCl₂·10H₂O crystal and 3CaO·Al₂O₃·3CaSO₄·30H₂O crystal which was observed by energy spectroscopy?EDS?and X-ray diffraction?XRD?.The Ca/Si ratio of C-S-H gel in hydration products varied from 0.83 to 1.40;the ratio of n C-S-H/n NaCl varied in the range of 3.43?32.71;the ratio of n C-S-H/n3CaO·Al₂O₃·CaCl₂·10H₂O varied in the range of 3.99?22.94;the ratio of n C-S-H/n3CaO·Al₂O₃·3CaSO₄·30H₂O varied in the range of 22.58?25.90.The application of quaternary binding material is not only conducive to the resource utilization of four types of industrial solid wastes:soda residue,slag,carbide slag and fly ash.Meanwhile,the development of new binding material system can reduce the pressure on the environment and land resources,and obtain higher economic and social benefits.