Research On The Preparation Of Active Admixture Employing Tungsten Tailings And Its Effects On The Performances Of Concretes

In recent years,the stocks of metal tailings have been on a high growth state in China,including the stock of tungsten tailings has more than 10 million t.Currently,the utilization efficiency of tailings is less than 10%.When the the preparation of gelled materials employing tailings,they have several shortcomings,such as active components of tailings which can not be fully stimulated,low early strength,and poor stability and so on.In this paper,the mechanical activation and mechanical-chemical activation methods are used to stimulate the activity of the tungsten tailings,the activated tailings are used to prepare gelled materials as active admixture,which can achieve the goals of increasing the strengths of all ages,improving the performance of cement and replacing cement partially.The conclusions are as follows:(1)Experiments of single grinding aids,composite organic grinding aids and organic and inorganic composite grinding aids are done.The grinding effect of H1 in grinding agent was best,the optimal dosage of H1 was 0.03%,the compressive strength after curing 28 d increased 16.0%,activity index reached 78.83%.When the mass ratio of H1 and C1 is 3:1,content is 0.03%,the grinding effect was best after organic grinding agent compound.The compressive strength of 3d test block increased 22.23%.The compressive strength of 28 d test block was 37.40 MPa,activity index reached 86.71%.The tests of organic-inorganic composite grinding show that when the mass ratio of H1 and C1 is 3:1(content is 0.03%)+G1(content is 0.3%),specific surface area increased to maximum 1159m2/kg,the compressive strength of 28 d test block increased 8.68 MPa,activity index reached 88.11%.(2)According to the result of orthogonal test and range analysis,the effect order of the four factors on the late compressive strength of the mortars: grinding time> content of H1> content of G1 > content of C1.The best condition of preparing cement mortar is as follows: grinding time is 30 min,dosage of H1 is 0.03%,dosage of C1 is 0.015%,dosage of G1 is 0.4%.The compressive strength of 28 d test block of verification test is 38.19 MPa,activity index reaches 88.55%.(3)Then the effects of different types of superplasticizer and different dosages of tungsten tailings on the mortars are analyzed.The results showed that: when grinding time is 30 min,dosage of H1 is 0.03%,dosage of C1 is 0.015%,dosage of G1 is 0.4% and dosage of J2 is1.2%,and dosage of tungsten tailings is 30%,3 days’,7 days’ and 28 days’ activity indexes of the mortars exceed 100%,surpassing the compressive strength of P.O42.5 cement in all ages.It is showed that the activated tailings can replace equivalent 30% P.O42.5 cement without affecting the strength of cement.(4)Test methods such as XRD,FTIR,SEM are used to analyze the grinding tailings and 3 days’ and 28 days’ mortars.The analysis of grinding tailings indicates that the level of quartz diffraction peaks of activated tailings decline significantly,which means that the crystallinity of quartz reduces gradually and trend of amorphous reinforces under the effect of mechanochemical process,silica and aluminum oxide in the tailings generate new aluminosilicate polymer.The analysis of mortars indicates that activated SiO2 in the mortars which is employed by activated tailings and Ca(OH)2 reacted with hydraulic calcium silicate hydrate,chemical bond of Si-O polymerizes to Si-O-Si bond gradually,the drgree of polymerization of silicon oxygen tetrahedron increases in the calcium silicate hydrate,its structure becomes more stably,the compressive strength of late hydration improves clearly.