The Study Of Alkali-activated OSR-Slag Composite Cementitious Material And Its Methods Of Quality Control

Oil shale is a kind of important energy mineral resource,for now mainly used for retorting and burned for power generation,partially relieving the pressure caused by the shortage of oil and coal resources.However,along with the utilization of oil shale in large scale,the huge solid waste of oil shale residue also brought severe pollution.The toxic agent contained in the waste would heavily contaminate the water source,land and endanger the living things around.So far,we are still in lack of a good treatment of these solid wastes,and there is an actual need to investigate a new effective way giving consideration of both environmental protection and reutilization.Thinking of the high content of sodium oxide and potassium oxide in the OSR,we prepared a new kind of alkali-activated OSR-Slag compound cementing material;We analyzed the early hydration properties of the alkali-activated OSR-Slag and concluded the evolution law of the hydration product structure at early paste stage.Then,we further investigated the performance and durability of the mortar and concrete.At present,broad sources of the row materials is the major obstacle to make good quality control,strength decreasing and Crystalline Bloom were commonly seen during the production of alkali-activated cementing materials.Here we proposed an R/Al quality control method for alkali-activated products,by adjusting the amount of the network former and network regulater;we could effectively improve the strength and durability of the products.This study may hopefully resolve the technical problem of the OSR reutilization,and offer theoretical support for the quality control of alkali-activated cementing products.Our researches are as follows:1.We looked into the early hydration properties of the alkali-activated OSR-Slag compound cementing material,and the result showed that the content of activator would considerably affect the setting time of paste stage,when the content of activator was of 7.5wt%,sharply reduced setting time can be observed in the process.On the other side,the variation in content of OSR and modulus of silicate sodium had little influence on the setting time.By analyzing the hydration heat process,the hydration of the alkali-activated OSR can be divided in four periods:fast reaction period,induction period,acceleration period and stable period.2.By test of XRD,FTIR,DSC,TEM and EDS,we learned that the hydration products of OSR-Slag paste were mainly composed by hydrate of sodium alumino silicate(Na₄Al₂Si₆O₁₇.2H₂O),amorphous gel?Na₂O-Al₂O₃-SiO₂-H₂O?and C-S-H gel.Giving the condition of same content of activator,three-dimensional network of gel were gradually formed at the first 5h inside the paste,with time growing,agglomeration would continually happen,filling the void and making the paste structure more compact.The variation of chemical component in raw material would also make a difference to the hydration process,when the OSR content was of60wt%,the paste showed highest hydration degree at same stage,meanwhile offered largest number of hydration products and denser structure.3.The mechanical property of the OSR-Slag mortar was mainly decided by the content of activator and the chemical components of raw materials.Under the condition of mortar with same mixture ratio,the more the content of activator,the better the strength of the harden mortar can be slightly observed.Base on the analysis of the requirement for engineering use,the optimal proportion of alkali-activated OSR-Slag mortar are as follows:activator of 5wt%and OSR of 30wt%.4.In this paper,we paid attention to the difference in chemical components and mixture ratio of alkali-activated cementing materials,which caused variation on the early strength and long-term strength of the mortar during our test.We also discussed the function rule of how raw materials components affect the depolymerization degree,repolymerization speed and the structure stability of the products during process.Thereafter we put forward R/Al control methods and regulating standards for alkali-activated cementing materials with different composition.?1?With content variation of Ca,Mg,Si and Al in the raw materials,there were different R/Al control methods fitting for different application needs.When?Ca+Mg?/?Si-Al?<0.8,we should ensure that?Na+K?/Al?1.When?Ca+Mg?/?Si-Al??0.8,we should ensure that?Ca+Mg?/?Si-Na-K??1.5.As the calculation result approach to the theoretical value,the soluble alkali content appeared fewer amounts in hydration products,and the Si-Al chains showed higher polymerization degree and growth in number.On the contrary,as the calculation result away from the theoretical value,the structure stability appeared worse and showed strength decreasing in long-term.?2?The R/Al result of microscopic hydration products would also influence the stability of entire products.By test of EDS,when R/Al result of microscopic hydration products and the interface zone in compound mortar was out of the given range,soluble alkali can be observed inside the structure,which would cause erosion as age growing,and weaken the bonding strength between mortar and aggregate,leading to the strength decreasing in long-term.Thus,the regional hydration products should also meet the requirement of R/Al control method.5.The optimal proportion of alkali-activated OSR-Slag concrete is as follows:activator of 5wt%,raw materials composition of 450kg/m³?30%OSR+70%slag?,sand of 642 kg/m³,water-solid ratio of 0.45,and the concrete compressive strength of88Mpa at 28d.By test of anti-carbonization and anti-chemical attacking,the OSR-Slag concrete showed excellent durability.