The Study Of Preparation And Properities Of Waste-based Geopolymer Materials

Geopolymer material is a kind of inorganic Si and Al cementing material, which containmuch non-amorphous and semi-amorphous similar-zeolites. The raw materials of geopolymermaterials are rich, which contain steel slag, fly ash, pulverized blast furnace slag, coal gangueand other industrial waste slags. Geopolymer materials are prepared and cured at roomtemperature. It provides an effective way to make these waste resource utilization, on theother hand, the preparation process is simple, low energy consumption and less pollution,which meet our country’s green sustainable development strategy. Using industrial wasteslags and adopting compression moulding to prepare geopolymer building blocks will hope tosubstitute for traditional clay bricks, which is energy-saving, land-saving and environmentalprotection. The emerging industries have good economic benefits, environmental benefits andsocial benefits.The raw materials of this paper are industrial slags such as steel slag, fly ash, pulverizedblast furnace slag and sand. Alkali-activator and compression moulding were adopted toprepare geopolymer materials. Through the properties’ comparison, the optimal preparationsystem was selected, that is steel slag-fly ash-pulverized blast furnace slag-sand system. Thenthe technological parameters of preparing geopolymer materials were optimized, using theoptimized technological parameters to prepare geopolymer samples to carry on the acid, alkali,sulfate erosion and freeze-thaw test. SEM and XRD were carried out to analyse the materials’microstructure and mineral composition. The main study results and conclusions are asfollows:The geopolymer materials of steel slag-fly ash system, steel slag-fly ash-pulverized blastfurnace slag system and steel slag-fly ash-pulverized blast furnace slag-sand system wereprepared respectively. Strength, volume density and water absorption are the examiningindexes to sort out the optimal preparation system of steel slag-fly ash-pulverized blastfurnace slag-sand system. The optimal raw materials ratio of steel slag-fly ash-pulverizedblast furnace slag-sand system is30%steel slag,30%pulverized blast furnace slag,10%flyash and30%sand. The28days compressive strength is78.8MPa, and its water absorptionrate is8.30%. The gel components of geopolymer materials’ hydration products are the co-existence of C-S-H gel and N-A-S-H gel, the hydration products of crystal are similar-zeolite, and its chemical formula may be (Mg,Ca)n(Si-O-Al-O-Si).The experiment results show that the best water addition is10%to prepare geopolymermaterial. In addition, the curing system, molding pressure, the types and dosage of activatorand so on also affect the properties of geopolymer materials to a large extent. The optimalcuring system is curing in the air and sprinkler maintenance, and the curing age is28days.The best molding pressure is30MPa, increasing the molding pressure will not improve theproperties of geopolymer materials and do great harm to the mold. The most appropriateactivator is sodium hydroxide, with the addition of sodium hydroxide increasing, the strengthof geopolymer materials presents the increasing trend. When the addition of sodiumhydroxide exceeds5%, the sample surface whiskering is serious, which will affect theproperties and appearance of the geopolymer materials. The later strength obtains someimprovement after the addition of polypropylene fiber, but the compressive strength and bulkdensity willn’t obtain obvious improvement and the water absorption decrease. The propertiesof geopolymer materials have no obvious improvement after the addition of rice hull.Using the optimal technological parameters to prepare a batch of geopolymer specimens,when the samples were cured28days, the experiments of acid corrosion, alkali corrosion andsulfate attack, freezing and thawing experiment, high temperature resistance andcarbonization test were carried out according to GB/T2542-2012Test methods for wallbricks. The results show that the4days’ water absorption is only1.44%, and the softeningcoefficient is0.89, which meet the standards of JC/T422-2007Non-fired rubbish ganguebrick. When the samples were immersed in different-concentration acid solution and sulphatesolution for60days, with the prolongation of immersing age, despite the samples have somequality loss and strength loss, the appearance of the geopolymer samples basically keep intact.When the samples were immersed in different-concentration alkali solution for60days, withthe prolongation of immersing age, the strength of geopolymer material appeare the trend ofgrowth, which suggests that geopolymer materials have excellent alkali resistance. Thegeopolymer materials can withstand30freeze-thaw cycles. When the samples were calcinedfor2hours at1000oC, the compressive strength of geopolymer materials is1.38MPa, and thecompressive strength of geopolymer materials is26.2MPa, Which suggests that geopolymer materials have perfect frost resistance and good high temperature resistance. With theextension of carbonization time, the samples presents firstly increases then decreases, but onthe whole, the weight gain rate is small. The experiment results show that geopolymermaterials have excellent durability performance.