Study On Rheological Properties Of Geopolymer Mortar Modified By Nano-SiO₂ And PVA Fibers

In recent years,more and more attention has been paid to environmental issues.Ordinary portland cement has clearly failed to meet the requirements for environmental protection,so more and more researchers have focused on geopolymers with excellent properties.Geopolymer is a new type of calcium-free aluminum-silicone cementitious material mainly composed of inorganic Al O₄ and Si O₄ tetrahedrons with a three-dimensional framework structure.It has excellent performance in durability,high temperature resistance and early strength.And it has the advantages of easy access to raw materials,low energy consumption during production,and low environmental impact.In the preparation of geopolymer mortars,fibers,nanoparticles,and water reducing agents are usually added to improve the properties of mortars.However,there are few studies on the effects of these additives on the performance of geopolymer mortars,and there are many types of mortar work.Sex evaluation methods.In view of this,this article uses alkali activator?mixed with water glass and sodium hydroxide?,metakaolin,fly ash and quartz sand as raw materials to prepare mortar.By adding different amounts of geopolymer mortar PVA fiber,nano-Si O₂,and polycarboxylic acid water reducer,and the workability and compressive strength of geopolymer mortar were measured using various test methods.The amount of PVA fiber,nano-Si O₂,and polycarboxylic acid water reducer added to the ground was studied.The influence of polymer mortar working performance and mechanical properties.The main research contents and results are:?1?By consulting the relevant literature at home and abroad and conducting preliminary trials,the preparation method and material ratio of geopolymer mortar were studied,and the blending amount of PVA fiber,nano-Si O₂ and polycarboxylic acid water reducing agent was determined As well as the preparation method of geopolymer mortar,26 groups of formulation ratios were formulated.?2?By carrying out rheological test,the rheological parameters of geopolymer mortar with different dosages of PVA fiber,nano-Si O2 and polycarboxylic acid water reducing agent were tested,and the blending of different PVA fibers,nano-Si O2 and polycarboxylic acid water reducing agent was studied.The variation rule of the rheological parameters of geopolymer mortar when the amount is measured.The results show that all the geopolymer mortars in this experiment conform to the Bingham model and can be regarded as Bingham fluids.The yield stress?and plastic viscosity?can accurately describe the mortar's rheological behavior.With the increase of the PVA fiber content,the static yield stress,dynamic yield stress and plastic viscosity of the mortar increase;as the nano-Si O2 content increases,the static yield stress,dynamic yield stress and plastic viscosity of the mortar first decrease With the increase of the amount of polycarboxylic acid water-reducing agent,the static yield stress,dynamic yield stress and plastic viscosity of the mortar all showed a decreasing trend.?3?Through the slump expansion test,L-shaped flowmeter test and consistency meter test,the workability of geopolymer mortar with different PVA fiber,nano-Si O2and polycarboxylic acid water reducer dosage was tested,and different The change rule of the performance of geopolymer mortar when the dosage of PVA fiber,nano Si O2 and polycarboxylic acid water reducing agent is mixed,and the influence of the dosage of PVA fiber,nano Si O2 and polycarboxylic acid water reducing agent on the working performance of geopolymer mortar was explored Mechanism,analyzed the correlation between the results measured by different test methods,and evaluated the accuracy and applicability of the results measured by different test methods.The results show that with the increase of the PVA fiber content,the mortar workability decreases and the thixotropy increases;with the increase of the nano-Si O2 content,the mortar workability increases first and then decreases,and the thixotropy decreases first and then increases;With the increase of the amount of polycarboxylic acid water reducer,the workability of the mortar increases and the thixotropy decreases.When the amount of nano-Si O2 is 1.0%,the workability of the geopolymer mortar reaches the best.The strongest correlation with the static yield stress and dynamic yield stress is the slump spread.At the same time,the final flow distance L of the L-type flow meter can also better characterize the static yield stress of the geopolymer mortar,and has the strongest correlation with the plastic viscosity.?T for L-type flow meter flow.?4?The cubic compressive test was conducted to measure the compressive strength of geopolymer mortar with different amounts of PVA fiber,nano-Si O₂ and polycarboxylic acid water reducing agent,and the effect of changing PVA fiber,nano-Si O₂ and polycarboxylic acid The variation law of compressive strength of geopolymer mortar when the amount of water agent is added.The mechanism of the influence of the amount of PVA fiber,nano-Si O₂ and polycarboxylic acid water reducer on the compressive strength of geopolymer mortar is explored.The results show that with the increase of the amount of PVA fiber or nano-Si O₂,the cubic compressive strength of the mortar tends to increase first and then decrease;as the amount of polycarboxylic acid water reducing agent increases,the geopolymer mortar's The compressive strength of the cube has risen and decreased,but overall it has shown a slight decrease.