Composition Design And Performance Optimization Of Fly Ash Lightweight Aggregate And Its Concrete

The demand for sand and gravel aggregates is rising as our country’s infrastructure growth accelerates.However,due to the national environmental protection policy restricting the mining of sand and gravel aggregates,the supply and demand of sand and gravel aggregates are unbalanced.At the same time,the annual output of fly ash in my country is extremely large,but the utilization rate of fly ash is low,and its potential activity is not well utilized.Therefore,it is of great significance to use fly ash lightweight aggregate to replace sand and gravel aggregate.Most of the current fly ash lightweight aggregates are produced by sintering process.Although they have high strength,they consume a lot of energy and pollute the environment.However,the nonburning fly ash lightweight aggregate process is immature,and generally has low mechanical strength and water absorption.Problems such as high rate.Therefore,the preparation of a high-performance and high-strength fly ash lightweight aggregate is of great significance for the application of lightweight aggregates in engineering.This article intends to prepare a high-performance and high-strength fly ash lightweight aggregate by studying the properties of fly ash lightweight aggregates with different excitation sequences and optimizing the preparation process of fly ash lightweight aggregates.The following aspects have been explored sexual and innovative work:(1)Study on the performance of fly ash lightweight aggregate mixed with activatorBy changing the sodium silicate modulus,content and slag content,the cylinder compressive strength,1h water absorption and bulk density of fly ash lightweight aggregates under different influencing factors were measured,and the effects of these three factors on the performance of lightweight aggregates were analyzed.The results show that the effect of sodium silicate modulus on the compressive strength of fly ash lightweight aggregate is related to the content of sodium silicate.When the content of sodium silicate is low,the compressive strength decreases with the increase of sodium silicate modulus;When the content of sodium silicate is high,the compressive strength first increases and then decreases with the increase of sodium silicate modulus;The compressive strength of fly ash lightweight aggregate first increases and then decreases with the increase of sodium silicate content.Slag content has great influence on the compressive strength of fly ash lightweight aggregate,and the compressive strength increases with the increase of slag content.(2)Study on the pore structure of fly ash lightweight aggregate mixed with activatorThe pore structure of fly ash lightweight aggregate was studied by mercury intrusion method,and the micro morphology of fly ash lightweight aggregate was observed by SEM.The results show that when the content of sodium silicate is low,the decrease of sodium silicate modulus can effectively reduce the porosity of fly ash lightweight aggregate and refine the pore structure of fly ash lightweight aggregate;When the content of sodium silicate is high,the porosity of fly ash lightweight aggregate first decreases and then increases with modulus;The increase of slag content can reduce the porosity of fly ash lightweight aggregate and refine the pore structure.(3)Study on the performance of externally excited fly ash lightweight aggregateBy changing the type and concentration of curing fluid,the cylinder compressive strength of fly ash lightweight aggregate is measured,and the influence of these factors on the cylinder compressive strength of fly ash lightweight aggregate is analyzed.The hydration products of fly ash lightweight aggregate were detected by XRD and FT-IR,and the influence of curing solution concentration on the hydration products of fly ash lightweight aggregate was analyzed.The results show that the cement content has great influence on the compressive strength of fly ash lightweight aggregate.Sodium hydroxide curing solution has the most obvious effect on improving the strength of fly ash lightweight aggregate,and the strength of lightweight aggregate first increases and then decreases with the increase of concentration.When the concentration is 30%,the compressive strength of fly ash lightweight aggregate reaches the maximum.(4)Study on the mechanical properties of fly ash lightweight aggregate concreteBy changing the type of aggregate,water cement ratio and mineral admixtures,the compressive strength of lightweight aggregate concrete is measured,and the influence of these three factors on the mechanical properties of lightweight aggregate concrete is analyzed.The results show that the lightweight aggregate with high compressive strength and low water absorption has less improvement on the mechanical properties of concrete than the lightweight aggregate with low compressive strength and high water absorption.The strength of lightweight aggregate concrete increases first and then decreases with the increase of water cement ratio.When the water cement ratio is 0.35,the compressive strength of lightweight aggregate concrete reaches the maximum.Adding mineral admixtures can improve the strength of lightweight aggregate concrete,silica fume is the best,slag is the second,fly ash has no obvious effect on the strength,and too much fly ash will reduce the strength of concrete.(5)Study on the transition zone of fly ash light aggregate interfaceThe influence of aggregate types,water cement ratio and mineral admixture(fly ash,slag and silica fume)on the performance of concrete interface transition zone is studied from the micro point of view.The results show that the higher the water absorption of lightweight aggregate,the better the strength of interfacial transition zone.The strength of the interface transition zone is greatly affected by the water cement ratio,and the microhardness decreases with the increase of water cement ratio.The microhardness of the interface transition zone increases with the increase of the mineral admixture content.The effect of silica fume is the best,slag is the second,and the fly ash is the worst.Moreover,the microhardness of the interface transition zone will decrease when the excessive fly ash is added.The paper has 50 pictures,29 tables,and 83 references.