Research And Application Of High-performance Alkali-free Liquid Accelerator For Tunnel

With the continuous development and construction of infrastructure such as high-speed railways and highways in the central and western regions of my country,jet concrete is widely used in the construction of tunnel projects.As the core exterior in the jet concrete,the liquid accelerator is increasingly demand.High-alkaline liquid accelerator is gradually eliminated due to its extremely corrosiveness and easily caused losses to the later strength of the cement.Therefore,the relevant r practitioners on the development and development of no（low）alkaline liquid accelerator,but it still faces many pain points such as high alkali content,high fluorine content,poor stability.Therefore,the research and development of a high-performance alkali-free liquid accelerator,the main research content is as follows:（1）First use a single component experiment and multi-component orthogonal experiment to prepare a high-performance alkali-free liquid accelerator mother solution,and then use the homemade active aluminum solution and inorganic tactile suspension to modify the high-performance alkali-free liquid accelerator mother solution.The best proportion of high-performance alkali-free liquid accelerator is high-performance alkali-free liquid accelerator mother solution:self-made active aluminum solution:inorganic tactile suspension=7:3:1.5%.（Among them,the proportion of the components in the high-performance alkali-free liquid accelerator mother solution is aluminum sulfate:oxalic acid:dihydrine:magnesium sulfate:silicon of gas phase:water=47:2.5:7:8:1.5:34）.The PH value of high-performance liquid-free fluid is 2.3,and the solid content is 52%.When the amount of high-performance alkali-free liquid accelerator condenser reaches 8%,the initial setting time of the cement slurry is2.4min,and the final setting time is 4.7min.Cement 6h compressive strength is 1.3MPa,1d compressive strength is 13.4MPa,28d compressive strength is 49.2MPa,and 28d compressive strength preservation rate is 106%.Can meet the performance requirements of cement setting time and compressive strength in the QCR 807-2020 specification.（2）It has studied the performance of high-performance alkali-free liquid accelerator under different experimental conditions.Among them,with the increase of the amount of accelerator,the shortening of the reference cement setting time and the development of the aging pressure strength have a favorable impact.Essence environmental temperature,water-ash ratio,and slow coagulation materials have a great impact on the promotion effect of high-performance alkali-free liquid accelerator.The development of the concrete compression strength in the later period is favorable.The powder and coal ash will extend the setting time of the cement slurry that is mixed with high-performance alkali-free liquid accelerator.Silicon ash will shorten the setting time of the cement slurry of the cement with high-performance alkali-free liquid accelerator.The adaptability of high-performance alkali-free liquid accelerator to three different ordinary silicate cement and stability at different environmental temperatures are better than homemade fluorine-containing alkali-free liquid accelerator.The stability is good.When the ambient temperature is 20°C,it can stably store 95d.（3）Study the impact of incorporating high-performance alkali-free liquid accelerator on concrete performance and durability.Adding high-performance alkali-free liquid accelerator alone can significantly improve the pressure of the concrete aging period,and its concrete 8h pressure resistance reaches 7.6MPa.The mixing of fluorine-containing alkali-free liquid accelerator alone has a significant inhibitory effect on the concrete 1d compressive strength.Adding high-performance alkali-free liquid accelerator will increase the ability to penetrate concrete and chlorine ions and carbonization capacity,but it will increase the risk of drying and shrinkage of concrete;The composite use of high-performance alkali-free liquid accelerator and early strong blending materia will further improve the mechanical properties of the ages of concrete.The anti-chlorine ion penetration ability and carbonization ability have increased,and the risk of inhibiting the drying and contraction of concrete.（4）The construction site is used for the construction site of high-performance alkali-free liquid accelerator,and its rebound rate can be effectively controlled in the actual application process.The rebound rate is low when the arch wall and the waist part of the arched waist are not sprayed under lower amount,Rebound rate is not more than 5%,Good adhesion after concrete spraying.The speed coagulation mixing can be improved when spraying the vault area to ensure a better jet effect.（5）Through XRD analysis and SEM micro-testing methods,the effects of high-performance alkali-free liquid accelerator on the hydration process and micro-structures of the alkaline liquid are analyzed,thereby revealing the mechanism of high-performance alkali-free liquid accelerator supercorpic agent.High-performance alkali-free liquid accelerator introduced a large amount of activity Al³⁺and SO₄^2-,which directly occurred with Ca²⁺in the cement,generated a large amount of calcium alum stones to shorten the cement setting time,increase the early cement strength,consume Ca²⁺to a certain extent to promote to a certain extent to promote to some extent to promote the promotion the hydration process of C₃A and C₃S,acupuncture-like calcium alum stones and C-S-H gels are overlapped,making the cement structure more dense,and it is conducive to the development of cement later strength.