Research On Acid Rain Corrosion Structure Repair Material

The chemical reaction between acid rain and mortar,concrete and brick will cause holes and cracks in the building materials and on the surface,which will reduce the quality and strength of the building and eventually lead to the destruction of the building.Acid rain pollution will not only cause extreme waste of energy and resources,but also cause huge economic losses.Based on the national key research and development plan project "Research on the Destruction Characteristics and Recovery Technology of Materials for Key Bearing Structures of Rail Transit in Complex Environments",the research on polypropylene fiber cement-based materials in acid rain environment as a repair material is mainly carried out as follows:(1)Comprehensively refer to the preparation technology of high-performance concrete and reactive powder concrete,select excellent raw materials,add silica fume,microbeads,slag,polypropylene fiber and high-performance water-reducing agent,etc.,and use orthogonal design experimental methods to study the acid rain The influence of various factors on the cement-based materials in the environment was analyzed and sorted.In the orthogonal test,the factors affecting the acid rain corrosion resistance of the cement-based materials were ranked as follows: water-binder ratio> fly ash content> slag,The composite ratio of microbeads and silica fume is> sand-rubber ratio,of which water-binder ratio is a significant influencing factor,and the others are not obvious.In the orthogonal two experiments,the influencing factors affecting the acid rain corrosion resistance of cement-based materials are ranked as follows: water-binder ratio >Composite ratio of slag,microbeads,silica fume>Sand-rubber ratio>Compound ratio of machine-made sand and quartz sand,the change of various factors has little effect on the acid rain resistance of the material.(2)The increase of the water-binder ratio increases the compressive strength loss rate of the test piece;the increase in the amount of fly ash is not good for acid rain resistance.The increase in the amount makes the compressive strength loss rate of the test piece increase;machine-made sand can be used instead of quartz Sand;the ratio of sand to glue in the preparation of fiber cement-based repair materials should not be too large;the composite ratio of slag,microbeads and silica fume within a certain range has little effect on the mechanical properties of cement-based materials.(3)The loss rate of compressive strength of ordinary concrete is 1.31-1.95 times that of the cement-based materials in the orthogonal one,and the loss rate of common concrete is1.48-2.40 times the cement-based material of the orthogonal two.The mass loss rate,strength loss rate,and neutralization depth of fiber cement-based materials under acid rain,dry and wet cycling are all less than that of ordinary concrete,indicating that the mix ratio of orthogonal one and orthogonal two has improved the mechanics of the material to a certain extent Performance,improve the density and impermeability of the material.(4)Carry out research and comparison of the quality,strength and neutralization depth of fiber cement-based materials under the combined action of simulated acid rain-load and dry-wet cycle.It reveals the effect of water-binder ratio,stress value and fiber content on the neutralization depth of cement-based materials under the action of acid rain-load.The smaller the water-to-binder ratio,the lower the compressive strength loss rate and neutralization depth of the test piece;there is a reasonable range of polypropylene fiber content.Under the action of no stress,30% ultimate stress and 50% ultimate stress,the loss rate of compressive strength of ordinary concrete is basically about twice that of cement-based materials.Further verification of the mix ratio of fiber-cement-based materials,to a certain extent,improves the material’s compactness and acid rain-load coupling corrosion resistance.(5)Under the action of acid rain-load and dry-wet cycle,the pore size distribution of cement-based materials shows a trend of increasing the proportion of macro pores and decreasing the proportion of micro pores.From a microscopic point of view,the cement-based composite material has a tight interface without obvious cracks or defects,and the fiber and the matrix are tightly connected.After acid rain-loading,C40 ordinary concrete generates a large amount of corrosion products such as ettringite in the internal bubbles,while the corrosion products such as ettringite in the bubbles of the cement-based fiber composite material are few or even non-existent.(6)Select three representative mix ratios to carry out the interface bonding test on the concrete specimens eroded by acid rain.Through the split-tensile test,the effects of grinding depth,interface roughness,and repair materials with different ratios on the interface bonding properties were studied.There are optimal values ??for interface roughness and grinding depth.As the water-to-binder ratio increases,the cleavage strength of cement-based materials gradually decreases,and before repairing corroded materials,the surface uses wire brushes to remove loose particles.The bonding effect can be ensured;the polypropylene fiber cement-based material and the ordinary concrete damaged by acid rain have strong bonding strength,which reflects the good repair performance of the fiber cement-based material.