Enhancement Of Chemical Reactions During CO₂Curing Of Concrete

The development of industrialization in modern society continuously promotessociety and economics moving forward; simultaneously the higher level ofSocio-economic improves higher development of industrialization. With the boomingprogress on urban construction transportation, living environment facilities wereincreasingly built, at a huge cost of environment, which means gradually increasedenvironmental pollution and global warming. Therefore, it’s been paid more and moreattention on the sustainable development of human society and the environment.During the large-scale civil constructions, the traditional materials and process is nolonger proper for sustainable development. It demands green environmental materials,which has to be more environmentally friendly, energy saving, high efficient and highdurability.CO₂is one of the main greenhouse gases. The CO₂emission of the cementmanufacturing industry accounts for about5%of the total CO₂emissions sourcedfrom human activities. The CO₂-curing concrete, as a very promising technology, notonly can fixed store CO₂through mineral absorption to achieve real environmentallyfriendly, energy saving, high efficient and high durability; but also can improve theconcrete performance after CO₂curing, shorten the curing time, saving energy. Itcan be viewed as a direction of green concrete material research and development.This paper’s achievements mainly focus on as follows:1. by researching the effect of remaining w/c ratio, an important factor, on CO₂curing results of the dry and hard concrete, the optimist remaining w/c ratio is around0.16⁰.20to gain the best CO₂results for concrete with0.35w/c ratio; from thetemperature curve, its peak temperature proceeds others when the remaining w/c isabout0.16⁰.20, which is very proper for the carbonation reactions.2. the repeated experiments results of CO₂curing of the dry and hard concretemixed with calcium carbonate powder, demonstrate its feasibility and repeatability ofCO₂curing degree and compressive strength;3. As CO₂curing of the dry and hard concrete mixed with calcium carbonatepowder, the effect of fineness and content of calcium carbonate powder on CO₂curingdegree and compressive strength was investigated. The temperature changes duringCO₂curing was recorded which reflects the reaction of kinetics intuitively; at thesame time, differences of CaCO₃content in paste specimens between before and after CO₂curing was researched though Differential Thermal Analysis method. The resultsshow that it gains better CO₂curing results when it’s with800mesh fineness and5%CaCO₃content.4. researches on the effect of remaining w/c ratio on CO₂curing degree andcompressive strength after CO₂curing of the foaming mortar and pastes; and theCaCO₃content of foaming pastes before and after CO₂curing through DifferentialThermal Analysis method shows that the CO₂curing degree increases andcompressive strength decreases with the foaming agent content. The mainly reason forthis phenomenon is that CO₂is more likely to penetrate into the internal specimenwith the higher porosity dues to the high foaming agent content.5. the effect of remaining w/c ratio on CO₂curing degree and compressivestrength after CO₂curing of the air entraining light aggregate concrete indicatesthere’s a Linear relationship between remaining w/c ratio and compressive strength,which can be described as y=-31.8x-10.89, Correlation coefficient R²=0.982. Itsintercept in the vertical axis can be explained as the theoretical maximumcompressive strength under the same water-cement ratio. Its Slope describes reducingdifficulty of compressive strength after CO₂curing with increases of the remainingwater-cement ratio.6. it’s found that lower RH in curing chamber gains better CO₂curing resultsthrough the research of CO₂degree,compressive strength and temperature monitoringduring CO₂curing by two controlling methods of Relative Humidity in sealed curingchamber.