硅酸盐水泥基CO_(2)泡沫混凝土的制备及机理

Preparation and mechanism of Portland cement⁃based CO_(2) foam concrete

煤电一体化基地运行产生大量CO_(2)引起的环境问题引起了极大的关注。利用坑口电厂CO_(2)制备泡沫混凝土材料不仅可应用于矿井充填,而且可实现坑口电厂CO_(2)的原位处理。为此,研发了一种兼具高强与固碳特性的CO_(2)泡沫混凝土材料,并探索了硅酸盐水泥基CO_(2)泡沫混凝土(CFC)的制备机理。通过碳酸化预处理水泥和物理发泡方式制备了硅酸盐水泥基CO_(2)泡沫混凝土,采用扫描电子显微镜(SEM)和傅里叶变换红外光谱仪(FTIR)、万能试验机、热重分析方法(TG)分别进行微观表征、力学性能测试、固碳能力测试,对CO_(2)对CFC干密度、孔隙率、抗压强度及固碳性能的影响规律及作用机理进行研究,分析了硅酸盐水泥中CO_(2)泡沫消泡机制,讨论了CO_(2)发泡硅酸盐水泥基混凝土机理。试验结果表明:得益于CO_(2)养护作用,CFC抗压强度明显提高;碳酸化预处理后CFC的7 d抗压强度提高44.6%,28 d抗压强度提高27.7%;碳酸化预处理可明显改善CFC泡孔结构,提高CFC的发泡效果,碳酸化预处理后CFC的孔隙率增大7.38%;CFC骨架的固碳率为5.70%~8.08%,具有明显的固碳潜力,但CFC制备工艺及参数仍需进一步改善以满足矿用需求。研究发现:硅酸钙矿物相与CO_(2)的矿化反应是CO_(2)泡沫消泡的主要原因,通过碳酸化预处理硅酸盐水泥浆体降低体系中硅酸钙矿物相及其水化产物含量、提高碳酸钙含量是制备CFC的关键。

The environmental problems caused by the large amount of CO_(2) generated in the operation of coal⁃electricity integration base have attracted a great concern.The foam concrete material prepared from the CO_(2) generated in the pit⁃head power plant can be used for mine filling,and can realize the in⁃situ treatment of the CO_(2) of the pithead power plant.Therefore,a CO_(2) foam concrete material with high strength and carbon fixation characteristics was developed,and the preparation mechanism of CO_(2) foam concrete(CFC)based on Portland cement was explored.The CO_(2) foam concrete based on Portland cement was prepared by carbonation pretreatment cement and physical foaming.Scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)were used for mi⁃croscopic characterization.Universal testing machine was used to test mechanical properties.Thermogravimetric analy⁃sis(TG)was used to measure the carbon fixation capacity.The effect of CO_(2) on the dry density,porosity,compressive strength and carbon retention of CFC was studied.The defoaming mechanism of CO_(2) foam in Portland cement was ana⁃lyzed,and the mechanism of CO_(2) foaming Portland cement based concrete was discussed.The experimental results show that the compressive strength of CFC was significantly improved due to CO_(2) curing.After carbonation pretreat⁃ment,the 7 d compressive strength of CFC increased by 44.6%,and the 28 d compressive strength increased by 27.7%.Carbonation pretreatment could significantly improve the cellular structure and foaming effect of CFC,and the porosity of CFC increased by 7.38%after carbonation pretreatment.The carbon fixation rate of CFC skeleton was 5.70%-8.08%,which has obvious carbon fixation potential.However,the preparation process and parameters of CFC still need to be further improved to meet the needs of mining.It was found that the mineralization reaction of calcium silicate mineral phase and CO_(2) is the main reason for the defoaming of CO_(2) foam.The key to the preparation of CFC is to reduce the content of calcium silicate mineral phase and its hydration products in the system by carbonation pre⁃treatment of Portland cement slurry,and increase the content of calcium carbonate.