MgO和CaO对碱矿渣混凝土抗碳化性能的影响

与普通硅酸盐水泥(OPC)混凝土相比,碱矿渣混凝土(AASC)的抗碳化性能较差.为了提高AASC的抗碳化性能,本文采用MgO和CaO代替部分矿渣制备AASC,研究了加速碳化环境下掺MgO和CaO的AASC在不同碳化龄期的抗压强度和碳化深度,并结合X射线衍射(XRD)、同步热分析(TG-DTG)和扫描电镜-能谱(SEM-...

Effects of MgO and CaO on the Carbonization Resistance of Alkali-Activated Slag Concrete

Compared with ordinary Portland cement (OPC) concrete, alkali-activated slag concrete (AASC) has poor carbonization resistance. In this paper, part of slag was replaced by MgO and CaO to prepare AASC to improve its carbonization resistance. The compressive strength and carbonization depth of AASC seeded with MgO and CaO under accelerated carbonization environment at different carbonization ages were studied. The modification mechanism of MgO and CaO on the carbonization resistance of AASC was analyzed by X-ray diffraction (XRD), simultaneous thermal analysis (TG-DTG) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). The results show that MgO and CaO promotes the formation of Mg-Al hydrotalcite and Ca-Al layered structure in AASC, respectively. These two hydration products absorb and consume CO₂ during the carbonization process, then alleviate the decomposition of C-S-H caused by carbonization. In addition, after accelerated carbonization, calcium magnesium carbonate and magnesium carbonate are formed in the AASC blended with MgO, and the amount of calcium carbonate in the AASC blended with CaO increase significantly. These carbonized products effectively fill the pores and hinder the further diffusion of CO₂ into the interior of AASC. Therefore, under the carbonization environment, the AASC blended with MgO and CaO has a higher compressive strength retention rate, a lower carbonization depth, and a better carbonization resistance than pure AASC.