大掺量矿渣水泥砂浆碳化过程研究

Research on Carbonation Progress of Mortar Containing High Amounts of BFS

矿物掺合料的引入会减少水泥砂浆内部碱性物质含量,同时其中的活性成分与氢氧化钙发生二次水化反应,进一步地减少了砂浆的碱性,从而降低了砂浆的抗碳化能力。本文通过热重-差示扫描量热试验研究了不同掺量粒化高炉矿渣引入对碳化产物和微观结构的影响。研究结果表明:喷洒酚酞指示剂显示为无色的碳化表层仍然存在少量的Ca(OH)2,这说明砂浆碳化存在部分碳化区;碳化反应物不仅包含Ca(OH)2,也包含水化硅酸钙凝胶(CSH gel),钙矾石(AFt),低硫型水化硫铝酸钙(AFm),硅酸二钙(C2S),硅酸三钙(C3S)等物质;此外,随着矿渣含量的提高,碳化速率增大,同时由于矿渣可以改善水泥浆体的孔结构,矿渣掺量在50%时,碳化速率最小。

Carbonation resistance could be reduced with the secondary hydration reaction between Ca （OH）2 and active ingredients of GBFS and the incorporation of mineral admixtures which could reduce the content of alkaline substances. In this paper, the effects of different content of BFS on carbonation products and microstructure were investigated with the TG-DSC test. The results show that a small amount of calcium hydroxide remains in the carbonation front where the mortar turns colorless, this can be accounted for existence of semi-carbonation zone. Carbonation reactants not only contain calcium hydroxide, but also some substances, such as CSH gel, AFt, AFro, C2S and C3S. In addition, the carbonation rate increases with the increases of GBFS amount. Meanwhile, the carbonation rate is the lowest while the GBFS content up to 50% due to a refinement of the pore structure of cement paste.