硫铝酸钙水泥制备及贝利特掺硼活化

Preparation of BeliteCalcium Sulfoaluminate Cement Clinker and Activation of Belite by Boron Dopants

摘要:

采用粘土、铝矾土、碳酸钙为主要原料制备以贝利特（C2S）、硫铝酸钙（C4A3S-）和铁铝酸钙为主导矿物的水泥熟料（BCSAF），分析熟料矿物组成对水泥净浆抗压强度发展的影响，并通过硼（B）掺杂对贝利特矿物进行活化，研究其对于熟料烧成工艺及水化性能的作用机理.采用X射线衍射、扫描电子显微镜和差热热重分析等测试方法表征熟料组成与结构.研究结果表明：C4A3S-有助于BCSAF水泥早期强度发展，而C2S主要影响BCSAF水泥的后期强度，铁铝酸钙有助于熟料烧成中的传质过程，但含量过高时，不利于获得具有较高水化活性的C2S.掺杂B可在常温下稳定α′C2S，活化贝利特矿物，提高BCSAF水泥熟料早期水化活性，同时降低烧成反应温度，促进反应进行，减少硅铝酸钙（C2AS）过渡相的生成，而显著提高水泥3 d抗压强度.

Abstract:

Belitecalcium sulfoaluminateferrite (BCSAF) cement clinker was prepared from clay, bauxite and calcium carbonate. The influence that the mineral composition has on the compressive strength of cement paste was then analyzed. Boron was doped as a stabilizer, and the effects that Boron has on clinker calcination and hydration were investigated. The structure and composition of the BCSAF clinker was analyzed based on Xray powder diffraction, scanning electron microscopy, and thermal analysis. The results demonstrate that the earlyage strength of the cement paste depends mostly on the hydration of calcium sulfoaluminate, and that belite hydration makes great contributions to the lateage strength development. Ferrite is beneficial to the mass transfer during calcination. However, when the ferrite content is too high, the activity of belite tends to decrease. The doping of Boron, on one hand, helps to stabilize the belite at the α’ polymorph, improving the hydration activity of BCSAF cement at early ages. On the other hand, it prompts the chemical reactions during the clinker calcination, and reduces the formation of the transient product, gehlenite. As a result, the compressive strength of the cement paste at 3 d age is improved due to the Boron doping.