海水对高贝利特硫铝酸盐水泥水化过程和力学性能的影响

Effect of Seawater on Hydration Process and Mechanical Properties of High Belite Calcium Sulphoaluminate Cement

研究了海水拌和与海水养护条件下高贝利特硫铝酸盐水泥(HB-CSA)和普通硅酸盐水泥(OPC)胶砂的抗压强度和抗折强度,采用等温量热法、X射线衍射分析法和热重分析法表征了两种水泥的水化过程和水化产物,分析了海水对HB-CSA水化过程和力学性能的影响。结果表明:海水拌和未明显影响HB-CSA的早期水化过程,海水拌和与海水养护未改变其主要水化产物类型;海水拌和显著加快了OPC的早期水化,海水中的氯盐与OPC的水化产物反应,导致水化氯铝酸钙(Friedel盐)的生成。海水拌和与海水养护对HB-CSA的抗压强度影响较小,但降低了OPC的后期抗压强度。海水养护对HB-CSA和OPC抗折强度的提高较为明显,钙矾石(AFt)含量的增加是抗折强度提高的主要原因。HB-CSA的水化产物中未见Ca(OH)2和单硫型水化硫铝酸钙(AFm),避免了海水侵入后过量CaSO 4·2H 2O和AFt生成造成的混凝土膨胀开裂和强度下降的危害。

The compressive strength and flexural strength of high belite calcium sulphoaluminate cement(HB-CSA)and ordinary Portland cement(OPC)mortars with seawater mixing and seawater curing were measured.The hydration processes and hydration products of HB-CSA and OPC were characterized by isothermal calorimetry,X-ray diffraction and thermogravimetric analysis.The effect of seawater on hydration process and mechanical properties of HB-CSA was analyzed.The results show that seawater mixing doesn’t significantly affect the early hydration process of HB-CSA,and seawater mixing and seawater curing don’t change the types of main hydration products.Seawater mixing significantly accelerates the early hydration of OPC.Chlorine in seawater reacts with OPC hydration products,resulting in the formation of Friedel’s salt.Seawater mixing and seawater curing have little effect on the compressive strength of HB-CSA mortar,but reduce the compressive strength of OPC mortar in the later age.Seawater curing significantly improves the flexural strength of HB-CSA and OPC mortars,and the increase of AFt content is the main reason for the increase of flexural strength.Because Ca(OH)2 and AFm are not found in the hydration products of HB-CSA,the damage of concrete expansion cracking and strength decline caused by generation of excessive CaSO 4·2H 2O and AFt after seawater intrusion are avoided.