加速碳化条件下海砂SAC混凝土性能劣化机理研究

Study on the Degradation Mechanism of Sea Sand SAC Concrete under Accelerated Carbonation

摘要: 本文研究了海砂硫铝酸盐水泥(SAC)混凝土加速碳化后碳化深度、抗压强度及Cl⁻固化率的变化规律，并与海砂普通硅酸盐水泥(OPC)混凝土对比，采用SEM和XRD实验进行微观性能测试，研究其加速碳化后性能变化的机理。研究表明，海砂SAC混凝土的碳化深度与海砂OPC混凝土的相比，加速碳化早期(14 d前)偏低后期偏高，海砂SAC混凝土的抗压强度和Cl⁻固化率均随加速碳化龄期的增加而降低。加速碳化28 d时的微观性能测试表明，海砂SAC混凝土完全碳化区主要水化产物AFt和Friedel’s盐与CO₂反应生成CaCO₃并释放出Cl⁻，导致其抗压强度和Cl⁻固化率降低。掺入偏高岭土能减小海砂SAC混凝土因碳化导致的抗压强度和Cl−固化率降低的幅度。

Abstract: This paper studies the concrete carbonation depth, compressive strength and Cl⁻ curing rate change rule of sea sand sulphur aluminate cement (SAC) compared with sea sand Portland cement (OPC) concrete after accelerating carbonation. It also studies the mechanism of the accelerated carbonization by SEM and XRD experiments. The results show that compared with sea sand OPC concrete the carbonation depth of SAC concrete early accelerated carbonization depth (before 14 day) is lower and later is higher, the compressive strength and Cl⁻ curing rate decrease with the increase of accelerated carbonization age. The microscopic performance test of accelerated carbonation at 28 day shows that the main hydration products in the carbonization zone of SAC concrete AFt and Friedel’s salts can react with CO₂ to produce CaCO₃ and release Cl⁻, as a result, its compressive strength and Cl⁻ curing rate decreased. In carbonized environment, addition of metakaolin can reduce compressive strength and Cl⁻ curing rate of SAC concrete.