Study on properties and degradation mechanism of calcium sulphoaluminate cement-ordinary Portland cement binary repair material under seawater erosion

For seeking repair materials suitable for Marine engineering, it is of great significance to study the seawater erosion resistance of calcium sulphoaluminate cement-ordinary Portland cement (CSA-OPC) blended system in tidal environment. In this study, the effects of OPC content on the compressive strength, mass loss, chloride ions of CSA-OPC blended system under the action of dry-wet cycle and artificial seawater erosion were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the erosion products and the morphology to reveal the degradation mechanism. The results showed that the compressive strength of CSA-OPC blended system was effectively improved by the addition of OPC at the artificial seawater environment. With the increasing OPC content, the compressive strength and combination rate of chloride ions increased first and then decreased. When the OPC content was 30 %, they reached the maximum. Additionally, the addition of OPC significantly increased the AFt content and led to a more dense matrix to prevent the erosion of ions. Moreover, the combination rate of chloride ions was enhanced by producing more Friedel's salts when OPC added. The above research results showed that CSA-OPC was a suitable repair material for Marine engineering under the appropriate OPC content.