Introduction The existing alkali-activated repair materials cannot adapt to the corrosion repair of concrete in marine engineering with high humidity and high salt environments. In this paper, a polyacrylic acid lotion (PAA) modified alkali-activated slag repair material with high strength, low shrinkage and high durability was developed by adding PAA to regulate the flexibility of the consolidation body, and its performance formation mechanism was analyzed. The results indicate that the mechanical properties of alkali-activated slag repair materials are positively correlated with the content of sodium silicate added when the modulus of sodium silicate is greater than 1.2. The optimal activating ratio for slag repair materials is 1.2 modulus and 15% content of sodium silicate. PAA filling in the gaps of amorphous cementitious substances in alkali-activated slag repair materials significantly enhances its mechanical properties, bonding properties, volume stability, and sulphate resistance.Methods A powder used was cement (i.e., P·II 52.5 grade Portland cement) mixed with slag (i.e., a granulated blast furnace slag) with a hydraulic coefficient of 2.18, an activity coefficient of 0.25, an alkalinity coefficient of 1.11, and a quality coefficient of 2.07. Alkali activator used was sodium silicate (with a modulus of n=3.3 and a Baume degree of 40) and sodium hydroxide(granular sodium hydroxide with a purity of ≥98%). The organic lotion was a polyacrylic lotion with a molecular weight of 3 000-5 000 and a solid content of ≥30%. The aggregate was river sand with the maximum particle size of of 2.5 mm, the bulk density of 1.6 g/cm3, and the apparent density of 2.5 g/cm3. Water used was tap water.Sodium hydroxide weighed was fully dissolved in sodium silicate under stirring magnetically. The solution was colourless and transparent, and there were no suspended sodium hydroxide particles in the solution. Subsequently, a beaker with the solution was covered with a thin film to prevent the evaporation of water due to the dissolution and heat release of sodium hydroxide. The solution was cooled to room temperature before use. The prepared solution was poured into a mixing pot, and mixed with the powder under stirring. After curing until the specified age, the relevant tests were conducted.The physical and mechanical properties of alkali activated slag repair materials were determined in accordance with the provisions of GB/T50081—2019 “Standard Test Methods for Physical and Mechanical Properties of Concrete”. The bond strength was measured via bond bending tests. According to GB/T 50082—2009 “Standard Test Methods for Long term Performance and Durability of Ordinary Concrete”, the shrinkage rate of alkali activated slag repair materials was measured by a contact method. According to GB/T 50082—2009 “Standard Test Methods for Long term Performance and Durability of Ordinary Concrete”, the sulphate attack resistance of the alkali activated slag repair material was determined, and the corrosion resistance coefficient (K) was used as an indicator to measure the sulphate attack resistance of the sample. The phase composition of alkali activated slag repair materials was analyzed by a model D8ADVANCE X-ray diffractometer. The main functional group composition and chemical bond types in alkali activated slag repair materials were characterized by a model TENSOR27 Fourier infrared spectrometer. The microstructure of alkali activated slag repair materials was characterized by a model ZEISS Gemini 500 scanning electron microscope.Results and discussion Increasing the modulus of sodium silicate can improve the strength of alkali activated slag repair slurry. Adding 15% sodium silicate with a modulus of 1.2 is an optimal excitation approach for slag repair materials. When the content of PAA is 1%, the flexural strength and compressive strength of PAA modified alkali activated slag repair slurry are increased by 7% and 14%, respectively, compared to alkali activated slag repair slurry, reaching 9.90 MPa and 57.87 MPa. High-temperature curing at 50 ℃ further improves the strength of alkali activated slag repair mortar, and the strength improvement of PAA modified alkali activated slag repair mortar is greater than that of unmodified mortar. After PAA modification, the bonding strength of alkali activated slag repair mortar is improved, and its resistance to sulphate attack is enhanced. The bonding strength of PAA modified alkali activated slag repair mortar is greater than 2 MPa, and the corrosion resistance coefficient is greater than 0.85, meeting the requirements of JC/T 2381—2016 for the bonding strength and corrosion resistance coefficient of repair mortar. The shrinkage rate of alkali activated slag repair mortar at all ages increases with the increase of sodium silicate modulus. The PAA modification further reduces the shrinkage rate of alkali activated slag repair mortar. When the PAA content is 1%, the shrinkage rate of alkali activated slag repair mortar is reduced by 54%. Conclusions The early flexural strength development of alkali activated slag repair slurry was slower, while the early compressive strength development was faster. Adding a small amount of (10%) sodium silicate could stimulate the activity of the slag, slightly improving the strength of the slurry, and significantly increasing the strength at 15% and 20% dosages. The addition of PAA did not change the product composition in the alkali activated slag repair material, but filled in the gap of amorphous cementitious material. Before PAA modification, the cross-section of the alkali activated slag repair material was smooth and flat. After PAA modification, the cracks on the both sides of the alkali activated slag repair material were connected by fibrous filaments, further enhancing the strength of the material.