Effect of Binary Defoamer and Air-Entraining Agent on Surface Morphology and Basic Properties of Fair-Faced Concrete

Green fair-faced concrete (GFFC) is characterized by low surface porosity and small pore sizes and is widely used in architectural concrete engineering. It remains challenging to meet the appearance quality requirements of GFFC with conventional mix ratios and additives. This paper introduces double-mix defoamers and air-entraining agents into GFFC slurry to further refine the internal bubble size of GFFC slurry, optimize the surface pore structure, and thereby improve the apparent morphology of cured GFFC. The effects of double-agent doping on the slump, mechanical strength, shrinkage performance and impermeability durability of GFFC were also investigated. The results show that, compared with the baseline, after binary doping of the defoamer and air-entraining agent, the slump loss over time of GFFC slurry has been significantly reduced; the average porosity of GFFC is 0.132%, and the maximum average pore diameter is only 1.01 mm, which is decreased by 57.35% and 67.68%, respectively; the 45 day shrinkage of the GFFC doped with 3‱ defoamer and 4‱ air-entraining agent is 338 × 10−6 with a decrease of 33.98%, and the resistance to 84d chlorine ionization migration coefficient is 1.3 × 10−12 m2/s with a decrease of 38.09%. These outcomes can effectively contribute to the pore refinement and apparent morphology improvement of GFFC doped with a binary defoamer and air-entraining agent.