Dong Lei, Meng Fei, Feng Pan, Ran Qianping, Pan Chonggen, He Jianming
School of Materials Science and Engineering, Southeast University, Nanjing 211189, China.
State Key Laboratory of High-Performance Civil Engineering Materials, Jiangsu Sobute New Materials Co., Ltd., Nanjing 211103, China.
Materials (Basel). 2023 Mar 9;16(6):2190. doi: 10.3390/ma16062190.
To reduce the inhibiting effects of polystyrene-based emulsion on the hydration process and strength development of cementitious materials, an amphiphilic diblock copolymer polystyrene--poly(acrylic acid) (PS--PAA) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and demonstrated in cement paste system for improving the resistance to water absorption without significantly reducing 28-day compressive strength. Firstly, the dissolved PS--PAA was added into water, and it quickly self-assembled into amphiphilic 80 nm-sized micelles with hydrophobic polystyrene-based core and hydrophilic poly(acrylic acid)-based shell. The improved dispersion compared to that of polystyrene emulsion may minimize the inhibiting effects on strength development, as the effects of PS--PAA micelle as hydrophobic admixtures on rheological properties, compressive strength, water absorption, hydration process, and pore structure of 28-day cement pastes were subsequently investigated. In comparison with the control sample, the saturated water absorption amount of cement pastes with 0.4% PS--PAA was reduced by 20%, and the 28-day compressive strength was merely reduced by 2.5%. Besides, the significantly increased hydrophobicity instead of slightly decreased porosity of cement paste with PS--PAA may contribute more to the reduced water adsorption characteristics. The study based on prepared PS--PAA micelle suggested a promising alternative strategy for fabricating polystyrene-modified concrete with reduced water absorption and unaffected compressive strength.
为降低聚苯乙烯基乳液对胶凝材料水化过程和强度发展的抑制作用，通过可逆加成-断裂链转移（RAFT）聚合合成了两亲性二嵌段共聚物聚苯乙烯-聚丙烯酸（PS-PAA），并在水泥浆体体系中进行了验证，以提高其抗吸水性，同时不显著降低28天抗压强度。首先，将溶解的PS-PAA加入水中，它迅速自组装成两亲性的80纳米大小的胶束，其核心为疏水性的聚苯乙烯基，壳层为亲水性的聚丙烯酸基。与聚苯乙烯乳液相比，其分散性的改善可能会使对强度发展的抑制作用最小化，随后研究了PS-PAA胶束作为疏水剂对28天水泥浆体的流变性能、抗压强度、吸水性、水化过程和孔结构的影响。与对照样品相比，含0.4%PS-PAA的水泥浆体的饱和吸水量降低了20%，28天抗压强度仅降低了2.5%。此外，含PS-PAA的水泥浆体疏水性显著增加而非孔隙率略有降低，这可能对降低吸水特性贡献更大。基于制备的PS-PAA胶束的研究为制备吸水率降低且抗压强度不受影响的聚苯乙烯改性混凝土提出了一种有前景的替代策略。
