掺新型耐盐高吸水树脂混凝土基本性能研究

Fundamental properties of concrete with a new type of salt-resistant super absorbent polymer

为了改善传统吸水树脂对混凝土后续养护效果不足的难题,并有效抑制养护后混凝土收缩开裂的风险,研发一种具有优异吸水-饱水-释水性能的新型耐盐高吸水树脂(salt-resistant super absorbent polymer, SRSAP)。采用坍落度试验、抗压强度试验、毛细吸水试验、抗氯离子渗透试验及干燥收缩试验等方法,依次研究SRSAP对混凝土新拌状态工作性能、基本力学性能、介质传输性能及干燥收缩性能的影响规律。试验结果表明,新拌混凝土的坍落度随SRSAP掺量的增加呈先增大后减小的规律,适当掺量可改善新拌混凝土的工作性能。SRSAP对混凝土抗压强度不利,但可改善其后期抗压强度发展。混凝土的毛细吸水系数前期随SRSAP掺量和水胶比的增加而增大,混凝土后期毛细吸水系数明显减小,仅为前期的10.1%~48.0%。SRSAP减小了长龄期养护混凝土的氯离子扩散系数,并降低了经海水浸泡180 d的混凝土内部氯离子浓度,说明SRSAP可明显改善混凝土的抗渗性;适量SRSAP可起到较好的内养护效果,减缓混凝土内部相对湿度降低速率和衰减程度,显著改善混凝土的早期干燥收缩,但对后期收缩值影响不大。综合混凝土工作性能、抗压强度、抗氯离子渗透系数、干燥收缩等各项性能指标,SRSAP在C40和C50混凝土中的推荐掺量为1 kg/m^(3)。研究结果可为新型SRSAP在混凝土中的应用提供理论依据和技术支持。

To improve the insufficient later curing effect of conventional super absorbent polymer and effectively relieve the shrinkage-cracking risk of concrete,a new type of salt-resistant super absorbent polymer(SRSAP)with excellent water-absorbing,water-holding and water-releasing capacity was introduced.The influences of SRSAP on the workability in fresh state,fundamental mechanical properties,transport properties,and drying shrinkage performances of concrete were investigated in sequence using slump flow tests,compression tests,water absorption tests,chloride penetration resistance tests and shrinkage tests.Results show that the slump flow first increases and then decreases with increasing SRSAP content,and proper SRSAP amount can improve the workability of fresh concrete.The incorporation of SRSAP is detrimental to the compressive strength of concrete,but it can improve the compressive strength development at late ages.The water absorption ratio of concrete first increases with increasing SRSAP content and water-to-binder ratio at early stages,but the ratio at late stages is considerably decreased and it takes up only 10.1%~48.0%of that at early stages.SRSAP can reduce the diffusion coefficient of chloride ion at long-term ages and decreases the chloride ion concentration after 180 d seawater immersion.It can improve permeability resistance.In addition,SRSAP offers modified internal curing effect,which decreases both the reduction rate and the total reduction of internal relative humidity,thus remarkably optimizing the drying shrinkage performances of concrete.Giving considerations to the workability,compressive strength,chloride penetration resistance and drying shrinkage,the suggested SRSAP content in concrete of Grade C40 and C50 is 1 kg/m3.The research results can provide theoretical foundation and technical support for the application of SRSAP in concrete.