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纤维和外加剂对泡沫混凝土收缩性能的影响
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Effects of Fiber and Admixture on Shrinkage Performance of Foamed Concrete
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    摘要:

    运用正交试验方法研究了水灰比、砂胶比、减水剂掺量对干密度为800 kg/m3的泡沫混凝土收缩性能的影响,得出了利于泡沫混凝土收缩性能的最优配合比. 基于该配合比,进一步研究了聚丙烯纤维、玻璃纤维、植物纤维、膨胀剂、减缩剂对泡沫混凝土收缩性能的影响,同时测试了其对流动性和抗压强度的影响,并利用雷达图分析了最佳外加组分,利用宏观孔结构和SEM电镜下的微观结构解释纤维和外加剂对其减缩的机理. 结果表明:综合考虑3 d自收缩和28 d干燥收缩率,最优配合比为水灰比0.5,砂胶比1.0,减水剂掺量0.5%. 纤维、膨胀剂、减缩剂均能有效降低泡沫混凝土的自收缩和干燥收缩,其抵抗收缩能力大小为:减缩剂>膨胀剂>纤维. 最佳外加组分为1%质量掺量的减缩剂,其能够在满足泡沫混凝土的流动度和抗压强度的前提下,降低泡沫混凝土37%的3 d自收缩和57.5%的56 d干燥收缩. 纤维的掺入引起部分泡沫的破碎,引起基体干燥收缩增大,但其对泡沫混凝土的物理约束作用使最终的干燥收缩降低. 膨胀剂和减缩剂减缩机理在于其自身的化学作用.

    Abstract:

    The effects of water cement ratio, sand binder ratio and dosage of water reducer content on the shrinkage of foamed concrete with dry density of 800 kg/m3 were studied by orthogonal test method to obtain the optimal mix proportion, which is beneficial to shrinkage performance of foamed concrete. According to this mix proportion, the effects of polypropylene fiber, glass fiber, plant fiber, expansive agent and shrinkage reducing admixtures on the shrinkage performance of foamed concrete were further studied. At the same time, the effects on the fludity and compressive strength were also examined. The best added component was analyzed by using the radar chart, and the mechanisms of the shrinkage reduction of fiber and admixture were explained by the macro pore structure and the microstructure under SEM electron microscope. The results show that,considering the 3 days autogenous shrinkage and 28 days drying shrinkage, the optimum mix proportion is 0.5 of water cement ratio, 1 of sand binder ratio, and 0.5% of the dosage of water reducer content. Fiber,expansive agent and shrinkage reducing admixtures can effectively reduce the autogenous shrinkage and drying shrinkage of foamed concrete, and the law of their shrinkage resistance is as follows:shrinkage reducing admixtures > expansive agent > fiber. The best addition component is 1% mass fraction of shrinkage reducing admixtures, which can reduce the 3 days autogenous shrinkage of the foamed concrete by 37% and the 56 days drying shrinkage by 57.5% on the premise of satisfying the fluidity and compressive strength of foamed concrete. Furthermore, the incorporation of fiber causes partial foam breakage, resulting in greater drying shrinkage of the matrix. However,its physical constraint on foamed concrete reduces the final drying shrinkage. The shrinkage mechanisms of expansive agent and shrinkage reducing admixtures lie in its own chemical action.

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龚建清,周孜豪.纤维和外加剂对泡沫混凝土收缩性能的影响[J].湖南大学学报:自然科学版,2019,46(5):76~85

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  • 在线发布日期: 2019-05-17
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