聚丙烯纤维增强玻化微珠保温砂浆的干缩开裂性能

Drying Shrinkage and Cracking Behavior of Polypropylene Fiber Reinforced Glazed Hollow Beads Thermal Insulation Mortar

关键词:  聚丙烯纤维  玻化微珠保温砂浆  干缩  硬化开裂  质量损失  孔径分布

Key words:  polypropylene（PP） fiber  glazed hollow beads thermal insulation mortar  drying shrinkage  cracking  mass loss  pore size distribution

摘要:

测试了聚丙烯纤维增强玻化微珠保温砂浆的干缩，采用圆环加速开裂方法对其早期硬化开裂进行了试验，研究了聚丙烯纤维掺量和尺寸对其干缩开裂的影响，用质量损失率来表征其失水量，并通过氮吸附方法分析了孔结构.结果表明：聚丙烯纤维增强玻化微珠保温砂浆的干缩随龄期呈快速期（7d前）、慢速期（7～365d）、亚稳期（365d后）3个阶段，第1阶段的干缩主要由砂浆的快速失水引起，后2个阶段的干缩归结于砂浆中小于50.0nm的孔结构，且与7.3～12.3nm的孔径分布线性相关；聚丙烯纤维的掺加未改变玻化微珠保温砂浆干缩3阶段的发展趋势，但可抑制其发展速率，降低裂缝开裂权重值，而且聚丙烯纤维的阻裂作用与其掺量和尺寸线性相关.

Abstract:

Drying shrinkage of polypropylene fiber reinforced glazed hollow beads thermal insulation mortar was measured by vertical length comparator, and cracking was measured by ring method. The influences of polypropylene(PP) fiber with different contents and lengths on the long term drying shrinkage and cracking were investigated. Mass loss was measured by weighting method to reflecting the water loss degree, and pore structure was characterized by nitrogen adsorption/desorption method, the correlation among them was researched. The results show that drying shrinkage process of polypropylene fiber reinforced glazed hollow beads thermal insulation mortar includes three steps with the curing time extension：the acceleration period（before 7d）, the deceleration period（7365d） and the metastable period（after 365d）. The drying shrinkage of mortar in the first stage increases quickly owing to the fast dehydration, but its development in the last two stages is attributed to pore structure of mortar with radius less than 500nm, which has linear relationship with the pore volume fraction of the pore with the sizes of 7.3nm to 123nm. And there is no change in the drying shrinkage development trending of glazed hollow beads thermal insulation mortar with the PP fiber addition and three steps with the curing time extension still takes place, but it restrains significantly drying shrinkage value at any curing time. The effect of cracking resistance of PP fiber enhaces with increasing fiber content and increment in length of PP fiber, which reduces the width and length of cracking and causes the total cracking values of mortar to reduce greatly.