Influence of the content and dispersion of limestone fines in the bond strength of mortar-brick interfaces

Abstract This study investigates the effects of the content and dispersion of limestone fine particles on the bond strength of mortar-brick interfaces. Mortars with 0%, 30% and 60% replacement of binder by limestone fines with a particle size distribution lower than cement. We also evaluated particle dispersion by adding 0.02% polycarboxylate-based dispersing admixture to the mortars applied on the surfaces of clay bricks treated with a water repellent. The rheological behavior of the mortars varied depending on the particle size of the limestone fines used and the admixture added, measured by a rotational rheometer. Despite a reduction in the mechanical properties, the 60% replacement of of binder by limestone fines, associated with the use of dispersing admixture can increase the bond strength of the mortar-brick interface by 76%. The increased adherence can be explained by the increased area or contact between substrate and mortar. The conclusion has practical implications, as it demonstrates that is possible to reduce the amount of matrix binder without changing bond strength.

摘要 本研究探讨了石灰石细粉的含量与分散性对砂浆-砖界面粘结强度的影响。研究采用粒径低于水泥的石灰石细粉替代胶凝材料，替代率分别设置为0%、30%与60%。此外，本研究还通过向施加于经疏水剂处理的黏土砖表面的砂浆中添加0.02%的聚羧酸系分散外加剂，对颗粒分散性进行了评估。通过旋转流变仪测试可知，砂浆的流变行为随所用石灰石细粉的粒径及所添加外加剂的不同而发生变化。尽管力学性能有所降低，但将60%的胶凝材料用石灰石细粉替代并配合使用分散外加剂，可使砂浆-砖界面的粘结强度提升76%。粘结力的提升可归因于砖基体与砂浆间接触面积的增大。本研究结论具备实际应用价值，其证实了在不改变界面粘结强度的前提下，可减少胶凝材料基体的用量。