The Role of Mortar Microstructure in Providing the Face Wall Structural Integrity

Abstract

The basic condition for proper function of a face wall in external environment is providing structural integrity within its entire period of usage. Structural integrity can be defined as construction ability to maintain bearing capacity, functionality and shape within acceptable ranges without arising state of emergency during exploitation. Wall structural integrity results first of all from construction mortar which, except for bearing function should also provide protection from entering water into the wall interior. The processes of water capillarity, drying, and freezing are dependent on microstructure and open porosity.In the article there are introduced tests of three mortars (cement, cement with plasticizer, and cement-lime based) formed in wall joints. In order to prepare mortar samples from joints of wall elements for porosimetry tests, mortar was separated from bricks in such way that whole joint was left intact. By breaking, each layer of mortar was divided parallel to the joint surface into three parts – two parts adjacent to brick base (each 1/4 of layer thickness) and the middle part sized 1/2 of joint thickness. By Mercury Intrusion Porosimetry the basic microstructure parameters were measured, as well as pore volume distribution in the function of their diameters as integral and differential relation. The analysis of pore volume variation for integral distribution let us state the pore sizes which as additional, are formed in mortar in the area of joint adjacent to wall element surface. Independently of mortar type, in this area there are additional pores created, which are responsible for capillary flow. In cement mortars there are additionally macropores created which decides about water migration through a joint and about its gas permeability.