Comparison between Water Penetration Test Results of Vertical and Horizontal Joints

A comparison was made between water leakage through deficient vertical and horizontal joints as shown in Fig. 19. The results reflect leakage rates of joints subjected to a water deposition rate of 4 L/(min-m2). The Y-axis provides the rates of leakage (L/min) across the horizontal joint; that of the X-axis for the vertical joint.

Results have been organized in terms of different crack lengths; cracks of 16 mm length are shown as circular data points, 8 mm as square points, and 4 mm as triangular points. The dotted lines delineate the outer boundary of the data and the oblique line joining points 0.0001 and 1 L/min on the plot indi­cates when the values of horizontal and vertical leakage rates are equal. A point falling beneath this line indicates that the leakage rate through the defect at the vertical joint is greater than the rate through the defect in the horizontal joint at the given test condition.

It is apparent from this plot that there can be substantial increases in leak­age rate of either vertical or horizontal joints and up to an order of magnitude difference.

The following was also evident:

• Overall, it is more likely that vertical joints will leak at higher rates than horizontal joints (ca. 59 %); as well, this was most prevalent at reduced water leakage rates (i. e., <0.005 L/min) where 81 % of the data points were those of the vertical joint having a greater leakage rate than that of the horizontal joint; on the other hand,

• At large crack openings (i. e., crack lengths of 8- and 16 mm, displace­ment of 1 and 2 mm) there is a greater chance (ca. 75%) that the rate of water leakage at the horizontal joint will be more severe than that of the vertical joint;

• Clearly the rate of water leakage depends on the nature of the crack opening (i. e., crack length and width); horizontal joints appear to be more susceptible to water leakage for joints having larger defect sizes.

Conclusions

1. For vertical joints evaluated in this study:

• There exists a linear relationship between crack width and joint dis-

image273

Water leakage of vertical joint (L/min)

placement for cracks introduced in a sealant at the sealant-substrate interface; as well,

• Larger crack lengths induce greater crack widths and crack sizes in extended joints;

• The size and shape of the backer rod affects the nature of water leak­age across the vertical joint.

2. For both vertical and horizontal joints evaluated in this study:

• The crack length and joint displacement provide a multiplicative ef­fect on water leakage rates;

• If a crack exists in a sealed jointing system, even if the joint displace­ment is 0 mm, water may penetrate the opening at the crack;

• The higher the quantity of water deposition on or air pressure differ-

ential across the specimen, the greater the rate of water leakage of the jointing system.

3. Additionally, it may be suggested that if the crack length in a joint of an actual building is known or verified from a field inspection, an estimate of the rate of water leakage can be calculated by using the information given above and provided information is also given on the expected climate loads impinging on the fayade.

It should be borne in mind that estimates provided in this initial series of tests only offer a gross approximation of leakage across a deficient joint and are based on the limited number of tests and test variations. The movement of water through small openings will be affected by the tortuosity of the leakage path and the nature of the materials along which it flows. Hence, other factors such as the type of sealant, backer rod, and substrate material to which the jointing product is adhered may affect water entry. For example, a deficient joint of sealant installed on a concrete substrate is not likely to comport itself in exactly the same manner as suggested by results on the leakage through cracks reported in this study when considering the idealized test conditions. Nonethe­less, these studies offer some initial measure of the degree of water penetration at deficient joints—additional studies using the same approach would help elu­cidate the likely variations in leakage rate across a deficient joint that would arise given for example, different sealant and substrate materials or crack lo­cation and crack size.

Acknowledgments

That portion of this work on vertical joints was conduced over the course of a ten month visiting researcher work term at the Institute for Research in Con­struction (IRC), National Research Council Canada, in Ottawa. The authors are indebted to the Tokyo Institute of Technology, Japan, for having provided fund­ing to Dr. Miyauchi for his stay at the IRC, and to the IRC for their support to the research conducted by Dr. Miyauchi and Dr. Lacasse.