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<br />time-consuming and thus increased the expense. It is highly desirable to use <br /> <br /> <br />a material which can be brushed on the wall. The trowelled-on coating (coat- <br /> <br /> <br />ing 4) sealed the cube against a water head with only a small leak mainly at <br /> <br /> <br />the cube-foundation interface (Figure 22). Coating 4 was not successful in <br /> <br />terms of durability. It expanded, cracked, and began to come off the wall <br /> <br /> <br />3 months after it was applied (Figure 23). <br /> <br /> <br />32. Three years after application of the brush-on coatings, coatings 6 <br /> <br /> <br />and 7 showed some cracking. Coating 7 lost its bond to the brick surface and <br /> <br /> <br />peeled off in various places. After 4 years of service, coatings 5 and 8 <br /> <br /> <br />showed no signs of cracking or loss of bond. <br /> <br /> <br />Mechanism of causing impermeability <br /> <br /> <br />33. One type of material (coatings 4, 5, and 7) was so impermeable that <br /> <br /> <br />it kept water completely away from the wall. The other type of material <br /> <br /> <br />(coatings 6 and 8) contained some agents which seeped into the voids of the <br /> <br /> <br />mortar joints and reacted with the cement causing expansion and a filling of <br /> <br /> <br />the spaces. One cementitious coating of each type (coatings 5 and 8) was <br /> <br /> <br />found to be successful after 4 years in the climate at Vicksburg, Mississippi. <br /> <br /> <br />34. MaterialS (Figure 24) was a coating with excellent impermeability <br /> <br /> <br />and bond characteristics. The darker material in this photo is coating 5. <br /> <br /> <br />Pigment can be used to make the cementitious coating the desired color. For <br /> <br /> <br />the maximum head of water tested (4 ft), coating 5 sealed the brick wall from <br /> <br /> <br />both the positive and negative sides of the wall. This coating was less <br /> <br /> <br />expensive than the proprietary products and would be excellent where a surface <br /> <br /> <br />coating is required. <br /> <br /> <br />35. Coating 8 was as successful as coating 5 and also sealed the brick- <br /> <br /> <br />veneer wall against 4 ft of water head from the negative and positive sides of <br /> <br /> <br />the wall. Coating 8 seeped into the pore spaces of the mortar joints; it was <br /> <br /> <br />observed to penetrate the joint and collect as a film on the opposite side of <br /> <br /> <br />the wall. Initially, the brick-veneer wall leaked a small amount, but as the <br /> <br /> <br />material seeped into the pore space, the leakage stopped. <br /> <br /> <br />36. The other three coatings initially caused the brick-veneer walls to <br /> <br /> <br />be impermeable to water when applied to either the positive or negative side <br /> <br />of the wall, but they were not durable and failed with the passage of time. <br /> <br />13 <br />