Rehabilitation of waterproofing coatings in flat roofs with liquid applied products

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1 Rehabilitation of waterproofing coatings in flat roofs with liquid applied products - Extended Abstract - Carlos André Pardal Leandro Quaresma Supervisors Researcher Jorge Manuel Grandão Lopes Professor João Pedro Ramôa Ribeiro Correia October 2015

3 1. Introduction A flat roof system is made of several elements, each one with its own function, the waterproofing coating being one the most relevant. Indeed, its correct performance prevents the water ingress to the underlying layers, thus contributing for the protection of the structure and to maintain its habitability conditions and/or its functionality. Since this kind of roofing is very common in Portugal [1], it is of the utmost importance to study the most frequent anomalies in the waterproofing coatings, their main causes and possible repairing and rehabilitation solutions. The causes for the most frequent anomalies in flat roof s waterproofing coatings can be divided into the following groups: design errors, application errors, external mechanical actions, environmental actions and lack of maintenance. The most common repairing solutions comprise the complete replacement of the waterproofing coating or the application of the same type of material in a limited and well defined area. A recent alternative consists of applying liquid applied waterproofing products over the area that needs to be repaired. Liquid applied waterproofing products currently existing in the market, due to their mechanical, physical and chemical properties, can be considered as a potential solution for the above mentioned purpose. However, to the best of the author s knowledge, there is no information available in the literature about the performance of this repair strategy. The main goal of this dissertation is thus to evaluate the suitability of liquid applied waterproofing products for the repair of waterproofing coatings made of prefabricated membranes. For this study, the mechanical actions on the waterproofing coatings are considered as the most important. Therefore, an experimental campaign was prepared, in which the performance of overlapping joints between the several prefabricated waterproofing membranes and the several liquid applied products was studied through shear and peeling tests. It was decided to include in this study the most relevant materials existent in the market, both for the prefabricated waterproofing membranes (oxidized bitumen, APP polymer bitumen, SBS polymer bitumen and PVC) [2] and for the liquid applied waterproofing products (fibrous acrylic, liquid rubber, bicomponent cementitious, polyurethane and liquid silicone). As mentioned, the topic of this investigation is currently underdeveloped and there is no regulatory documentation applicable to this specific repair approach; therefore, in the performed tests it was necessary to use and adapt the European standards and directives applicable to prefabricated waterproofing coatings. 2. Experimental programme 2.1. Objectives The experimental campaign described below was developed in order to achieve the goals established for the present dissertation. These goals are, essentially, the characterization and the evaluation of the overlapping joints quality between new flexible prefabricated waterproofing sheets and liquid applied waterproofing products, in order to determine the suitability of the latter for the repair and rehabilitation of waterproofing systems composed by the former. Due to the lack of regulatory documentation applicable to the specific subject of this dissertation, an extensive and careful review of the technical literature was performed, namely about the materials involved in the experimental campaign. After selecting the materials to be used, the respective manufacturers were contacted and requested to provide the samples needed to perform the tests, both for the prefabricated membranes and the liquid applied waterproofing materials; for the latter, suppliers were also asked to indicate a representative to correctly apply their products. Alongside the main experimental campaign, oriented towards the understanding 1

4 of the behavior of the overlapping joints, and consisting of shear and peeling tests, complementary tensile tests were also performed in all the materials involved, allowing gathering more experimental information of great importance for this dissertation s conclusions. As mentioned above, since at present there is no regulatory documentation applicable to the specific type of repair operations investigated in this dissertation, namely regarding the performance of mechanical tests with liquid applied waterproofing products, it was necessary to adopt the same type of documentation applicable to flexible prefabricated waterproofing membranes Materials Since the main subject of this dissertation is the characterization and evaluation of the performance of overlapping joints between flexible prefabricated waterproofing sheets and liquid applied products, there was no need to set certain common parameters. One decided to choose solutions as resistant as possible, according to the manufacturers indications, mainly regarding the reinforcement, the mechanical characteristics and the products application quality. Another factor for the choice of the several materials was their significance in the market. The selected membranes for this study, as well as their main characteristics, are described in Table 1. The choice for the polyester felt reinforcement was due to the fact that this solution presents, when compared to glass fiber reinforcement and for similar conditions and dimensions, higher extension capacity under tensile stresses. Table 1 Prefabricated membranes and their main characteristics. Membrane Oxidized bitumen APP polymer bitumen SBS polymer bitumen Mass (kg/m 2 ) Width (mm) Reinforcement Finishing Polyester felt Polyethylene film Polyester felt Polyethylene film Polyester felt Polyethylene film PVC Polyester felt - The liquid applied waterproofing products, used in this study, are presented in Table 2, together with their main characteristics, as per the respective manufacturers. Concerning the application conditions and techniques, storing and curing processes, all manufacturers recommendations were followed. Also in this case the most resistant solutions were selected and whenever possible the polyester felt reinforcement was incorporated. However, in two products, according to manufacturer s suggestion, the glass fiber reinforcement was used and in two other products there was no reinforcement at all, as this is the usual application process in a jobsite. The systems tested to assess the performance of the overlapping joints resulted from the combination between all the liquid applied waterproofing products and all the new prefabricated waterproofing membranes. 2

Product Table 2 Liquid applied products and their main characteristics.

0 - Solvent 1 Bi-component cementitious 3.6 2.0 Polyester felt Aqueous 21 Polyurethane 2.2 2.0 Glass fiber Solvent 7 Liquid silicone 2.5 2.

Equipment For the determination of the mechanical properties of the materials and the overlapping joints, a universal mechanical testing

4. Test procedures Figure 1 Universal mechanical testing machine.

for this kind of membranes. For all mechanical tests performed, the specimens were cut from the membranes longitudinal direction.

5 Product Table 2 Liquid applied products and their main characteristics. Consumption (kg/m 2 ) Width (mm) Reinforcement Base Curing (days) Fibrous acrylic Glass fiber Aqueous 21 Liquid rubber Solvent 1 Bi-component cementitious Polyester felt Aqueous 21 Polyurethane Glass fiber Solvent 7 Liquid silicone Aqueous Equipment For the determination of the mechanical properties of the materials and the overlapping joints, a universal mechanical testing machine, with a 5 kn capacity load cell, was used. Two metallic jaws were attached to both edges of the machine, as illustrated in Figure Test procedures Figure 1 Universal mechanical testing machine. For the collection of samples of bituminous and plastic membranes the NP EN [3] standard was used, that defines the sampling procedures for this kind of membranes. For all mechanical tests performed, the specimens were cut from the membranes longitudinal direction. For the products application it was necessary to previously prepare special devices that are depicted in Figure 2. The applications were all performed by specialized technicians from each of the manufacturers in order to guarantee its best quality. For those applications different tools were used, such as trowels, paint rollers and brushes. a) b) c) Figure 2 Application devices for: a) tensile tests; b) shear tests; and c) peeling tests. 3

All products were applied in two coatings with a 24 h period between them, with the exception of the fibrous acrylic, where a 48 h period was needed, as per manufacturer s indication.

For the tensile test, the prefabricated membranes and the liquid applied product specimens were obtained as per the NP EN 12311-1 [4] and the EN 12311-2 [5] standards.

Regarding the peeling test, the standards used were the NP EN 12316-1 [8] and the EN 12316-2 [9] for the bituminous and the PVC membranes, respectively.

6 All products were applied in two coatings with a 24 h period between them, with the exception of the fibrous acrylic, where a 48 h period was needed, as per manufacturer s indication. With the exception of the liquid rubber, with a 1 mm width, all products were applied in order to achieve a final width of 2 mm. For the tensile test, the prefabricated membranes and the liquid applied product specimens were obtained as per the NP EN [4] and the EN [5] standards. For the shear test, the specimens were cut as per the NP EN [6] and the EN [7] standards, for the bituminous membranes and the PVC membrane, respectively. Regarding the peeling test, the standards used were the NP EN [8] and the EN [9] for the bituminous and the PVC membranes, respectively. Figure 3 illustrates, as an example, the different stages of the peeling test specimen manufacturing process. a) b) c) Figure 3 Different stages of the peeling test specimen manufacturing process: a) application; b) cutting; and c) final specimen. After the gathering of all the specimens for the several kinds of tests, they were properly conditioned in a ventilated room until the tests were performed. For the development of the tests the specimens were introduced in the universal mechanical testing machine, installed in a heat-controlled room, as per the specific standards. The tests were completely monitored by a computer connected to the machine and the force and the elongation values were registered. The tests were carried-out until the complete failure of the specimen and the failure mode of each specimen was properly registered. 3. Results and discussion 3.1. Mechanical performance of materials Prefabricated membranes Figure 4 presents a summary of the tensile tests performed on prefabricated membranes in terms of their maximum load. The results obtained show that the membrane that presents higher resistance is the PVC one. Regarding the bituminous membranes, the oxidized bitumen is the one that has the highest tensile strength value, followed by the APP polymer bitumen membrane and by the SBS polymer bitumen membrane, wherein these last two present similar values. Figure 5 shows the failure modes obtained for the different prefabricated membranes, when subjected to the tensile test. 4

Tensile maximum force (N) 1400 1200 1000 800 600 400 200 0 OXI BIT APP SBS PVC Figure 4 Maximum tensile force

a) b) c) d) Figure 5 Failure modes for prefabricated membranes: a) Oxidized bitumen; b) APP polymer bitumen; c)

Comparing these results to those obtained by António [10], it appears that the only membrane whose results

studies this membrane incorporates a polyester felt reinforcement.

7 Tensile maximum force (N) OXI BIT APP SBS PVC Figure 4 Maximum tensile force (standard deviation as error bars) of the prefabricated membranes. a) b) c) d) Figure 5 Failure modes for prefabricated membranes: a) Oxidized bitumen; b) APP polymer bitumen; c) SBS polymer bitumen; and d) PVC. Comparing these results to those obtained by António [10], it appears that the only membrane whose results present the same order of magnitude is the APP polymer bitumen, and this is due to the fact that in both studies this membrane incorporates a polyester felt reinforcement. Regarding the remaining membranes, the resistance values obtained are significantly higher than the ones obtained by António [10], since in this study membranes with glass fiber reinforcement were used, unlike the ones in this dissertation, which incorporate polyester felt reinforcements. 5

8 Tensile maximum force (N) Liquid applied products Figure 6 presents the maximum tensile force measured in the different liquid applied waterproofing products. It can be seen that the one with the highest tensile resistance was, by far, the bi-component cementitious system, followed by the polyurethane, the fibrous acrylic and, for substantially lower values, the liquid silicone and the liquid rubber. The significant variation between the obtained values for the bi-component cementitious and the other products is due to the fact that the bi-component cementitious was reinforced with polyester felt, in contrast with the fibrous acrylic and the polyurethane that were reinforced with glass fiber. The liquid silicone and the liquid rubber were applied with no reinforcement. It is worthy to note that the decision of applying reinforcement or not and its typology was defined according to the manufacturers indications Fibrous acrylic Liquid rubber Bi-component cementitious Polyurethane Liquid silicone Figure 6 Maximum tensile force (standard deviation as error bars) for the liquid applied products. Figure 7 shows the failure modes obtained for the different liquid applied products, when subjected to the tensile test. Comparing the results obtained here with the ones reported by Feiteria [11], it can be concluded that, for the same application and reinforcement conditions, the values orders of magnitude are similar for all the tested products. 6

a) b) c) d) e) Figure 7 Failure modes for liquid applied products: a) fibrous acrylic; b) liquid rubber; c) bicomponent cementitious; d) polyurethane; and e) liquid silicone.

verification. Table 3 Mechanical characteristics obtained from the tensile tests for the prefabricated membranes and for the liquid applied products.

7 Yes APP polymer bitumen 743.87 ± 78.0 91.85 ± 7.7 Yes SBS polymer bitumen 736.22 ± 121.3 94.85 ± 5.7 Yes PVC 1228.53 ± 85.7 46.37 ± 4.4 Yes Fibrous acrylic 185.78 ± 18.1 21.

31 ± 5.3 219.39 ± 20.9 --- 3.2. Mechanical performance of overlapping joints 3.2.1. Shear tests In the shear tests, it was found that, in general, with the exception of the

maximum resistance capacity of the overlapping joint.

9 a) b) c) d) e) Figure 7 Failure modes for liquid applied products: a) fibrous acrylic; b) liquid rubber; c) bicomponent cementitious; d) polyurethane; and e) liquid silicone. Table 3 presents a summary of the mechanical characteristics obtained in the tensile tests for all the materials and the respective UEAtc technical guides requirements verification. Table 3 Mechanical characteristics obtained from the tensile tests for the prefabricated membranes and for the liquid applied products. Elongation in the UEAtc Tensile maximum Membrane / liquid product maximum force requirements force (N) (mm) verification Oxidized bitumen ± ± 2.7 Yes APP polymer bitumen ± ± 7.7 Yes SBS polymer bitumen ± ± 5.7 Yes PVC ± ± 4.4 Yes Fibrous acrylic ± ± Liquid rubber ± ± Bi-component cementitious ± ± Polyurethane ± ± Liquid silicone ± ± Mechanical performance of overlapping joints Shear tests In the shear tests, it was found that, in general, with the exception of the bi-component cementitious product, all the liquid applied products presented failure modes in the repair (liquid) product itself, therefore not being possible to mobilize the maximum resistance capacity of the overlapping joint. In the cases of the fibrous acrylic and of the polyurethane, given the UEAtc technical guides [12, 13], it was considered that the joint s mechanical performance was satisfactory, since the minimum requirements were fulfilled. For the liquid rubber and for the liquid silicone, although failure occurred outside the joint, it was not possible to determine the joints 7

10 Shear maximum force (N) performance, since the maximum force values were too low. Regarding the bi-component cementitious specimens, these broke in the overlapping joint, given the minimum requirements set by the UEAtc technical guides [12, 13], it was considered that the quality of their joints is satisfactory when connected to the oxidized bitumen and the APP polymer bitumen membranes, while when connected to the SBS polymer bitumen and the PVC membranes they were unsatisfactory. Figure 8 summarizes the maximum shear force obtained for the several liquid applied waterproofing products, when connected to the several prefabricated waterproofing membranes. Analyzing the graphic it is possible to verify that the products that are capable of mobilizing higher resistance, regardless of the failure location (in the joint or in the repair product), were the bicomponent cementitious and the polyurethane, followed by the fibrous acrylic, the liquid silicone and, finally, the liquid rubber Fibrous acrylic Liquid rubber Bi-component cementitious Polyurethane Liquid silicone Oxi Bit APP SBS PVC Figure 8 Shear maximum force. It can also be seen that, with the exception to the bi-component cementitious, for each liquid applied product the shear test specimens failure occurred for values of the same magnitude as the ones registered in the respective tensile test. For the bi-component cementitious product, it was found that the maximum shear force in the overlapping joint was significantly lower than the tensile resistance of the product. Still analyzing figure 8, it is possible to infer that, for the only liquid applied product whose failure occurred in the overlapping joint, the bi-component cementitious, its bonding to the prefabricated membranes is better with the oxidized bitumen, followed the PVC and the APP polymer bitumen membranes and, finally, by the SBS polymer bitumen membrane. Figure 9 illustrates some examples of the failure modes obtained in the shear tests. 8

a) b) c) Figure 9 Different failure modes in the shear tests; a) oxidized bitumen with bi-component cementitious; b) APP polymer bitumen with liquid rubber; and c) PVC with polyurethane. 3.2.

overlapping joint and for very low force values, causing the joints mechanical performance to be considered as unsatisfactory, according to the minimum requirements set by the UEAtc technical guides

For the liquid rubber, even though the failure mode occurred in the repair product, the reduced force values obtained make the performance of the joints to be classified as unsatisfactory as well.

11 a) b) c) Figure 9 Different failure modes in the shear tests; a) oxidized bitumen with bi-component cementitious; b) APP polymer bitumen with liquid rubber; and c) PVC with polyurethane Peeling tests The peeling tests results for the prefabricated membranes and liquid applied products specimens showed that, with the exception of two distinct cases, all specimens failed at the overlapping joint and for very low force values, causing the joints mechanical performance to be considered as unsatisfactory, according to the minimum requirements set by the UEAtc technical guides [12, 13]. The referred exceptions were the liquid rubber connected with all the prefabricated membranes studied and the fibrous acrylic product when connected to the PVC plastic membrane. For the liquid rubber, even though the failure mode occurred in the repair product, the reduced force values obtained make the performance of the joints to be classified as unsatisfactory as well. Regarding the fibrous acrylic, it was found that when connected to the PVC membrane, the specimens failed in the repair product close to the overlapping joint, which means outside the joint. Despite this fact, since the obtained force values do not meet the minimum requirements set by the UEAtc guides [12, 13], the quality of the joint was considered as not satisfactory. Figures 10 and 11 present respectively the specimens peeling maximum force and peeling medium force for all the liquid applied products connected to all the prefabricated membranes. It can be seen that for the bituminous membranes the values are too low, which means a weak bonding performance, with the exception of the liquid rubber, for which the same conclusions do not apply. Regarding the peeling tests performed over the PVC membrane, it was found that for the fibrous acrylic, for the polyurethane and for the liquid silicone the peeling maximum force values are significantly higher when compared with the other membranes, even though they are also very low. Comparatively, it is shown that, with the exception of the connection with the SBS polymer bitumen membrane (to whom the polyurethane shows the best bonding performance), it is the fibrous acrylic product that presents the best bonding performance to the prefabricated membranes, followed by the polyurethane, the bi-component cementitious and, finally, the liquid silicone, even though this last repair product presents a better bond to the PVC than the previous. Regarding the liquid rubber, as mentioned before, given the low force values obtained, since the overlapping joint resistance was not mobilized, it is not possible to make any comparison. Figure 12 illustrates some examples of the failure modes obtained in the peeling tests. 9

Peeling medium force (N) Peeling maximum force (N) 100 90 80 70 60 50 40 30 20 Fibrous acrylic Liquid rubber Bi-component cementitious

90 80 70 60 50 40 30 20 Fibrous acrylic Liquid rubber Bi-component cementitious Polyurethane Liquid silicone 10 0 Oxi Bit APP SBS PVC Figure

a) b) c) Figure 12 Different failure modes in the peeling tests; a) oxidized bitumen with fibrous acrylic; b) SBS polymer bitumen with liquid

12 Peeling medium force (N) Peeling maximum force (N) Fibrous acrylic Liquid rubber Bi-component cementitious Polyurethane Liquid silicone 10 0 Oxi Bit APP SBS PVC Figure 10 Peeling maximum force Fibrous acrylic Liquid rubber Bi-component cementitious Polyurethane Liquid silicone 10 0 Oxi Bit APP SBS PVC Figure 11 Peeling medium force. a) b) c) Figure 12 Different failure modes in the peeling tests; a) oxidized bitumen with fibrous acrylic; b) SBS polymer bitumen with liquid silicone; and c) PVC with liquid rubber. Table 4 summarizes the mechanical characteristics obtained from the shear and peeling tests, as well as the verification of the UEAtc technical guides compliance and the overlapping joints performance. Since in all cases the requirements for peeling were not fulfilled, the overall 10

13 performance of all repair systems tested was not satisfactory. It is worth mentioning that this performance evaluation was made considering the standards applicable to prefabricated membranes, as there is still no specific regulation for liquid applied products. Table 4 Mechanical characteristics from the shear and peeling tests for the overlapping joints between the prefabricated membranes and the liquid applied products. Oxidized bitumen APP polymer bitumen SBS polymer bitumen PVC Repair system Fibrous acrylic Maximum force (N) Shear Elongation in the maximum force (mm) UEAtc requirements verification Maximum force (N) Peeling Medium force (N) UEAtc requirements verification ± ± 1.7 Yes ± ± 0.9 No Liquid rubber ± ± ± ± 1.5 No Bi-component cementitious ± ± 0.6 Yes 6.60 ± ± 0.6 No Polyurethane ± ± 1.0 Yes 8.72 ± ± 0.3 No Liquid silicone Fibrous acrylic ± ± ± ± 0.2 No ± ± 1.0 Yes ± ± 0.2 No Liquid rubber ± ± ± ± 1.1 No Bi-component cementitious ± ± 7.8 Yes 6.22 ± ± 0.3 No Polyurethane ± ± 6.6 Yes 7.75 ± ± 0.6 No Liquid silicone Fibrous acrylic ± ± ± ± 0.1 No ± ± 1.1 Yes ± ± 2.6 No Liquid rubber ± ± ± ± 1.1 No Bi-component cementitious ± ± 12.4 No 6.47 ± ± 0.3 No Polyurethane ± ± 18.3 Yes ± ± 1.8 No Liquid silicone Fibrous acrylic ± ± ± ± 0.1 No ± ± 0.8 Yes ± ± 14.6 No Liquid rubber ± ± ± ± 1.4 No Bi-component cementitious ± ± 0.4 No 6.47 ± ± 0.2 No Polyurethane ± ± 1.7 Yes ± ± 1.7 No Liquid silicone ± ± 19.1 Yes ± ± 5.6 No 4. Conclusions This paper presented an experimental investigation about the performance of different liquid applied products to repair various prefabricated waterproofing membranes. Performance was evaluated by means of shear and peeling tests and the UEAtc requirements applicable to prefabricated membranes were considered as a reference. For all cases tested, in light of the requirements set by UEAtc (for prefabricated membranes), the overlapping joints performance proved to be unsatisfactory. Although requirements for shear tests were fulfilled in most cases (where the best performance was provided by the bi-component cementitious and polyurethane products), the requirements for peeling tests were never fulfilled. Therefore, according to the presented conditions and considered parameters, the results obtained show that with the exception of the liquid rubber product, whose testing results were not 11

14 conclusive, none of the liquid applied products studied (fibrous acrylic, bi-component cementitious, polyurethane and liquid silicone) would be suitable for a rehabilitation or repairing intervention on flat roof s waterproofing coatings constituted by oxidized bitumen, APP polymer bitumen, SBS polymer bitumen or PVC prefabricated membranes. 5. Acknowledgements The author wishes to acknowledge the Supervisors for their advice, LNEC and IST for funding the research and providing the resources, the companies Imperalum, Texsa, Danosa, Renolit, Matesica, Henkel and Sika for supplying the materials and providing application support. 6. References [1] Instituto Nacional de Estatistica (INE), Surveys 2001: Final results: XIV population general survey: IV general housing survey (in Portuguese), INE, Lisbon, [2] Lopes, J. G., Revestimentos de impermeabilização de coberturas em terraço. Informação técnica de edifícios, ITE 34, LNEC, Lisboa, [3] European Committee for Standardization (CEN), NP EN Flexible sheets for waterproofing. Bitumen, plastic and rubber sheets for roof waterproofing. Rules for sampling (in Portuguese), IPQ, Caparica, [4] European Committee for Standardization (CEN), NP EN Flexible sheets for waterproofing. Determination of tensile properties. Part 1: Bitumen sheets for roof waterproofing (in Portuguese), IPQ, Caparica, [5] European Committee for Standardization (CEN), EN Flexible sheets for waterproofing. Determination of tensile properties. Part 2: Plastic and rubber sheets for roof waterproofing, CEN, Brussels, [6] Instituto Português da Qualidade (IPQ), NP EN Flexible sheets for waterproofing. Determination of shear resistance of joints. Part 1: Bitumen sheets for roof waterproofing (in Portuguese), IPQ, Caparica, [7] European Committee for Standardization (CEN), EN Flexible sheets for waterproofing. Determination of shear resistance of joints. Part 2: Plastic and rubber sheets for roof waterproofing, CEN, Brussels, [8] Instituto Português da Qualidade (IPQ), NP EN Flexible sheets for waterproofing. Determination of peel resistance of joints. Part 1: Bitumen sheets for roof waterproofing (in Portuguese), IPQ, Caparica, [9] European Committee for Standardization (CEN), EN Flexible sheets for waterproofing. Determination of peel resistance of joints. Part 2: Plastic and rubber sheets for roof waterproofing, CEN, Brussels, [10] António, D., Rehabilitation of waterproofing coatings in flat roofs. An experimental study on the connection between new and aged membranes, Dissertation to obtain the Master degree in Civil Engineering, IST, Lisbon, [11] Feiteira, J., Liquid applied products based waterproofing systems in flat roofs. An experimental study on the systems mechanical behaviour, Dissertation to obtain the Master degree in Civil Engineering, IST, Lisboa,

15 [12] Union Européenne pour l Agrément technique dans la construction (UEAtc), M.O.A.T. nº 64:2001 Technical Guide for the assessment of roof waterproofing systems made of reinforced APP or SBS polymers modified bitumen sheets, UEAtc, Garston, [13] Union Européenne pour l Agrément technique dans la construction (UEAtc), M.O.A.T. nº 65:2001 Technical Guide for the assessment of non-reinforced, reinforced and/or backed roof waterproofing systems made of PVC, UEAtc, Garston,

Rehabilitation of waterproofing coatings in flat roofs

Rehabilitation of waterproofing coatings in flat roofs An experimental study on the connection between new and aged membranes - Extended Abstract - Diogo Manuel de Oliveira António Supervisors: Researcher