The environmental impact of service life-extending repair for corrosion damaged reinforced concrete balconies: a case study in a coastal context

. Nowadays a vast number of concrete structures are approaching the end of their expected service life. The need for sustainable rehabilitation (maintenance and repair) is urgent and due to the expected deterioration of buildings and civil structures, there will be a great need for preventive and/or curative interventions in the near future. More than 2/3 of the damage to reinforced concrete structures is linked to reinforcement corrosion, which can affect the durability of the structure and the residual load-bearing capacity. With the necessary transition towards a circular economy and the Sustainable Development Goals in mind, it is important to deviate from considering only the technical requirements and initial costs during the design of concrete structures. Hence, the environmental impact over the entire life cycle and the intended service life extension need to be considered as well. A typical residential building in a Belgian coastal environment with damaged reinforced concrete balconies is selected as case study to evaluate different frequently used repair techniques (i.e. patch repair, conventional repair, galvanic cathodic protection, impressed current cathodic protection and total replacement) by means of a life cycle assessment. Several sensitivities are mapped by analysing the influence of the intended service life extension, the volume and configuration of the construction, the repair mortar composition and the application of coating/waterproofing. It was stressed that these uncertainties could have a substantial effect on the environmental impact and highlight the domains where further research is needed (e.g. assumed life span and composition of repairs). Due to this manner, it is not possible to identify one environmental optimal repair method. However, for a short service life extension (e.g. 5y) small interventions like patch repair seem to be more sustainable while methods like cathodic protection and conventional repair are preferable for longer service life extensions (e.g. 40y).


Introduction
Due to a peak in the construction of reinforced concrete (RC) structures in the 1960s and 70s, the number of concrete structures in need of repair actions is increasing at a fast pace.Not only because they have already surpassed their initial estimated technical life span but also because they had started showing deterioration signs in many cases after several decades.This is also illustrated by an increasing number of failures, demonstrated by frequent occurring news articles [1][2][3].Such damage can be addressed through concrete repair by which substantial service life extensions of damaged concrete structures can establish but at what environmental cost?More than 2/3 of the damage to RC structures is in a way related to corrosion of the reinforcement [4].It can be induced by carbonation of the surrounding cementitious matrix and/or chloride ingress.In coastal environments, the latter is the most dominant damage cause.Corrosion affects the durability of RC structures and in a well-advanced stage, it is usually manifested in the form of (i) cracking and spalling of the concrete cover caused by the larger volume of the corrosion products and (ii) reduction of the cross-section of the rebars resulting in a reduced carrying capacity of the element.By uniform (due to carbonation) or local (pitting corrosion initiated by chlorides) corrosion, the structural safety (SS) can be affected.This severe corrosion is caused by damaging the concrete cover which is one of the most protective mechanisms against exposure conditions (water, O 2 , CO 2 & other aggressive effects).
To deal with damaged concrete structures, either the entire construction is demolished and reconstructed, or the damaged part is repaired.Additionally preventive actions (e.g.coatings) can be undertaken to prolong the residual service life.With regards to the repair, many different options to prevent or stop the corrosion process are available.However, to narrow the scope, five frequently used repair techniques are selected and analysed in this study: (i) patch repair (PR), (ii) conventional repair (CR), two electrochemical treatments to stop the corrosion process: (iii) galvanic cathodic protection (GCP) and (iv) impressed current cathodic protection (ICCP) and (v) total replacement of the element (NEW).According to Krishnan et al. [5] the halo effect and residual chloride effect limit the service life extension of patch repair to five MATEC Web of Conferences 364, 04024 (2022) https://doi.org/10.1051/matecconf/202236404024ICCRRR 2022 years, leading to additional major repair after this period due to continued corrosion.For conventional repair, a service life extension of 20 years can be reached and is believed to be a realistic target [6].With respect to cathodic protection (CP), Van den Hondel and van den Hondel [7] concluded that life time extensions of 15-20 years (and maybe even more) may be well achievable.Moreover, according to Wilson et al. [8] and Krishnan et al. [5], galvanic cathodic protection should be the most suitable for small and targeted repairs, repairs where budget costs are limited and repairs where the life expectancy has to be around 10-14 years.Besides, impressed current cathodic protection is generally used to treat significant corrosion problems at large structures and surface areas, where the life expectancy should be more than 25 years.
Both strategies, reconstruction and repair, have different environmental consequences.The first option is a more material intensive solution, inducing the need for more cementitious materials (mortar, concrete) and generating waste streams.This might not be the optimal solution from an environmental point of view, given the large environmental impact of cement and concrete production.Current climate objectives and the need for a transition towards a more sustainable and circular economy (CE) scream for more attention about the environmental impact of products, processes and services.Repair and refurbishing strategies can address these issues, confirmed by Ferreira et al. [9] who showed that refurbishment is environmentally beneficial compared to a new equivalent construction.Moreover, repair and rehabilitation become even more important because climate change is stated to have a big impact on corrosion acceleration and the degradation of RC structures in the future [10].In addition, the construction sector can be considered as one of the key actors in the global stage of sustainability, according to Maxineasa and Taranu [11].Also the selection of sustainable repair and rehabilitation systems to reduce the environmental impacts of concrete structures could have a high value [12].However, before conclusions on environmental performance can be drawn, a quantitative assessment is needed, for example by means of life cycle assessment (LCA).
LCA is a method which creates opportunities with regards to well-informed decision making for optimization of the environmental performance of products, processes and services over a life cycle perspective.However, very limited research has been done about the sustainability assessment of concrete repair techniques.In general, there is a lack of LCA results of service life-extending concrete maintenance and repair.This is confirmed by Palacios-Munoz et al. [13] who mentioned that most of the literature on LCA focuses on new construction while refurbishment is dealt with a lower extent.In addition, Vilches et al. [14] mention that most LCAs of buildings focus on energy refurbishment, while there are almost no LCA studies that consider the environmental impact of building system reparations.
A limited amount of studies were found that environmentally compare different repair methods for RC structures.Firstly, Andrade and Izquierdo [15] rated five techniques for RC structures in general from less to most beneficial in the following order: electrochemical treatment -inhibitors -cathodic protection -hydrophobic agents -patching.In contrast, Årskog et al. [16] rated generally hydrophobic treatment before patch repair in a comparison between the two.For bridges, the following order was obtained by Navarro et al. [17]: stainless steelgalvanized steel -organic inhibitor -migratory inhibitor -ICCP -sealant product -hydrophobic treatment.Another study by Habert et al. [18] concluded the sequence of conventional repair after an ultra-high-performance fiber RC solution.Lastly, Wittocx et al. [6] determined the environmental impact of five repair options for three service life extensions of balconies (i.e. 5, 20, 40 y.).For a short service life extension patch repair was indicated as the most beneficial.For 20 and 40 years, a change was seen to conventional repair and GCP before ICCP.Demolition and rebuilding was found to be a bad option environmentally speaking.The existing studies treat a variety of repair methods for different constructions, making it challenging to compare results.One must be aware of the fact that LCA studies on rehabilitation and repair of concrete structures are strongly case dependant.
In this paper, the knowledge gap of the environmental assessment (LCA) of RC repair strategies will be tackled.More particular, the goal is to estimate the environmental impact of five different repair technologies for corrosiondamaged reinforced concrete balconies, given that the deterioration diagnosis and damage assessment are already done adequately on beforehand.Three service life extensions of 5, 20 or 40 years are evaluated by means of LCA.In an earlier case study, a residential building with 15 balconies (20mx1m) was evaluated (30 m³ concrete in total) [6].For comparison, a smaller residential building with 20 separated balconies (2mx1m) is now analysed (4 m³ concrete in total).In this manner, the effect of another balcony configuration can be analysed because, in particular, more balconies are needed for the same balcony area resulting in a higher share of edges.More insights are received about the environmental impact characteristics of concrete repair and which method is preferred above the other ones.This can be useful for repair selection in practice considering the necessary transition towards a sustainable economy.Additionally, other sensitivities are investigated to address the strong and weakly influential parameters: (i) the volume and configuration of the to be repaired construction, (ii) the influence of the intended service life extension, (iii) the repair mortar composition and (iv) the composition and application of coating/waterproofing.

Research methods
The consequential methodology is followed in this LCA study, so the change to environmentally relevant flows is described as a response to possible decisions.It is assumed that the corrosion process has not yet corroded the reinforcing steel rebars of the cantilevered element to a degree in which the bearing capacity is no longer guaranteed.The initiation phase is reached and propagation of corrosion already started, however without affecting the load bearing capacity of the cantilevered balconies yet.The condition will be evaluated based on the Dutch Standard NEN 2767 [19], with a condition score 1 as target for the repair.This means only incidental minor imperfections are accepted.Due to the different intended service life extensions (i.e. 5, 20 and 40 y.), multiple functional units (FU) are evaluated.Therefore, the FU can be described as: "the service life extension of 20 cantilevered reinforced concrete to excellent condition for an additional lifetime extension of 5, 20 and 40 years.The balconies have the following properties: 1 m x 2 m × 0.1 m (length x width x height) and are reinforced with a double steel mesh 8/8/150/150 mm".As a more technical approach on concrete repair is intended, other aspects such as renewal of the railing, renewal finishing top of the balcony, insulation of the façade, etc. are not considered in this study.
Due to the limited protecting concrete cover, the high exposure to outdoor conditions and the high social impact of failure, concrete balconies are selected as a case study.Based on the information of an existing building, a simulated residential building situated near the Belgian coastline (saline environment) is selected for the evaluation.The building has 10 floors with 2 individual balconies on each floor, which result for the balconies in 4 m³ total concrete volume, 88 m² of exposed concrete surface and approximately 556 kg of steel reinforcement (Figure 1).Moreover, the finishing consists of a levelling layer of 2,5 cm and ceramic tiles.When the former is removed due to the repair it is replaced by a concrete screed.For the main scenario, the residential building is analysed for the three FUs (i.e. 5, 20 and 40 y.) and for the five repair methods (i.e.PR, CR, GCP, ICCP and NEW).The techniques, selected materials and execution methods are chosen according to the principles of EN 1504-9 (2008) in order to fulfil the technical requirements [20].The potential of the repair methods to extend the service life is based on experience of professionals in concrete repair (repair contractors, suppliers of repair products, architect offices, investigation bureaus, etc.) in the Belgian context and supported by expert judgement [6].An overview of the potential service life extension, the performed activities and the maintenance strategy for the different repair techniques is shown in Table 1.Importantly, at all repair scenarios, a protective coating is provided on the underside and edges of the balconies.This assumption was made to keep the finish level the same for the various options.The assumptions of Table 1 are made based on previous research [6].Furthermore, based on some identified uncertainties of this research, several sensitivity analyses are performed.Furthermore, a schematical overview of the life cycle of each repair is shown in Figure 2.For PR, the transition to a lighter colour means the execution of the same repair again as intervention 1, including exactly the same activities.For CR, GCP and ICCP, the transition means the execution of a 'big' intervention, which can be seen in the footnote of Table 1.Lastly, the volume of concrete (in %) that is removed at each intervention is shown below the bar of each repair.The ecoinvent database v3.5 (consequential system model) was used to model background processes and its principle of marginal supplier identification.For materials or processes for which no ecoinvent records were available, an approximation is made based on expert judgements, literature and available proxy records in the database.Moreover, the ReCiPe 2016 v1.04 method was applied.This method implements both midpoint (problem-oriented) and endpoint (damage-oriented) categories and contains a set of weighting factors allowing the calculation of a single score impact.Endpoint results are easier to understand, but tend to be less transparent and more subjective [21].This study takes both endpoints and midpoints into account.Similar trends are found for the midpoint indicators compared with the endpoint results.However, for several midpoints (e.g.ionizing radiation, freshwater eutrophication, marine eutrophication, terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity, human non-carcinogenic toxicity, land use, mineral resource scarcity, and water use consumption) widely varying outcomes are achieved.Only the endpoint impact is presented in this manuscript because a detailed analysis of the midpoints is beyond the scope.Full details can be found in the annex/supplementary information.

Sensitivity analysis
In order to investigate some uncertainties of previous research four sensitivity analyses (SA) are performed.In the first one (SA 1) the influence of the balcony configuration and volume of the to be repaired construction is investigated.SA 2 determines the influence of the intended service life extension.Furthermore, at SA 3, the repair mortar composition and the effect on the environmental cost are examined.Lastly, SA 4 investigates the consequence of the coating/ waterproofing composition and utilization

SA 1
In this SA the reference scenario (20 individual balconies: 2,0 m edges/m² balcony area) is compared with a much bigger building (15 continuous balconies: 1,1 m edges/m² balcony area).In this manner, the influence of the configuration (continuous vs separated balconies) on the environmental performance of the repairs is determined.Continuous balconies have in percentage fewer edges, so less concrete coating is needed.In addition, at CR fewer sides are taken into account as balcony nose that needs to be repaired.The biggest effect is expected at ICCP because the number of electronic components is not linearly increasing together with the volume of concrete per balcony.The ranking of repair methods based on their environmental impact can therefore change at the big building (BB).

SA 2
Previously, the assumed service life extension is set based on expert judgement.However, literature reports often other values.A first difference is noticed for GCP where a service life of 10-14 years was found [5,8].In addition, a service life of 5 years was proposed by Krishnan et al. [5] for PR due to the high possibility of damage within this period.In order to the effect of these service life reductions, a sensitivity analysis is performed with a service life extension of 5 and 14 years for PR and GCP respectively.

SA 3
Due to the lack of data, the composition of repair mortars is not generally known because suppliers won't give detailed information about their products.The most influencing factor is the amount of repair mortar, so therefore three mortars with different Portland cement content are investigated: 800 (reference), 700 and 900 kg cement/m³ repair mortar.

SA 4
The biggest impact is contributed by the finishing; i.e. coating, screed, primer, waterproofing and reinforcement mat.Wittocx et al. [6] highlighted the importance of the finishing which has a contribution of 33 to 61% to the total life cycle impact.The coating and waterproofing in the main scenario are assumed to be composed out of polyurethane.This exists out of a hard (e.g.toluene diisocyanate) and a soft (e.g.polyol) segment [22].However, the exact contribution is not known due to lack of data (sensitive information of the suppliers).Therefore, the assumed composition from Wittocx et al. [6] is changed.For the coating and waterproofing based on polyurethane, the effect of a reduced amount of hard segment is investigated.The hard segment content is reduced from 21 % to 18 % for the coating and from 30 % to 25 % for the waterproofing.Furthermore, the effect of an acrylate based concrete coating instead of a polyurethane based one is also determined.Lastly, the influence of no coating for GCP and ICCP (only a conductive coating for ICCP) is also analysed.It can be assumed that a coating is not necessary to protect the reinforcement against corrosion when a system with cathodic protection is used.

Results and discussion
In this section, the results of the study are shown.First, the results from the LCA study of the main scenario are discussed.After this, the sensitivity analyses are analysed.

Main scenario
The contribution of the four life cycle phases to the environmental impact at a service life extension of 40 years (besides PR: 20 y.) is shown in Figure 3.It can be seen that overall the finishing (see Table 1) involves the highest impact.Only at the ICCP scenario, the steel protecting actions impact is higher than this of the finishing.The figure is very useful to indicate in which areas of the life cycle improvements could or could barely be made.Therefore, for PR and CR the most progress is possible at the finishing followed by the concrete repair.Moreover, this is first the finishing followed by the steel protecting actions for GCP.This is the same for ICCP but in the opposite order.At the scenario NEW the finishing has again the highest improvement potential, closely followed by concrete repair with 27 %.In Figure 4, the cumulative impact of the main scenario is shown on a timeline which shows when an impact occurs as a result of an intervention.For FU 1 and 2, PR is the most environmentally friendly option with a total impact of 22 Pt and 98 Pt respectively.For a short service life extension (i.e. 5 y.), it can be seen that the other techniques are much more costly regarding the environmental impact (4,53 to 8,35 times higher).This can be explained by the low labour intensity of PR in comparison with the other repairs.Nevertheless, for FU 2, GCP has an impact of 100 Pt which is really close to this of PR.This makes it also a valuable option for a service life extension of 20 years.Certainly when the multiple disturbances of PR are considered.Further on, GCP is closely followed by CR with a value of 110 Pt.ICCP and NEW have a much higher impact of 178 Pt and 198 Pt respectively.For FU 3, CR is expected to have the lowest environmental cost of 136 Pt, followed by GCP with 152 Pt.Again, ICCP and NEW have an extra impact of respectively 66 % and 118 % compared to CR.This implies that, environmentally speaking, ICCP or NEW should not be chosen as repair technique for a service life extension from 1 to 40 years.The extremely high impact of ICCP can be explained by the high need of electronic components due to the high number of small balconies which makes this method inappropriate for this type of configuration/small building.Lastly, it is important to consider the additional impact for a service life extension from 20 to 40 years.For the scenario NEW, CR, GCP and ICCP is this respectively 14 %, 24 %, 52 % and 66 % with respect to their own impact at year 20.How smaller the percentage, how smaller the extra environmental cost to extent the RC structures for again 20 years.It shows where the big maintenance intervention has a low or high impact relative to the total service life and so also where or not improvements are possible at this stage.

SA 1
The same trends as in the reference scenario can be seen for all the FU's at a much bigger building (15 continuous balconies, 30 m³ of restored concrete) in Figure 5. PR is again the most optimal repair with an impact of 157 Pt for FU 1 and 771 Pt for FU 2. However, the order of CR and GCP switched, and their impact is really close to this of PR with 715 Pt and 738 Pt respectively.The reason that CR is now more environmentally friendly than GCP is due to the continuous configuration.Due to this manner, fewer edges are present so fewer meter balcony noses need to be repaired.In addition, ICCP becomes more advantageable towards the other repair scenarios (expect NEW) for FU 2 with a value of 775 Pt.Moreover, for FU 3, ICCP becomes the second most optimal option after CR.This scale-effect can be explained by the non-linearly increase in components for the ICCP-system.A much lower number of electric components per m² of balcony due to the continuous balconies and the need for also one router for the whole project result in a lower environmental impact/m² of balcony.To conclude, CR is expected to be the most environmentally friendly repair option for a service life extension of 40 years.Compared due to the results of Wittocx et al [6], some of the results of SA 1 are unexpected.In their paper, the same building is analysed but gives another ranking for the environmental costs at the different FU's.The difference in the magnitude of the values can first be explained by the different normalization/weighting sets of the ReCiPe method.They used ReCiPe 2008 v1.13 while in this paper ReCiPe 2016 v1.04 is used.However, it should be expected that more or less the same results (ranking of repair strategies) are received.The most likely explanation is the difference in the composition of the repair mortar.When with the composition of Wittocx et al. [6] the amount of Portland cement per m³ mortar is calculated, a value of above 1000 kg/m³ is obtained while a value of 800 kg/m³ was opted.Therefore, it can be concluded that at the study of Wittocx et al. [6] a too high cement content was considered causing a much higher impact due to the frequent use of mortar.

SA 2
In the second sensitivity analysis, the influence of the reduction of the service life for PR from 7 to 5 years and for GCP from 20 to 14 years, is analysed.A visualisation of the cumulative impact is shown in Figure 6.For FU 1, it is obvious that the same sequence is maintained because the changes have no influence on a service life extension until 5 y.Regarding the other FU's some changes are visible.First, only the change for PR is assumed.In this case, PR becomes the third worst repair option for FU 2 with an impact of 145 Pt (48 % higher).So for a service life extension of 20 years, it is advised to perform CR or thereafter GCP (in the case of a life span of 20 y.).However, when a service life extension of 14 years is assumed for GCP, it becomes the third worst option while it was at the main scenario the second (and almost the first) one.Moreover, the service life reduction has also a significant effect on FU 3 by which CR becomes clearly the most environmentally friendly option.Lastly, it can be concluded that until an extension of 12 years, PR repair should be applied.For a longer period until 20 years, GCP is the best option if a life span of 20 years can be guaranteed.If not (so 14 years instead), CR is better to apply.For FU 3, CR remains in all cases the best option.

SA 3
The effect of the cement content variation for the applied repair mortar is shown in Figure 7.Only the cumulative impact of PR is visualized because at this repair the mortar usage has by far the highest contribution to the environmental impact (i.e.40 %).During the life cycle extension of 20 years, a total of 2378 kg R4 repair mortar (800 kg cement/m³ mortar) is used at PR, while the next highest amount 952 kg is for CR (i.e. 29 % of impact).Therefore, the biggest effect can be seen at the PR scenario.As can be seen in the figure, the effect of the cement content is rather small by which the order of optimal repair will not change rapidly.However, when the magnitudes of the impact are considered for FU 2 which is 98, 95 and 101 Pt for 800, 700 and 900 kg cement/kg mortar respectively, it can be concluded that with the latter PR repair goes over GCP which has still a value of 100 Pt with 900 kg cement/m³ mortar.Due to the change of a higher cement content, the impact of PR rises for about 2,74 % while this is only 0,36 % for GCP.So, only where the difference of impact between these repairs is lower than 2,38 %, the ranking can change.Due to the difference of 2 %, the impact of PR becomes higher than GCP for the main scenario.When the big building is considered (SA 1), the percentage for PR rises to 2,84 % due to the higher cement content.The next favourable repair is CR which has an increase of 0,57 % with 900 kg/m³.A difference of max 2,27 % is here possible.With the impact of 711 Pt and 715 Pt respectively, the ranking of most favourable option will not change at the BB.Therefore, it can be stated that the influence of the cement content is rather small and only an order change is possible when the impacts are close to each other.Nevertheless, more variations of the composition of repair mortars are possible (e.g.type and amount of chemicals) and could be investigated.

SA 4
In the last sensitivity analysis, the effect of the application and the composition of concrete coating and/or waterproofing is investigated.First, the influence of a change in composition (15 % less hard segment) of the concrete coating and waterproofing is analysed.The cumulative impact can be seen in Figure 8.The effect of the different compositions can be indicated as very small.The sequence from the lowest to the highest increase for the environmental impact compared to the main scenario for FU 2 is as follows: ICCP, New, PR, CR and GCP with a value of 0,29 %; 0,31 %; 0,33 %; 0,47 % and 0,69 % respectively.For FU 3, the values are similar but some changes for the 2 nd decimal are present.However, overall it can be concluded that small changes in the composition have not a significant effect while high amounts are used (coating: 43,2 kg and waterproofing: 114,4 kg).Secondly, the effect of an acylate based coating instead of a polyurethane based coating can be seen in Figure 9.While the impact goes from 0,201 Pt/kg to 0,169 Pt/kg (instead to 0,198 Pt/kg at the first part of SA4), still no big changes can be seen.The environmental impact decreases obviously but the order of the most favourable repair stays the same.Nevertheless, the impact of PR FU 2 with an acylate coating decreases with 4,19 %.For example, GCP is the next one with a decrease of 1,55 %.For FU 3 has NEW the highest gain of 2,44 %.Therefore, a reasonable effect can be achieved by the use of an acrylate coating instead of a polyurethane one.Lastly, the consequence when no coating is applied at the GCP and ICCP scenario is evaluated.As can be seen in Figure 10, it has a significant effect.Besides for FU 1, GCP becomes generally the most beneficial repair method.In addition, the impact of ICCP experiences a big decrease of 9,20 % for FU 3.However, it remains still the scenario with the biggest environmental impact.Even a decrease of 18,11 % is observed for GCP at FU 3.For FU 2 (or FU 1), the reductions are smaller with a value of 13,80 % for GCP and 7,62 % for ICCP.To conclude, the application of coating has a significant impact and big volume repairs result in a high impact reduction, in percentage but certainly in absolute values.

Conclusion
Sustainable repair of the existing damaged building stock is a key factor for reducing the environmental impact during the total service life.In order to assess this impact, a quantitative tool named LCA can be used for evaluating and comparing different repair techniques and facilitating the decision making.In this paper, a residential building in a Belgian coastal environment with 20 damaged reinforced concrete balconies (4 m³ and 88 m² exposed surface) is selected as case study.As corrosion is responsible for more than 2/3 of the concrete damage, corrosion is assumed as the damage cause.Five frequently used repairs are considered for the evaluation through LCA: (i) patch repair, (ii) conventional repair, (iii) galvanic cathodic protection, (iv) impressed current cathodic protection and (v) total replacement of the element.The environmental friendliness is evaluated for three service life extensions (i.e. 5, 20 and 40 years).
For a service life extension of 5 years, PR is by far the preferred option to pick.However, for an extension of 20 years, the interpretation is less straight forward.In this case, PR is still the favourable option, but GCP is really close to this with only 1,7 Pt difference.Thirdly, CR is indicated as the best one for a service life extension of 40 years.Total replacement (NEW) is found to have the highest impact in all cases.Moreover, it could also be concluded that ICCP is not environmentally effective in the case of small buildings with many loose elements.This is, among other things, the reason why four alternative scenarios were investigated: the influence of the intended service life extension, the volume and configuration of the to be repaired construction, the repair mortar composition and the composition and application of coating/waterproofing.
Further research is needed about the composition of repair materials such as repair mortar and coatings.In this paper, a small effect was seen due to small variations in the content.However, specific chemicals could have a considerable impact.In addition, more research can be done about the service life extension of repairs by which the highest effect on the environmental cost was determined.
To conclude, it is not possible to generalize the conclusions of this study due to the case-dependency.Nonetheless, this comparison was made with a previous case study analysing a much bigger building and to some extent similar conclusion could be drawn.

Figure 1 .
Figure 1.(a) example existing residential apartment building, (b) case study simplification

Figure 2 .
Figure 2. Schematical overview life cycle repair methods for 3 FUs

Figure 3 .
Figure 3. Environmental impact per life cycle phase for PR (FU2) and CR, GCP, ICCP and NEW (FU3), *: not a repair action but new reinforcement placement

Figure 7 .
Figure 7. Cumulative total impact SA3 at PR for FU1 and FU2