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Measures for concrete repair and corrosion control

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In the first of the two-part series, Upen Patel, Business Director, BASF India, explained various factors responsible for the corrosion of concrete. In this second and last part, the author explains various components and the materials used to deal with the problem of deterioration of concrete.Once concrete repairs and strengthening was considered as an activity of rejuvenating the old structures and making them capable of loadings and environmental stresses in the future life. Today we are constructing more advanced and ever more-demanding structures with complex detailing and concrete repairs and strengthening starts during the construction stage itself. The complex and fast pace construction methods with reduced emphasis on adequate quality assurance results in to construction errors and creates needs for repairs and strengthening during construction. With the complex performance demands of the new structures and ever longer life expectancies makes concrete repairs, strengthening and protection procedures more and more demanding. This article is an attempt to present the fundamentals of concrete repairs and strengthening in a step-by-step process and focuses on the advantages and disadvantages of current practices and provides an insight in the futuristic but more simple to adopt techniques.Treatments of cracks:The most important criteria for selecting the right material for crack injection is based on the structural status of the crack. Is the crack alive or dormant? This can be checked by monitoring the crack width. If the crack is live, stressed are still like to relieve and hence to avoid further cracking at any other location. It is important to inject and seal the live crack with flexible injection resin such as polyurethane based. The dormant structural cracks can be sealed with epoxy/ polyurethane resins meant for structural bonding. In case if the sealing is only meant for water tightness same can be achieved by injecting with the re-swell able acrylate injection resins. The surface cracks found within the concrete covers can be open, routed and sealed used acrylic sealers as they are superficial nature but needs effective sealing as can leads to other form of corrosion/deterioration. Many hairline cracks formed on the surface of concrete cannot be opened and sealed and can be coated and sealed with high-elongation, flexible acrylic protective coatings instead.Surface preparation for volume replacementsThe surface preparation is a pre-requisite for an effective volume replacement job. Following components explains the surface preparation tasks.??Remove all identified defective concrete??Saw cut perimeters – 15mm depth??Expose steel unit no corrosion is evident??Expose the full circumference of the steel and beyond by 25mm.??Priming of the rebars: Prime immediately after cleaning. Apply a continuous coat of active zinc rich epoxy primer or appropriate corrosion protection system. Attention must be paid to the underside of the bars.??Priming of the concrete: Depending upon the need of the volume replacement materials, apply right primer. In case of chloride contaminated area use epoxy bonding agent.Cosmetic volume replacement:While replacing the concrete volume within the cover is defined as cosmetic repairs. The aim is to replace defective, deteriorated concrete cover with impervious polymer-modified mortar. The most cost effective repair materials are ready to use re-profiling mortars or to use site-batched polymer modified repair mortars with 1:5:15 proportion of polymer: cement: sand. These mortars are not capable of achieving the high compressive strengths but are able to provide effective corrosion barrier at economical costs. As the repair is within the cover zone, it does not have significant barring on the overall strength of the structure. The ready to use re-profiling mortars are shrinkage compensated and have good thixotropy enabling up to 50mm thickness built-ups in single operations; while polymer modified site batched mortars may need multi-layer applications on thick applications.Structural volume replacements:While replacing the volume of the concrete beyond concrete cover, it is very important that the member under repair is relived from the imposed loads by supports. Surface preparation is very important and any negligence may cost the success of the structural repairs. There are many options available for volume replacement such as micro concrete, single components patch repair mortars, two-component patch repair mortars, spray applied micro-concrete, site batched polymer modified mortars, self compacting concrete, shotcrete, pre-places aggregate concrete. Large volume concrete repairs can be conducted using self-compacting concrete, shotcrete or pre-placed aggregate concrete provided the interface between new and old concrete is taken care properly. Generally in India the 1st choice for volume replacement remains as form and pour micro-concrete while spray applied micro-concrete is very popular internationally due to reduced need for shuttering and ready availability of spray applied micro-concretes. Patch repair mortars if need to be used must be ready to use, one component type with fibre modification to avoid chances of cracking. Products like two-component polymer modified mortars and site-batched polymer modified mortars known for their low compressive strengths and can not be used to repair high grade concrete. In most parts of India, it’s not practical to produce site-batched polymer modified mortars with >M20 grade compressive strengths due to limitation of local fine aggregate gradation! If such low strength mortars are used to replace concrete, it leads to higher stress concentration on the rest of the structure resulting in to further distress and deterioration.Special application:Application such as under water, chemical exposures, pavement repairs, and abrasion/impact damage as well as heritage restorations requires additional considerations while repairs and now many specialized products are available for such applications some of them are summarized as below:Underwater repairs??Micro-concrete: Emaco S46UW – Anti-washout grout??Patch repair mortar: Emaco S90 – Thixotropic patching mortar??Crack injection resins: Concresive 1316 – Water insensitive resin??Re-profilinfsealing mortar – Subcote S – Resin basedChemical resistance situation??Epoxy concrete – Concresive 2929??Patch repair mortar – Concresive ERL – Epoxy liner??Re-profiling / sealing mortar – Concresive 2200 – Resin basedPavement repairs??Patch repair mortar – Emaco R650 – Rapid hardening cementitious??Re-profiling mortar – Concresive 1418T- Rapid hardening, resinousCorrosion controlWhile repairing the deteriorated structure it’s of utmost importance to prevent the rest of sound structure from getting deteriorated by implementing proper corrosion control measures. There are various options available the right selection needs to be based on the need of the situation and the practically of the options. Following is the basic introduction with the advantages and disadvantages of some of the most popular option:Film forming coatings – Acrylics and resin based coatings??Limited life expectancy (5-10 years)??Limited crack bridging limits performance on cracked substrate??No passivation of corroding reinforcementMigrated corrosion inhibitors – surface applied method??Easy to use??Effectiveness depends on chemical types and concrete porosity??Not effective against carbonation, sulphates, ASRCathodic protection – impress current method??Good life expectancy (>20 years)??Very expensive??Destructive, slow and time consuming??High application skills required??Power breakdown can disrupt the protection??No protection against carbonation, sulphate, ASR attacksCathodic protection – Impress current method??Low to medium life expectancy (5 – 10 years)??Destructive method, requires replacements in future??Lump-sum application, design guidelines not followed??Not practical in heavy reinforced members??Corrosion continues; instead of steel embedded zinc corrodes??Not effective against carbonation, sulphates, ASR.Protectosil CIT – Organo-functional silane based system??Spray applied – easy to use??Organo functional silane based – deep penetrative??Monomer structure – chemically reacts, no degradation in UV??Corrosion inhibition effect – repassivates rebar??Effective in all four types of corrosion as it hydrophobize concrete??Well-established and tested worldwide??Non destructive method??Measurable reduction of corrosion current??Effective till treated concrete thickness lasts!Other important aspects of repairsWhile right diagnosis and selection of materials is the core of the repair project; other aspects such as preparation of drawings and specifications, selection of right contractor, execution of the work to the specifications, adequate quality control are equally important. Repair project is more specialised and good site management and construction practices have to be followed. Also at the end of the job all the records relating to the diagnosis, material selection and execution of the work shall be maintained and preserved for any reference needs in future.Conclusion:With the right focus on the causes, evaluation and selection of correct repair materials; the resultant repairs would be long lasting and we would be able to avoid expensive repetitions of repairs in the future.(Extract from the paper presented by the author at the Construction Chemicals International Conference 2012 held in Mumbai)

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Concrete

ACC launches ‘Bagcrete’, a pre-blended concrete solution

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The company’s ongoing innovation process is consistent with ACC Bagcrete

ACC, the cement and building material company of Adani Cement and part of the Adani Group, has been a pioneer in building innovative concrete solutions. The company’s ongoing innovation process is consistent with ACC Bagcrete, a proportional balance of premium components produced to generate high-quality concrete mix.

The company has added a new product dimension to the building industry with ACC Bagcrete, a hassle-free, smart, and user-friendly concrete solution for all types of construction demands. A stronger, more durable final product is produced as a result of the pre-blended components being meticulously measured to ensure uniform quality.

The product was created to offer the best compressive strength (10 MPa to 80 MPa), exceptional workability retention, and unmatched ease of placement, a trifecta of attributes that set it apart from competing products. In contrast to traditional concrete, which necessitates the mixing of various components on-site, it is a pre-blended mixture of cement, sand, and aggregates. For building projects that call for a quick and effective application method, ACC Bagcrete is ideal.

There are two functional variants of the versatile building material ACC Bagcrete: dry-mix and wet-mix. The dry-mix is pre-blended concrete that may be used right away with just the addition of water. wet-mix is pre-mixed, immediately usable concrete that doesn’t require any additional mixing before use. This can be especially helpful in places with scarce water supplies or where conventional concrete mixing techniques are impractical. Both kinds of ACC Bagcrete are of exceptional quality and effectiveness. This unique concrete solution is ideal for remote job sites and maintenance projects since it can be easily transported in the form of bags, enhancing productivity.

Ajay Kapur, CEO, Cement Business, said “We are dedicated to pursuing product innovations and offering the finest products and services to our customers. We have always strived to create products of the highest calibre in order to meet the varied needs of our customers and assist them in constructing robust structures. ACC Bagcrete is a unique product that not only meets but also exceeds the demands of our customers.”

The prestigious university IIT Bombay has recently reaped significant benefits of using ACC Bagcrete for a special need in its R&D Lab of Civil Engineering Department. The M80 Grade ACC Bagcreate has also been used in various NHPC projects in spillway repair. ACC Bagcrete is a unique solution that guarantees minimal waste, accelerates construction, and improves longevity with constant quality. In conclusion, dry-mix concrete is a versatile and convenient option for construction projects of all types.

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Concrete

Ambuja Cements’ loyalty programme wins top award

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Has been awarded as the ‘Most Innovative Loyalty Programme of the Year’

Ambuja Cements, the cement and building materials company of Adani Cement and part of Adani Group, has been awarded the ‘Most Innovative Loyalty Programme of the Year’ at the Customer Fest Leadership Awards 2023 for its Contractor Loyalty Programme – ‘Ambuja Abhimaan’. This award acknowledges the Company’s exceptional efforts in creating and maintaining an outstanding loyalty programme that has helped build strong relationships with its contractor partners.

The evaluation of nominations was conducted by an eminent jury panel of experts, and Ambuja’s innovative and transformational initiatives such as skill upgradation programmes, family engagement and social welfare, talent hunt contests, and business aid to contractors were highlighted. These initiatives differentiated Ambuja from competitors and helped win the award under the Customer Loyalty – Organisational category. The event featured more than 50+ renowned brands across various industries.

Ajay Kapur, CEO, Cement Business, said, “Ambuja has always been synonymous with strength, and we are honoured to be recognised for our strong commitment and efforts that go beyond cement. This award is a testament to our commitment to delivering exceptional experiences to our partners and customers. We thank the jury panel and all the participants for acknowledging our efforts towards customer centricity and innovation.”

Ambuja Abhimaan, a differentiated long-term loyalty programme has achieved many milestones, including recognition as one of the best mobile loyalty programmes, engaging and benefiting 1.2 lakh+ key contractors.

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Concrete

Ambuja places order for capacity expansion of 14 MT cement

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This will enable the production of blended green cement of 14 MT

Ambuja Cements, the cement and building material company of the diversified Adani Group, placed orders to expand clinker capacity by 8 million tonne at Bhatapara and Maratha units on the highest ESG standards with 42 MW of WHRS, provision to utilise 50% AFR and provision to operate on green power.

The capacity expansion projects will enable the production of blended green cement of 14 million tonne, post all requisite approvals. These projects will generate substantial value for the existing business and enable more employment and growth opportunities in the States, beneficial for all stakeholders.

These projects are expected to be commissioned in 24 months and the capex will be funded from internal accruals.

Ajay Kapur, CEO, Cement Business, said, “These brownfield expansion projects are part of our strategy to double our production capacity over the next five years from the current capacity of 67.5 MTPA. Our ongoing investments in capacity expansion and sustainability will enable us to achieve our long-term objectives, as we remain committed to delivering sustainable growth and value to our stakeholders.”

The Company remains committed to achieving significant size, scale, and market leadership with a strong emphasis on margin expansion and world-class ESG standards.

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