Overview
Concrete repair covers a broad range of interventions — from shallow surface defect rectification (surface scaling, honeycombing, pop-outs) to deep structural patch repairs of spalled columns and beams where reinforcement has corroded through. The common requirement across all these defect types is that a deteriorated concrete section must be removed, the substrate prepared to a sound and clean base, exposed reinforcement treated where present, and the void reinstated with a repair mortar that bonds durably to the parent concrete and matches or exceeds its original structural and durability properties.
Prisci Constructions specifies polymer-modified cementitious repair mortars — from Fosroc's Renderoc range, BASF's MasterEmaco range, Sika's MonoTop range, Pidilite Dr. Fixit, and Sunanda repair products — all pre-bagged, factory-controlled systems with published tensile bond strength, compressive strength, and carbonation resistance data. Site-mixed cement-sand mortars are never used for structural or semi-structural repair; they shrink on curing, debond from the substrate within 2–5 years, and offer no corrosion protection to the reinforcement beneath.
Where carbonation is identified as the underlying cause of corrosion, repair mortar alone is only half the solution. After patching, an anti-carbonation protective coating is applied to all concrete surfaces on the repaired structure — not just the patched areas. This arrests the advancing carbonation front in the surrounding sound concrete and prevents the well-documented "halo effect," where new corrosion initiates in a ring around repairs within 5–10 years of the original work.
Common Problems We Solve
- Concrete spalling from beam soffits, column faces, and slab edges exposing rust-stained, corroded reinforcement bars
- Honeycombing — interconnected voids in structural concrete from inadequate vibration during casting, leaving permeable, weak zones
- Delamination of the concrete cover — sections that sound hollow on tap-testing and are progressively separating from the parent body of concrete
- Surface scaling and aggregate pop-outs on slabs and external facades, reducing cover depth and accelerating carbonation front penetration
- Active cracking with rust staining at crack edges, indicating ongoing rebar corrosion driving further concrete fracture from within
- Construction cold joints and pour lines that never bonded, creating planes of weakness and uncontrolled water ingress paths through the structure
Root Causes
- Carbonation of concrete — atmospheric CO2 reacts with calcium hydroxide, reducing the concrete pH below 9 and depassivating the protective oxide layer on steel reinforcement
- Chloride ingress from coastal environments, industrial process chemicals, or contaminated mix water reaching threshold concentrations at the rebar depth
- Inadequate concrete cover to reinforcement during original construction, allowing carbonation to reach and depassivate the steel within 10–15 years
- Poor original concrete quality — high water-cement ratio, low cement content, or insufficient vibration creating honeycombing and permeable sections
- Mechanical impact or abrasion damage in industrial and heavy-traffic areas exceeding the original concrete's surface wear resistance
- Construction errors — cold joints between pours, premature formwork removal before concrete gains adequate strength, or incorrect reinforcement positioning
Our Approach
A systematic defect survey is completed before any repair work is specified. Visual mapping and tap-testing identify all spalled, hollow, and cracked areas. Carbonation depth is measured on core samples using phenolphthalein indicator. Rebound hammer readings confirm concrete strength. The cause of deterioration is established per defect area before the repair strategy is written.
The repair system is matched to the defect type and depth: thin-bed polymer-modified mortar for surface defects; thixotropic high-build mortar for overhead and vertical spall patching; form-and-pour fluid mortar for deep section reinstatement. Rebar treatment products and the final anti-carbonation protective coating are specified as part of the same repair scope — repair without protection is a short-term intervention.
Concrete removal is taken to a sound substrate confirmed by tap-test and rebound hammer. Reinforcement is cleaned to Sa 2.5 and treated with Fosroc Nitoprime Zincrich before mortar encapsulation. Repair mortar is applied in controlled layers per manufacturer's maximum thickness. On completion, pull-off adhesion tests are conducted and anti-carbonation coating is applied to all concrete surfaces.
Materials Used
Repair mortar selection is based on defect depth, element orientation (vertical, overhead, or horizontal), and required working time. We carry a range of systems across leading manufacturers and select the appropriate product for site conditions on the day of application — not the cheapest option on the price list.
Our Process
Defect Survey and Root-Cause Identification
All defective areas are mapped on an elevation drawing with measured dimensions. Tap-testing extends the survey beyond the visible spall boundary to locate delaminated concrete that has not yet fallen. Carbonation depth is measured on freshly broken core faces using phenolphthalein indicator — the colourless zone confirms the carbonation front depth. Rebound hammer readings are taken across all elements to identify zones of reduced concrete strength. The output is a repair schedule with area quantities, depth classifications, and cause of deterioration per zone.
Concrete Break-Out to Sound Substrate
All delaminated, carbonated, and deteriorated concrete is removed by pneumatic chipping hammer or disc cutter to a sound substrate confirmed by tap-test and rebound hammer. All saw-cut or chipped edges are made perpendicular or slightly undercut — feathered edges are never accepted as they debond under thermal cycling. Where reinforcement is buried, the break-out extends to a minimum 20mm behind the bar to allow the repair mortar to fully encapsulate the rebar. Dust, loose material, and contamination are removed by high-pressure air blast.
Reinforcement Cleaning and Section Loss Assessment
Exposed reinforcement bars are mechanically cleaned to Sa 2.5 (near-white) standard using angle grinder or needle gun to remove all loose scale, active corrosion product, and contamination. Bar diameter is measured with a calliper to quantify section loss. Any bar with section loss exceeding 20% of cross-section is reported to the structural engineer for assessment before repair proceeds — supplementary bars may be required. Flash rusting after cleaning is addressed immediately before mortar application.
Reinforcement Treatment with Nitoprime Zincrich
All cleaned reinforcement is immediately coated with Fosroc Nitoprime Zincrich — a zinc-rich epoxy-modified primer that provides galvanic protection and re-establishes a passive environment around the steel surface. Two brush-applied coats are applied, each allowed to reach the specified touch-dry state before the next. This step is critical for preventing corrosion re-initiation at the repair boundary (the halo effect) and is non-negotiable in our repair specification.
Bonding Agent Application and Repair Mortar Layering
The concrete substrate is pre-wetted to saturated-surface-dry (SSD) condition. Fosroc Nitobond AR cement-based bonding slurry is scrubbed into the substrate and allowed to reach a tacky, not wet, state before mortar is applied. Pre-engineered polymer-modified repair mortar (Fosroc Renderoc LA, BASF MasterEmaco S488, Sika MonoTop-412N, or Sunanda Renu Crete as appropriate) is gauged strictly to the manufacturer's water ratio and applied in layers not exceeding 25mm per lift for hand application, or 50mm for thixotropic grades. Each layer is cross-hatched in the green state before the next lift. The finished surface is tooled flush to the original concrete profile.
Curing, Pull-Off Testing, and Anti-Carbonation Coating
Repaired surfaces are cured under wet hessian or plastic sheeting for a minimum of 7 days. After cure, pull-off adhesion tests are conducted on a sample of patches per IS 13311 — minimum 1.0 MPa acceptance for structural elements. All test results are recorded and submitted to the client. Anti-carbonation elastomeric coating (BASF MasterProtect 8000CI or Fosroc Dekguard Elastic) is then applied in two coats to all concrete surfaces on the structure — repaired and unrepaired — providing a full-surface CO2 barrier to prevent future carbonation-driven corrosion.
Frequently Asked Questions
Related Projects
Concrete Defects on Your Structure?
Our engineers carry out a site assessment and provide a repair specification within 48 hours. Free site visit available for qualifying projects in Hyderabad, Telangana, and Andhra Pradesh.