Overview
Injection grouting involves drilling ports at calculated intervals along a crack or at the face of a void-affected area, then pumping liquid grout material under controlled pressure. The material penetrates hairline cracks down to 0.1mm width that no surface coating can reach, cures in place, and either seals water pathways (polyurethane foam) or restores structural monolithicity (epoxy resin).
Prisci Constructions uses three primary injection materials depending on the application: hydrophilic polyurethane foam for active water-bearing cracks (reacts with water to expand and seal the crack); rigid epoxy resin for structural crack repair where tensile strength recovery is needed; and cementitious micro-fine grout for void filling in masonry and behind shotcrete linings.
We have deployed injection grouting on defence structures in Secunderabad Cantonment (including bomb shelters and underground facilities), HPCL tank foundations, and water retaining structures across Telangana and Andhra Pradesh.
Common Problems We Solve
- Active water gushing or dripping through cracks in basement walls, retaining walls, or tunnels
- Structural cracks in columns, beams, or slabs requiring watertight and load-carrying repair
- Hollow-sounding areas behind wall plaster or behind concrete lining indicating voids in the substrate
- Seepage through construction joints in water retaining structures, tanks, and sumps
- Water entry through cold joints in RCC slabs and walls where pour sequences were not properly treated
- Delaminated shotcrete or plaster with voids behind — grout injection pins the layer back to the substrate
Root Causes
- Structural cracks from overloading, differential settlement, or shrinkage providing open water pathways through the section
- Construction cold joints in multi-pour structures left without waterstop or inadequately bonded
- Honeycombing in concrete from inadequate vibration during casting — open voids connected to water-bearing soil
- Corrosion-induced cracking where rebar rust expansion has split the concrete cover, allowing direct water ingress
- Earthquake or dynamic load-induced cracking in previously sound structures reopening dormant crack planes
- Chemical attack (sulphate or chloride) dissolving cement paste and creating permeable pathways in the concrete matrix
Our Approach
Crack width is measured with an optical crack gauge. Flow rate of active seepage is estimated. Ground penetrating radar (GPR) or impulse hammer testing identifies void locations and extents. We determine whether the crack is dormant (epoxy) or live (PU foam) and whether structural repair is also needed.
Port spacing, drill angle, and depth are calculated based on element thickness and crack geometry. Injection material is selected (PU foam, flexible PU resin, rigid epoxy, or micro-fine cement). Injection sequence (low-to-high for waterproofing, end-to-end for structural) is designed before drilling commences.
Ports are drilled, packers seated, and injection proceeds under controlled pressure with visual monitoring at adjacent ports to confirm material travel. On completion, ports are sealed flush with repair mortar and surface crack is routed and sealed. Post-injection inspection confirms leak arrest.
Materials Used
Injection material selection is the most critical engineering decision in grouting — the wrong material in the wrong application will fail; we specify based on crack activity, water presence, required strength, and element type.
Our Process
Crack Mapping & Port Layout
All cracks and seepage points are mapped on an elevation drawing. Port positions are marked at calculated spacings (typically 150–300mm centres, drilled at 45° angle to intersect the crack midpoint through the section thickness). For voids, hammer sounding identifies the hollow zone boundary.
Drilling & Packer Installation
10mm or 13mm holes are drilled to the calculated depth using a rotary hammer drill. Rubber injection packers with one-way valves are installed and hand-tightened. Drill dust is removed from each port with compressed air before packer seating to ensure good sealing.
Surface Crack Sealing (V-Groove)
For PU and epoxy injection, the crack surface is V-grouted with a fast-setting epoxy mortar between ports. This prevents blowout of injected material through the crack face and forces the grout to travel laterally through the full crack depth before reaching the surface.
Injection Under Controlled Pressure
Injection pump is connected to the lowest (or end) packer and material pumped at the specified pressure (typically 0.3–0.5 MPa for epoxy; 0.2–0.3 MPa for PU foam). Injection continues until material appears at the adjacent port — confirming travel through the crack — then that port is sealed and injection moves to the next.
Curing & Packer Removal
Injection material is allowed to cure (PU foam: 30–60 minutes; epoxy: 24–48 hours) before packers are removed. Packer holes are patched flush with a thixotropic epoxy mortar (Fosroc Nitomortar or BASF MasterEmaco). Crack face is ground flush with the structural surface.
Post-Injection Verification
Water is applied to the treated surface (or the structure is returned to service and monitored) to confirm leak arrest. For structural epoxy injection, pull-off tests can be performed to confirm adhesion. A grouting record — materials used, pressures, volumes injected per port — is submitted to the client.
Frequently Asked Questions
Related Projects
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