In-situ Pull Off & Crack Sealing

PULL OUT TEST (Adhesive test & tension Strength) The pull out test was carried out to determining the adhesive strengthen on the concrete structure and the tension strength of the existing concrete where the R.C deck slab required for the strengthening works of carbon fiber E200 with 150mm width and 1.4mm thickness. The tester was able to measure the adhesive strength of primer applied to the carbon fiber or coating applied. The pull out test was required in the frequent of 1per 100m run or 2 nos per project. For the current project each span was required 2 nos of pull out test.

The surface preparation of the exiting deck slab was done on 2 days before the pullout test. The selected location was marked and grinded to the course aggregates. Clean with the solvent clean (thinner) to ensure the surface was free of dust and un-sound concrete. The dollies used was 50mm diameter each 4 nos of the testing. The sikadur- 31 CF normal was used to bond the dolly on the soffit of slab.

After the 48 hours for the primer to set and cure, the contractor (structural repair) carried out the test using the pull off tester DYNA

DYNA Pull-Off Tester Ref. Standards: BS 1881 Part 207, ASTM C 1583, ASTM D 4541, ACI 503-30 & DIN 1048 Part 2 Application:   

Measuring the adhesive strength of applied coatings e.g. plastic or concrete coatings, mortars, plasters, bituminous coats and coatings on metal Determining the surface strength of concrete and other materials Ideal for the evaluation of tensile strength in concrete renovation

Tighten the draw bolt and slowly turn the Hydraulic pump and consistently until the dolly was pull off. The Digital manometer was display the readings in unit of Mpa with the setting of 50mm dolly used.

Frequent of test = 2 nos per project or 100m per 2 nos samples Failure Mode (A= Existing Substrate , B= Repair material , C= dolly ) Failure Mode 1 100% Bond failure at dolly (100% B/C) Failure Mode 2 100% Cohesive failure of repair material (100% B) Failure Mode 3 100% Bond failure of repair material (100% A/B) Failure Mode 4 Partial Bond failure and cohesive failure of repair material (.....% A/B,....%B) Partial Bond failure and cohesive failure of existing substrate (.....% Failure Mode 5 A/B, .....%A) Failure Mode 6 100% Cohesive failure at dolly (100% A) A = Existing Substrate ( R.C Slab) B = Repair Material C = dolly

CRACK SEALING (Injection Method) Application Procedure After the crack mapping carried out by the contractor, the further remedial works was to seal the crack to prevent further corrosion to the reinforced- bar.

Crack width measures

crack line marking (Length + width)

Make a series of holes sufficient for surface packers along the crack line with width more than 0.25mm.

Clean the surface with brush and make sure the surface is dry and clean.

Insert the appropriate injection packer in the holes (drilled in packer) or place above (surface packers) and seal the entire working surface with epoxy adhesive (sikadur 31- CR normal)

Ensure all crack surfaces and seal entire working surface was fully sealed to avoid leakage during the injection process.

Pressure Pump (Manual) Epojet LV (grout material)

Installed the pipe to the surface packer and tighten it, apply the pressure slowly and observed the resin epoxy injected into the crack through the packer until the epoxy overflow from the nearby packer.

Clamp the O-ring to tighten the surface packer to prevent the epoxy resin leak. After the resin epoxy was set. The epoxy adhesive which used to cover the entire crack line to the sealing purpose was removed. The post inspection can be carried to observe the sealing works.