Concrete Mender™ Bond Strength

Why it works…

The Science Behind Roadware

 

How strong is the bond between Roadware 10 Minute Concrete Mender and the surrounding concrete?

To find out, we contacted Prof. David A. Lange, Department of Civil Engineering, University of Illinois at Urbana-Champaign.

Dr. Lange used standard ASTM testing methods to measure the bond between Roadware 10 Minute Concrete Mender and the surrounding concrete?

 

Roadware 10-Minute Concrete Mender:

Evaluation of Bond Strength

Prof. David A. Lange, Ph.D., P.E., FACI

Department of Civil Engineering

University of Illinois at Urbana-Champaign

December 20, 2001

  

Introduction:

The bond strength of Concrete Mender was evaluated using procedures of ASTM C882 -99 “Standard Test Method for Bond Strength of Epoxy-Resin Systems Used With Concrete by Slant Shear.” This report describes the procedures and results of the test.

 

Test Procedures and Results:

 ASTM C882-99 provides procedures by which the bond strength of epoxy-resin systems are measured. The bond strength is determined by using the epoxy-resin system–or in this case, Concrete Mender–to bond together two equal sections of a 3 by 6-in. portland cement mortar cylinder, each section of which has a diagonally cast bonding area at a 30° angle from vertical. After suitable curing of the bonding system, the test is performed by determining the compressive load required to fail the composite cylinder.

 

Plain 3 by 6 in. mortar cylinders were cast for use as substrates. The mortar mix design (SSD) was 10 lb Type I portland cement, 30 lb river sand, and 4.8 lb water. After two days of curing, the cylinders to be used as substrates were sawn at a 30° angle from vertical into two equal sections. At 14 days, the surfaces of the sawn sections were sandblasted to achieve greater surface texture. Four extra cylinders were cast to be tested in compression to determine the strength of the mortar. All of the cylinders and sections were cured at 100% RH for 14 days and allowed to air dry for 14 additional days. The 28-day strength of the mortar determined as an average strength of the four whole cylinders was 6400 psi, well in excess of the 4500 psi required by ASTM C882-99 for the substrate material.

 

The composite cylinders were fabricated by bonding two matched cylinder sections together. The procedure for Cylinders #1 and #4 was generally in accordance with ASTM C882-99 Section 10.3.2 which is intended to be used for low viscosity bonding systems. In brief, the two cylinder halves were primed with neat Concrete Mender, positioned with a gap of approximately 0.02 in., wrapped with a self-adhesive aluminum foil except for a single opening, and then Concrete Mender was poured into the exposed joint opening until completely filled. The procedure for Cylinder #6 was generally in accordance with ASTM C882-99 Section 10.3.3 which is intended to be used for mortar bonding systems. In brief, the two cylinder halves were primed with neat Concrete Mender, a mortar of Concrete Mender and quartz sand was troweled onto one surface, the second cylinder half was then placed onto the mortar bed, and the cylinder was squeezed together by hand to form a bonded composite cylinder. All of the composite cylinders were cured for four days before testing.

 

Cylinders #1, 4, and 6 had very high bond quality with little or no trapped air. Typical photos are shown in Figures 1 and 2.The compressive loads required to fail the composite cylinders #1, 4, and 6 were 28516 lb, 29445 lb, and 26125 lb, respectively. ASTM C882-99 instructs the bond strength of the composite cylinders to be calculated by dividing the load carried by the specimen at failure by the area of the bonded surface (14.13 in.2). The average bond strength of the three composite cylinders was 1984 psi.

Conclusions:

Concrete Mender has a bond strength of 1984 psi as measured in accordance with ASTM C882-99.

Fabrication of test specimens must be done with particular care to avoid entrapment of air. One method of reducing the risk of entrapped air is to use a Concrete Mender mortar for bonding the composite cylinders.

 

Concrete Mender™ ASTM C882-99 Core Sample

 

Figure 1. Specimen 4 with good interfacial contact.

[Split cylinder strength = 2084 psi]

 

882fig1

 

Figure 2. Specimen 6 with good interfacial contact and greater mortar thickness.

[Split cylinder strength = 1849 psi]