AASHTO/NTPEP Rapid Set Concrete Patching Materials

Transcription

1 AASHTO/NTPEP Rapid Set Concrete Patching Materials User Guide 2015 Introduction: The National Transportation Product Evaluation Program (NTPEP) was established to minimize the amount of duplicative testing of transportation materials performed by AASHTO member states by providing a process where manufacturer/suppliers submit their products to NTPEP for laboratory and/or field testing. The results of the testing are then shared with member Departments for their use in product quality verification. Test results are available at This document is intended to provide guidance in the use of data generated from the Standard practice for NTPEP Evaluation of Rapid Set Patching Materials for Portland Cement Concrete which describes the policies and testing protocols for the evaluation of these products. State and industry representatives have collaborated in the design of this program with the goal of providing a comprehensive testing regimen that can be used to evaluate concrete patching materials. This standard practice has been balloted and accepted by member departments. The document can be found at Member departments interested in being represented on this technical committee can contact a NTPEP representative at In keeping with the NTPEP philosophy of purely testing materials, no conclusions are provided with the test results. The evaluation of test results is left up to each member department. The intent of this guidance document is to provide background information that will assist users in interpreting results provided. This document has been developed by the Rapid Set Concrete Patching Materials Technical Committee. The parameters listed herein are offered as a conservative assessment of the expected performance of the rapid set concrete patching systems submitted for evaluation in this program. Key Aspects of the Program: The standard practice describes requirements and testing criteria for the NTPEP evaluation of rapid set concrete patching materials for Portland cement concrete. The concept of this practice is to evaluate off the shelf products. Products must be packaged as typically sold to consumers. Product samples that are prepared specifically for this program will not be accepted for testing. Products that are intended for horizontal use or both horizontal and vertical/overhead use will be subjected to field and laboratory testing. Products that are intended for vertical/overhead use only will be subjected to laboratory testing with no field trial. Field testing of products for horizontal use will be required for initial product submittals and will not be required for retesting. The test number shall indicate the Rapid Set Concrete Patching materials designation (RSCP), the year of submission, submission cycle for the year, and a sequential sample number (RSCP-Year-Cycle-Sample No.). For example: RSCP It is intended that products will be submitted for retesting every 5 years based on the year indicated in the NTPEP number. Products that are not submitted for retesting will be removed from DataMine.

2 All testing will be in accordance with the appropriate AASHTO or ASTM testing methods as detailed in the standard practice. Some methods have been modified to meet the needs of this Technical Committee and the agencies utilizing the program. The standard practice includes testing for cementitious, polymer and polymer modified products. Lab testing is performed by a NTPEP contracted and qualified independent lab. The field evaluation is performed on a concrete bridge deck by a member state, currently Ohio DOT. All lab and field test data collected is made available through the NTPEP DataMine at Access to proprietary data is limited to the submitting manufacturer and registered representatives of member departments of transportation. Non-proprietary data is available to all users. While NTPEP works to make the product evaluation process comprehensive to meet the requirements for AASHTO member departments, all test data should be carefully reviewed by the specifying agency and in the context of field experience with these products. Specific field conditions related to exposure are not accounted for in this controlled evaluation of product performance. With this in mind, the review of the laboratory and field data produced through this evaluation program should be viewed as a tool in making reasonable judgments and selections of materials. Additional Resources: ASTM C 928, Standard Specification for Packaged, Dry, Rapid-Hardening Cementitious Materials for Concrete Repairs ACI 546.3R-14, Guide to Materials Selection for Concrete Repair Terminology: Cementitious Product is a dry, cementitious mortar or concrete material. Polymer Product is a composite material formed by polymerization of a monomer and aggregate mixture in which the polymerized monomer acts as the sole binder for the aggregate. Polymer concrete uses a polymer binder in place of Portland cement. Polymer-Modified Concrete is Portland cement concrete with polymer solutions added to the mix to achieve certain properties. Like Portland cement concrete, the primary curing mechanism for polymer-modified concrete is hydration of the cement binder Neat refers to a product that is tested as packaged with no added components except for water or liquid. Extended refers to a product that is tested with the specified addition of aggregate to the packaged product, along with the water or liquid. Product Category indicates whether the product is a Cementitious, Polymer-modified, or Polymer product. Product Use indicates how the product is intended to be used. Use can be Horizontal, Vertical/Overhead, or Both Horizontal and Vertical/Overhead. Product Application indicates whether the product has been evaluated as a neat product, and extended product, or as both neat and extended. DataMine is the NTPEP online database where results from this program can be viewed. The website is Review of Evaluations and Significance of Data Generated The standard practice provides details regarding the standard testing that is used for evaluation of these products. The following discussion and suggested parameters for acceptance of products is intended only as a guide. The descriptions and suggested values are abbreviations (and some modifications) of information found in ACI 546.3R-06, ASTM C 928 and other referenced specifications. Individual agencies may elect to only utilize a portion of these tests and the suggested values may be altered to correspond to the needs of their agency.

3 CEMENTITIOUS CONCRETE MATERIALS Standard/Method Description Typical Value Suggested Value AASHTO T 198 (ASTM C 496) Splitting Tensile Strength Tensile Strength is the maximum unit stress a material is capable of resisting under axial tension loading. The splitting tensile test applies a compressive force along the axis of an unconfined cylinder supported on its side, causing it to split along its axis. This psi >400 psi AASHTO T 161 (ASTM C 666), Procedure A and Procedure B AASHTO T 277 (ASTM C 1202) AASHTO T 22* (ASTM C 39) ASTM C 882* test is performed at a sample age of 28 days. Freeze/Thaw Some repair materials, including concrete, are susceptible to deterioration when exposed to cycles of freezing and thawing in a saturated condition. The expansion and migration of water can generate destructive internal pressures. This test method exposes the material to freezingand-thawing cycles and records the change in dynamic modulus of elasticity and mass loss of the specimens. Per the RSCP work plan, concrete specimens are cured for 28 days prior to the start of this test. Procedure A freezes and thaws the specimens in water. Procedure B freezes the specimens in air and thaws them in water. A complete test consists of 300 freezing-and-thawing cycles. A durability factor (DF) greater than 90 for Procedure A and 80 for Procedure B is generally considered to represent a material that will be durable under freezing-and-thawing conditions. Chloride Ion Penetration Permeability is the ability of a material to transmit or resist the penetration of water and water-borne chemicals. The permeability of a repair material is important in environments where the repair material or substrate concrete is vulnerable to freeze/thaw damage of saturated concrete, corrosion of embedded reinforcing steel, alkali-aggregate reactions, or sulfate attack. The permeability can be determined by its resistance to chloride-ion penetration. AASHTO T 277 provides an indication of a materials resistance to chloride-ion ingress in a short period of time, typically 6 hours. This program performs T 277 at a sample age of 28 days. Compressive Strength Compressive strength is the measured maximum resistance of a material to axial compressive loading, expressed as force per unit crosssectional area. Compressive strength is determined by applying an increasing axial compression load until the specimen is unable to support that additional load. The ultimate load is divided by the cross-sectional area to determine the ultimate failure stress. The test for this work plan utilizes 4 x8 cylindrical test specimens. The required early strengths should be based on the application that the material is being utilized for. Higher 1 hour or 3 hour strengths may be required when the pavement or structure must be opened to traffic at a referenced time. Compressive strength at 28 days should be at least that of the substrate concrete. Bond Strength using Slant Shear Bond Strength (adhesion) is the resistance of the repair material to separation from the substrate concrete. It is essential that the repair material has sufficient bond strength such that the repair does not separate from the substrate concrete. Slant shear bond tests measure the resistance to sliding between the repair material and the concrete substrate along an inclined surface. The measured bond strength is somewhat suspect in that the results have been found to be highly dependent on the compressive Procedure A DF 300 cycles Procedure B DF at 300 cycles DF 300 cycles DF >80 at 300 cycles Coulombs Coulombs Historical RSCP Data 1 hr: psi 3 hrs: psi 1 day: psi 7 days: psi 28 days: Historical RSCP Data 1 day: psi 7 day: psi Refer to ASTM C 928 Per ASTM C day: 1000 psi 7 days: 1500 psi

4 ASTM C 1583 AASHTO T 160* ( ASTM C 157) AASHTO TP 95 * As modified by ASTM C 928 strength of the substrate concrete and the surface roughness of the bonding surface. High bond strength is particularly important for shallow repairs that do not contain reinforcing steel and for thin overlays. Bond Strength by Direct Tension Unlike C 882 which attempts to determine bond strength through a complicated interaction of forces, this test method directly measures the tensile load required to separate the patching material from the substrate. This test is performed at sample ages of 1, 7, and 28 days. This test is a 2014 addition to the RSCP work plan and recommended values are not yet available. Length Change Volume stability refers to initial and long term changes in linear dimensions or volume of the repair material after placement. Volume stability properties affect the compatibility of the repair material with the substrate concrete. Most cementitious materials undergo early shrinkage within the first few hours to days after application. Shrinkage occurs as the material is exposed to ambient drying conditions. Rapid setting repair materials typically contain expansive agents to offset shrinkage. It is therefore also important to evaluate both the shrinkage characteristics of the materials stored in air as well as expansion characteristics for materials stored in water. Surface Resistivity - The electrical surface resistivity of concrete can be used as an indicator of permeability. Devices that are suitable for this test utilize an array of 4 electrodes that are placed in contact with the concrete sample. The 2 outer electrodes apply an alternating current across the sample. The resultant potential difference is measured between the 2 inner electrodes. A calculation based on current used, resultant potential, and sample area results in a value for resistivity, expressed in Kilohms-centimeters (k -cm). This test is performed at a sample age of 28 days psi psi % to -0.12% Per ASTM C 928 Allowable increase after 28 days in water Allowable decrease after 28 days in air k -cm k -cm

5 POLYMER CONCRETE MATERIALS Standard/Method Description Typical Value Suggested Value ASTM C 531 (modified) Linear Shrinkage and Coefficient of Thermal Expansion - This test method covers the measurement of the linear shrinkage during setting and curing and the coefficient of thermal expansion. The coefficient of thermal expansion is the change in linear dimension per unit length of a material per degree of temperature change. In situations where temperature is not controlled, such as in exterior and some interior applications, it is desirable for the repair material to have a coefficient of thermal expansion similar to that of the substrate concrete so that the two materials behave similarly under daily and seasonal temperature variations. In ASTM C 531, the linear shrinkage of the material is the first portion of the test method. The linear shrinkage is calculated from the difference between the initial length measurements of the specimens from the length measurements of those same specimens subjected 2x10-6 to 8x F Comparable to the substrate to an accelerated curing process. Those test specimens are then utilized to determine the coefficient of thermal expansion. The coefficient of thermal expansion is calculated by measuring the change in length of the material specimens at a constant humidity between temperatures, typically 73 and 210 deg. F. The results are reported as strain per deg. F. of temperature change. ASTM C 579 ASTM C 881 ASTM C 882 (as modified by C1439) Compressive Strength Compressive cube strength is the measured maximum resistance of a material to axial compressive loading, expressed as force per unit crosssectional area. Compressive strength is determined by applying an increasing axial compression load until the specimen is unable to support that additional load. The ultimate load is divided by the cross-sectional area to determine the ultimate failure stress. The RSCP workplan specifies that this test is conducted on 4 x 8 cylinders. The required strengths should be based on the application that the material is being utilized for. Higher early strengths may be required when the pavement or structure must be opened to traffic at a referenced time. Gel Time - This test method determines the time after mixing when a material gels or begins to set. For this test method, the material is placed into an 8-oz. unwaxed paper cup immediately after mixing. The specimen is then probed with a wooden tongue depressor every two minutes until the time at which a soft, gelatinous mass forms in the center of the sample or the material begins to set up. Bond Strength using Slant Shear Bond Strength (adhesion) is the resistance of the repair material to separation from the substrate concrete. It is essential that the repair material has sufficient bond strength to the substrate concrete such that the repair does not separate from the substrate concrete. Slant shear bond tests measure the resistance to sliding between the repair material and the concrete substrate along an inclined surface. The measured bond strength is somewhat suspect in that the results have been found to be highly dependent on the compressive strength of the substrate concrete and the surface roughness of the bonding surface. This test involves casting a cylinder right cylinder of substrate mortar or concrete, using a dummy section to form a 7 day: >5000 psi 7 day: >5000 psi 30 Minutes Minimum 1 day: psi 7 day: psi 28 day: psi ASTM C Minutes Minimum 1 day: 1000 psi 7 days: 1500 psi

6 ASTM C 884 AASHTO T 277 (ASTM C 1202) ASTM C 1583 planar bonding surface that is 30 degrees off the longitudinal axis of the cylinder. The bonding surface is prepared by sandblasting, and the test material is cast on top of the substrate to complete the right cylinder. At the appropriate age, the test specimen is loaded to failure in compression. The stress at fracture is determined by dividing the ultimate load by the elliptical area of the bonding surface to determine the bond strength. If the specimen does not fail at the bond line, the bond strength is considered to be at least the resulting failure stress. Thermal Compatibility This method is a qualitative evaluation of the ability of a repair material to stay bonded to the substrate when subjected to temperature changes from 73F to -6F. Products that fail this test will most likely have a much higher coefficient of thermal expansion than the substrate. Results are also affected by the bond strength and flexibility of the repair material. The coefficient of thermal expansion is the change in linear dimension per unit length of a material per degree of temperature change. In situations where temperature is not controlled, such as in exterior and some interior applications, it is desirable for the repair material to have a coefficient of thermal expansion similar to that of the substrate concrete so that the two materials behave similarly under daily and seasonal temperature variations. If the coefficients vary significantly, the differential movements due to temperature fluctuations could affect the performance of the repair, and should be accounted for in the repair design. In ASTM C 884 a concrete substrate with an epoxy resin overlay is cycled through a temperature range between 73 and -6 o F five times. If the epoxy resin debonds or if either material shows cracking, the epoxy resin fails the test. Chloride Ion Penetration Permeability is the ability of a material to transmit or resist the penetration of water and water-borne chemicals. The permeability of a repair material is important in environments where the repair material or substrate concrete is vulnerable to freeze/thaw damage of saturated concrete, corrosion of embedded reinforcing steel, alkali-aggregate reactions, or sulfate attack. The permeability can be determined by its resistance to chloride-ion penetration. AASHTO T 277 provides an indication of a materials resistance to chlorideion ingress in a short period of time, typically 6 hours. This program performs T 277 at a sample age of 28 days. Tensile Bond Strength C 1583 is a direct tensile bond test that can be used both in the laboratory or in the field to measure the bond strength of the repair materials to the substrate. Test results are greatly affected by the strength of the substrate and the level of surface preparation. Laboratory testing will normally be conducted using properly prepared substrates with a minimum compressive strength of at least 4000 psi. Failure mode is an important part of the interpretation of the test results. Failure modes are in the substrate, at the bond line or in the repair material. Pass/Fail Pass Coulombs Coulombs 1 day: psi 1 day: psi 7 day: psi 7 day: psi 28 day: psi 28 day: psi

7 POLYMER-MODIFIED CONCRETE MATERIALS Standard/Method Description Typical Value Suggested Value AASHTO T22* (ASTM C 39) Compressive Strength Compressive strength is the measured maximum resistance of a material to axial compressive loading, expressed as force per unit crosssectional area. Compressive strength is determined by applying an increasing axial compression load until the specimen is unable to support that additional load. The ultimate load is divided by the cross-sectional area to determine the ultimate failure stress. The test for this work plan utilizes 4 x8 cylindrical test specimens. The required early strengths should be based on the application that the material is being utilized for. Higher 1 hour or 3 hour strengths may be required when the pavement or structure must be opened to traffic at a referenced time. Compressive strength at 28 days should be at least that of the Historical RSCP Data 1 hr: psi 3 hrs: psi 1 day: psi 7 days: psi Refer to ASTM C 928 AASHTO T 160* (ASTM C 157) ASTM C 884 AASHTO T 277 (ASTM C 1202) substrate concrete. Length Change Volume stability refers to initial and long term changes in linear dimensions or volume of the repair material after placement. Volume stability properties affect the compatibility of the repair material with the substrate concrete. Most cementitious materials undergo early shrinkage within the first few hours to days after application. Shrinkage occurs as the material is exposed to ambient drying conditions. Rapid setting repair materials typically contain expansive agents to offset shrinkage. It is therefore also important to evaluate both the shrinkage characteristics of the materials stored in air as well as expansion characteristics for materials stored in water. Thermal Compatibility This method is a qualitative evaluation of the ability of a repair material to stay bonded to the substrate when subjected to temperature changes from 73F to -6F. Products that fail this test will most likely have a much higher coefficient of thermal expansion than the substrate. Results are also affected by the bond strength and flexibility of the repair material. The coefficient of thermal expansion is the change in linear dimension per unit length of a material per degree of temperature change. In situations where temperature is not controlled, such as in exterior and some interior applications, it is desirable for the repair material to have a coefficient of thermal expansion similar to that of the substrate concrete so that the two materials behave similarly under daily and seasonal temperature variations. If the coefficients vary significantly, the differential movements due to temperature fluctuations could affect the performance of the repair, and should be accounted for in the repair design. In ASTM C 884 a concrete substrate with an epoxy resin overlay is cycled through a temperature range between 73 and -6 o F five times. If the epoxy resin debonds or if either material shows cracking, the epoxy resin fails the test. Chloride Ion Penetration Permeability is the ability of a material to transmit or resist the penetration of water and water-borne chemicals. The permeability of a repair material is important in environments where the repair material or substrate concrete is vulnerable to moisture-related deterioration, such as freezing-and-thawing damage of saturated concrete, corrosion of embedded reinforcing steel, alkali-aggregate reactions, or sulfate attack. The permeability can be determined by its resistance to chloride-ion +0.02% to -0.12% Pass/Fail Per ASTM C 928 Allowable increase after 28 days in water Allowable decrease after 28 days in air Pass Coulombs Coulombs

8 ASTM C 882* ASTM C 1583 AASHTO TP 95 AASHTO T 161 (ASTM C 666) Procedure A and Procedure B * As modified by ASTM C 928 penetration. ASTM C 1202 was developed to provide an indication of a materials resistance to chloride-ion ingress in a short period of time, typically 6 hours. This program performs T 277 at a sample age of 28 days. Bond Strength using Slant Shear Bond Strength (adhesion) is the resistance of the repair material to separation from the substrate concrete. It is essential that the repair material has sufficient bond strength to the substrate concrete such that the repair does not separate from the substrate concrete. Slant shear bond tests measure the resistance to sliding between the repair material and the concrete substrate along an inclined surface. The measured bond strength is somewhat suspect in that the results have been found to be highly dependent on the compressive strength of the substrate concrete and the surface roughness of the bonding surface. High bond strength is particularly important for shallow repairs that do not contain reinforcing steel and for thin overlays. Bond Strength by Direct Tension Unlike C 882 which attempts to determine bond strength through a complicated interaction of forces, this test method directly measures the tensile load required to separate the patching material from the substrate. This test is performed at sample ages of 1, 7, and 28 days. This test is a 2014 addition to the RSCP work plan and recommended values are not yet available. Surface Resistivity - The electrical surface resistivity of concrete can be used as an indicator of permeability. Devices that are suitable for this test utilize an array of 4 electrodes that are placed in contact with the concrete sample. The 2 outer electrodes apply an alternating current across the sample. The resultant potential difference is measured between the 2 inner electrodes. A calculation based on current used, resultant potential, and sample area results in a value for resistivity, expressed in Kilohms-centimeters (k -cm). This test is performed at a sample age of 28 days. Freeze/Thaw Some repair materials, including concrete, are susceptible to deterioration when exposed to cycles of freezing and thawing in a saturated condition. The expansion and migration of water can generate destructive internal pressures. This test method exposes the material to freezingand-thawing cycles and records the change in dynamic modulus of elasticity and mass loss of the specimens. Per the RSCP work plan, concrete specimens are cured for 28 days prior to the start of this test. Procedure A freezes and thaws the specimens in water. Procedure B freezes the specimens in air and thaws them in water. A complete test consists of 300 freezing-and-thawing cycles. A durability factor (DF) greater than 90 for Procedure A and 80 for Procedure B is generally considered to represent a material that will be durable under freezing-and-thawing conditions. Historical RSCP Data 1 day: psi 7 day: psi Per ASTM C day: 1000 psi 7 days: 1500 psi k -cm k -cm Procedure A DF 300 cycles Procedure B DF at 300 cycles DF 300 cycles DF >80 at 300 cycles