Long-Term Performance of Epoxy Adhesive Anchor Systems (2013)

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F-1 A P P E N D I X F Early-Age Concrete Evaluation—University of Stuttgart

F-2 EARLY-AGE CONCRETE EVALUATION—UNIVERSITY OF STUTTGART This section presents the test program conducted at the IWB laboratory of the University of Stuttgart to investigate the effect of early-age concrete on the short-term performance of three adhesive anchor systems. Test Apparatus This section describes the test apparatus used for early-age concrete evaluation used at the IWB laboratory of the University of Stuttgart. Short-Term Anchor Pullout Test Apparatus The testing apparatus for the short-term test (Figure 1) used a 3.5” diameter x 0.04” thick Teflon PTFE (Polytetrafluoroethylene) confining sheet with a 1” diameter hole in the middle placed under an 1.2” thick steel equilateral triangle (12” sides) confining plate. The confining plate had an insert with a 13/16” (20 mm) diameter hole to fit around the anchor. The confining sheet was used to correct for any surface irregularities in the concrete. A tripod was placed on the confining plate which supported a 22-kip hydraulic ram, bearing plate, 45-kip load cell, and a ball and socket hinge plate. The anchor was connected to a pulling assembly through a 0.55” (14 mm) hole and secured with two high-strength nuts. The pulling assembly was connected to a 5/8” (16 mm) diameter loading rod which passed though the ram, load cell, and ball and socket hinge above and was secured with a nut. A separate rig (Figure 2) held an LVDT which was connected via a steel cable to a magnet placed on top of the anchor.

F-3 Figure 1: Short-term testing apparatus. Figure 2: LVDT rig. Initial Surface Absorption Test Apparatus An initial surface absorption test (ISAT) apparatus (Figure 3) provided by IMPACT Test Equipment Ltd. was used to evaluate the initial absorption of the top formed surface of the concrete as well as the surfaces of the drilled hole. This apparatus consisted of a reservoir of water which maintained an 8” (200 mm) head above the surface of the concrete. The reservoir was attached to a 3.3” (85 mm) diameter clear cap secured to the surface of the concrete by a clamp and screws with plastic inserts. A small capillary tube was also connected to the cap in order to provide precise measurements of water flow at specific times. Figure 3: ISAT equipment.

F-4 Rebound Hammer A rebound hammer by Suspa DSI GmbH (Figure 4) was used to measure the concrete hardness. This hammer would drive a weight into the surface of the concrete by means of a spring and record the rebound distance. A scale on the side of the hammer could be used to determine the “hardness” in terms of a 6” cube compressive strength. Indention Hammer An indention hammer (Figure 5) was also used to measure the concrete hardness. This hammer would drive a 0.4” (10 mm) diameter ball into the surface of the concrete by means of a spring. The average diameter of the indention would be measured and a graph could be consulted to determine the “hardness” in terms of a 6” cube compressive strength. Figure 4: Rebound hammer. Figure 5: Indention hammer. Specimen preparation The test specimens consisted of three parts; the concrete test member, the adhesive, and the anchor rod. Concrete Test Member The concrete test members for the early-age concrete investigation tests were poured in 50” x 50” x 16” high density overlay plywood forms. Minimal reinforcement of two 6 mm steel reinforcing bars were placed along the top and bottom edges for crack control. Two ¾” diameter by 9.5” long PVC pipes with PVDF filter covers were placed in one corner at 1.5” and 3” from the top test surface to allow for temperature and humidity sensors to be placed later. Four temperature and humidity sensors were cast into one slab but were destroyed during casting.

F-5 All the test blocks were cast on July 8, 2011 at the Friedrich Rau GmbH & Co precast concrete plant in Ebhausen, Germany. In order to provide a smooth testing surface the blocks were cast upside down against the high density overlay plywood. Concrete with round river gravel without any admixtures was specified with a mean compressive strength between 3630–5080 psi during testing. The slump measured 1.5” and the casting temperature was 68°F (20°C). Both 4” x 8” cylinders and 6” cubes were cast. On July 9, 2011, the day after casting, the forms were removed and the slabs were shipped to the IWB laboratory in Stuttgart, Germany on July 11, 2011, the third day after casting. The concrete test members were maintained in the IWB laboratory thereafter. The 4” x 8” cylinders and 6” cubes were delivered to the MPA laboratory at the University of Stuttgart for compression and split-tensile testing. Concrete compressive strength was determined by testing both the 4” x 8” cylinders in general accordance with ASTM C39 and the 6” (15 cm) cubes in general accordance with DIN EN 12390-3. Split-tensile strength was determined by testing both the 4” x 8” cylinders in general accordance with ASTM C496 and the 6” cubes in general accordance with DIN EN 12390-6. The compression and split-tensile tests were conducted at the MPA testing laboratory at the University of Stuttgart on a Form+Test Prüfsysteme universal testing machine (Figure 6) calibrated by MPA in May 2011. The cylinders were ground smooth on a Form+Test Seidner cylinder grinding machine (Figure 7) prior to testing. Concrete compression and split-tensile versus age relationships were determined by testing at 4, 7, 14, 21, and 28 days.

F-6 Figure 6: MPA universal testing machine. Figure 7: MPA cylinder grinding machine. Table 1 and Table 2 present the compression strength and split-tensile strength results respectfully for the 4” x 8” cylinders and 6” concrete cubes. Moist cured cubes typically test about 15% stronger than moist cylinders [Mehta and Monteiro (2006)] due to more confinement based on their geometry. The cubes and cylinders in this test program tested from 30% to 40% higher than the cylinders. This can be explained by the fact that these specimens were all air cured and the different volume to surface area ratio of the two different specimens. Cubes have a larger volume to surface area and thus will dry more slowly than cylinders resulting in higher compressive strengths. Table 1: Early-age concrete compression strength results. Age (days) 4” x 8” Cylinders (psi) 6” Cubes (psi) Ratio Cubes/Cylinders 4 2,080 2,790 1.34 7 2,350 3,280 1.40 14 2,850 3,860 1.35 21 3,040 4,090 1.35 28 3,250 4,230 1.30

F-7 (days) Cylinders (psi) (psi) cubes/cylinders 4 200 260 1.30 7 250 270 1.08 14 270 330 1.22 21 290 300 1.03 28 270 290 1.07 Adhesive The same three adhesives identified earlier were used in this portion of the project. The three adhesive products were stored in the IWB laboratory and maintained within the temperature and humidity range specified by the manufacturers prior to installation. Anchor Rods The anchor rods were 14.9 [203 ksi (1400 MPa) 90% yield strength] ½” (12 mm) diameter steel threaded rod fabricated by Hersteller. This grade of steel has a specified yield strength of 183 ksi and a specified tensile strength of 203 ksi. The anchor rods were cut to a length of 6.7” from 8” stock and the top end ground and chamfered with a bench grinder and steel brush to remove burrs and to clean up the threads in order to install the nuts. The bottom end of the anchor was ground to a 45° cone (Figure 8) in order to fit into a centering guide placed at the bottom of the drilled hole. Figure 8: Anchor showing 45° cone to fit into centering guide. Instrumentation Measurement Displacement. Direct measurement of the anchor displacement was measured by a Novotechnik LVDT. The LVDT was mounted in a separate rig and connected via a steel cable to a magnet placed on the top of the anchor (Figure 2). Table 2: Early-age concrete split-tensile strength results. Age 4” x 8” 6” Cubes Ratio

F-8 Load. The tension in the anchor was measured indirectly as a compressive reaction of the hydraulic ram in the test apparatus. The load was measured by a Hottinger Baldwin Messtechnik 45-kip load cell. The load cell was excited and measured by the NI Diadem software. Temperature and Relative Humidity. Internal temperature and relative humidity in each concrete test slab was measured by Sensiron SHT71 temperature and humidity sensors. Four sensors were cast within one control slab and two empty PVC pipes were cast into every test slab to allow for later insertion and removal of additional sensors if necessary. The four Sensiron SHT71 sensors cast directly into the concrete slab were constructed similar to those as discussed by Rodden (2006). Each sensor was placed in a 4” long ¾” diameter PVC pipe. One end was covered with a Polyvinyldenfluorid (PVDF) filter by Thomapor with 0.2 m openings. The other end was packed with foam insulation and a PVDE disk to provide a backing for a silicon seal. The entire assembly (Figure 9) was later wrapped with duct tape for extra protection. The pipes were tied to rebar and the centerlines were placed 1.5” and 3” below the top of the testing surface, 2-¼” from each other, with the center of the entire assembly 8” from the corner (Figure 10). Two 9.5” long by ¾” diameter PVC tubes with same PVDF filter on one end and covered with duct tape were cast in each test slab. The pipes were attached to a plastic plate with holes taped over and connected to the side of the form. The pipes were tied to rebar and the centerlines were placed at 1.5” and 3” below the top of the testing surface and 9.5” and 10.5” from the corner of the slab (Figure 10). The Sensiron SHT71 sensors were inserted into the test slab after casting and several days prior to testing and packed with foam insulation and sealed with duct tape. The sensors were monitored by the Sensiron EK-H4 evaluation kit and recorded to a text file.

F-9 Figure 9: Sensiron sensor assembly. Figure 10: PVC pipes and Sensiron sensors placed in forms prior to casting. Ambient temperature and relative humidity of the laboratory were monitored and recorded by a Lufft Opusio sensor at 10 minute intervals. Time. Time was measured using the computer’s internal clock. Instrument Calibration Displacement. The LVDTs were calibrated by IWB every 3 months against calibrated ceramic gages over their working range of 10 mm at 2 mm increments. Load. The Hottinger Baldwin Messtechnik 45-kip load cell was calibrated on December 11, 2009, by MPA. The load cell was calibrated over a range of 0 to 45 kips with data points every 4.5 kips. Temperature and Humidity. The Sensiron SHT71 temperature and humidity sensors were calibrated by the factory. The Lufft Opusio ambient temperature and humidity sensor was calibrated by IWB on January 22, 2010 against a TESTO calibrated temperature gage. Data management and acquisition An NI Diadem 10.2 program (Figure 11) was used for the short-term tests in one of five test cabinets, which included a computer, data acquisition hardware, and two hydraulic pumps. Load and displacement were recorded at 0.2 second intervals and a load versus displacement curve was displayed on the screen for real-time feedback. Load was applied by a hydraulic pump and controlled by valves integral with the test cabinet. The latest data readings were displayed on the screen and the data was recorded to a Microsoft Excel spreadsheet following the test.

F-10 Figure 11: Screenshot of NI Diadem 10.2 data acquisition program. Installation procedure The installation procedure generally followed the procedure described in the section “Anchor Pullout Tests—University of Stuttgart” except the anchors were allowed to cure for 24 hours prior to testing. Testing procedure Short-Term Test Procedure A 0.04” thick PTFE confining sheet and 1.2” thick steel confining plate with 13/16” (20 mm) diameter hole insert were placed over the anchor and the pulling assembly was attached to the anchor. A 3/16” gap was left between the confining plate and the pulling assembly to allow for rotation of the coupler in order to prevent bending forces from being transferred between the anchor and the loading rod. The short-term test apparatus was placed over the anchor as discussed earlier.

F-11 The Lukas Hydraulik GmbH 22-kip hydraulic ram was placed on the tripod and connected to the test cabinet hydraulic pump. The loading rod was then connected to the coupler. The Hottinger Baldwin Messtechnik 45-kip load cell was placed on top of a loading plate on top of the ram. A ball and socket hinge was placed on top of the load cell and the loading rod nut was hand tightened to remove slack in the system. A magnet was placed on top of the anchor and connected to a Novotechnik LVDT mounted in a separate rig via a cable The load and displacement values were the zeroed in the NI Diadem 10.2 program. The test was started and load rate was controlled by the operator to achieve a failure in one to three minutes. Initial Surface Absorption Test Procedure Initial surface absorption was measured in general accordance with BS 1881 using an ISAT apparatus provided by IMPACT Test Equipment Ltd. A 3.3” (85 mm) diameter plastic cap was clamped to the top surface of the concrete with a steel bar using screws and plastic inserts. This cap was connected via rubber tubes to a reservoir of water and a capillary tube. The reservoir maintained an 8” (200 mm) head of water during the duration of the test. At 10 minutes, 30 minutes, and 60 minutes the tube connecting the reservoir to the cap was clamped allowing water to flow into the cap from a capillary tube. A scale created from the calibration procedure in BS 1881 was used to determine the amount of water entering the cap over a 1 minute period. Three repetitions of were conducted on the top formed surface of the concrete test block. A modified ISAT was developed to determine the initial surface absorption of the sides and bottom of a hole drilled in concrete. Three 0.55” (14 mm) diameter by 4.5” (115 mm) deep holes were drilled and cleaned according to the cleaning procedure for adhesive A. The 3.3” (85mm) diameter cap was clamped over a hole and the same procedures for the above-described ISAT were performed. The initial surface absorption of the sides and bottom of the drilled hole were determined by removing the influence of the top formed surface of the concrete specimen based on the tests performed on the top surface only. An allowance was made for the chipped area around the top of the hole (Figure 12) as this surface would be more similar to the side of the hole than to the top formed surface. The

F-12 diameter of the chipped area was measured in four directions (Figure 13) and their results averaged to determine an equivalent circular area. Figure 12: Chipped area around top of hole. Figure 13: Jig to measure the diameter of the chipped area in four directions. The initial surface absorption is defined as “the rate of flow of water into concrete per unit area at a stated interval from the start of the test and at a constant applied head” (BS 1881). BS 1881 presents the standard initial surface absorption test (ISAT). The ISAT is intended to be used on a flat surface of concrete. Below is the rationale behind the development of a modified ISAT of bore holes for adhesive anchor testing. In general, the initial surface absorption can be calculated as: = · Eqn. 1 where: I = initial surface absorption [ml/m2·s], V = volume of water measured in the capillary [ml], A = surface area through which water is passing [m2], and t = measured time interval (60 seconds) [s]. For the standard ISAT on the top formed surface of concrete the equation can be written as: = · Eqn. 2 where:

F-13 • I1 = initial surface absorption of the top formed surface [ml/m2·s], • V1 = volume of water measured in the capillary [ml], • A1 = surface area of the reservoir [m2], and • t = measured time interval (60 seconds) [s]. For adhesive anchor applications it is desirable to determine the initial surface absorption of the surfaces of the drilled hole. In order to determine this, the ISAT reservoir was placed over a hole drilled in concrete and the initial surface absorption of the water passing through the combined surface area of the top formed surface and the surfaces of the drilled hole is defined as: Eqn. 3 where: • I2 = initial surface absorption of the top formed surface and hole combined [ml/m2·s], • V2 = volume of water measured in the capillary [ml], • A2 = surface area of the top formed surface and the hole combined [m2], and • t = measured time interval (60 seconds) [s]. During drilling it is common that the top surface of the concrete chip or spall around the edge of the hole. For this reason it is desirable to divide the total surface area (A2) into distinct areas (Figure 14): Eqn. 4 where: • AS = area of the unchipped top formed surface, • AC = chipped area of the spalled top surface around the hole due to drilling, and • AH = area if the sides and bottom of the drilled hole.

F-14 Figure 14: A2 sub-areas. It is reasonable that the initial surface absorption of the surfaces of the drilled hole (AH) is different than that of the top formed surface (AS). Furthermore, it was assumed that the chipped area (AC) is more similar to that of the sides and bottom of the drilled hole (AH) than to the top surface of the concrete (AS). Therefore the areas AC and AH can be combined into another area (ACH) where: Eqn. 5 where: • ACH = area of the chipped surface and drilled hole. This combined area (ACH) will have a distinct initial surface absorption (ICH) different than that of the top surface of the concrete (IS). It is also reasonable then to assume that the initial surface absorption (I1) is the same as the initial surface absorption of the unchipped top surface portion (IS), or, Eqn. 6 Substituting Eqn. 2 and Eqn. 3 into Eqn. 6, Eqn. 7

F-15 Solving for VS, Eqn. 8 It is obvious that the total volume of water (V2) is the sum of the volume of water passing through the distinct parts of the wetted surface, or, Eqn. 9 where: • VS = volume of water passing through the unchipped top formed surface, • VC = volume of water passing through the chipped area of the spalled top surface around the hole, and • VH = volume of water passing through the area if the sides and bottom of the drilled hole. Combining VC and VH, Eqn. 10 where: • VCH = volume of water passing through the area of the chipped surface and drilled hole. Substituting Eqn. 8 into Eqn. 10, Eqn. 11 Rearranging, Eqn. 12 Referring to Eqn. 1, the initial surface absorption of the chipped are and the hole can be written as, Eqn. 13 Substituting Eqn. 12 and Eqn. 5 into Eqn. 13, the initial surface absorption of the surface of the drilled hole plus the chipped area around the edge of the hole can be defined as:

F-16 Eqn. 14 Rebound Hammer Test Procedure Concrete hardness was measured with a rebound hammer in general accordance with ASTM C805 using a Suspa DSI GmbH Original Schmidt hammer. The hammer was used in the vertically downward position in the general location of the installed anchors. These tests were conducted after the anchor pullout tests in case the hammer caused cracking in the early-age concrete. The average of ten readings was reported and a 6” cube concrete compressive strength was estimated using a scale provided by the manufacturer. Indention Hammer Test Procedure Concrete hardness was also measured with an indention hammer in general accordance with DIN 4240. The hammer was used in the vertically downward position on the full load setting in the general location of the installed anchors. These tests were conducted after the anchor pullout tests in case the hammer caused cracking in the early-age concrete. As allowed by the test standard, carbon paper was used to better distinguish the indention. Two orthogonal diameters were measured of each indention and their values averaged. The average of twenty readings was reported and a 6” cube concrete compressive strength was estimated using a scale provided by the manufacturer.