Construction Summary

Table 5.3 summarizes some of the statistics regarding each support condition type. The time estimates are approximate based on notes taken on site as well as time-stamped photos and videos.

It should be noted that eight panels were placed for the Asphalt-Supported condition, so the milling and panel placement times are referring to a slightly larger section. Furthermore, the milling time for Asphalt-Supported panels includes the time for both the original milling, and the second round of milling when the crew was called back to the site.

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Table 5.3: Summary of Construction Activities

As shown in Table 5.3, the required amount of bedding grout varied between the different support conditions. The Grout-supported panels required the most bedding grout and this was an expected result as the levelling bolts were used to produce a void beneath the panels to be filled by grout.

The Grade-supported panels required the least bedding grout, indicating that the graded material and the bottom surface of the panels aligned well, with few voids between the two surfaces. The relatively high bedding grout requirement of the Asphalt-supported panels indicates that the ±3mm surface tolerance of the milled surface was not achieved, and substantial voids beneath the panels required filling with bedding grout.

Each night, two 6-person crews of Dufferin workers were on site. Generally, they divided up as panel placement and grouting crews, however these divisions were fluid as each night required different activities, including helping to install instrumentation.

Grouting was not performed in a linear order, and often included parallel tasks occurring at once.

Therefore, estimating the times of each grouting operation was not undertaken. Generally, it was found that there was sufficient time in each case to grout the panels that were placed the previous night. On September 21^st and 22^nd portions of two sections were grouted in one night, though for different reasons.

Bedding Grout Bags per slab 12 4 14

Overall Time On Site (hr:min) 9:00 10:00 9:15

Time of 2nd Lane Closure 10:50 PM 10:15 PM 10:00 PM

*average time per meter length of 3.66m lane. Milling machine was considerably faster at 1.2 m width

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The following section summarizes some of the findings and notable points from each night of construction. The findings applicable to all support conditions are outlined first, followed by those specific to each separate support condition.

5.4.1 General Findings

1) Some flexibility was observed in lane closure times (specifically Lane #2). The effects of stricter closure times are difficult to gauge based on this trial procedure.

2) Milling equipment can do a transverse milling pass, which greatly reduces the amount of handwork required at nightly milling extents although this process did inflict damage on the adjacent HMA pavement. Some chipping of remaining HMA is still required, but only at the corners, as opposed to the full lane width.

3) The milling method used on this project could not accommodate depth and cross slope inputs as originally hoped for. By referencing the milling off of a ski riding along the edge of the existing shoulder, the depth and cross slope can only be made relative to that reference plane. After all passes were finished, the depth and cross slope needed to be checked before the milling team can leave the work zone . This was done using stringlines, levels, and measuring tapes on site, with some success. Ideally, the miller should start on the high side of the lane (ie. adjacent to Lane 2 for Lane 3 milling) to ensure the cross slope is maintained across the lane width.

4) Care should be taken to adhere to the limits of the milled area. Accidentally extending the milled width resulted in a need to install edge grout on the same night that the panels were placed. This could have greater impact in future applications in which the edge gap is significantly smaller to avoid hollow structural steel.

5) As a follow up to Point 4), the edge grout detail on this project provided a level of redundancy in the case of milling errors such as the one experienced. The edge-grouting crew was able to fill the void in order to reinstate traffic with little delay.

6) Overall, milling time was significantly reduced as familiarity with the strategy was gained.

7) It was found that the remaining HMA thickness after milling was approximately 140 mm.

8) The first panel in each support condition presented difficulties with base preparation. It was found to be very difficult to achieve a smooth surface using chipping hammers. This

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would be remedied in part by removing the temporary end panel prior to milling, which is a consideration for future applications.

9) Unloading procedure should be reviewed for safety. The panel truck parked in lane adjacent to traffic made potential interactions between the two possible. Cranes with long cable lengths appear to make the possibility of a panel swinging out into traffic likely although that risk can be managed by mandating the use of tie ropes during placement.

Positioning the panels on the shoulder or in the same lane may provide a larger buffer between the panels and traffic, however this alignment is often not practical or possible on three lane highways.

10) Bedding grout initially required mixer clean-outs every 4 batches (16 bags), but this was eventually reduced to clean-outs every 7 batches (28 bags). This is partially due to increased efficiency of mixer discharge as soon as grout is prepared. This improved throughout the course of construction. Grout crew members need to be careful to observe for signs of grout setting-up (steam), as this can bring grouting to a stop for the night.

11) Water content of constituent materials needs to be accounted for. In the case of edge grout, the high moisture in the pea-gravel caused the material to segregate upon placement, leaving a honeycombed surface that is expected to ravel relatively quickly. The water proportioning of the grout should be done incrementally if the moisture contents of the materials are unknown. In the case of the CTBM, the water content in the sand caused the material to clump and begin hydrating on site while being mixed in the concrete truck. A trial batch of CTBM should be made before it is sent to the job site to make sure it is dry enough to be graded and compacted efficiently, to avoid the clumping observed on this project. Alternately, the cement could be added and mixed with the sand on site just prior to placement.

5.4.2 Asphalt-Supported Trial

1) This strategy was not flexible in responding to milling mistakes. The precise HMA profile that is required means that milling must be done to tight tolerances. Depth and slope tolerances of the milled surface were found to be the most difficult to achieve.

2) Once milling tolerances were achieved, the placement of panels progressed quickly.

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1) Depth of milled surface presented problems. Changes in milling depth from the previous night may have contributed to this. This strategy allowed for flexibility to accommodate changes in milled depth.

2) Placement of screeding rails requires a minimum of three persons. Proper planning is required for their placement.

3) Extra machinery (screed, rails, and tamper) produces greater potential for break-down on site, (ie. the handle on the screed was broken on site). Also, the rails that the screed ran on have the potential for tripping workers entering and leaving the milled area. The rails also interfered with the location of the trucks bringing the panels to be unloaded.

4) Hardened CTBM beneath temporary panel required extra effort for removal the following night. This issue would not be critical if temporary panels were removed prior to milling, or if there wasn’t a transition between support conditions between nights.

5.4.4 Grout-Supported Trial

1) Positioning the crane ahead of the panels being placed worked reasonably well. This orientation meant that the cab of the truck was not an obstacle as panels were rotated away from the cab.

2) High-torque impact wrench is required in order to effectively lift panels prior to grouting.

Extended pipe wrench was found to work well as a redundancy but required significantly more effort and time.

3) When raising the panels, enough levelling bolts should be present on-site to engage all levelling lifts. Issues were avoided in this instance, but if all levelling lifts were required, there were not enough bolts.

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