the second pour and de-mold

We learned so much from the first pour and we were determined to make sure the second and final cement pour went well. We had some additional challenges with the pour in that the school year was quickly coming to a close and Jasmine had professional commitments looming.  We also had to wait for the benches to cure in 30 days before they could be sealed with a protective concrete sealant. All of this needed to be done technically before the contract expired, at the end of June. Based on our tight scheduling constraints, we decided to pour on Tuesday and then de-mold on the Friday, May 17th the last Professional Development Day of the year.  This meant that the second de-molding day would sadly not have students present.  At this point however, we felt the process had been celebrated and the important learning had been achieved.  The actual molds would not be altered in any way, so that part would not be a surprise to the students.  We wanted a second crack at the perfection of the visual ideas, not to recreate the entire project.

We did need a crew to help and our incredible grounds and maintenance staff stepped up and came to our aid.  They were fantastic in that they came in strong numbers and cheerfully flipped, unbolted and lifted the final pieces in the rain. I can't say how thankful we were to them for their help.  The results were truly fantastic - the second time was the charm!

So what did we do differently? First of all we allowed an extra day for the pieces to solidify along with the daily watering.  The weather was cooler and wetter this week which helped our cause.  Jasmine took all that she had learned from the various experts consulted and hung the rebar without the use of the wooden planks across.  The theory was that the wood prevented the cement underneath from drying at the same speed as the concrete surrounding it, causing the cracking. She also worked carefully to push the concrete into all the nooks and crannies in the book stack mold to avoid those pesky bubbles. She also gave the side of the mold a couple of whacks with a rubber mallet to agitate any remaining bubbles away from the edges and up to the surface.

We all held our breath when the de-molding began. What we found cheered us beyond belief.  Everything was better.  The detail was better.  The bubbles in the book stacks were greatly diminished. Even the pop can came out intact (Jasmine cut it out this time to be sure).  And best and most importantly of all, there was not a single crack to be found.  Each and every bench was perfectly structurally intact. Now all we had to do was wait for the cement to cure and be sealed. After that, we could get to the work of installation.

De-molding Day

 Wow! So much has happened so quickly and time has flown by!  Let's begin with our de-molding day. Two days after the pour we were ready to take off the mother mold and release the cast concrete underneath.  We were careful to keep the concrete moist and protected from the elements so that there were no sudden changes in humidity/temperature while we waited for the big day.  The Richmond News offered to come to help us document this exciting part of the process.  You can find a link to their story at http://www.richmond-news.com/Richmond+students+create+with+school+mind/8363275/story.html

Our students, Jasmine and a crew from our grounds and maintenance team worked tirelessly for hours to remove the molds and reveal the cement underneath.  The process involved first sliding the molds off of the sand and onto a wooden board.  Then many hands worked to flip the heavy piece so that we could access the hard outer shell and begin the process of unbolting it.  After all the hardware was removed, Jasmine used a chisel to separate the hard pieces and reveal the softer pink rubber mold underneath. Next Jasmine carefully peeled the inner mold off to reveal the detailed, now concrete, objects underneath.  We then cleaned and reassembled the molds so that we could potentially make more benches.  We quickly covered each piece with burlap sacks and sprayed them with a hose to help further protect the concrete from cracking.

 Unfortunately, we discovered that there was cracking already.  We were unsure of the extent and the reason for the damage, but as we continued to release each mold it was clear there was a problem with the concrete setting around the rebar suspension system. Looking at the images you can see fissures appear at the same spot on each bench which gave us our first clue. They each appear right above where the clamps, wooden pieces and wire were placed to keep the heavy rebar - commonly used in cement to add extra strength - from falling to the bottom of the mold (see previous post).  It did not dampen the day for us as the cracks were not wide, the pieces seemed solid and we thought we could simply reinforce the benches to make them work at this point.  There were some more minor issues with tiny air bubbles in the book stacks and the pop can did not come out in one piece, but we felt we could deal with these things. Just seeing each bench revealed was like magic.  It still took our breath away to see how clear objects like the banana or the gum wrapper came out.

After the initial joy of the day passed, we had to reflect on what the reality of the cracking meant.  The benches could not be counted on to stand up over time or function properly.  With our cold winters it would mean that water could easily get into the cracks and freeze, turning our beautiful benches into rubble in no time.  Jasmine was understandably not comfortable with delivering less than perfect pieces and after all the hard work and learning we all desperately wanted this project to end happily.  So we were incredibly relieved when the City of Richmond Public Art Program said they would cover the cost of a second pour as our budget had run dry.  It was a generous solution to a difficult situation.  Jasmine launched a thorough review of the first process and consulted additional industry experts so they could pinpoint the reason for the cracks and how we could avoid them in the second pour.  We really thought we had allowed for every possible variable through our first intensive consultation and planning process from the first pour, but as so often happens in art, something unexpected happens. We were so very lucky to have a second chance to get it right, and we were not going to waste it.