Emsworth Lock & Dam
We worked on two major projects on at the Emsworth Lock and Dam.
In the early 1980s we supplied all the concrete for the last major reconstruction of Emsworth Lock and Dam. The General Contractor was Morrison Knudsen, a large national/international contractor. Much of the concrete was supplied by loading our trucks onto a ferryboat and taking them out to the placement site. Often times a pump was located on the ferry with the trucks and the trucks would jockey around to position themselves at the pump. Other times the pump was situated on a work barge tied to the lock wall and the trucks would discharge from their place on the ferry into the pump hopper with all the chutes down.
The next part of the project occurred in 2009 we began work again on the Emsworth Lock and Dam. The front channel portion of the Lock was being repaired. The project involved several caissons and scour protection at the bottom of the river. The scour protection was converted to large precast slabs that would be placed by divers on the river floor. Concrete Concepts Inc. was awarded the precast on the job and began casting these large sections.
Concrete mixers on ferry boat - early 1980s
A large portion of the ready mixed concrete on the job required an anti-washout concrete design. In combination with the anti-washout properties, we were also required to provide self consolidating properties to the mix. The Self Consolidating Concrete (SCC) was required due to the rebar density within the caisson as well as the distance the contractor had to pump the concrete. The anti-washout properties prevent the concrete from separating when the concrete is dropped through water. The traditional design used by the Army Corps of Engineers was modified to provide a more fluid and cohesive mix. The testing performed was to determine the percentage of cementitious wash-out which was basically tested dropping a sample of concrete contained in a porous basket through a column of water. Traditional numbers for the wash-out test were around 5% wash-out with a maximum of 8%. After several iterations of the concrete design and optimizing each component of the mix, we were able to achieve a wash-out below 2%. This combined with the fluidity of the mix proved to be one of the best anti-washout concrete designs the contractor has ever placed.
We also did some smaller jobs at Emsworth, which resulted in our developing a mix that we poured into 4 three yard concrete buckets, that were sitting on a work barge on Saturday morning. The concrete was not placed until Sunday afternoon, when the contractor had removed some existing concrete and replaced it with the concrete we provided. Key point was the use of a set retarding admixture properly dosed and controlled in the mix. The concrete went into the buckets at a 9” slump and was placed the next day at a 6” slump.
These are good examples of the flexibility and ingenuity we can provide our customers on highly technical and uniquely challenging projects.