WATER STORAGE CASE STUDY

Project: Alley 111 Mixed-Use Condo Building
Location: Bellevue, Washington
Architect: GGLO
Building Envelope Consultant: Morgan Design Group
Shotcrete Contractor: Air Placed Concrete
General Contractor: Exxel Pacific
Ready Mix Provider: Cadman (Heidelberg Cement)

The Project: The new 12-story Alley 111 mixed-use high-rise in downtown Bellevue, Washington, included a water-retention vault to capture and store stormwater per the city’s building code for backup fire-suppression purposes. The LEED-eligible retention vault will also collect water from the exterior building envelope so this grey water can be metered, stored, or repurposed for non-potable water uses.

The Challenge: Planning for a watertight vault inside a building required consideration of different options while still working within the building schedule and budget.

The Solution: The vault, located at one corner of the foundation of the high-rise structure, used two of the outer foundation structural walls and two interior walls to create the rectangular vault. The interior walls were constructed using a conventional double-formed method, while the outer structural walls were constructed by shotcrete placement. Crystalline concrete admixture was used in the concrete batch mix, creating waterproofing for the two structural walls as well as the interior walls and slab. The structural walls were constructed using a blind-side shotcrete method to ensure that it is watertight.

Results: The developer’s confidence in the crystalline waterproofing solution helped the project team save forming costs and accelerate the project schedule.

SHOTCRETE CASE STUDY

Project: Thames Tideway Tunnel – Western Section
Location: London
Contractors: BAM, Morgan Sindall, and Balfour Beatty Joint Venture

Project: Thames Tideway is London’s new “super sewer” running from Acton to Beckton. It is being built to prevent millions of tons of pollution from reaching the River Thames.

The Waterproofing Challenge: During the design phase, technical discussions were held between SMR Projects and the joint-venture designers Morgan Sindall Underground Professional Services. These discussions were to explore how crystalline technology could assist in reducing the permeability of the concrete. This was especially important across the construction joints. Trials were undertaken in conjunction with a ready mix company to establish how the crystalline technology behaved within the very specific mix design. The trials were needed to prove its watertightness over standard tunnel construction methods. A number of trials were set up with and without crystalline products for a clear comparison.

The Successful Solution: The trial results proved that the addition of crystalline admixture to the concrete gave the greatest protection against permeability. The growth of the crystals across the joint gave a seal in excess of what was thought possible. When tested across the 45-degree “day” joint, cores were taken through the joint in three axes to test for water permeability, and the results were more than enough to confirm that this technology was superior.

Based on these results, some design changes were implemented. The Western Section of the Thames Tideway was originally planned to be constructed using a sprayed-concrete primary liner and a cast-in-place secondary liner with a waterproof membrane placed in between the two layers. The trial results satisfied the stakeholders enough that the addition of the crystalline admixture was enough to remove the membrane first in one connector and then in the whole Western Section. The crystalline admixture was incorporated within the sprayed concrete used on the primary liner, awaiting the secondary liner to be cast directly against it.

Results: The crystalline admixture waterproofed the concrete and joints during the hydration period of the concrete. It also provided additional benefits over and above nonactive pore-blocking admixtures by having the ability of self-heal cracks up to 0.4 millimeter. Furthermore crystalline technology is proven in new sewage and wastewater treatment structures. It is excellent at handling chemical attack in severe biochemical conditions.