Hale Kalele

Hale Kalele is a P3 mixed-use development featuring an affordable rental tower, Juvenile Center (JSC), and six-level parking structure. The tower sits atop the JSC podium that contains administrative space, offices, and shelter services. The JSC is operated by the Hawaii State Dept. of Justice and the tower is operated by the developer’s managing agent.

The tower is designed with a minimum anticipated use of 75 years, so the durability of the tower was carefully considered. The team selected an all-reinforced concrete system using tunnel form construction which includes casting of the floor and walls simultaneously to speed construction. Another benefit of this method is that many of the interior walls are also cast as load-bearing concrete walls. This creates added durability within the units and reduces the need for framed walls. The final design becomes a very efficient reinforced concrete system where most all the reinforcement is based on code minimums and slab and wall thicknesses are controlled by minimum thicknesses for fire resistance and sound transmission.

The project team spent extra time and energy to be mindful of the project’s carbon footprint. CarbonCure was incorporated into the construction which consists of trapping CO2 and injecting it into the concrete mix. CarbonCure uses clean technology to create concrete with less cement, reducing the carbon footprint without comprising strength. This required commitment from all stakeholders including the concrete supplier HC&D to identify and address concerns with the use of this new technology.

Achieving the required concrete strengths was a concern. When construction started there was minimal test data available for CarbonCure in higher strength concrete needed for the tower. Since this would be the tallest building to date using CarbonCure, the project team and HC&D implemented a stepped process in its incorporation in the concrete mixes. This included progressively increasing the amount of CO2 injection while decreasing the amount of cement as the tower went vertical. Additional concrete testing was conducted by BASE and HC&D to track the progress and allow for further reduction of cement content. By the time typical tower floors were reached, there was enough data to justify the proposed final mix and the project achieved a 5% reduction in cement requirements. The success of Hale Kalele has become a model for other concrete buildings, small and tall, to reduce their embodied carbon.