New Caltrans Concrete Parking Lot Helps Reduce Urban Heat Island Effect in Downtown Sacramento

The parking lot adjacent to the Caltrans Headquarters in Downtown Sacramento had a couple of problems – the asphalt was in a state of disrepair due to cracking and it was hot, really hot. When the air temperature was 96 degrees, the parking lot radiated at 127 Fahrenheit.

Caltrans addressed the needed parking lot work from a sustainability perspective. Aware of the cost savings that concrete pavement delivers thanks to reduced maintenance, the primary focus of this project was to reduce the urban heat island effect through concrete pavement’s cool quality. Using higher reflective surfaces like concrete reflect more of the sun’s rays (versus absorbing them) thereby reducing the ambient temperature. Buildings use reflective roofs or green roofs with native grasses and plants to mitigate this effect. By reducing the ambient temperature even a few degrees, surrounding buildings will experience a reduction in air conditioning demand. Even a slight decrease means significant, cumulative savings over time, and that translates to reduced CO2 emissions and greater pedestrian comfort on ground level.

Dulce Rufino Feldman, Ph.D., P.E., Senior Concrete Pavement Design Engineer for Caltrans, partnered with Southwest Concrete Pavement Association’s Executive Director Charles Stuart, California Nevada Cement Association’s Technical Director Clay Slocum, and Cemex’s Sustainable Infrastructure Solutions Manager Michael Smith to develop a plan to transform the key piece of Downtown Sacramento real estate from a heat sponge to a cool, reflective parking lot that would require little to no maintenance for decades to come.

Working together, it was decided that the best solution would be a thin concrete pavement.  Cemex’s mix design included 30% slag for lower carbon and a slightly lighter surface to improve reflectivity. Precise planning enabled the entire project to be completed within just two weeks, with the project consultants on site for both days of the pour to ensure quality and performance standards.

The result is a cool new parking lot that now during the hot Sacramento summer months effectively reflects more of the sun’s rays and registers a surface temperature significantly lower than the previous asphalt pavement.