The growing popularity of pervious concrete pavement applications has increased the need for development of quality control and quality-evaluation test procedures that are suited specifically for pervious concrete rather than for traditional concrete.
Pervious concrete is desired for its role in stormwater management and runoff control and is often used for parking lots, ferry terminal holding lanes, low volume roads, and other light-duty applications. Pervious concrete contains little or no sand, creating a substantial void content, and that produces a system of highly permeable, interconnected voids that drains quickly. That characteristic provides many environmental, economic, and structural advantages.
This brief study took a few preliminary steps toward developing appropriate quality control and quality-evaluation test procedures by identifying suitable specimen sizes for testing, proper methods of casting and compacting specimens at the job site, the compatibility of fresh and hardened physical properties, and proper curing methods for compressive strength testing. Researchers investigated the effects of specimen size on the physical properties of pervious concrete, such as hardened porosity and density, as well as compressive strength (f’c). In addition, the project investigated the effects of four different curing regimens, featuring different combinations of air and moist curing, over a four-week curing period on the 28-day compressive strength for two specimen sizes.
Pervious concrete was sampled from a Washington State Department of Transportation (WSDOT) paving project at the Vashon Island Ferry Terminal. Forty-eight 4-in. and 40 6-in.-diameter cylinders were cast and tested. The 4-in. and 6-in.-diameter cylinders demonstrated comparable values of hardened porosity and density, implying that either size specimen would be suitable for use in quality control testing. Hardened densities obtained in the laboratory from cast cylinders were within 2 percent or less of the fresh densities obtained for the mixture in the field, demonstrating the suitability of the implemented specimen casting and compacting methods.
The compressive strength of the smaller cylinders was higher than that of the larger cylinders by 8 to 19 percent, depending on the curing method. The combination of two weeks of air curing and two weeks of moist curing resulted in the highest 28-day compressive strength for both specimen sizes. Four weeks of air-only curing yielded the lowest compressive strength. The findings of the study should be expanded to include more mixtures and testing.
Authors:
Somayeh Nassiri
Milena Rengelov
Zhao Chen
WSU Department of Civil and Environmental Engineering
Sponsor: WSDOT
WSDOT Technical Monitor: Mark Russell
WSDOT Project Manager: Lu Saechao