Assessing the performance of sustainable and luminescent concrete sealers
Soy methyl ester polystyrene (SME-PS) is an alternative sealer that has been put through a variety of tests in the lab. The goal of this research is to quantify the sealer’s effectiveness at protecting concrete in the field. SME-PS is comprised of a renewable resource and a waste product; soybeans and waste styrofoam respectively. SME-PS is hydrophobic and absorbs into the surface of the concrete therefore, it reduces the ingress of water and other materials contained in the water such as deicers. Moreover, it has proven to have similar performance compared to other sealing techniques in shorter, more aggressive tests. However, a need exists to understand the performance of SME-PS over longer periods of time. Approximately 4 years ago, two field locations located in Indiana - one on US 231 in Lafayette and another on 126th Street in Fishers - were sealed with SME-PS to address this need. This work revisits these sites to identify if any new damage has occurred since the time of SME-PS application. Cores were taken from the two test sections. A new test method was developed to test sealer performance in concrete pavements. This test uses a titration technique to determine chloride ingress from the surface of the concrete pavement saw cut. SME-PS shows similar performance in some locations while in others the chloride content is 20% higher when compared to the filler and backer rod. Compared to the unsealed pavement joints, both SME-PS and filler/backer rod sealant show a reduction in chlorides of about 40-50%. One observation made while preparing some of the cores for titration was that the depth of the saw cut varied greatly which start to influence results since deicers come in from the top surface. Another important caveat of the titration test is that it does not distinguish between free chlorides and bound chlorides. It is important to account for these discrepancies when interpreting the results of the test and subsequently determining sealer performance. This work encompasses the first results obtained from the field. It is important to continue sampling in order to determine how long the SME-PS compares with current sealants over a longer duration of time. In addition to the two locations on Indiana roads, 60 concrete slabs made according to Indiana Department of Transportation (INDOT) specifications were cast at the Center for Aging Infrastructure (CAI). These slabs are exposed to the environment and deicers are sprayed on the surface to accelerate chloride ingress. Continuing data acquisition from these two experiments will help users understand how long their concrete remains sealed and when reapplication is recommended. The second portion of the work highlights the mixture of SME-PS with a luminescent powder for use as a glow in the dark (GITD) concrete sealer. The luminescent powder, strontium aluminate, luminesces in the dark after being excited by light. The luminescent sealer could be used to increase concrete service life, supplement streetlights, and increase the travelling public’s safety at night. A test procedure was developed to quantify the sealer luminance and duration. Quantification of the sealer’s luminescent properties is key to evaluating the performance. The results of the tests indicate the sealed luminescent surface emits light (i.e., glows) for approximately 1 to 50 hours in a dark space after excitation depending on application rate, particle size, exposure time and orientation in the field.
Weiss, Purdue University.
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