Field Implementation of Rubberized Chip Seal

Chip seals have been widely used as a pavement maintenance surface treatment due to its competitive cost and construction time. Recently, the research team developed a rubberized chip seal where natural aggregate is replaced with crumb rubber obtained from recycled tires. During this study, a total of 108 laboratory specimens and a field chip seal section with different crumb rubber replacement ratios were investigated. Aggregate macrostructure, retention, and skid resistance were measured. The crumb rubber showed a remarkable performance in aggregate retention measured using the Vialit and Pennsylvania tests. The values of the mean texture depth of rubberized chip seal specimens were significantly higher than those of the conventional chip seal. Finally, while a reduction in the British Pendulum Number (BPN) was recorded with an increase in the crumb rubber replacement ratio immediately after construction, after a period of more than a year of service life in the experimental section road, the rubberized chip seal segments recorded a much higher BPN compared to that of the conventional chip seal segment. Furthermore, it is recommended also to increase the curing time for chip seal, regardless of aggregate type, to at least six hours to improve the performance of the chip seal.

VIEW FINAL REPORT

Report number: cmr18-012
Published: December 2018
Project number: TR201804
Authors: Ahmed Gheni, Alireza Pourhassan, Mohamed ElGawady, Yasser Darwish, and William Schonberg
Performing organization: Missouri University of Science & Technology

Characterization and Performance of Zero-Cement Concrete

This study has investigated the feasibility of using five different types of class C fly ashes (FAs)  sourced from Labadie, Jeffrey, Kansas City, Thomas Hill, and Sikeston power plants in the state of Missouri to synthesize zero-cement concrete (ZCC) for different structural and repair applications. Alkali activator (Alk) consisting of sodium silicate (SS), Na2SiO3, and sodium hydroxide (SH), NaOH were used to synthesize the ZCC. Slag, crumb rubber, and air-entraining admixture (AEA) were used in a few mixtures as additives to improve the durability of the ZCC. Approximately 300 mortar and concrete mixtures were prepared during this study to investigate the mixing procedure, water/FA, Alk/FA, SS/SH, curing regime, fresh properties, mechanical properties, durability, repair applicability, and cost analysis of the ZCC. A 5000 psi MoDOT conventional concrete (CC) mixture was also prepared and tested for comparison purposes. This study revealed that ZCC can be used as a replacement for CC. ZCC showed good workability and adequate compressive strength for structural applications ranging from 3,660 psi to 7,465 psi based on the curing regime and source of FA. Some ZCC mixtures successfully passed 300 cycles of freeze and thaw per ASTM C666-15 procedures A and B. Furthermore, the drying shrinkage values of the ZCC specimens at all ages were significantly lower than those of the corresponding CC specimens. ZCC also presents higher corrosion resistance compared to CC. ZCC mixtures have a low to moderate permeability and chloride ion penetrability, while the CC mixture showed a high permeability and chloride ion penetrability. Finally, ZCC can be used as a repair material for existing concrete structures. The bond between ZCC as a repair material and CC as a host material was adequate and comparable to the bond between CC and CC.

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Report number: cmr18-011
Published: December 2018
Project number: TR201614
Authors: Eslam Gomaa, Simon Sargon, Cedric Kashosi, Ahmed Gheni, Mohamed ElGawady, William Schonberg
Performing organization (s): Missouri University of Science & Technology