Concrete Technology for Transportation Applications (2019)

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113 Conclusions From the results of the literature review and of the survey responses, a number of key conclusions have been drawn: 1. The literature review showed that implementation of traditional, emerging, and new concrete technologies has resulted in major benefits to the transportation infrastructure. The benefits include accelerated construction, replacement and repair of pavements and bridges (UHPC, HESC, VHESC, RCC, and PCP), better performance, and improved durability (HSC, SCC, ICC, and PEM), control of temperature in massive structural members to mitigate thermal cracking and improve durability (TCMC), and enhanced sustainability and environmental benefits (RCA and PC). 2. The survey responses from 40 states showed that the top three most implemented concrete technologies are HSC (40 states), SCC (38), HESC (37) and LMC (31), and the least imple- mented technologies are UHSC ≥ 10,000 psi (69 MPa) (15), PC (14), and ICC (9). 3. The survey also showed the following results: a. Fourteen states (Delaware, Florida, Georgia, Illinois, Kansas, Louisiana, Maine, Missouri, New York, Ohio, Pennsylvania, Vermont, West Virginia, and Wyoming) have experimented with or implemented technologies other than those discussed in this report. b. Only three states (Florida, Maine, and Kansas) reported depletion in quality aggregates. However, another 13 states (Idaho, Louisiana, Minnesota, Montana, New Jersey, New York, North Dakota, Oregon, Pennsylvania, South Carolina, Texas, Utah, and Vermont) predicted shortages in the future. The remaining 24 states reported no shortages. c. Thirteen states (Alabama, Florida, Illinois, Maine, Massachusetts, Michigan, Missouri, New Jersey, New York, North Dakota, Oregon, Rhode Island, and Texas) reported current shortages in the availability of fly ash, 16 other states (Arizona, Arkansas, Colorado, Connecticut, Delaware, Georgia, Idaho, Minnesota, Mississippi, Montana, Nebraska, North Carolina, South Dakota, Tennessee, Vermont, and Washington) predicted future shortages, and the remaining 12 did not report any shortages. d. The top solutions offered to address the shortage of fly ash include expansion of the use of slag, use of alternative pozzolans such as metakaolin, and import of foreign ash and use after reprocessing for a lower LOI, or import ash from other states. e. The most widely used recycled or reclaimed material in concrete applications is RCA. Fifteen states (Alabama, Colorado, Connecticut, Florida, Illinois, Michigan, Minnesota, Missouri, New York, Ohio, Texas, Washington, West Virginia, Wisconsin, and Wyoming) use RCA in pavements, and 5 states (Alabama, Connecticut, Illinois, New York, and Texas) use RCA in structural applications as well. C H A P T E R 5 Conclusions and Technology Information Gaps

114 Concrete Technology for Transportation Applications f. Seven states have experimented with the use of other reclaimed materials in concrete mixtures. Five states (Florida, Georgia, North Carolina, Oregon, and Wisconsin) have conducted research on the use of shredded or crumbed tire rubber. Four states (Florida, New York, North Carolina, and Wisconsin) have reported research on the use of bottom ash as an ingredient in concrete mixtures. Three states (Florida, New York, and Wisconsin) have experimented with the use granulated glass in concrete. Two states (Florida and New York) have experimented with municipal waste ash, and Georgia and Rhode Island have used plastic bottle fibers. Florida has also conducted research on biomass ash. g. The top five barriers to implementation of concrete technologies by the state include: – Technology not sufficiently proven to be adopted (30 states), – Too expensive to use (28 states), – Lack of experience and not enough training (27 states), – No specifications or construction guidelines available (23 states), and – Industry resistance (21 states). h. Other notable responses on the issue of barriers to technology implementation include the following: – Lack of experience by agency and local industry, – Concern about potential reduction in concrete mixture quality, – Ability to assess long-term concrete durability with some technologies, – Implementation challenges, and – Time constraints and cost-effectiveness. Gaps in Concrete Technology Information Also, gaps in the information pertaining to specific technologies were identified and are provided for further attention. Among the information gaps are the following: 1. The level of training needed to successfully implement new technologies is not to the expectations of many state DOTs. 2. The need for air entrainment in HSC and UHSC to resist freeze-thaw actions has not been completely settled in the research community. 3. Unanswered questions remain about the use of SCC in pavement repairs and slab replacements. 4. Some states indicated that sources of lightweight aggregates for ICC are not available at convenient locations to make them cost-effective. Also, there seems to be uncertainty about the expected ICC performance using lightweight aggregate from different sources. 5. Most mixtures used to produce UHPC are proprietary. This causes an increase in construc- tion costs according to the survey responses. 6. With respect to TCMC, there does not seem to be consensus among the states, industry groups, or published research on the limit of the maximum core temperature and tem- perature differential between the core and the surface of the structure. Also, the question of accuracy of numerical modeling is an area of concern. 7. There does not seem to be well-defined, acceptable procedures for maintenance, reservation, and panel replacement in a posttensioned PCP. 8. Two main obstacles remain that limit expanding the use of RCC in highway pavements. These are control of surface smoothness and absence of effective load transfer or dowel bars to increase the load-carrying capacity at joints and prolong their performance. 9. The two major gaps in the PC technology are lack of a specialized machine to place and uniformly compact the material without damaging its void structure, and avail- ability of guidelines for design, construction, QC testing, and preventive maintenance of PC pavements.

Conclusions and Technology Information Gaps 115 10. The most common distress problem when using HESC in replacement panels and slabs is premature cracking from thermal and nonuniform shrinkage stresses. Many states do not seem to have effective measures to mitigate the problem or guidelines to assist in deciding when to repair or to remove the damaged slabs. 11. The long-term performance of VHESC repair materials is not well understood, particularly impact of type of application and weather conditions. Issues such as premature setting, excessive shrinkage and cracking are also areas of concern. 12. The states have shown interest in the feasibility of using alternative pozzolans to supplement the expected shortages in traditional fly ashes. However, they are concerned about the impact of the alternative pozzolans on short- and long-term performance of concrete.