SECTION 5

Business Case for and Barriers to Adoption of UHPC-C

The evaluation focused on the business case for and barriers to adoption of UHPC-C as opposed to CC-C. Data were gathered primarily through stakeholder interviews, using Rogers’ Diffusion of Innovation Theory as a guide. Rogers’ theory explores how, why, and how rapidly innovations are adopted through five key product characteristics: relative advantage, compatibility, complexity, trialability, and observability (Rogers 2003). In this section, preliminary results are presented for each characteristic. In sum, the research found that

1. The absolute advantages of UHPC compared with conventional concrete (increased strength, durability, and impermeability) are substantial, but the relative advantages are strongest in areas with the most exposure to precipitation and freeze–thaw cycles.
2. Other than the price of UHPC material, compatibility may be the most significant barrier to adoption of UHPC-C and the ABC methods it enables because these are disruptive technologies.
3. UHPC-C use requires some additional training on appropriate design, construction, and field application methods, as well as on practices for inspection and quality management, although the added complexity is not generally substantial.
4. TFHRC support has been and could continue to be instrumental in trialability, especially as less-tested generic mixes are developed.
5. Observability is a potential barrier to UHPC-C adoption, given the different time spans of benefits versus costs. TFHRC research, however, has allowed owners to observe early signs of UHPC-C performance benefits, playing a valuable role in encouraging field applications.

5.1 Relative Advantage

Relative advantage is the degree to which an innovation is an improvement over an alternative technology. Research and interviews suggest that the main advantages of UHPC compared with conventional concrete are its increased strength, durability, and impermeability. The impermeability of UHPC is especially helpful for deck connections in areas with high precipitation and freeze–thaw cycles, given the exposure for these bridge elements. For other deck connections, however, interviewees indicated that the performance of CC-C or steel bolts is generally sufficient, reducing the relative advantage of UHPC-C. The main alternatives to using prefabricated deck slabs are to pour and field-set a solid deck in place or to use lateral slides, whereby a solid deck is poured and field-set in an area adjacent to the bridge being constructed and then slid into place. In either case, the associated connections are beneath a solid deck and, provided the bridge does not cross a body of water, are less exposed to water.

Both existing literature and stakeholder interviews indicated that the absolute performance benefits of UHPC over conventional concrete are substantial. In the literature, Piotrowski and

Schmidt (2012) predicted UHPC to have a 100-year life span, compared with a 50-year life span for conventional concrete. Interview respondents noted similar, although admittedly hyperbolic, sentiments that UHPC “lasts forever” and will “never” require maintenance.² Interviewees also indicated that UHPC performance attributes enable up to a 50% reduction in material requirements compared with conventional concrete. For deck connection applications, the material reduction can reduce spatial requirements for construction zones and increase space allotted to traffic, thereby improving work-zone safety.

5.2 Compatibility

Compatibility is how consistent a new technology is with current procedures and the needs of potential adopters. Other than the price of UHPC material, this aspect may be the most significant barrier to adoption of UHPC-C and the ABC methods it enables. Interviews indicated that ABC and UHPC are disruptive technologies. Many bridge construction companies have already invested in conventional concrete and mixers, as well as workers, to build bridge components on site. ABC alters the business model by shifting work away from construction companies toward off-site PBE suppliers. UHPC also mixes best in more efficient—and therefore more expensive—concrete mixers, and some proprietary UHPC suppliers require that users rent mixers from them. Securing the needed equipment can create time lags and add expense to any UHPC application, including UHPC-C. In addition, UHPC cures at higher temperatures than conventional concrete. Shifting construction schedules or weatherizing the pour area can add more delays and expenses.

Specifically pertaining to materials costs, a few interviewees mentioned the “Buy America” requirement for the steel fibers as a deterrent. Domestic cost-competitive production of steel fibers would be beneficial for UHPC producers.

5.3 Complexity

Complexity is the ease with which an innovation can be understood and used. UHPC-C use requires some additional training on appropriate design, construction, and field application methods, as well as on inspection and quality management. Taking advantage of the reduced material requirements of UHPC-C compared with CC-C requires updated design practices. If UHPC is adopted for more and larger bridge components than connections, designs will need to be altered more drastically and will require updated standards, models, and training. Similarly, because UHPC performs differently than conventional concrete, inspection practices must be different; conventional concrete is typically tested by stress-testing cylinders, while UHPC is better tested by forming test cubes. Interviews indicated, however, that such minor testing differences are not a major barrier to UHPC-C adoption.

Although interviews indicated that the training needed for construction and field application methods is generally simple and can be completed in a day, the larger hurdle is changing behavior or finding construction managers and workers willing to train to use a new material. As an example, one owner agency explained that during an early UHPC-C application, the contractor did not take seriously the requirement to complete a mockup before entering the field for construction. Once the contractor got to the site, they realized they were not fully prepared for the different curing characteristics of UHPC and ultimately wasted expensive material.

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² Predicting service life entails much uncertainty and is influenced by many factors, including climate, traffic, and stress conditions.

When completing an ABC project, contractors are frequently penalized heavily, sometimes by the hour, for construction delays. Being prepared for proper UHPC-C application is vital to avoiding such delays. In addition, because field conditions vary throughout the United States, best practices for UHPC-C application vary as well. For example, UHPC does not cure as quickly in cold temperatures, and interventions are needed to heat the surface in these conditions. Contractors need to be able to adjust the UHPC mix under such field conditions.

To ensure proper UHPC field application, some proprietary UHPC suppliers require that a representative from their company be on site during construction. Although this presence could be viewed as a benefit in the form of helpful expert consultation, some stakeholders noted that it adds nonnegligible logistical complication, time, and, therefore, expense to UHPC use.

5.4 Trialability

Trialability is the ability of potential adopters to test an innovation. Many owner agencies do not have the capacity to test the strength and durability of (especially large) UHPC bridge components. Trialability is an area in which TFHRC support has been and could continue to be instrumental. Although the proprietary blend Ductal has undergone extensive testing and its properties are widely disseminated, generic mixes have less testing data available for contractors.

Many stakeholders indicated that the cost of proprietary UHPC is the main barrier to adoption. Although an increase in the number of competitors in the proprietary market is seen as a positive step toward cost reduction, several stakeholders indicated that the development of generic mixes that rely on locally sourced materials would do more to reduce costs enough to justify substantive UHPC use. Yet, the key barrier to developing generic UHPC mixes, interviewees said, is a lack of trialability. Stakeholder interviews highlighted the need for additional standards on baseline properties and testing for generic UHPC mixes to help increase trialability—and thereby trust in the ability of these mixes to compete with proprietary blends.

5.5 Observability

Observability is the ability of an innovation to demonstrate tangible results that will convince possible adopters. A potential barrier to UHPC adoption noted in stakeholder interviews is the different time spans of its costs versus its benefits: UHPC costs are observable and immediate, whereas the main benefits of UHPC are increased life span and performance. Stakeholders noted that agency workers and politicians would not hold office for the estimated 100-year life span of a bridge with PBEs and UHPC-C. Hence, although many believe that the life-cycle benefits of UHPC use will substantially outweigh the costs (estimating costs and benefits was a key objective of this evaluation), a lag in realized benefits that extends beyond the duration of accountability for decision makers might skew benefit–cost perceptions.

Although life span and performance can be observed only over long periods of time, cracking of closure pours and water leakage into the structure can be early indicators of problems with concrete connections. Stakeholders said that such early indicators are much rarer for UHPC-C than for CC-C, which they saw as clear evidence of superior performance. A valuable role of TFHRC UHPC-C research and outreach has been encouraging and (indirectly) supporting field applications throughout the United States, thereby allowing owners to observe early signs of UHPC-C performance benefits.