一个用于指定新混凝土技术的框架

Foreword Novel concrete technologies have becomeincreasingly popular as an effective methodfor reducing the greenhouse gas emissionsassociated with concrete construction. savings. However, implementing these technologies requires change from the business-as-usual approach, and the rapidly changing landscape increases the complexity ofspecifying novel products. This guidance document uses past project experience withnovel concrete technologies to show how they can be implemented on projects, settingforth a basic framework for designers, contractors, and owners. Methodology Why do we need this framework? as high alumina cement (HAC) was developed. Itgained popularity in the UK during the 1950s due toits rapid strength development properties. However,following several high-profile structural failures in the1970s, it was discovered that HAC naturally undergoesa chemical reaction called “conversion.” During thisreaction, the solid fraction of the reacted cement reducesin volume, increasing porosity and decreasing materialstrength. Exposure to water and high temperaturescan significantly accelerate this reaction. As a resultof the structural failures, HAC was effectively bannedfrom use in structural applications in the UK.Clearly, there is risk involved in adopting novelconcrete technologies. However, relying on traditional with cement production has been recognized acrossboth the public and private sectors. Policies requiringor incentivizing low carbon concrete have expandedrapidly, while private sectors continue to explore financingmechanisms, such as book-and-claim models, to accelerateinvestment and adoption. This framework outlines howstakeholders can leverage innovative concrete technologiesto drive industry decarbonization, while ensuring thesesolutions are rigorously vetted and carefully specified. concrete mixtures also carries significant risk: thelonger we continue emitting greenhouse gases intothe atmosphere, the greater the risk of sea level rise,uninhabitable temperatures, food shortages, andirreversible loss of ice sheets and permafrost, amongother effects.1As cement production accounts forapproximately 8% of global carbon dioxide emissions,2decarbonizing the concrete industry will be key inlimiting the worst effects of climate change.3 Covered concrete technologies component of ready-mix concrete, whether cementitious materials,aggregates, admixtures, or water. Particular attention is givento cementitious materials due to the disproportionately highembodied carbon impact of cement, as shown in Figure 2. Thenovelty of a technology depends on how extensively it has beenadopted, how different it is from existing technologies, and theduration over which its field performance has been verified.Whether a technology is considered novel is ultimately a subjectivedecision that will vary by mix design, application, and project.Generally, this framework is most appropriate for technologieswith a minimum Technology Readiness Level (TRL) of 7.While the concepts in this framework can be applied globally tode-risk novel technologies, it is written in the context of standards adopted in the United States, particularly ASTM standards. Somenovel technologies, such as ground glass pozzolans, fall undertheir own ASTM standards. However, certain conventionallyadopted ASTM standards also encompass technologies that maybe considered novel. For example, while fly ash has been usedin concrete mixtures since the mid-1900s, mixes containinghigh percentages of fly ash may still be considered noveldue to a lack of demonstrated long-term performance.Furthermore, because concrete is a localized material, the noveltyof a technology can be region-specific. A 25% fly ash mix may be A framework for specifying novel concrete technologiescommon in some areas but considered novel in others. In thesecases, elements of the framework should still be applied to verifyperformance within commonly adopted local concrete mixtures andto familiarize suppliers and contractors with novel technology use. Identifying novel concrete technologies While the designation of a technology as novel is subjective, thefollowing questions can be used to establish whether a technologyshould be considered novel and utilize the proposed framework.If “no” is answered to at least one of these questions, the technologycan be considered novel. available in the local market?2.Has the technology been successfullyused on a completed project in the sameapplication being considered?3.Are the concrete subcontractor and ready-mix supplier familiar with the technology?Table 1 lists examples of novel technologies, as well are always emerging, this list is not exhaustive. Understanding and mitigating risk technology, it is essential to first assess the level ofassociated risk. Four main factors influence this risk:1.Importance of the structure to human welfare and functioning of society (ASCE Risk Category I, II, III, or IV).2.Criticality of the element in w