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, setting Methodology Why do we need this framework? In the early 1900s, an alternative type of cement knownas 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 reduces The need to address the carbon emissions associatedwith 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 accelerate concrete technologies. However, relying on traditionalconcrete 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,2 Covered concrete technologies This framework applies to any novel technology used as acomponent 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. de-risk novel technologies, it is written in the context of standardsadopted 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 used common 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 technology available in the local market?2.Has the technology been successfully used on a completed project in the sameapplication being considered? 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 When evaluating the use of a novel low carbon concretetechnology, it is essential to first assess the level ofassociated risk. Four main factors influence this risk: of society (ASCE Risk Category I, II, III, or IV).2.Criticality of the element in which the technology is applied (nonstructural vs. structural vs. key structural element).3.Exposure category (e.g., exposure to freeze-thaw cycles, sulfates, chlorides, and moisture, among others).4.Novelty of the technology, based on its previous usage (e.g., only lab tested, used for a demonstration project, orincorporated into full-scale applications) and the durationand availability of in-field performance monitoring. in Figure 4, there are multiple opportunities to mitigate riskthroughout the design and construction process. In this document,these processes have been split into three phases: prescreening,prequalification, and quality control and monitoring. Risk mitigation timeline The structural engineer should engage with the owner to communicate thebenefits and risks of using a novel concrete technology, and to establish a risk The structural engineer should continueto monitor the performance of the novel mitigation strategy tailored to the specific project where the technology is beingconsidered. In early cost and schedule estimates, include allowances for additionaltesting and performance mockups that may be required, as well as potentialimpacts to the construction schedule. The novel concrete technology should bethe p