ERI: Mechanism for Improved Strength in Fast Pyrolysis Biochar Concrete

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。这一工程研究启动(ERI)项目将集中于阐明导致快速热解生物炭混凝土强度提高的机制。生物炭是一种由生物质热解而成的富含碳的材料。生物炭是通过生物质在无氧或有限氧环境中的热分解而产生的。由于生物炭高度稳定，嵌入的碳不易分解，在数百年或数千年的时间里缓慢释放二氧化碳。这会导致大气中碳的长期去除，使生物炭成为一种强大的碳固存材料。生物质的快速热解还会产生生物油和合成天然气，可以产生能源，减少化石燃料的使用。近年来，生物炭作为一种用于混凝土的固碳剂获得了发展势头。然而，这一应用仅利用了慢速热解生物炭，其性质与本项目采用的快速热解生物炭有很大不同。通过使用快速热解生物炭，初步研究表明，当用生物炭取代15%的水泥重量时，混凝土的强度提高了近40%。生物炭替代水泥的比例为15%，可以抵消与混凝土相关的温室气体排放至少48%；生物炭替代水泥的比例为32%，将使混凝土成为一种碳负向建筑材料。为了实现这一目标，确定了三个主要目标：1)表征三种不同的快速热解生物炭产品的微观结构和物理化学性质；2)表征由这三种生物炭产品制成的胶凝材料的微观结构和化学成分；以及3)分析所得到的混凝土的强度行为和强度-微结构关系。此外，该奖项有助于培养一名女研究生，并将为中学女孩提供研究机会，旨在解决青少年女孩对STEM的兴趣/能力与女孩在以后选择的职业道路之间的差距。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This Engineering Research Initiation (ERI) project will focus on elucidating the mechanisms that lead to improved strength in fast pyrolysis biochar concrete. Biochar is a carbon-rich material made from the pyrolysis of biomass. Biochar is produced via the thermal decomposition of biomass in a zero or limited oxygen environment. Since biochar is highly stable, the embedded carbon is resistant to decomposition, slowly releasing CO2 over hundreds or thousands of years. This results in long-term removal of carbon from the atmosphere, making biochar a powerful material for carbon sequestration. Fast pyrolysis of biomass generates also a bio-oil and synthetic natural gas, which can generate energy and decrease the use of fossil fuels. Recently, biochar has gained momentum as a carbon sequestering agent for use in concrete. However, this application has only utilized slow pyrolysis biochar, which has much different properties than the fast pyrolysis biochar adopted in this project. By using fast pyrolysis biochar, a preliminary study shows that when 15 percent of cement weight is replaced with biochar, the strength of concrete increases by nearly 40 percent. At 15 percent biochar to cement substitution, the biochar can offset the greenhouse gas emissions associated with concrete by at least 48 percent; at 32 percent biochar to cement substitution, the biochar would make concrete a carbon negative building material. To accomplish this goal, three primary objectives are identified: 1) to characterize the microstructural and physiochemical properties of three distinct fast pyrolysis biochar products; 2) to characterize the microstructure and chemical composition of cementitious materials made with these three biochar products; and 3) to analyze the strength behavior of the resulting concretes and the strength-microstructure relationship. Furthermore, this award contributes to the education of a female graduate student, and will provide research opportunities for middle school girls with events designed to address the reported gap between STEM interest/aptitude in adolescent girls and girls’ chosen career paths at later ages.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.