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Title:Carbonated foamed cellular concrete
Author(s):Montemayor Cantu, Roberto Jesus
Advisor(s):Lange, David A; Roesler, Jeffery R
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Foamed Cellular Concrete
Sustainable Concrete
Lightweight concrete
Aerated concrete
Carbon dioxide sequestration
Abstract:FCC is a class of cementitious material whose fresh and hardened properties are primarily controlled by the quantity of stabilized air bubbles in the paste. The density of cellular concrete usually ranges from 300 kg/m3 to 1800 kg/m3 and has been used for applications such as thermal insulation, dead load reduction, and lightweight fill. Foamed Cellular Concrete (FCC) is one potential material solution to decrease the carbon footprint of the concrete industry through natural or accelerated carbonation. Although concrete has been essential for the growth of societies, it also is responsible for 6% of the global carbon dioxide (CO2) production. Creation of Portland cement produces about 0.8 tons of CO2 per ton of cement. However, hardened cementitious paste (Used in FCC or conventional concrete) can re-absorb up to 65% of the emitted CO2 through the carbonation reaction. The Portland cement hydration primarily produces calcium hydroxide (CH) and calcium silicate hydrate (CSH) that will carbonate in the presence of CO2 and water to produce various phases of calcium carbonate. The carbonation reaction with the hydrated cement microstructure increases the concrete's density and compressive strength and produces a more dimensionally stable product. Concrete carbonation has two main limitations. First, carbonation reduces the pH of the concrete, which leads to increased susceptibility to steel corrosion. Secondly, the carbonation rate is dependent of the diffusion of CO2 molecules through the paste. Normal-weight concrete shows slow CO2 diffusion and reaction rates at atmospheric conditions. Foamed Cellular Concrete (FCC) is an ideal concrete material for CO2 sequestration since CO2 increases the compressive strength of FCC, steel reinforcement is generally not present, and its cellular structure achieves a diffusion coefficient significantly higher than normal weight concrete. Additionally, FCC can be produced with materials that are available in existing concrete producers, and can be designed to meet a large number of applications already exposed to atmospheric CO2, i.e., sidewalks, retaining walls, and energy absorbing systems. The thesis objective is to evaluate the use of FCC as an alternative for CO2 sequestration. The main hypothesis is that the cellular structure of the FCC will allow faster CO2 absorption and higher compressive strength through the carbonation reaction. FCC samples with densities ranging from 320 to 1,011 kg/m3 were prepared. The samples were cured at three different carbonation conditions: 1) moist curing room with 100 relative humidity, 2) carbonation chamber with high CO2 environment, and 3) continuous airflow with continuous air flow and atmospheric CO2 levels. After 28 days the samples were tested on dry density, compressive strength, carbonation depth, and thermogravimetric (TGA) analysis. The FCC samples cured in the carbonation chamber achieved an average increase in density of 18% compared to the samples that were cured in the moist curing room. The increase in density resulted in higher compressive strength for all the tested samples (carbonated and non-carbonated). The relationship between density and strength followed an exponential trend. The carbonation depth results and TGA analysis confirmed the carbonation potential for FCC. Carbonated samples (carbonation chamber and continuous airflow) with a dry density of 320 kg/m3 achieved a carbonation depth greater than 24 mm with a CO2 absorption of about 24% per dry weight of the sample at 28 days. Normal weight concrete with typical diffusion coefficients would have theoretically taken 100 years to achieve the same carbonation depth as the FCC samples tested. An initial design framework was developed to estimate the FCC density, carbonation time, cement content, and CO2 footprint reduction based the desired FCC strength and curing conditions.
Issue Date:2020-12-11
Rights Information:Copyright 2020 Roberto Jesus Montemayor Cantu
Date Available in IDEALS:2021-03-05
Date Deposited:2020-12

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