A number of recent studies have identified and begun to quantify increased susceptibility of the infrastructure to climate change–induced carbonation of reinforced concrete. In this paper, the results of a study are presented which uses an updated empirical model to predict the diffusion coefficient of carbon dioxide (CO2) in concrete and thereafter, predict carbonation depths for a number of urban environments in the United States. Data from newer climate forecasts from the 5th Intergovernmental Panel on Climate Change assessment report are used to generate predictions for carbonation depths in four U.S. cities of varying geographic and climatic conditions (Los Angeles, Houston, Chicago, New York City). Results confirm that carbonation depths will increase in the future because of climate change. The magnitude of the increase is dependent on the climate-change scenario considered and the geographic location of the city. Whether or not the increases will require building code changes to increase concrete cover or improve concrete quality will be dependent on actual construction practices for the city in question., Peer-reviewed article, Published. Received: January 05, 2015; Accepted: July 30, 2015; Published online: October 28, 2015.
There is nearly unanimous consensus amongst scientists that increasing greenhouse gas emissions, including CO2 generated by human activity, are effecting the Earth’s climate. Increasing atmospheric CO2 emissions will likely increase the rates of carbonation in reinforced concrete structures. However, there is a lack of reliable models to predict the depth of carbonation as a function of time. To address this deficiency, a numerical model involving simultaneous solution of the transient diffusion and reaction equations of CO2 and Ca(OH)2 was developed. The model successfully includes the effects of variations in various properties such as porosity, humidity, temperature, atmospheric CO2 concentrations and chemical reaction rates. The applicability of the model was confirmed after calibration using data from accelerated carbonation experiments, and the model is used to evaluate the possible effects of climate change by inputting various future climate scenarios in Part 2., Peer-reviewed article, Published.
In Part1 of this paper, a carbonation model was developed and experimentally veriﬁed which was able to forecast carbonation depth of a concrete specimen considering varying ambient temperature, humidityand CO2 concentrations. Part 2 of the paper applies the carbonation diffusion/reaction model developed in Part 1 to predict the effects of global climate change on the carbonation of concrete. Climate scenarios were formulated and combined with the model for two major Canadian cities, Toronto and Vancouver. Results show that for undamaged and unstressed concrete, climate change will signiﬁcantly affect carbonation progress. The model showed that for unloaded, non-pozzolanic concrete, ultimate carbonation depths in Toronto and Vancouver could be up to 45% higher. For in-service structures under load, the rates of deterioration are likely to be even faster. This is a cause for concern, and much further effort must be devoted to fully understand these phenomena., Peer-reviewed article, Published. Received 18 October 2011; Revised 21 April 2012; Accepted 24 April 2012; Available online 10 May 2012.
There is nearly unanimous consensus amongst scientists that increasing greenhouse gas emissions, including CO2 generated by human activity, are affecting the Earth’s climate. Increasing atmospheric CO2 emissions will likely increase the rates of carbonation in reinforced concrete structures.In this paper, the serviceable life, from construction through to cracking due to carbonation induced corrosion of concrete infrastructure is considered in various cities throughout the world. It was concluded that global climate change will affect the progression and will result in much higher ultimate carbonation depths in the long term., Peer-reviewed article, Published. Received 23 May 2012; Revised 1 October 2012; Accepted 9 November 2012; Available online 25 December 2012.
Carbonation in concrete is a natural chemical process by which atmospheric CO2 reacts with calcium oxide in the Ca(OH)2 and CSH phases in hydrated cement paste to form CaCO3. The carbonation rate in the atmosphere is too slow for laboratory testing, and therefore, it is usually accelerated by using relatively higher CO2 concentrations. However, there exists some disagreement as to what CO2 concentration, humidity and temperature should be specified when conducting an accelerated carbonation test. In this study, samples of hydrated cement paste were carbonated at different CO2 concentrations, and analysed using the x-ray diffraction technique. The results show that the morphology of CaCO3 formed at higher CO2 concentrations is different from that of CaCO3 formed at natural concentrations. It should be recognized that the diffusion coefficient measured at higher concentrations will not be exactly the same as that from naturally carbonating concrete due to the formation of these morphologically different products., Article, Published.
Proceedings of 3rd International Building Physics Conference: 27 August 2006, Montreal, QC. A two-dimensional heat, air and moisture transport model called hygIRC is adapted to simulate a well-documented field exposure of an aerated concrete wall section. Difficulties are encountered due to a few missing information on boundary conditions of the exposure and hygrothermal properties of aerated con-crete. The paper presents how these inadequacies were overcome to simulate the hygrothermal behavior of the wall section. Appropriate assumptions were made due to justifiable reasons. Then the model provides temporal and spatial distributions of temperature and relative humidity for an extended period that are in ex-cellent agreement with the documented field data. The paper presents the justifications for the assumptions and the comparison of experimental and simulation results., Conference paper, Published. A version of this document is published in: 3rd International Building Physics Conference, Montreal, QC., August 27, 2006, pp. 321-328.
Concrete structures are almost certain to contain cracks due to different physiochemical mechanisms. The formation of cracks is sure to affect its durability by altering ion and fluid transport properties. This includes the incursion of CO2 into the structure. There presently exists no consensus on how to model the effects of structural cracking on carbonation progress within concrete structures. This paper first examines the concept of effective diffusion based on simultaneous diffusion of CO2 through sound and cracked concrete and then considers a series diffusion concept where CO2 diffuses first into the crack, and then outwards into the sound concrete. It is concluded that the effective diffusion concept is not valid for structurally cracked concrete. Instead, research efforts should be concentrated on developing a two–phase series diffusion model., Peer-reviewed article, Published.