The phenolphthalein indicator method, the pH of slurries method, X-ray powder diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR) are all commonly associated with evaluating the carbonation front depth in concrete. Recent research (using a closed chamber method) has indicated that stabilized peat is a net sink of carbon dioxide (CO2) (at least in the short term), as the binder takes in CO2 both from the atmosphere and any CO2 released by oxidized peat. Therefore, the application of carbonation depth techniques to stabilized peat are of interest and are explored in this paper for the first time as a precursor to developing a greater understanding of the carbonation process in this material. The carbonation fronts obtained by XRD, loss on ignition, and FTIR all arose at similar depths, as these methods all identify the depth at which the calcium carbonate concentration is elevated with respect to the baseline (i.e., the maximum advancement of the carbonation front). In contrast, the phenolphthalein method underestimated the carbonation front considerably. The pH of the stabilized peat slurries method gave the depth at which leaching of calcium hydroxide and calcium ions occurred, rather than a carbonation depth, and exceeds the depths determined from the other techniques. Advantages and disadvantages of all techniques are discussed.

In addition to the customary drivers of cost and timely project delivery, embodied energy (EE) and embodied carbon (EC) have come to prominence in recent years as major design considerations in all aspects of large-scale road construction projects. An assessment of road construction necessitating the excavation or alteration of peat should consider the impact on carbon stored within the peat and the greenhouse gases potentially released. A methodology for calculating the environmental impact of constructing roads on peat is presented in this paper. Furthermore, the paper describes the application of this methodology (focusing on EE and EC calculations) to a case study; a section of the M6 motorway in Ireland for which excavate-and-replace was the ground improvement method (Scenario ER). A range of peatrelated factors impacting on EE and EC estimates were examined, including materials, transport and machinery, as well as more unfamiliar factors such as peat drainage, drainage systems, restoration, slope stability and clearance of vegetation/forest. Comparisons of total EC are investigated under various management practices and restoration techniques for peatlands, assessing their strength in terms of hydrology and carbon storage potential. The total EC and EE for road construction to the sub-base level (and implications thereof) of the 2.14 km section of the M6 discussed in this paper was 17220 tCO2eq (8047 tCO2eq/km) and 54541 GJ (25487 GJ/km) respectively, with carbon loss from excavated peat accounting for 62% of the total EC. Two other ground improvement method scenarios for constructing this section of road were also considered: Scenario S, soil-mixing and Scenario ER+P, an appropriate combination of excavate-and-replace and piling. Scenario S gave rise to a total EC of 25306 tCO2eq (11825 tCO2eq/km) and a total EE of 164364 GJ (76806 GJ/km) while Scenario ER+P gave rise to a total EC of 17048 tCO2eq (7966 tCO2eq/km) and a total EE of 92706 GJ (43320 GJ/km). In this study, Scenario ER was the preferred technique as it had EC comparable to Scenario ER+P and the lowest EE. On the other hand, Scenario S was the least favourable due to the high EC and EE of the binder. However, this paper shows that the EC and EE can be decreased dramatically by changing the binder proportions. Furthermore, the EC of Scenarios ER and ER+P can also be significantly reduced if alternative restoration techniques are employed for excavated peat.3

A modal shift to cycling has the potential to reduce carbon emissions in the transport sector. However, the carbon footprint of constructing new cycling routes, particularly greenways, has not been previously considered and has the potential to negate carbon savings of the modal shift of many commuters. This paper, using a case study of a greenway in Ireland, describes a methodology for calculating the carbon costs and savings associated with cycle route construction. By carrying out a life cycle assessment (LCA), the case study greenway was found to embody 67.6 tCO 2 e/km; the carbon savings of shifting one passenger kilometre travelled (PKT) from driving a car to cycling were found to average 134 gCO 2 e. In the case study, a shift of 115 commuters per year (253,000 PKT) is required to 'balance' or offset the carbon footprint of one 10 km asphalt greenway (assuming a 20 year life cycle). The methodology presented can be used to ensure the efficient and sustainable design of cycle networks internationally.

Mass stabilisation, a ground improvement solution used for construction in peatlands, involves mixing suitable dry binders into the peat to create a homogenous mass, that strengthens and stiffens the peat. A previous pilot study of the carbonation process in stabilised peat showed that it can be a net sink of CO2, as the binder takes in CO2 from the atmosphere and any CO2 released by oxidised peat due to carbonation. In this study extensive laboratory experiments were undertaken to investigate the key factors affecting the CO2 intake rate. A closed chamber method was applied over approximately 6 months to stabilised peat to calculate this rate. The studies revealed that both an increased cement content and a larger surcharge contributed to a larger CO2 intake rate. These intake rates decreased logarithmically with time, and surcharge was found to be a less dominant factor in influencing the CO2 intake rate over time. It was observed that the CO2 intake rate declined when a decrease in CO2 concentration occurred, and the replacement of cement with ground granulated blast-furnace slag had a negative effect on the CO2 intake rate due to its lower carbonation potential. Furthermore, a high water table resulted in a decrease in the CO2 intake rate. These laboratory results have highlighted that dry soil-mixing has a minimal on-site impact in environmental terms, and the consideration of the factors affecting flux rates will allow geotechnical engineers to make more informed decisions on the suitability of this technique for construction projects. Table 5-Boundary conditions for input variables for sensitivity analysis for Studies A and B Study A Study B

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