Abstract Thoughts About Concrete

The production of cement is a major source of anthropogenic (i.e. human-made) carbon dioxide. In fact, its impact is comparable to that of using fossil fuels to transport goods and heat buildings.

It uses limestone, which contains carbon dioxide that has been locked away for a geologic time, and a portion of this is released in the process of cooking it into a material called clinker. Eventually, the cement will re-absorb some, but not all of the CO2 released this way. Cooking the limestone to 1500 C takes a lot of energy too, and in an intensity that makes it difficult to produce cleanly. There's also the costs and impact of the limestone quarrying and transportation to consider.


Another problem is disposal: Construction waste makes up a large part of what goes into landfills, and cement products like concrete and mortar potentially make up a large part of that. This is from buildings being demolished or renovated, from road construction, and from the occasional truckload of concrete that is mixed but can't be poured at the right time.

So I wonder, in my limited understanding, if it's possible to take cement products and reclaim some of the cement. Currently, concrete is recycled to reduce its landfill impact and the need to mine gravel and other fill. However, that seems to be all it's used for - simple rocks rather than the magic gluestone stuff that holds skyscrapers up.

Curing is a one-way chemical process (I think), and that there's a lot of fill that's added to cement to make concrete, so maybe it's just too hard to be profitable. Fresh cement powder is so fine that it would be a stretch to call it dust, so a tremendous amount of mechanical grinding would be necessary to get concrete down to a point where the fill could be removed from what was cement powder before curing.

Has anyone given serious thought to a chemical or biological means of doing this however? If lichen can break down solid rock, could concrete gravel be broken down or separated into something finer with a plant, enzyme, or type of bacterium? Can the curing process be undone by similar means that leaves behind clinker as a waste product?

Similarly, could wet concrete mix be saved for another time in the cases where it spoils from water contamination or when it can't be poured when intended? Could aging or damaged infrastructure be reinforced or renewed by drilling into it and injecting something to force it to re-cure?

Just some thoughts from someone ignorant on the limitations of infrastructure.  Comments, corrections and discussion about this would be very welcome.

Here's a general statement to close -- climate change won't simply be fixed by driving hybrids and using recycle bins. It's a complex problem and solving it will be the great work of this and the next generation.

http://en.wikipedia.org/wiki/Environmental_impact_of_concrete

http://en.wikipedia.org/wiki/Concrete_recycling

R Package Spotlight - stringr

One of my ongoing projects is to maintain a database of international cricket games, which I do by scraping the text from ESPN Cricinfo. For this kind of work, the R package 'stringr' is essential.

R Package Spotlight - xtable

xtable is an R package on CRAN that converts output into LaTeX code for a table of that output.

For writing papers, it has cut the time it takes to produce and manage a table by a factor of 3 or 4.

SPSS Guide for Basic Practice of Statistics

I've made some major updates to this introductory guide to SPSS. (Google docs link, but you can download from there)

It's a guide to using SPSS to answer homework problems from Basic Practice of Statistics (BPS), by Moore, Notz, and Flinger. Although it was originally made for a specific stats for social sciences course, I hope it's applicable beyond that.

The biggest change from the 2012 and 2013 versions is that the guide is no longer tooled around Elementary Statistics for Social Sciences by Levin, Fox, and Forde. Those versions will not be posted here because this 'elementary' textbook is better at teaching fear than statistics. Consequently the GLM procedure and logistic regression chapters have been removed from the SPSS guide.

The updates also includes more information about data manipulation specific to 'Basic Practise' such as random selection, sorting, and weighting data.

There is already a larger, official SPSS companion for this textbook, but my guide is intended to provide just what a novice student needs to get through their course, rather than be a comprehensive reference.

This work is freely available to share and was originally commissioned with a research grant from Simon Fraser University in 2012.