Lightweight Concrete – An International Perspective：質混凝土–國際視角

1、design of appropriately constructed facilities to cope with global warmingbyted bremnerprofessor emeritus & honorary research professoruniversity of new brunswick, fredericton, nb, canadaprague october 2012current best estimates forecast only minor warming in the equatorial regions including ind

2、ia while large temperature rises are now occurring in the polar regions.2note: india has very low surface temperature increase between 1976 and 2001.3warming world45the cumulative effects of our past and present action have set in play dynamic forces that will destroy the planet unless we act in a m

3、ore decisive way. simply to stop peddling on a bicycle going down a progressively more steep hill will not avert disaster.there are many examples of this with perhaps the most serious in the arctic where the organic rich permafrost is thawing, and their decay will cause release of green house gases

4、that in turn cause global warming. if not now, eventually the process becomes self sustaining without input from us.6to avert disaster, global warming caused mainly by greenhouse gases must be reduced everywhere in all possible ways. excessive behavior of humans is the main cause but fortunately peo

5、ple can change their ways quickly, as witness:ussr morphing into separate countries.reduction of acid rain in eastern north america.elimination of ddt in canada in 1957.elimination of lead in gasoline in canada and the us.mandating sustainable forest usage in most of the world.7as producers of const

6、ruction materials we have:1. reduced carbon dioxide emission from cement manufacture by up to 50% by replacing cement with fly ash, slag and silica fume.2. recycled metals with 60% of steel being made from scrap.3. perfected the art of recycled asphalt.4. through the use of insulation and green roof

7、s reduced the energy required for heating and cooling buildings.5. developed an accounting procedure to evaluate the carbon foot print of our constructed facilities.8unfortunately, as designers of constructed facilities, we have not come up with new design concepts that reflect the needs of a world

8、under stress. this includes strategies to cope with rising sea levels and to provide affordable housing and effective public transportation.9a canadian cement company had this slogan bravely stated in bold red letters on the bottom of its correspondence, “concrete for permanence”. in the 1960s the u

9、se of air entrainment with a high enough cement content and a low water content was intended to assure customers that the concrete would be durable for eternity. unfortunately alkali aggregate reaction, delayed ettringite formation and corrosion of embedded reinforcement shortly led to the removal o

10、f the slogan.10veigh, in his book “conception of the theory of environmentally compatible structures and structural materials (ecs)”, emphasizes the need to rethink how most buildings are constructed, and stresses what can be learned from nature. surface structures rather than post and beam structur

11、es clearly make the most effective use of our new materials. also, if trends in the cost of energy continue, then solutions to global warming problems will need more complex structures. 11the first step is to realize that affordability is of prime concern to avoid a u.s. housing crisis type problem.

12、 recent advances in the use of foam and cellular concrete indicate that this relatively mature technology can be used for low-cost housing, although it is considerably underutilized at the present time.12the term “environmentally compatible structures” encompasses both the risk from the materials an

13、d the risk posed by the structure itself. in the case of materials there is a well-developed understanding of the need to guard against the use of hazardous materials such as asbestos, arsenic and mercury from the combustion of coal. less well appreciated are the hazards associated with the short an

14、d long term effects of effluents created by the mining industry.13in places where rising sea levels and storm surges are likely to occur, retreating in an orderly manner seems the only practical approach. a report prepared for the canadian department of the environment by the round table on climate

15、change (report no, 4) indicates a strong preference for this approach (6). this study found that building dykes to hold back the sea was highly uneconomical and totally impractical, if not impossible, in many threatened sites.14in the past two decades the type of constructed facilities needed by the

16、 military has changed somewhat as we go from multi-national wars to national wars. an example of recycling military discards is in moscow where an abandoned inter-continental missile silo became the foundation for a very large vibrating table for research on earthquake resistance of high-rise buildi

17、ngs, but this is still an exception. 15in both developed and developing countries there is a need to recognize the fragility of the situation. in the developing world, changes need to be made to alleviate financial crises that inevitably must result in more economical and more appropriate housing an

18、d public facilities. in north america and in most of the developed world we have built extravagantly, and now smaller and more modest housing is necessary. 16the level of funding needed to solve the problems associated with global warming on a government, industrial and individual basis is likely to

19、 be unavailable. those of us involved in providing solutions must manage to do business in a cost-conscious and more stressed world, while at the same time producing more appropriate constructed facilities.17setting national limitskyoto protocol (2008) most nations commit to limits on greenhouse gas

20、 emissions.durban negotiations (2011) china and india can avoid any legal limits on their fast-rising carbon emissions. european countries make progress but usa and canada renig.? protocol (2015) negotiation of rules for greenhouse gas emissions.? (2020) negotiated rules will come into effect.global

21、 warming (2030) will have exceeded the tipping point for maintaining a sustainable planet.18countryco2 emission per person in 109 tonnes% of world sharerank per person 200819902008quitar25.253.5 0.2 1usa19.119.518.1 12canada16.216.4 1.8 15china 2.2 6.823.3 78ecuador 1.6 2.2 0.1120brazil 1.4 1.9 1.3124india 0.8 1.