INVESTIGATIONS REQUIRED FOR SUSTAINABLE RESTORATION

INTRODUCTION TO THE SESSION SPONSORED BY

ACI 437- STRENGTH EVALUATION OF EXISTING CONCRETE BUILDINGS

AT THE ACI CONVENTION- DENVER, COLORADO

MARCH 18, 1996

Merle E. Brander, Session Chairman

Our question today is, “Do engineers have a responsibility to perform services in such a manner as to sustain the world’s resources and protect the natural and cultural environment” as suggested in the proposed 8th canon of the Code of Ethics for civil engineers? And if so, how do we make sustainability a standard consideration in our practice of engineering?

I’ve been told that the reason there are so few authentic primitive log cabins around the country is that they deteriorated down to nothing in a relatively short time. In the days when primitive log cabins were a primary form of housing, rebuilding was limited only by how far one had to drag the heavy logs over uncleared land and how much muscle was required to hoist those logs into place.

Nowadays, reconstruction of even a modest building is costly, not only in terms of money spent, but also in terms of resources used. Our limitations are no longer rough terrain and the sweat of our brows. Now we are limited instead by cost and consumption and a desire to leave the world essentially intact for the next generation.

Former Wisconsin Senator Gaylord Nelson, the founder of Earth Day, reported that on the first Earth Day in 1970, the concern was not to maintain the system in which we live, but rather to clean it up. At that time Americans weren’t worrying about consumption, but since then we have come to realize that we cannot continue to consume goods as we do, depleting the resources we have so long taken for granted. We now understand that consumption is a major concern and must be curtailed. With that new realization the issue of “sustainable development”, which was popularized at the 1992 Earth Summit in Brazil, is finally getting some consideration.

So what does that have to do with ACI? ACI is about construction. Construction is a primary means of consumption and, since ACI is at the forefront of construction activity in the United States, it is time for ACI members individually and collectively to get on board the environmental train and begin finding ways to reduce the consumption of construction.

One way is to make the structures we build sustainable over the long term, thereby reducing the need for additional construction. Unlike the simple logs of the cabin, that deteriorated naturally back to earth and became fodder for new trees, today’s building products made of resources that are frequently nonreplenishable. Also, the variety of materials used and the impact those materials can have on the environment makes disposal of some of the products difficult and costly. Gone are the days when deteriorated building components could be simply sandblasted, because now we know that the sand used in that process is an environmental airborne hazard requiring special precautions. Gone are the days when we could pull off old roofs and toss them casually into the landfills, because now we understand that some of those old roofs were made of materials that can cause health problems. Sometimes measures taken to deal with problem construction are themselves problems for the environment. So what can we do? One answer is to make the structure sustainable so frequent repairs are not required.

The practice of designing and building for sustainability has been encouraged and is becoming a reality for some of the new construction that is taking place, but what do we do with the structures we already have? We don’t need to wait for new construction to make sustainability a part of the planning for construction. Repairs, too, can be made sustainable, as we will hear today.

The goal of sustainability must be part of the initial planning for construction or major repair of a structure. The structural engineer designing the structure or the repairs should at the same time also be projecting the performance of that structure for the anticipated life. He or she should be able to identify components or areas of the structure that are vulnerable to deterioration and specify replenishable or replaceable protection that can be maintained to prevent that deterioration. We have so much information available today about why and how deterioration occurs that we are very well equipped to sort out the variables and deal with the troublemakers, such as chlorides in concrete, moisture, carbonation, and alkali aggregate reaction.

As we move into the new century, we will become even more predictive in our approach to design and repair of structures. Restoration for sustainability is serious business for our earth. It must start in the minds of those who can appropriately investigate problems with structures and identify restoration procedures and materials that will make repairs for those structures sustainable over the long term.