Issues with Portland Cement

Dr. Nabil Taha has over 27 years of structural engineering experience. Prior to opening his own engineering firm in Oregon in 1997, he was a Professor of Engineering at Northern Montana State University and at Oregon Institute of Technology. He has structural expertise in a wide range of building systems and can answer questions related to virtually any common building method. His focus is on green design and he is always willing to trying something new. Dr. Taha is dedicated to future sustainability through innovation; he creates solutions for beautiful sustainable and safe structures by melding old and new technologies. He loves a good challenge. He is Licensed in twenty three states and can design buildings and/or consult to assist with structural permitting in these states as well as internationally. As a prior College Professor, Dr. Taha is a teacher at heart. He loves to share his knowledge and offers educational seminars and trainings for the do-it-yourselfers and professionals alike. Dr. Taha's goal is to continue to grow and provide knowledge and services for those trying to make their dream project a reality. No project is too big or too small. For information about Dr. Nabil Taha and his engineering firm see www.structure1.com

Questions and Answers

Q: I am looking to use local sand and gravel deposits to build an environmentally friendly home on an island that I have purchased in the Philippines. I will install a 10KW wind turbine to provide power to run the house and desalination. Will grow/raise all food and plan to replant indigenous plants to accelerate repair of fire damaged forest. Due to the remoteness I will need to used the previously mentioned aggregates but they are very salty. Additionally I will probably need to use sea water as the mixing liquid - is this possible? I don't mind buying and using special cement as it will all need shipping in anyway. Hope you can help. The house will be single storey but would need a concrete roof to provide typhoon protection - I have doubts about using rebar with such a concrete too. Hope you can point me in the right direction.

A: Thank you for planning to build environmental friendly home. Sea water tends to corrode the rebar in the concrete. That is why drinking water is what is recommended for mixing concrete. If it is absolutely not available, we have to check other means, but it maybe costly. The roof is the main item that will need the most rebar. If drinking water is not available, then we will need to use a different material other than concrete for the roof. A well designed timber roof, for example, will resist hurricanes and typhoons. We do it all the time in Hawaii and the Caribbean.

Q: I live in Canada and we are about to purchase a stucco home. We have visited New Mexico many times and I just love the look of the adobe homes. I would like to paint this stucco home so it has the look of terra cotta and also do the front door in a turquoise colour. There are so many shades of these colours. Can you tell me where to find the true New Mexico colours for this project?

A: (Kelly) While it is possible to paint stucco, a much better choice is to have a professional apply a color coat of stucco of the color that you want. This is a much more permanent solution that is less likely to chip or wear away over time. If you check with a professional stucco company, I'm sure that they will show you a color sample chart with a wide array of colors that will resemble what you remember and will appeal to you.

Q: I'm planning to build a thick-walled (24") reinforced concrete two story house. It would roughly measure 60 x70' and be built in Florida. What kind of a footing am I going to have to budget for? How deep, how wide? And the foundation? We could assume that the soil is a bit more wet than other areas and I don't have to worry about frost lines.

A: A foundation for two story house could be 2 feet, 6 inches wide and 12 inches deep with rebar at 12 inches on centers. However, you need to check with a local licensed engineer to check your local soil condition, wind and seismic loads and other requirement from your local building department.

Q: If I built a 20' ft shaft 5' x 5' would it be best to use centre blocks with rebar and concrete or make forms with rebar concrete. The shaft will be dug by hand straight down and will have a concrete roof and a side door entrance that is just below the roof. I will have a door near the bottom for root cellar entrance. I'm thinking the best way is to make the walls in sections and anchor them in place while I dig out the next section then build another form and fill in the gaps as the walls dry. Any suggestions?

A: You can do the shaft in either reinforced concrete blocks Masonry or reinforced concrete. Both will work just fine. You just need to use the right amount or rebar in the masonry and/or concrete. I suggest the you consult with a local licensed engineer for your project.

Q: I am doing a design project for my final year civil engineering graduation in the topic of an underground shelter. I know how to design an underground reinforced concrete storage tank. Can I use the same procedure for underground shelter as well?

A: (Kelly) In general I would say that, yes, you could base a shelter on a similar design, but you would need to assure sufficient ventilation for human occupation.

Q: I am pursuing design and Construction of Multi Disaster Homes in the USA, Normal Concretes fail at High Temperatures and against Earthquakes.

A: Not if it is designed correctly according to the expected loads. Also, concrete homes get damaged from fire mainly for two reasons: Bad details of the roof at the ridge and eave. Big windows where the fire breaks the glass and enters the house..