CFA Board Member Changes Her Name
CFA board member Amanda Herbert married Josh Morris on Saturday, May 24th, 2003, in Allegan, Michigan. The couple exchanged vows in the company of family and friends, including CFA members: Charles Engelken, Bill Esker, Terry Lavy, Greg Peacock, and Arie Van Wyk.
Congratulations Amanda Morris! Best wishes to you both!
CFA Website – Accessing and Working with Documents Online
Over the past couple of issues we have spent time together investigating the use of our member/non-member site access and dealing with the issues of membership maintenance and event registrations. This time around, I am taking you on an educational trip on the interaction with this site to view documents that we are providing to the membership. These documents include issues like The Business Owner, Concrete Facts – the CFA Newsletter, Board agendas, Board minutes and other electronic versions of our various brochures and informational offerings.
Documents that we make available to CFA members are placed on our server in a format known as PDF. This stands for Portable Document Format and is a universal file type created by Adobe to allow distribution of high-quality web documents across all platforms. To view these documents, the only requirement is that you have the software Adobe Reader installed on your computer. Nearly all computers will have this already as it comes with a wide variety of software packages to view help files and other important documents. In the event that you don’t have this software, it can be easily obtained for your computer from Adobe’s website at http://www.adobe.com/products/acrobat/readstep2.html.
The installation is quite quick and very easy should you need to get the program or be interested in updating to the latest.
With that straight, let’s go see some of the documents that you will be interested in looking at and some of the options you will have once you select a document for viewing. Once you have logged on to our site and you are now looking at the Welcome screen (something I hope each of you have been successful in doing, see fig. 1), you will need to select the menu item Publications and then View from the drop-down box (fig. 2).
CFA Newsletters – Concrete Facts
What do you do when you get in a situation and recall that the solution may have been in a newsletter a couple of years ago? How can you share an article written about your company with a new employee or a colleague but can’t remember where you placed it? How can you contact a company about a product that you saw featured in a newsletter a few months ago and realized that you haven’t been keeping your issues stored in your reference binder? These questions and many more can be asked over and over from the wealth of information that is presented in each issue of Concrete Facts. Luckily, we have designed a place where you can go to find articles that have been published in our newsletter and obtain a copy of the past issue.
When you have selected View from the Publications menu. You will see a table on the left of your screen that contains the CFA newsletters that are currently available for you to research. These newsletters are listed by their volume and issue number. The 2003 year is Volume number 10. You have two primary steps to take in your research process.
Step 1: Look through the Table of Contents of a Volume. You will see a button in each row for a given newsletter that says Table of Contents. Selecting this button will take you to a screen where you will be able to view the articles that were contained in that issue (fig. 3). Once you have finished looking through this issue’s contents, select the Close button to return to the publication tables.
Step 2: View the newsletter you are interested in. After you have located the newsletter you are interested in reading, you will select the View button. There may be a delay depending on the speed of your connection but once you have selected this button, your browser will begin building the newsletter in a separate window. Please remember that you may need to exercise some patience here as it takes a while to build a 32-page full color newsletter over a dial-up connection. When the document is finished building, your new window will look similar to the image in figure 4.
Your browser has been modified with additional features from Adobe Reader. The main buttons you will be using are Save, Print, Navigate and Zoom. You can find all of these in the pull-down menus but you should also know that each has buttons for quick use (figs. 5-8). Selecting Save will allow you to place a permanent copy of this issue on your computer for later use or reading when you get a full chance. The Navigate buttons are the best way to work through the document quickly. The left and right arrow buttons go page by page while the arrow buttons with a line take you immediately to the front or back page of the document. The Zoom buttons are important since you will not likely be looking at the entire page when it opens in your browser. If you want to see the full page as you scroll through the document, you can select the button that looks like a full page of paper inside a window. If you want the page to show up at or return to 100% zoom, you simply select the button that looks like a full page. Finally, if you want to read a given section and want to bring the width of the paper to fit your screen, you select the button where the paper width fits in the window but you don’t see the whole sheet. Again, all of this can be obtained from the menus at the top of your screen as well.
When you have finished looking through the document, simply exit this window as you would any normal website window with File and Close or selecting the “X” in the upper right corner. This will once again show the screen with the Issue tables. If you want to return to the Welcome screen you select the Close button, however if you want to leave completely, just continue closing like a normal window.
The Business Owner
Looking through issues of The Business Owner should be performed with the same steps describing the newsletters above. You will see this table on the right side of the publications screen. Again, table of contents are available for your viewing as well as the complete issues.
We are working continuously to add back issues periodically. If you have a specific article or issue in mind that you don’t see, please contact us and we will make that one a priority. We hope to have the entire history available by the end of this year.
Future Still Hopeful for Residential Construction Market
Construction Market Outlook of 2003 Second Quarter CONDENSED FROM FMI ANNUAL CONSTRUCTION OUTLOOK PUBLICATION
Construction, like many other industries, suffered a disappointing start to 2003. However, residential construction proved to play a crucial role in the construction industry as a whole. To sum up the second quarter, the boom in residential construction may have peaked, the commercial construction depression may have bottomed, and a public construction sector isn’t looking so predictable. The reason, in part, for the discouraging outlook of the second quarter was the uncertainty created from the war with Iraq. Many companies put a freeze on hiring to see what the outcome of the war was, which further hindered the already stagnant labor pool. The number of unemployed who continue to file for benefits after the initial claim rose to its highest level in three and a half months, according to the U.S. Department of Labor. Poor employment growth created a decrease in consumer confidence. The Conference Board’s consumer confidence index was the lowest it has been since October of 1993 when it reached a low of 60.5.
However, this gloomy employment and consumer confidence data may not win out in the long run. There are a few key facts to note about February’s weak economic numbers, which may make the future look a bit brighter. One factor in the low numbers is the calling up of the reservists. According to the U.S. Department of labor, approximately 150,000 reservists were called into active duty in February. These reservists called to active duty are not included on employer payrolls. If the worker is not replaced, then the data shows a decrease in the employer’s job count. A second factor is the severe weather the nation had this winter, which probably lead to a decline in hiring, as well as consumer purchasing in February. A third factor is that February has fewer days than any other month, which most likely affects the retail sales data. Finally, the fourth factor to note is that people seem more confident with the job market than the employment numbers suggest. According to job trends analyzed by Challenger, Gray & Christmas, Inc., this is shown through the number of workers reentering the job market, voluntarily leaving their jobs, or starting their own businesses. Bottom line – even though the numbers seem discouraging, the economy still seems to be on the mend.
In the construction industry, as well as in the U.S. economy has a whole, residential construction has been crucial for the past two years. This is largely due to the ample demand driven by underlying demographic and lifestyle preferences. However, while the long-term demand should remain steady, the short term drivers of demand – weather, conditions, consumer sentiment, and builder sentiment – were off in February.
The value of new residential construction raised 0.3% to a seasonally adjusted rate of $328.1 billion. New home sales fell 15% to a seasonally adjusted annual rate of 914,000 units in January. By February, the seasonally adjusted annual rate was 854,000 units, the slowest pace since August of 2000. The total months’ supply of new homes for sale increased from an average of four months to four and a half. Sales of existing U.S. homes fell 4.3% in February to a seasonally adjusted annual rate of 5.84 million units, according to the National Association of Realtors.
Residential builders cut back on new housing construction in February. Single-family housing authorizations were at a seasonally adjusted annual rate of 1,315,000, below the annual rate in January. Housing starts dropped 11% from January to February. February’s rate is also down 9.3% compared to the estimate rate in February 2002.
Whether February’s weak numbers is a one-time occurrence or not, the possibility of rising mortgage rates and a level of mortgage defaults determined unacceptable to bank regulators are two factors that can potentially hinder the residential construction market in the next 12 months. While mortgages are a hot item of the year, over 80% of their volume was refinancing. Interest in obtaining financing for a new home is growing less quickly.
With an increase interest in mortgages came an increase in the number of mortgage bankers, which has grown by 122,000, according to the U.S. Department of Labor. This inflation of bankers results in a lot of new mortgage bankers approving a lot of new mortgages – some which should not be approved. The repercussions of such occurrences may be increased foreclosures, which could result in tightened standards on home mortgages. Evidence of such repercussions appeared for the second consecutive edition of the Federal Reserve Board’s January 2003 senior loan officer opinion survey on bank lending practices. Not to mention, the number of banks tightening their standards edged up 1% from the 10% reported in the October survey. The evidence is minimal at this point, but tightened home mortgages standards could in the end greatly influence residential construction.
Mortgage rates are not the only thing to keep an eye on in the months ahead. According to the Department of Energy, the U.S. average retail price for regular gasoline increased 2.8 cents per gallon as of March 3rd to reach 168.6 cents per gallon, which is 54.2 cents per gallon higher than a year ago. Mortgage rates and oil prices relate from a long-term perspective. Residential mortgage rates are influenced by the rate of consumer price inflation (as measured by the rate of change in the consumer price index), and oil and other energy prices constitute a portion of the consumer price index (CPI). In January and February, the CPI rose 0.3% in January and 0.6% in February, with increases in oil, energy and food prices. If oil prices continue to increase, then inflation is passed down the supply chain to consumers, borrowing rates, including mortgages, could be affected. In turn, producers, wholesalers, and retailers will swallow the increased oil-driven producer inflation, and corporate profits will continue to suffer. This would be followed by continued poor employment and investment growth. It’s a nowin situation that nobody wants, and can hopefully be avoided through victory in Iraq.
New Home Sales Rise Beyond The One-Million Mark in April
Sales of new single-family homes rose 1.7% in April to a seasonally adjusted annual rate of 1.03 million units, according to the Commerce Department. It is the third time this year that new-home sales went above the million-unit mark. New-home sales rose in three out of four regions in April, with gains of 13.4%, 0.6%, and 4.3% recorded in the Midwest, South, and West, respectively. In the Northeast, where shifting weather patterns have caused wild fluctuations for several months, sales fell nearly 18%. “Sales of both new and existing homes were slightly above their first quarter averages in April, and the fundamentals of this housing market continue to exhibit remarkable strength looking forward,” notes David Seiders, chief economist, National Association of Home Builders (NAHB).
Getting the Most Out Of Your Cylinders
Dr. Heather Brown, Ph.D. Associate Professor, Concrete Industry Management Program Middle Tennessee State University
What could possibly go wrong? The better question to ask when talking about accurate cylinder breaks is what can’t go wrong. 6” by 12” concrete cylinders are the standard of checking in-place compressive strength for job performance, acceptance, checking mix proportion adequacy and gathering strength data for future quality control. The measured results are dependent upon adhering strictly to standardized uniform procedures, as outlined in ASTM C31 (casting cylinders), ASTM C617 (capping cylinders), ASTM C39 (breaking cylinders) and various other prescribed testing protocols. It is not surprising that problems can arise from failure to adhere to these various specifications and it is very important to realize that nearly all testing errors produce lower strength results. Some consequences of falsely low results are unnecessary delays, costly follow up testing, wasteful over-design and rejection of good concrete.
Here are some key steps that must be properly completed to insure accurate 28-day cylinder breaks.
• Sampling – technicians are required to obtain at least two portions from the middle third of the load. Remixing ensures consistency of the sample. Adhering to the maximum interval of fifteen minutes between obtaining the sample and casting the cylinders is important. Each set of cylinders must come from a single truck.
• Casting – technicians must choose the appropriate mold material, properly fill and consolidate cylinder molds, and ensure both good end condition and cylinder uniformity.
• Initial curing – this is critical to the accuracy of a cylinder. Temperatures lower than the specification (60-80 degrees F) can cause up to 7% loss in strength while exposure to freezing temps can cause up to 56% strength loss. High temperatures may boost early strengths but 28-day strengths will suffer. Cylinders must be properly stored in the field, in an environment that insures both proper temperature and moisture conditions and should be brought into the lab within 48 hours of casting
• Transporting cylinders – improper timing of moving cylinders can cause a loss of up to 7% in compressive strength. Proper handling during transport also prevents loss of cylinder strength.
• Laboratory curing – Wet curing in a 73 +/- 3 degree F environment maximizes the hydration of the cement, and is required by the specifications. This curing should begin as soon as cylinders are received in the lab and continue until the time for breaking the cylinder.
• Capping – this involves paying attention to the end condition and the capping material. The capped ends must be flat, perpendicular to the specimen axis, parallel to each other and not excessively thick. The capping material should not induce a stress distribution in the cylinder that would cause inaccurate measured results.
• Testing – this step involves attributes of the compression machine such as loading rate, specimen misalignment, loading platens, seating behavior and machine calibration. To ensure a properly working machine, refer to ASTM C39 for rules to check compliance.
• Reporting – the last step is to properly record the results of the test, including a post-failure inspection report on the type of cylinder break. Dissemination of the results to all parties, including the ready mix producer, is essential to identify any problem areas and to confirm successful mix performance.
The table shown below is an example of how many things can actually affect the strength of a cylinder. To get more detailed information about these variables, there is information in an NRMCA Publication No. 179 by David N. Richardson.
Testing Concrete
The concrete testing process garners little attention from the construction industry – until a problem occurs. At that point, everyone is intensely interested and all the parties involved become, for the most part, adversaries.
Here’s a true example from a personal experience. A commercial project with a lot of structural concrete allowed the general contractor to do the concrete testing. Subsequently, the GC assigned this responsibility to a laborer who had not received the proper training (and who was not ACI certified). Not surprisingly, several cylinders were not prepared according to the specification, resulting in some cylinders that displayed extensive honeycombs (voids) when the molds were removed. Instead of rejecting these cylinders due to their obvious lack of proper consolidation, the engineering firm allowed the cylinders to be broken, and then held up the job when the cylinders failed to make the required strength. The burden of proving that the inplace concrete met the strength specification now fell on me (the ready mix producer), in spite of the very obvious fact that this responsibility was being transferred to me on the basis of defective, non-standard cylinders. Subsequent coring demonstrated the in-place concrete strength to be fine, and GC had to foot the bill for several thousand dollars of coring expense, plus the delay to the job.
Procedures and specifications for concrete testing are well defined and generally accepted by all parties as fair and reasonable – the problem occurs when these well-defined specifications are not followed throughout the testing process. Unfortunately, failure to follow the mandated specifications is often more common than compliance. This problem is exacerbated when non-standard cylinders are allowed to be tested instead of being immediately rejected.
The following story highlights some of the most common problems encountered at various stages in the process. Armed with this important information, resolve to eliminate these specification violations from your next (or even your existing) projects – everyone will benefit.
Anderson Receives Lifetime Achievement Award
Daniel P. Anderson received a Lifetime Achievement Award from the American Society of Concrete Contractors (ASCC) at the association’s annual conference in Dallas, Tex., September 18, 2003. The award is given to outstanding individuals in the industry, for the body of their accomplishments furthering concrete construction.
Anderson began his career in the concrete industry in 1969 when he joined the staff of Concrete Construction magazine. From 1985 to 1999 he was president of The Aberdeen Group which published Concrete Construction and two other industry – related magazines, and produced The World of Concrete exposition. Anderson organized the first World of Concrete in 1975.
He served on the Board of Directors of ASCC as well as on several ASCC committees for several years. He is also a past member of the Market Development Committee of the American concrete Pavement Assn., and the Promotion Committee of the National Ready Mixed Concrete ASSn. Anderson has been a member of the American Concrete Institute for 25 years.
The ASCC is a non-profit organization dedicated to enhancing the capabilities of those who build with concrete, and to providing them a unified voice in the construction industry. For more information visit their website at www.ascconline.org.
Foundation Builders, Inc.: A Solid Company with Loyal Employees
Foundation Builders, Inc. of Greeley, CO started out as a four-man company in 1972; however, it is far from a small concrete company now. There are currently 70 men and women employed at Foundation Builders, Inc. Owner Jack Renfroe and son Scott, are thankful for the quality of people working at Foundation Builders, Inc. and the repeat business from general contractors.
The secret to the success of Foundation Builders, Inc. is the employees. The supervisor and scheduler of foundation work. Tom Neumaler, has been with the company for 31 years. Car Joerschke, a Fassl Crane operator has 26 years of service; and Linn Rowe, the foundation field supervisor, has 20 years of service with Foundation Builders, Inc. The solid years of service continue on down to the office manager, who recently completed her 16th year. Jack and Scott are proud of their employees and the dedication they have provided to Foundation Builders, Inc. To the Renfroes, their service is invaluable.
Good equipment and capable employees provide high standards that distinguish Foundation Builders, Inc. from its competitors. They strive to provide consistency and accuracy in each and every project. “Our goal is to train versatile employees so if one crew leaves a site, another crew can come in and pick up where the other left off with little questions asked,” states Scott Renfroe. “Our company is known for high quality and we’re given a lot of high end difficult jobs for that reason – we want to maintain that,” he further explains.
Other reasons for the company’s success are company habits and procedures. Foundation Builders found a solution to high turnover in establishing a safety program. Included in this program are post employment physicals, which determine each employee’s physical capabilities. Scott explains, “If a guy has had a knee injury, we know about it. Then we put them in the right jobs.” When placed in the right jobs, employees are less likely to hurt themselves because they are physically capable of doing the job correctly. Since incorporating this safety program, the company’s workman’s compensation insurance has substantially decreased. Scott explains, “Injuries are down from 10-15 per year to only two so far this year. It costs us money but saves us a lot more in the long run.” Foundation Builders, Inc. is now a company conscientious of their employee’s safety with dedicated employees.
With experienced employees, Foundation Builders, Inc. is able to focus on providing high quality services. Until recently, their main service was residential foundation work, pouring up to 300 foundations per year; however, in the past couple of years foundation work has faltered due to the economy. Fortunately, Foundation builders, Inc. was able to market other services, commercial work and flatwork, to pick up the slack. Jack states, “Commercial has become as important as housing in the past couple of years.”
Foundation Builders, Inc. contributes a lot of their success to their membership in the Concrete Foundation Association. As a member, they can communicate with other members about questions and problems they have in order to quickly reach a conclusion. “Being able to talk to members is huge,” Scott states, “Getting that kind of information is priceless.” The CFA membership is a place to go where they get answers from experience contractors. Scott explains, “It’s hard to go across the street, ask a competitor a question, and get an answer.”
The Renfroes also appreciate the educational opportunities that CFA provides, such as Foundation Fundamentals, which improve the employee’s knowledge in the industry. The more knowledgeable their staff is, the better prepared they are for high-end difficult jobs. The World of Concrete is another opportunity that Foundation Builders, Inc. takes full advantage of. Jack, Scott, Tom, and Brad attend the show every year and when schedules and budgets allow some crew foreman also attend. “We try to take a few men every year to the trade-show. We all look around and then report back to one another about what we saw.” Jack explains. “We have made a lot of purchases this way.”
Foundation Builders, Inc. is not always able to attend CFA events, but by networking with other members they are still informed of the latest information. “We’d like to go to a lot more meetings but it doesn’t always work out.” Jack Explains. “When we can’t attend, it’s great that we can talk to members who did go, and find out what went on.”
The Renfroes are thankful for the success of Foundation Builders, Inc. Their goals are to always do what is right, to treat people fairly, to have every employee and past employee to trust Foundation Builders, Inc. to do a job for their parents, and turn every contractor into a repeat customer. A future goal is to play a more active role in their community. With a company built on loyal employees, quality work, the best equipment, and the benefits of their CFA membership, Foundation Builders, Inc. is bound to achieve those goals.
Cold Weather Research Update: Strengths Proved Good, More Research on Long-Term Durability
Cold weather is a comin’… scratch that, it’s here! Companies throughout the CFA are gearing up with this in mind as they turn he calendar from October to November and recognizing that special considerations are needed for placing concrete during colder weather. However, at an increasing rate, the CFA is hearing that code restrictions imposed by inspectors and officials are becoming overly conservative. One common denominator is that residential construction continues to march ahead at a high rate, and restrictions concerning concrete placement have a definite economic impact on everyone involved in the construction and sale of homes. Success is certainly to be found in learning what steps are need to lengthen the construction season and how you can keep the projects “flowing” despite freezing conditions.
This is a primary reason why the CFA initiated a cold-weather research project two years ago to study the affects cold temperatures have on the strength gain and durability of concrete in residential walls. While the study is not complete, it is time to begin implementing this research to resolve the issues that have occurred in the past and will certainly come about again this year between contractors, ready-mix producers and building inspectors.
Research began with laboratory testing at Master Builder’s research laboratory in Cleveland, OH. Phase I featured a matrix of 36 mix designs developed based on both “typical” cold-weather mixes and standard mixes used by the cold-weather committee members from Ohio to Minnesota. Over 650 cylinders were cast from these 36 mix designs. The raw materials were stabilized to approximately 68ºF prior to mixing. Once the cylinders were cast, maturity probes were inserted and then all were immediately placed into temperature controlled rooms of 30ºF and 50ºF. The committee identified these two ambient temperatures as the most common targets for increased concern coming from inspectors and officials.
A correlation between predicted maturity curves and the actual performance was one principal target for this research. In order to achieve this correlation, temperature probes were inserted through the top of many of the cylinders to record the data until testing. The cylinders cast in the laboratory were kept in the respective temperature-controlled rooms until the time each was broken. This occurred at 1,2,3,7,14, and 28 days. Breaks were then correlated with the predicted strengths obtained from maturity prediction using the Con-Cure maturity system (www.concure.com).
Phase II in the research program included real world testing of walls. The research committee selected six of the best performing, economical mix designs from Phase I to subject field conditions. Osborne-Medina Concrete in Medina, OH volunteered their plant, materials, and equipment for the site of the full-scale tests. CFA member Tri-County Excavation of Richfield ,OH, provided the man-power and conveyer to set and fill the forms provided by Western Forms (www.westernforms.com) . Once again, the mixes were produced with 68ºF components and placed into the forms on January 10, 2003. The ambient temperature at time of placement was approximately 22ºF and dropping. According to recorded weather records for Wayne County Airport, the Medina area did not feel temperatures above freezing for 20 days after the pour. In fact, the records show an unofficial low of -19ºF on January 27, 2003.
The research was conducted in a similar fashion to the Phase I procedures. Maturity meters were inserted in to the walls to record concrete temperatures, while other data-loggers recorded ambient temperatures. In addition to the walls, cylinders for all mixes were cast and placed in one group under a blanket. The volume of concrete in the combined cylinder set equaled the amount of concrete in one of the wall sections. Two walls were cast with each mix (twelve total) and one wall of each received a blanket “cap” that is, a 6-ft. blanket lain over the top 2 to 2+ feet.
The wall forms were stripped at the end of 24 hours (ambient temperature was 20ºF). Following from removal, cores were taken from each wall. Two locations were cored, one near the top (under the blanket for the “capped” walls) and one near the center of each wall section. These core samples were then broken along with the matching cast cylinders stored under the blanket. This process was repeated to match the laboratory cylinder sets at 1,2,3, 7, 14, and 28 days and the results compared to the maturity predictions made with Con-Cure as well as the results from Phase I.
The committee gained a wealth of knowledge from the significant testing. There are additional results that are being sought in order to closely determine what recommendations should be made industry-wide. Phase I resulted in the identification that all 36 mixtures and 44 curves achieved the designed 28-day strengths even when cured under very cold temperatures (near freezing the entire 28 days). There were not failed mixes. Phase II provided further conclusive evidence that the design mixtures selected performed well by once again achieving acceptable strengths from cylinder breaks. This was despite the fact that the probes recorded concrete temperatures dropping in some of the leaner sample walls below 32ºF in as little as 11 hours.
The committee was also able to substantially prove that maturity prediction “accurately” estimated the strength gain of the mix designs for both laboratory and field-cured concrete. Perhaps the most significant aspect of the results was that the restrictions for placing concrete in residential foundation wall applications based on ACI 306 appear to be overly restrictive.
It should also be noted that under petrographic exam, some field samples showed varying degrees of microfracturing and ice crystal implants because they were cured well below freezing. While the strengths were good, further study on the long-term durability in a basement wall, using the leaner mixes and under these conditions is being done. Although it is still undetermined whether walls subjected to the frozen state will exhibit higher permeability and lower surface durability, the volume of data supports the empirical evidence that had been gathered over the previous two winters.
What does this information mean to contractors heading into the difficult winter months?
The CFA has offered guidelines for cold-weather concreting over the past few years for purchase. These guidelines, published in 1997 and based on common thought at the time, use target mix designs for specific ambient temperature ranges. Our research shows that ambient temperature only “affects” concrete temperature and that maturity is much more closely dependent on the temperature of the concrete. Basing the practices used and/or the rules and restrictions during cold weather on ambient temperature is without basis.
This testing also concludes that some of the parameters for the prior guidelines are consistent with intelligent concrete practices and must continue to be followed. The components of concrete should be stored and mixed to achieve a minimum delivery temperature of 60ºF (with an ideal temperature of 65ºF or higher). Additional water in these mixes produces a significantly slower strength gain and much higher risk of freeze damage. The committee verified, during this testing, that the use of blankets, even if only over the tops of the walls extended the time it took the concrete to the ambient conditions. This step is valuable depending on mix design and other conditions, when the ambient temp is near or below freezing.
Let’s take a look at some of the key results of this Study:
Confirmation of the obvious
- There are no single, simple answers. This means that multiple mixture designs and protective measures have shown suitability under sever conditions.
- Good mix designs can withstand colder temperatures than lean designs. Variables such as water/cement ration, admixture choice and delivery temperature are all critical factors.
- A blanket statement that “I can pour any mix I want, any time I want,” is just as wrong as a statement saying you can’t pour concrete in cold weather.
- Pour any time you; morning is best when the sun is expected to have an impact, but above all monitor concrete temperatures and maturity.
- Type III cement will perform better in colder weather than Type I
- Calcium Chloride is still the best “Bank for you Buck” but will not correct problems associated with poor mix design, high W/C ratios, or low concrete temperatures.
- Any given mix is certain to harden at a slower rate in cold weather than it would in warm weather. Make certain your field people are thinking of this as it could create safety concerns (i.e. walls failing during premature backfills, haunches ripping loose because of insufficient tensile strength, etc.).
Among the “news flashes”:
- If cold weather concerns are critical to a contractor or supplier, he should pick two to four mixes for varying degrees of cold weather exposure and know when to use them. Maturity testing should be used on each localized mix to confirm performance.
Warning to all wall contractors and ready-mix suppliers who read this:
The addition of water on-site beyond what is allowed by the constraints of the mix design will render all of the above factors meaningless and would result in an unsafe condition. The practice of adding extra water to improve workability is quite possibly the main reason building officials shut jobs down in the cold in the first place—because such “wet” mixes have a much higher likelihood of being damaged in freezing weather! It is such a prevalent practice that the sentiment among building inspectors is generally “Better safe than sorry.” Moral of the story: Keep the water/cement ratio where it should be – consider using water-reducing admixtures instead of water.
The most important result of this study is that during sub-freezing conditions, contractors should follow a maturity-prediction procedure for validating their individual mix designs that they work out with their ready-mix producer and then monitor the performance of those mixes with measuring devices to ensure that they are maintaining suitable concrete temperatures and achieving suitable maturity. For more information on these results and the availability of a research report contact Jim Baty (jbaty@cfawalls.org) at CFA headquarters (866-CFA-WALL) or one of the following Cold-Weather Committee Members.
- Chairman – Terry Lavy, Lavy Concrete Construction, Piqua, OH at 937-773-3963 or terry@lavyconcrete.com
- Brad Barnes P.E., North Central Engineering, LTd., Canton, OH at 330-454-1113 or TBBPE@aol.com
- John Gnaedinger P.E., ConCure Corporation, St. Louis, MO at 636-386-4800 or John@concure.com
Stay Tuned Folks, We’re Not Done!
Topsail Island Concrete Homes Stood Tall for Hurricane Isabel
In mid-September, the nation’s eyes were fixed on the North Carolina coast as the most powerful Atlantic hurricane in five years was predicted to hit the state. With storm warnings ranging from Category 2 to Category 5, residents braced for Isabel. CNN covered the event from North Topsail Island, a stretch of the state’s coastline routinely hammered by such storms and coincidentally the site of six town homes built using cast-in-place removable form concrete construction method. Isabel hit land as a Category 2 storm with sustained winds just below 100 mph. But for Dave Pfanmiller, builder of the new cluster of town homes toured by many CFA members during the 2003 summer meeting, this storm was no big deal. Dave was thankful the hurricane wasn’t worse but knew the homes would stand up to a greater test.
These upscale homes built by Security Building Group (SBG) of Raleigh, NC, withstood the high winds and heavy rains doled out by Isabel. “While the homes weren’t put to the real test, a Category 5 storm, the y fared very well,” stated Dave Pfanmiller of SBG. There was no damage to the town homes or to the most buildings on the island. There was damage to unanchored mobile homes and poorly constructed vinyl-sided and older homes. “The upshot of the hurricane, for these homes and our current homeowners, is that we gained another two feet of dune,” says Dave.
Hurricanes are a way of life for coastal communities. More than ever, developers and homeowners are looking to concrete as their home material of choice to protect their investment from even the fiercest of storms.
For more information about above-grade, cast-in-place concrete construction projects in North Caroline contact Dave Pfanmiller at 919-427-0251.
