Deicer Scaling Resistance of Concrete Mixtures Containing Slag Cement Phase 2: Evaluation of Different Laboratory Scaling Test Methods, TPF-5(100), 2012

With the use of supplementary cementing materials (SCMs) in concrete mixtures, salt scaling tests such as ASTM C672 have been found to be overly aggressive and do correlate well with field scaling performance. The reasons for this are thought to be because at high replacement levels, SCM mixtures can take longer to set and to develop their properties: neither of these factors is taken into account in the standard laboratory finishing and curing procedures. As a result, these variables were studied as well as a modified scaling test, based on the Quebec BNQ scaling test that had shown promise in other research. The experimental research focused on the evaluation of three scaling resistance tests, including the ASTM C672 test with normal curing as well as an accelerated curing regime used by VDOT for ASTM C1202 rapid chloride permeability tests and now included as an option in ASTM C1202. As well, several variations on the proposed draft ASTM WK9367 deicer scaling resistance test, based on the Quebec Ministry of Transportation BNQ test method, were evaluated for concretes containing varying amounts of slag cement. A total of 16 concrete mixtures were studied using both high alkali cement and low alkali cement, Grade 100 slag and Grade 120 slag with 0, 20, 35 and 50 percent slag replacement by mass of total cementing materials. Vinsol resin was used as the primary air entrainer and Micro Air® was used in two replicate mixes for comparison. Based on the results of this study, a draft alternative test method to ASTM C762 is proposed.

HR-243 Production and Evaluation of Calcium Magnesium Acetate, Febrauray 19, 2001

Calcium magnesium acetate (CMA) has been identified by Bjorksten Research Laboratories as an environmentally harmless alternative to sodium or calcium chloride for deicing highways. Their study found CMA to be noncorrosive to steel, aluminum and zinc with little or no anticipated environmental impact. When used, it degrades into elements found in abundance in nature. The deicing capabilities were found to be similar to sodium chloride. The neutralized CMA they produced did cause scaling of PC concrete, but they did not expect mildly alkaline CMA to have this effect. In the initial investigation of CMA at the Iowa DOT laboratory, it was found that CMA produced from hydrated lime and acetic acid was a light, fluffy material. It was recognized that a deicer in this form would be difficult to effectively distribute on highways without considerable wind loss. A process was developed to produce CMA in the presence of sand to increase particle weight. In this report the product of this process, which consists of sand particles coated with CMA, is referred to as "CMA deicer". The mixture of salts, calcium magnesium acetate, is referred to as "CMA". The major problems with CMA for deicing are: (1) it is not commercially available, (2) it is expensive with present production methods and (3) there is very little known about how it performs on highways under actual deicing conditions. In view of the potential benefits this material offers, it is highly desirable to find solutions or answers to these problems. This study provides information to advance that effort.

Production and Evaluation of Calcium Magnesium Acetate, HR-243, 1982

Calcium magnesium acetate (CMA) has been identified by Bjorksten Research Laboratories as an environmentally harmless alternative to sodium or calcium chloride for deicing highways. Their study found CMA to be noncorrosive to steel, aluminum and zinc with little or no anticipated environmental impact. When used, it degrades into elements found in abundance in nature. The deicing capabilities were found to be similar to sodium chloride. The neutralized CMA they produced did cause scaling of PC concrete, but they did not expect mildly alkaline CMA to have this effect. In the initial investigation of CMA at the Iowa DOT laboratory, it was found that CMA produced from hydrated lime and acetic acid was a light, fluffy material. It was recognized that a deicer in this form would be difficult to effectively distribute on highways without considerable wind loss. A process was developed to produce CMA in the presence of sand to increase particle weight. In this report the product of this process, which consists of sand particles coated with CMA, is referred to as "CMA deicer". The mixture of salts, calcium magnesium acetate, is referred to as "CMA". The major problems with CMA for deicing are: (1) it is not commercially available, (2) it is expensive with present production methods and (3) there is very little known about how it performs on highways under actual deicing conditions. In view of the potential benefits this material offers, it is highly desirable to find solutions or answers to these problems. This study provides information to advance that effort. The study consisted of four principal tasks which were: 1. Production of CMA Deicer The objective was to further develop the laboratory process for producing CMA deicer on a pilot plant basis and to produce a sufficient quantity for field trials. The original proposal called for producing 20 tons of CMA deicer. 2. Field Evaluation of CMA Deicer The objective was to evaluate the effectiveness of CMA deicer when used under field conditions and obtain information on application procedures. Performance was compared with a regular 50/50 mixture of sand and sodium chloride. 3. Investigation of Effects of CMA on PC Concrete The objective was to determine any scaling effect that mildly alkaline CMA might have on PC concrete. Comparison was made with calcium chloride. 4. Determine Feasibility of Producing High Magnesium CMA The objective was to investigate the possibility of producing a CMA deicer with magnesium acetate content well above that produced from dolomitic lime. A high magnesium acetate content is desirable because pure magnesium acetate has a water eutectic of -22 F° as compared with +5 F° for calcium acetate and is therefore a more effective deicer.

Evaluation of Concrete Sealers for Use on Bridge Pier Tops and Abutments, R-242, 1971

Many reports have been written concerning investigations of concrete sealants. The primary concern of most investigators is the protection of bridge decks from de-icing chemicals which cause surface scaling and, when allowed to permeate to reinforcing steel, result in deep spalling and general concrete deterioration. The problem of protecting abutments and pier tops from salt solutions entails a significantly different approach than the problem of protecting bridge decks. The epoxy resins become eligible as a protective material since one need not be concerned with slipperiness or its abrasive characteristics. Protection with linseed oil at regular intervals would prove bothersome because of the inaccessibility of pier tops after the deck is placed. The primary purpose of this investigation was to evaluate various commercial products in terms of their ability to prevent concrete scaling of bridge abutments and pier tops which are subject to salt water deterioration.

Evaluation of the Concrete Admixture Gla-Zit, MLR-81-5, 1983

A concrete admixture, Gla-Zit, was evaluated in 1970 by the Iowa State Highway Commission and found to be lacking in providing beneficial effects to concrete. This current evaluation is similar to that conducted in 1970 with slight modifications in the actual concrete mixes studied. At the request of the manufacturer, all concrete mixes containing Gla-Zit were non-air entrained. Concrete properties examined were compressive strength, salt scaling resistance, absorption, resistance to chloride penetration, and freeze-thaw durability. The differences found in the mixes studied are much more attributible to air entrainment, or the lack thereof, than the influence of Gla-Zit. The study re-affirms that it is necessary to have properly air entrained concrete to lessen the detrimental effects of freeze and thaw and scaling caused by salting. There is no data in the study to suggest that Gla-Zit has any significant effect on any of the concrete properties examined.

Bridge Deck Waterproofing Membrane Study, R-262, 1974

One of the main problems of bridge maintenance in Iowa is the spalling and scaling of the decks. This problem stems from the continued use of deicing salts during the winter months. Since bridges will frost or freeze more often than roadways, the use of deicing salts on bridges is more frequent. The salt which is spread onto the bridge dissolves in water and permeates into the concrete deck. When the salt reaches the depth of the reinforcing steel and the concentration at that depth reaches the threshold concentration for corrosion (1.5 lbs./yd. 3 ), the steel will begin to oxidize. The oxidizing steel must then expand within the concrete. This expansion eventually forces undersurface fractures and spalls in the concrete. The spalling increases maintenance problems on bridges and in some cases has forced resurfacing after only a few years of service. There are two possible solutions to this problem. One solution is discontinuing the use of salts as the deicing agent on bridges and the other is preventing the salt from reaching or attacking the reinforcing steel. This report deals with one method which stops the salt from reaching the reinforcing steel. The method utilizes a waterproof membrane on the surface of a bridge deck. The waterproof membrane stops the water-salt solution from entering the concrete so the salt cannot reach the reinforcing steel.

Air Content and Permeability of PCC Pavements: 1909 to 2006, MLR-05-02, 2007

Portland cement concrete pavements have given excellent service history for Iowa. Many of these pavements placed during the 1920’s and 1930’s are still in service today. Many factors go in to achieve a long term durable concrete pavement. Probably the most important is the durability of the aggregate. Until the 1930’s, pit run gravel was the most predominant aggregate used. Many of these gravels provided long term performance and their durability is dependent upon the carbonate fraction of the gravel. Later, limestone (calcium carbonate) and dolomite (calcium, magnesium carbonate) sources were mined across Iowa. The durability of these carbonate aggregates is largely dependent upon the pore system which can cause freeze thaw problems known as D-cracking, which was a problem with some sources during the 1960’s. Also, some of these carbonate aggregates are also susceptible to deterioration from deicing salts. Geologists have identified the major components that affect the durability of these carbonate aggregates and sources are tested to ensure long term performance in Portland cement concrete. Air entrainment was originally put in concrete to improve scaling resistance. It is well known that air entrainment is required to provide freeze thaw protection in concrete pavements today. In Iowa, air entrainment was not introduced in concrete pavements until 1952. This research investigates properties that made older concrete pavements durable without air entrainment.