Concrete products can benefit from water repellent treatments. Post treatment application can reduce water/moisture absorption, reduce effloresce, improve freeze/thaw resistance and reduce rebar corrosion. These materials have numerous applications in highway and bridges, parking structures, airport runways, water ways, marine structures; all of which are exposed to salt spray and other harsh environmental factors.
When concrete is cast, water is used in excess in order to have proper workability and flow characteristics. The water that is not consumed in the hydration process will evaporate out of the concrete, and this process will leave behind capillary pores. These pores can allow water and salts to penetrate the concrete causing deterioration. Using a penetrating water repellent as a surface treatment can help reduce water absorption and the penetration of de-icing agents. There are also water repellants that can be used as an integral admixture.
The Azelis Construction Lab evaluated the performance of silicates in masonry water repellents with the purpose of generating performance data for our customers, helping them determine if it the right technology for their formulations.
Method
The Azelis Construction Solutions lab worked with water repellent treatments on repair mortar, with the objective to seal the surface to protect against scaling associated with deicing salts. The construction lab performed the ASTM C672 scaling test to determine the treatment’s scaling resistance. This is an aggressive test meant to simulate years of wear and salt exposure upon the surface of mortar or concrete.
A commercially available repair mortar system was used for testing as the objective was to determine the improvement in scaling resistance from either an untreated system or one that employs a sealing treatment. The treatment was applied in accordance with the recommendations using standard commercially available spray equipment which allows for a continuous spray while passing over the test specimens. For complete details, refer to Application & Procedure below*
Performance Results
The concrete repair sealant formula using Silblock WMS showed very good performance in the freeze-thaw cycles. Azelis tested a competitive silicate technology and statistically the Silblock WMS formula outperformed the competitive material in cumulative weight loss through the cycling.
Conclusions:
Using a penetrating silicate to protect the surface of concrete or mortar can be beneficial to its longevity and durability. Depending on the application, Azelis recommends using Silblock WMS penetrating silicate to achieve a water repellent concrete surface. Silquest A-137 is the silane technology on which Silblock WMS emulsion is based and can be used alternatively. Both products have tremendous benefits in concrete waterproofing applications and may be used as a topical additive or as an integral part of the admixture.
Interested in improving water repellency of your formulas? Contact your Azelis representative or try our iChat service to find out more on these products and other ways we can help you improve the performance of your formulations.
*Application & Procedure
The repair mortar was cast into specimens as prescribed in ASTM C672 and cured for 28 days. Afterwards, the silicates sealants were applied on respective specimens according to application instructions. The specimens dried for an additional 7 days. The coated specimens were compared to control specimens without coatings.The specimens were then prepared by placing a sealed dam around the perimeter of the surface to hold in the scaling solution. Each specimen surface was covered with ¼ inch depth of 4% calcium chloride solution. The specimens were subjected to 50 cycles: 16-18 hours in freezer, thawed at room temperature for 6-8 hours.Every 5 cycles, the surface was washed and new solution was applied. The discarded solution was poured into a 200 mesh sieve and the surface was washed over the sieve to collect any scaled material. This scaled material was weighed to obtain a quantitative measurement. The ASTM standard outlines a visual performance rating on a subjective scale from 0 to 5 (5 representing severe damage).
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