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Basement Waterproofing - New Construction
NCC Basement Waterproofing Site spend most of our time today working on the more complex area of waterproofing in refurbishment projects, however our waterproofing experts have a full knowledge of the approach and systems for new build projects and so we provide some of this useful information on these pages for the guidance and assistance of our customers and their clients. Waterproofing systems for new construction projects can include externally applied waterproofing barrier protection, integral watertight construction and internally applied waterproofing barrier protection.

Waterproofing Type A: Barrier Protection - Externally Applied (in accordance with BS 8102: 2009 Type A)
This is the most widely used, the most cost effective and easiest applied basement waterproofing solution for waterproofing below ground in most new construction works. Externally applied basement waterproofing barrier protection systems, include traditional and polymer modified bitumen coatings, polymer modified cement slurries or synthetic resin based waterproofing coatings, which all have different characteristics. However they all require adequate access to the base and external walls before, during and after their construction, followed by additional protection being provided before backfilling with soil. Careful detailing, the connection and sealing of any joints, pipe entry’s and service ducts is also essential. [Unfortunately this is not so common!!]

Specific waterproofing systems and product characteristics are covered more extensively in the 'Basement Waterproofing Products' and 'Basement Tanking Products' pages of this website. If you have any other specific questions or you need more specific information or advice on externally applied Type A: Externally Waterproofing Barrier Protection products or systems, please call any of our offices and one of our waterproofing experts will be pleased to assist you.

Waterproofing Type B: Structurally Integral Protection
(In accordance with BS 8102: 2009) Type B: Structurally integral Waterproofing is generally only suitable for new basements and below ground structures that can be designed and built to prevent water ingress, together with the additional prevention of water vapour ingress when required. This is because the waterproofing strategy and its elements are designed and built into the new structural framework and external building envelope. Service entries are particularly vulnerable to water penetration, so where they cannot be avoided, they should be carefully detailed, for example by incorporating hydrophilic gaskets and sealants to minimize any risk of future water ingress. Obviously this is not normally possible with an existing structure and building envelope. In refurbishment situations, then Waterproofing Type A: Barrier Protection or Waterproofing Type

C: Cavity Drained Protection, or a combination of systems, is likely to provide the best solution – According to the specific project’s requirements. For more details please refer to the ‘Existing Basement Waterproofing’ Pages of this website. The Component Materials for Reinforced Concrete Basements and Structures with Type B: Structurally Integral Waterproofing Protection The reinforced concrete itself plays a major part in Type B Structurally Integral systems and this is achieved by a combination of important factors in the structures design and construction. These include ensuring the correct concrete thickness and reinforcing steel dimensions and positioning, plus the concrete mix design and the correct placing and curing of the concrete. Reinforced concrete should now be designed and constructed in accordance with BSEN1992. Concretes meeting at least the minimum design requirements for structural use and durability in the ground, and that are properly placed and compacted are likely to have good resistance to the transmission of liquid water. A degree of resistance to water vapour transmission is also achieved by such concretes, dependent primarily on the section thickness. However the many variable factors involved mean that achieving such a ‘waterproof’ concrete in this way has considerable risk and it is recommended to take the additional step of using a watertight concrete design mix that includes a waterproofing additive such as Sika 1+ or Sika Waterproofing Powder, together with a high range water reducing admixture such as Sika Viscocrete. Crack widths in the concrete should also be controlled by using the appropriate design, concrete mix (for example a minimum of 350kgs OPC, the addition of micro-fibres and a water : cement ratio of 0.45 or less, etc.), close supervision of the concrete placing, compaction and curing, especially in relation to temperatures and winds that can cause excessive rates or levels of evaporation to adversely affect the quality of the concrete surfaces. The pattern of leaks and seepage encountered in such structures is often associated with poor joints, cracks or other discontinuities such as service penetrations. Service entries are particularly vulnerable to water penetration, so where they cannot be avoided, they should be carefully detailed, for example by incorporating hydrophilic gaskets and sealants (e.g. SikaSwell P Profiles and SikaSwell S Sealants – available from NCC Basement Waterproofing Site) to minimize any risk of future water ingress.

1. Watertight Concrete Using Waterproofing Admixtures
There is a range of products, generally categorized as waterproofing admixtures, which increase the inherent resistance of concrete to water and water vapour. In a recent USA report ACI 212.3R - 10 ‘Report on Admixtures for Concrete’ - There is a new addition of ‘Chapter 15 - Permeability Reducing Admixtures' - (PRA's). This is interesting because it clarifies the differences between the alternative materials used to produce waterproof concrete. Firstly it defines two Categories of PRA (Permeability Reducing Admixtures):

PRA-N's - For use in Non-hydrostatic pressure situations, and PRA-H's - For use in Hydrostatic pressure situations. This American report then defines 3 types of PRA materials: 1. Hydrophobic water repellent materials (includes stearates - i.e. Sika Waterproofing Powder & Sika 1+). Mostly these are PRAN's except the 'Polymer' types which can be PRAH's (i.e. Everdure Caltite). However when combined with high range water reducing admixtures these are also PRAH’s, suitable for hydrostatic pressure situations. 2. Fine solids or densifiers (includes colloidal silicates - i.e. Sika 1 Liquid). These are also generally PRAN's, again until combined with high range water reducing admixtures, when these materials are also PRAH’s, suitable for hydrostatic pressure situations. 3. Crystalline growth products - 'active' hydrophilic materials that form Calcium Silicate Hydrates in the pores (i.e. Xypex / Kryton type) These are actually PRAH's in their function, but these materials need to be used in conjunction with high range water reducing admixtures to control the other workability, compaction, curing and crack control demands of the concrete. In summary all 3 types of materials are suitable as water permeability reducing admixtures, but their correct use is dependent on the overall concrete mix design and the other specific concrete and project requirements. Therefore this mix design should be developed with a single manufacturer’s materials that are designed for this purpose. In the UK and ROI, the NCC Basement Waterproofing Site specialists usually work with the concrete technologists at Sika to achieve the optimum solution for our customers and their clients. Waterproofing admixtures for use in concretes for Type B: Structurally Integral Waterproofing systems should always be used in conjunction with the right selection joint waterproofing systems and systems to ensure that any penetrations through the concrete, such as service ducts etc., are also securely watertight. Generally we recommend that these components are also supplied by the same overall ‘Waterproofing System’ manufacturer and will include a whole range of ‘Waterstops’ including Waterbars (e.g. Sika PVC and Elastomer Waterbars), Injection Hoses (e.g. Sika Injectoflex and Sika Fuko Hoses), Hydrophilic Profiles (e.g. SikaSwell P Profiles) and Sealants (e.g. SikaSwell S Sealants and Sikaflex Construction Joint Sealants).

2. Joint Waterproofing Systems – Water-Stopping Solutions
Waterstop systems should be used to provide enhanced resistance to water penetration at all joints in the reinforced concrete structure, e.g. at all of the construction or day-work joints, service entries or other penetrations, in addition to all of the movement / expansion joints. The positioning of the waterstop(s) (external and/or internally mounted) should also be appropriate for the design exposure, the method of construction and the level of risk or seepage that is allowed. Particular attention should be given to the waterstop(s) in movement / expansion joints although these should normally be avoided by good design wherever possible in water retaining basements and other structures. In accordance with the recommendations of BS 8102: 2009, the principal types of waterproofing systems to ensure that all of the joints and any penetrations are securely watertight can be

classified as the following. a) Passive Waterstop sections: These are Waterbars (sometimes also confusingly called ‘waterstops’ which is the term used to cover all types of joint waterproofing system generically):- Mostly they are produced as extruded flexible profiles of PVC, or Elastomer (vulcanised synthetic rubber) that are designed to be cast into the concrete on both sides of the joint, either at the concrete surface or in the centre of the reinforced concrete section, where they form a physical barrier to water penetration. This is done primarily through greatly increasing the length of path any water ingress would have to take. In addition to the PVC and Elastomer types of waterbars there are also special steel and other metal sections that are sometimes produced for extreme situations and even hybrid combinations of the metal and plastic types for special situations in major civil engineering works. b) Active Waterstop Sections - or Hydrophilic Seals: These waterstop sections are usually preformed extruded profiles or gun-applied sealant grade of hydrophilic material that is fixed or applied on one side of the concrete joint or penetration in the centre of the section before casting the next concrete pour. The hydrophilic material is then designed to swell on contact with water effectively sealing the joint, if and when any water is able to penetrate to this point in the joint. They can be used as a sole joint waterproofing and sealing system, or as a composite product or combined solution with passive waterstop sections. c) Injectable hoses or other sections Injectable hoses or other sections are usually produced from PVC or other plastic material and they are available in a range of different profiles and sections. These include local simple or complex valve systems, which allow micro-cement or resin based injection sealing materials to be injected and in some instances, re-injected, to seal any voids or leaks in the joint. These waterproofing hose sections are fixed to the construction joint surface before casting the next concrete pour. The injection of the sealing solution into the joint can be scheduled on completion of the structure, or for if, as and when required. The nature of all of these structurally integral waterproofing systems is such that they must be always individually designed and specified on each structure As a result, many components such as connection pieces, terminations and complex watertight joint details can also then be custom made / prefabricated under factory conditions, for delivery and rapid, easier and more secure assembly on site. The installation of these systems on site should also be monitored and supervised by the Waterproofing Specialist in the project professional team. Individual project waterproofing advice for each project is always required. Fortunately this can be given by the experts in any of our offices, so please call any of our offices (telephone numbers on the left of this page) and one of our waterproofing specialists will be happy to assist you.

Remedial Works in New Construction Basement Waterproofing:

When the External (Type A) or Integral (Type B) waterproofing system has been damaged – for example during installation and there is no longer a possibility to replace it, or if a decision is made to upgrade the level or Grade of waterproofing during the construction works on site; (this is not so unusual in our experience of projects who did not initially prepare and plan correctly, but that we have been eventually invited to assist and able to rescue!) -Then it is generally a Type A Barrier Waterproofing solution that is required, but this time internally applied. Waterproofing Type A: Barrier Protection - Internally Applied (in accordance with BS 8102: 2009 Type A) These systems are primarily designed for use refurbishment basement waterproofing works, but they may also provide useful solutions for other remedial and repair actions in new basement construction projects i.e. leaks or other problems due to the waterproofing system or components being damaged during the concreting or other work by different trades working on new construction projects. (Electricians and Plumbers can be the biggest potential ‘waterproofing criminals’ from our experience, or the installers of new plant and equipment drilling holes in the structure for their holding down bolts!)
Stopping water intrusion Concrete crystalline waterproofing the right choice for demanding projects.

By Les Faure Below the water table, preventing the deterioration of concrete structures, a problem induced by water penetration, often needs to work both ways: stopping water from coming in, and protecting the concrete from corrosive water/vapor formed in the interior. This double-edged objective was a top priority for Conrad Ettmayer, P.E., LEED AP, the structural engineer overseeing the three-phase construction of the Wisconsin Institutes for Medical Research (WIMR) at the University of Wisconsin in Madison. Ettmayer is principal and director of structural engineering at Harwood Engineering Consultants, based in Milwaukee. The three project phases consist of three towers, the first of which serves as headquarters of the UW Carbone Cancer Center. The tower also is home to imaging sciences, with medical physics occupying the lower level and radiology on the first floor.

FROM LEFT TO RIGHT: By means of diffusion, the reactive chemicals in the crystalline technology use water as a migrating medium to enter and travel down the capillaries of the concrete. The process precipitates a chemical reaction between the crystalline chemicals, moisture, and the byproducts of cement hydration, forming a new non-soluble crystalline structure. This integral structure fills the capillary tracts, rendering the concrete waterproof.

For Ettmayer, part of his attention focused on an underground concrete utility tunnel below the entire structure (including the tower's first two floors, which also are underground). The tunnel is completely submerged below the water table. The cruciform-shaped tunnel totals about 800 linear feet with internal dimensions averaging 8 feet-by-8 feet. "When you have high-pressure steam lines, chilled lines and electric lines all winding through a tunnel where people have to walk, it would be dangerous from a safety standpoint for water to infiltrate through the concrete walls. Not to mention that water penetration can lead to concrete and interior steel corrosion," Ettmayer said. "At the same time, the lines themselves can produce water or humidity, which can attack the concrete from the interior." Ettmayer and the general contractor, Oscar J. Boldt Construction, decided the challenge of rendering the tunnel watertight was beyond the capability of an exterior membrane alone, and wanted a "belt-and-suspenders" approach. They decided to formulate the tunnel's concrete with Xypex Admix C-1000 crystalline waterproofing admixture to prevent water intrusion. The crystalline technology uses water in the capillary tracts as a diffusing medium to carry waterproofing chemicals into the concrete. The chemicals migrate through the waterways of the saturated pore network, where they react and grow non-soluble, needle-like crystals that plug the pores. Within a couple weeks of crystal growth, liquids can no longer pass through and the transmission of gases is significantly restricted. The effect is integral and permanent. Jeff Niesen, vice president for construction management at Boldt, said the site of the project itself presented unique water challenges. "The variety of soils on-site couldn't easily be made to resist the groundwater pressure from the adjacent Lake Mendota — the surface of which is about level with the worksite — so they had to change the site dewatering method from suction to deep well," Niesen said.

The initial concern was that the tunnel, being submerged, could possibly float, thus endangering some of the research and medical care operations. To prevent that eventuality, the tunnel was overbuilt with extra-thick concrete casing for weight, to keep it from moving. Also, the concrete was formulated with the crystalline waterproofing admixture to prevent water intrusion. Niesen said that seeing is believing. "As expected, the tunnel's interior has remained dry," Niesen said. "The way the Xypex technology works allows you to see where it has done its job. You can actually see where the crystallization has occurred to plug a hairline crack." Ettmayer said his engineering firm has started using crystalline waterproofing as a "standard operating procedure" for tunnels subject to the water infiltration risk. "I'm a believer in it," he said.

A portion of the University of Wisconsin School of Medicine concrete was formulated with crystalline waterproofing admixture to prevent water infiltration.

Concrete waterproofing through crystallization was recently used in the construction of the University of New Mexico's Tri-Services Laboratories building in Albuquerque, which is partially below grade.

The crystalline technology also was recently used in another university-owned medical research and services building in Albuquerque, N.M.: The University of New Mexico's Tri-Services Laboratories building. The complete building measures 187,000 square feet. Adjacent to the University of New Mexico Health Sciences campus, the $86 million, five-story building (one story is partially below grade) will accommodate the New Mexico Department of Health Scientific Laboratory Division, the New Mexico Department of Agriculture Veterinary Diagnostic Services and the New Mexico Office of the Medical Investigator. George H. Bradley, P.E., principal and senior partner at Chavez-Grieves Consulting Engineers, Inc. in Albuquerque, served as the project's structural engineer. "The Tri-Lab building has a lower level that has full soil retaining at one end and no soil retaining at the other end of the building due to the slope of the site," Bradley said. "The architect was concerned about water intrusion into this lower level. Of course, waterproofing was provided at the outside of the concrete retaining walls as well as a vapor barrier below the slabon-grade. However, since this building was a high profile state office building, he was looking for additional waterproofing to be certain of its success. We suggested that Xypex be utilized as an admixture in the concrete walls and the concrete slab-on-grade. It was utilized and as far as we are aware, it is performing satisfactorily." Concrete waterproofing by crystallization — used in the construction industry for 40 years in more than 70 countries — takes advantage of concrete's inherent water permeability to deliver

crystalline chemicals that plug the material's pores and bridge micro-cracks that occur as the concrete dries and shrinks. The crystalline waterproofing technology can be easily introduced into new concrete as an admixture, a dry-shake product, or a surface-applied coating. For existing (i.e., cured) concrete, surface-applied coatings are used. Because concrete is permeable to liquids and gases, porous conditions can create multiple problems within a building or other structure due to moisture penetration. The infiltrating water, and harmful chemicals dissolved within, also can compromise the concrete. The key to waterproofing concrete as a means of corrosion-prevention in below-grade applications is density. This includes wastewater treatment plants. Paul Steward, P.E., vice president, structural engineering services, at Thatcher Engineering in Minneapolis, is a veteran of more than 50 WWTP projects, from new construction to forensic corrective work. "When done right, concrete waterproofing by crystalline technology does an excellent job of densifying the concrete, making it more resistant to chemical attack," he said. Concrete waterproofing by crystallization is generally less costly and more convenient than external barrier approaches. Crystalline waterproofing makes the construction process greener by eliminating the need for membranes manufactured with plastics, asphalt, polymer resins, solvents, aromatics and other materials with high energy manufacturing costs. A November 2010 report about concrete waterproofing using crystalline technology (ACI 212.3R-10) by the American Concrete Institute noted that "the crystalline deposits develop throughout the depth of the concrete and become a permanent part of the concrete mass… (and) resist water penetration against hydrostatic pressure." Concrete waterproofing using crystalline technology is an integral and permanent solution — as well as reliable, green and less costly. Concrete waterproofing by crystallization also provides everyone in the design and construction community, including structural engineers, one other important benefit: peace of mind. Les Faure is the advertising and promotion director for Xypex Chemical Corporation (www.xypex.com). He has been working with crystalline concrete waterproofing for 25 years.

Xypex vs Hycrete
For more than thirty years, proprietary Xypex Crystalline Technology has set an international standard of excellence in concrete waterproofing. Throughout the years many companies have tried to enter the integral waterproofing market. Noticing Xypex's success they have tried to compare themselves to Xypex. Hycrete is the latest company trying to build off of the success of Xypex. Hycrete once marketed a product they called "Hycrete Damp Guard." Hycrete has since renamed this product to "W500," which appears to be a play off of Xypex's C-500 admix product. Now Hycrete states that their "W500" product is superior to Xypex. However, here is a quote from

Hycrete's website: "Hycrete W500 is only used to limit moisture absorption in concrete. Users should not expect a 'watertight' system when using Hycrete W500, unless a secondary waterproofing system is used in conjunction with Hycrete W500." This website has been created to show that Hycrete is not in fact an equal to Xypex. We will include actual testing, company information, and marketing strategy. The following charts are from a Hycrete vendor's presentation depicting testing results intended to promote Hycrete. Note that even testing for Hycrete purposes shows that Xypex is still a superior product.

Note that in the above test, product "H" (Hycrete) reduced the compressive strength of the concrete by about 25% compared to the control, and product "X" (Xypex) increased the strength by approximately 3%.

In above test, Hycrete reduced the compressive strength of the concrete by 15%, while Xypex increased strength by 12%.

In the above absorption test, Hycrete tests better than Xypex. This particular test appears to be the only source for Hycrete's claim that their product is "superior" to Xypex. However, it is important to keep in mind that "low absorption" does not mean "waterproof." Since Hycrete apparently has a lower absorption rate, one might think that it would have lower permeability and do better on a rapid chloride test. However, as the next graph shows, Xypex holds up much better than Hycrete when it comes to permeability and actual waterproofing.

Note that Xypex reduces rapid chloride permeability significantly, compared to Hycrete. Any claim that Hycrete is less permeable than Xypex (based on the absorption testing shown above) does not square with the fact that Hycrete allows in more chlorides. The level of chloride permeability that Hycrete exhibits makes concrete using Hycrete more susceptible to rebar corrosion, as compared to the control. Comparison The primary difference between Xypex Admixture and Hycrete Admixture is that Xypex is a hydrophillic product, while Hycrete is hydrophobic, as stated in Hycrete literature. Hydrophobic materials are water-repellant, whereas Xypex is a water-proofing product designed to withstand high hydrostatic pressure. Xypex has three different Admix products (C-500, C-1000 and C-2000) which are specifically designed for various ambient conditions and mix designs. These products are packaged in pails, bags and dust free, water soluble bags. Hycrete has one liquid admixture.

Permeability Xypex has been extensively tested using the Army Corps of Engineers CRD-C-48-73 method, as well as the European test procedure DIN 1048, at pressures equal to 350 feet of hydrostatic pressure. These test procedures are designed specifically to determine the permeability of concrete substrates. Only limited permeability testing of Hycrete is available. The only published permeability test data is based on ASTM-D5385, which is designed to test membranes. It is interesting to note that no concrete mix design is given, nor does it appear that a control sample was used. The test was conducted at 100 psi. Compressive Strength Xypex Admixtures will increase the compressive strength of the concrete from 5%-20% depending upon the amount of dosage and cement content. Hycrete, according to their company data sheets, actually reduces the compressive strength, which is generally true of water repellent materials. To compensate for reduced compressive strength, they suggest that you add water-reducers, additional cement, super-plasticizers, or lower the W/C ratio to regain compressive strength back. Note that adding additional products to compensate for lost compressive strength will increase the cost of a cubic yard of concrete. Self Healing of Cracks Xypex will self heal cracks of a width of 0.4mm (1/64 inch), all while under hydrostatic pressure. Hycrete was tested with sound waves for the ability to self heal cracks, but the results do not state the width of crack that Hycrete can self heal. Chemical Resistance Xypex has been tested using ASTM C267-77. Xypex is highly resistant to most aggressive chemicals up to a pH range of 3.0 - 11.0 in constant contact, and 2.0 - 12.0 in periodic contact. There is no chemical resistance testing available for Hycrete, therefore it is not known what pH range Hycrete is able to withstand. Dosage / Mix Design Xypex Admix dosage is 2-3% by weight of Portland cement. Xypex does not require a specific W/C ratio or minimum amount of cement. Hycrete requires 1 gallon per c.y. with a maximum .40 / W/C ratio. Note that on some test reports up to 2 gallons of Hycrete was added, but the recommondation on their data sheet is that you only add 1 gallon.

Summary Xypex is one of those rare materials that continue to get better over time. The reaction that Xypex generates in the capillary tracts of the concrete will create a non-soluble, inert, mineral, crystalline structure that continues to develop and densify over time. Hycrete, in their own literature, describes their product with words such as "water-borne surfactant" (a soap-like material) and "bipolar hydrocarbon chain." As with anything carbon based, it will degrade over time. The above comparison information was taken from the official Data Sheets from each company's web site.

Water is the enemy of hardened concrete. It causes expansive damage when it freezes, carries corrosive salts to attack the reinforcing steel, reacts with certain aggregates to cause disruptive expansion, and provides an essential ingredient for the growth of mould. Water-retaining structures like reservoirs, dams, and waste treatment facilities must prevent water from escaping; other structures such as tunnels and buildings must prevent water from entering. For as long as anyone can remember, the construction industry has used the word ‘waterproof’ to describe construction materials. People commonly refer to something as being waterproof if it holds water in or out and does not leak. However, the word waterproof is technically not defined this way. Most dictionaries define it as being impervious to water, that water cannot penetrate it at all. This raises a serious question: Can anything really be completely impervious to water? The American Concrete Institute (ACI) is an international organization dedicated to the advancement of knowledge about concrete. Recognizing the problematic nature of the term ‘waterproof,’ ACI has discouraged its use, stating: Because nothing can be completely ‘impervious’ to water under infinite pressure over infinite time, this term should not be used. Instead, ACI has over the years preferred to use the term ‘watertight.’ However, its definition of this word is very similar to that of waterproof (which, in practice, remains far more frequently employed). Another commonly used industry term is ‘dampproofing,’ which is defined by ACI to mean: Treatment of concrete or mortar to retard the passage or absorption of water. The word is typically used to describe liquid coatings or plastic sheets applied to the outside of concrete in contact with damp soil. Its goal is to prevent the absorption/wicking of moisture by the porous concrete. Waterproof, watertight, dampproof… the trouble has been all three of these terms are imprecisely defined and tend to overlap each other in common use. This is especially

problematic when they are used to define admixture products because testing methods and performance standards are relatively new and still being developed. Where does the performance of a dampproofing admixture end and a waterproofing admixture begin? How can a professional expect to write a proper specification using such terms?

Advent of permeability-reducing admixtures Permeability-reducing admixtures are not new; people have been adding things to concrete to reduce its permeability for centuries. These range from plant and animal products to modern plasticizers. Additionally, supplementary cementitious materials (SCMs)—such as silica fume, fly ash, and slag—are technically not categorized as admixtures, but can nonetheless be added to a concrete mixture to reduce permeability. The ACI sub-committee responsible for concrete admixtures is Technical Committee 212, Chemical Admixtures. Its members recognized something needed to be done to clarify any confusion. Professions needed more precise language with clearly understood meanings. Standardized testing methods and performance criteria that could be included in written specifications was also necessary. The revised technical document, ACI 212.3R-10, Report on Chemical Admixtures for Concrete, contains a completely new section specifically written to address issues relating to permeability—reducing admixtures. This Chapter 15 describes three general categories for these materials:
  

hydrophobic or water—repellent chemicals designed to increase water repellency and reduce absorption (e.g. stearates, soaps, and oils); finely divided solids to fill up space and densify the concrete (e.g. clay, silica, silicates, and polymers); and crystalline chemicals, which are hydrophilic chemicals that react with cement and water to fill the pores with crystalline structures that offer permanent water resistance through self-sealing.

Since products may contain one or more of these materials, they cannot simply be classified based on their ingredients alone. Instead, Chapter 15 classifies permeability-reducing admixtures by their ability to resist hydrostatic pressure:
 

permeability-reducing admixtures for non-hydrostatic conditions (PRANs); and permeability-reducing admixtures for hydrostatic conditions (PRAHs).

Most products will fall into the PRAN classification. Water-repelling or hydrophobic materials can be very effective at preventing water absorption into concrete. They work by way of surface tension in the same way fabric treatment repels spills on clothing and furniture. They can be easy to use and cost—effective for applications not subjected to hydrostatic conditions. However, even a modest amount of this pressure can overcome and push past the surface tension created by these materials. If acted on by water under pressure, concrete protected by only a PRAN may allow water to pass through. Another term, ‘finely divided solids,’ refers to materials that improve the packing of the concrete’s ingredients, causing its pores to be as small as possible. These materials may also act to block the pores with loose particles. The category includes:
  

clay materials that swell in contact with water (eg. bentonite); polymer admixtures that form globules meant to plug the concrete’s pores; and silicates such as sodium silicate, which also works by reducing pore size or plugging pores.

All these materials can significantly reduce permeability. However, because they cannot reliably plug all the pores and because they are unable to bridge cracks, they cannot be counted on to withstand hydrostatic pressure, especially over extended periods. For these reasons, finely divided solids are also classified as PRAN. Crystalline chemicals react with water and the cementing materials in concrete or mortar to form distinct crystalline structures within the pores and small cracks of the concrete. These crystals effectively block the concrete’s pores in a similar way to the finely divided solids. Additionally, these crystalline structures have the ability to bridge small cracks. Since any concrete structure has a high likelihood of developing cracks, this bridging ability is critical to successfully creating a watertight structure. Further, since crystal formation only takes a small amount of crystalline materials in reaction with a larger amount of water and cementing materials, the admixture is not used up. This means when new cracks form later, and moisture begins to penetrate the concrete, more crystals grow to seal the crack. This self-sealing ability is unique to crystalline materials. Consequently, crystalline products have been shown to withstand very high hydrostatic pressures over long periods. Specifiers should be aware not all products calling themselves ‘crystalline’ actually fall into this category—some merely crystallize as they harden or dry. For example, sodium silicate is a

solution that forms a crystalline structure as it dries, whereas ‘true’ crystalline materials are PRAHs that cause a chemical reaction to form distinctly new crystals. More importantly, the material remains continuously reactive, allowing new crystal formation in the face of future moisture penetration. To be a PRAH, the crystalline material must possess this self-sealing ability. Testing methods Various testing methods have been used to indicate the permeability of concrete. Perhaps the most often referenced being ASTM C1202, Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration, more commonly known as the rapid chloride permeability (RCP) test. There is much debate over the value of this method; its accuracy is an issue, as results from identical test specimens are often found to vary greatly from each other. More importantly, the test does not actually measure permeability—it deals with electrical conductivity, and there are many factors influencing this attribute beside permeability. Other common test methods measure capillary absorption or wicking potential of concrete. These are useful for PRANs, but are inappropriate for PRAl·is because they exert no hydrostatic pressure. A suitable testing method for PRAHs must directly measure permeability of the concrete when it is subjected to hydrostatic pressure. Chapter 15 cites U.S. Army Corps of Engineers (USACE) CRD C48-92, Standard Test Method for Water Permeability of Concrete, and two nearly identical European tests that accomplish this goal:
 

Deutsches Institut fur Normung (DIN) 1048-Part 5, Testing Concrete: Testing of Hardened Concrete (Specimens Prepared in Mould); and British Standards (BS) EN 12390-8, Testing Hardened Concrete: Depth of Penetration of Water Under Pressure.

Each of these methods subject concrete specimens to water under pressure for a time. They measure the actual penetration and transport of water within the concrete matrix. Methods such as these come closest to replicating the actual service conditions of concrete in water-retaining structures in the field. Practical application Chapter 15 of the ACI report recommends using a permeability-reducing admixture in any concrete that will benefit from moisture protection. Choosing to specify a PRAN or PRAH depends on the presence or absence of hydrostatic pressure. PRANs are appropriate for applications where resistance to water and waterborne chemicals may be needed, but hydrostatic pressure is absent. Foundations in contact with damp soil, concrete masonry units (CMUs), and exposed slabs, columns, or beams are just a few examples. Where resistance to water under hydrostatic pressure is required, a PRAH must be used. Examples of these are:

   

foundations below the water table; tunnels; subways and other below—ground structures; and water—retaining structures.

Where the application is critical, it may be worthwhile to include a PRAH instead of a PRAN even when hydrostatic pressure is not expected. Elevator pits are a good example of this. The final sections of Chapter 15 give advice for proportioning, batching, and quality control— much of which is good practice for most concrete work. Conclusion ACI-212’s new Chapter 15 has given design/construction professionals several new tools. The identification and categorization of different materials shows not all permeability—reducing materials are the same. Its classification of various admixtures based on performance rather than chemistry has a more practical benefit. Chapter 15 also introduces new, descriptive, and much more precise language to employ in specifications. The Portland Cement Association (PCA) has already adopted this new language and included PRAN and PRAH in its book, Design and Control of Concrete Mixtures. Chapter 15 recommends improved testing methods that closely replicate the real world. All of this helps industry professionals to choose the proper product for their application. With the assistance of ACI 212’s new Chapter 15, Canadian engineers and architects can now agree that when protecting concrete from water not under pressure, a PRAN should be specified. In cases when one is building a watertight structure, a PRAH is what is needed. Notes Despite the first word in its initialism, ACI has purview in Canada. In fact, this year’s annual conference was held in Toronto in October. Visit www.concrete.org/Technical/CCT/ACI—Terminology.aspx. Kevin Yuers is a veteran of the construction industry having spent many years running his own contracting company before joining Kryton International in 1994. He is the vice-president responsible for product development and technical services at the crystalline concrete waterproofing company Yuers is an active member of several industry and business associations and has travelled extensively throughout the world. He has written numerous articles and is the named inventor on patents related to the concrete industry. Yuers can be contacted at (800) 2678280.

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