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We are glad to inform you that PENETRON® and PENETRON ADMIX®, were given the Golden Awards, in all categories of crystalline products, for total concrete protection of new and existing structures.
Looking At The ACI 212.3R-10 Report On Chemical Admixtures For Concrete
The “Report on Chemical Admixtures for Concrete” published by the American Concrete Institute (ACI 212.3R-10 / January 2011) includes a chapter on permeability-reducing admixtures (PRAs). These PRAs (permeability reducing admixtures) include a wide range of admixtures than can be used to reduce permeability in concrete. More specifically, it describes two PRA categories:
- Permeability-Reducing Admixture for Non-hydrostatic conditions (PRAN) – previously referred to as a “damp proofing admixture,” where resistance to water under pressure is very limited and not suitable for concrete exposed to water under pressure
- Permeability-Reducing Admixture for Hydrostatic conditions (PRAH) – or a “waterproofing admixture” that is sufficiently stable to resist water under pressure and is used for watertight construction for tanks, foundations, and containment structures, etc.
In general, the performance of a permeability reducing admixtures depends on whether it is a PRAN or PRAH.
PRANs consist of either hydrophobic or water-repellent chemicals (soaps and long-chain fatty acid derivatives, vegetable oils and petroleum), finely divided solids (talc, bentonite, silicious powders, clay, hydrocarbon resins, and coal tar pitches) or chemically active fillers (lime, silicates, and colloidal silica). They are most widely used for damp proofing protection under non-hydrostatic conditions.
PRAHs include finely divided solids (such as colloidal silica), hydrophobic pore blockers and crystalline admixtures. However, finely divided solids, including colloidal silica, are typically used under non-hydrostatic conditions and only some of the polymer materials can be categorized as PRAHs. Hydrophobic pore-blocking materials are used only under non-hydrostatic conditions. Crystalline hydrophilic polymers (latex, water-soluble, or liquid
polymer) are only used in hydrostatic conditions.
Crystalline admixtures resist water penetration against hydrostatic pressure and have proven to be the most effective PRAH products with clear advantages over hydrophobic materials based on other mechanisms or polymer coalescence, or other fillers in terms of sealing cracks, long-term effectiveness, enhanced durability of the concrete structure, etc. Finally, they are able to bridge cracks formed by thermal or mechanical movement.
Only crystalline admixtures can be classified as true PRAHs products. As described in the table on page 2 of the ACI 212.3R-10 document on admixtures (“Admixtures, their characteristics & usage”), only crystalline hydrophilic polymers (latex, water-soluble, or liquid polymer) can be used in hydrostatic conditions.
Advantages of a PRAH
The proprietary active ingredients in a crystalline PRAH react with water and cement particles in the concrete to increase the density of calcium silicate hydrate (CHS) and/or generate pore-blocking deposits in the existing micro-cracks and capillaries to resist water penetration. As hairline cracks form over the life of the concrete, crystalline admixtures continue to activate in the presence of moisture, sealing additional gaps.
As noted in the ACI report: “To resist hydrostatic pressure, PRAHs employ a pore-blocking mechanism from crystalline growth, polymer coalescence, or other filler, although the ability to withstand hydrostatic pressure will depend on how completely the pores are blocked and the stability of the deposits under pressure. The distinction should be made based on the admixture’s demonstrated ability to reduce water penetration under the expected
The pore-blocking mechanism is based on proprietary active chemicals blended with a mixture of cement and
Because PRAHs based on polymer coalescence or other fillers are unable to withstand high hydrostatic pressure, they cannot be considered “true” PRAH admixtures. The pore-blocking mechanism in crystalline-based PRAHs is based on proprietary active chemicals blended with a mixture of cement and sand, which respond permanently and comprehensively to moisture and changes even when exposed to high hydrostatic pressure.
Unlike hydrophobic materials – such as the PRAN products discussed above – crystalline admixtures are hydrophilic. The crystalline deposits develop throughout the concrete, becoming a permanent part of the concrete mass when exposed to water. PRAHs make external waterproofing membranes redundant, even for concrete under high hydrostatic pressure.
PENETRON PRAH Technology: Testing Under High Hydrostatic Conditions
Similar to the general process described for crystalline PRAH admixtures above, the active ingredients in PENETRON ADMIX® react with the by-products of cement hydration in the presence of water in fresh and hardened concrete structures. These reactions extend hydration and form additional calcium silicate hydrate molecules along with insoluble crystals throughout the concrete matrix. These insoluble formations precipitate within the natural pores and capillaries of the concrete mix to dramatically reduce the permeability of the concrete.
When PENETRON ADMIX® is added to concrete during batching, the resulting crystalline lattice also permanently seals hairline cracks as they develop over the lifetime of the concrete. PENETRON products have been extensively tested in the laboratory under high hydrostatic conditions (including ASTM D5084, NBR 10.787/94, USAE CRD C48, BS EN 12390-8 and DIN 1048-5 Water Permeability). In these tests, the resulting crystalline lattice effectively reduces the permeability of the concrete samples when compared to the control samples; leakage in the treated concrete was eliminated, even when exposed to high hydrostatic test conditions.
The following examples show the improvements from the permeability-reducing reactions of PENETRON ADMIX® under high hydrostatic conditions.
Over the past few years crystalline admixtures including Penetron Admix have been widely established and accepted as the only true Permeability Reducing Admixtures for Hydrostatic conditions (PRAH) as classified by the American Concrete Institute (ACI).
Crystalline admixtures are hydrophilic materials that react with water in concrete to form an insoluble crystalline structure that seals pores, micro-cracks and capillaries. The formation of crystals in the capillary matrix significantly reduces concrete permeability. The result is a permanently dry concrete structure that is protected against the ingress of water and water-borne chemicals even under high hydrostatic pressure.
This method of protection has been proven to significantly slow down deterioration processes in concrete, enhancing durability and extending the service life of treated structures.
Contrary to crystalline admixtures, hydrophobic or water repellant chemicals such as pore blockers, fall under the category of Permeability Reducing Admixtures for Non-Hydrostatic conditions (PRAN). These materials can include various soaps, oils and long-chain fatty acids and are designed to repel water by covering the walls of pores and capillaries with a water repellant lining.
Due to their repellant mode of action hydrophobic materials are effective in reducing capillary absorption under non-hydrostatic conditions. Therefore manufacturers of these materials usually recommend absorption testing to demonstrate the performance of their products.
Common standards for capillary absorption testing include ASTM C1585 (Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes) and BS EN 1881-122 (Testing Concrete Part 122: Method for Determination of Water Absorption).
The general procedure to measure absorption of water into a treated concrete sample used in these standards is done by drying the specimen in an oven to ensure no water or moisture is contained. The weight of the dry sample is recorded before it is submerged in water for several minutes/hours. After the sample is removed from the water the weight is determined again and the water absorption is calculated according to a formula defined in the respective standard. The obtained results are usually compared against a control sample.
“Absorption tests are suitable for PRAN’s as they do not apply water under pressure. Hydrophobic pore blockers only have a limited resistance against hydrostatic pressure mainly due to the fact that the capillaries are not physically blocked. The repelling function only withstands low water pressure in order to minimize water ingress due to rain or dampness.”
The main reason for this is that hydrophobic materials are unlikely to coat all pores uniformly. In addition larger voids and cracks cannot be sufficiently protected. This usually results in a hydrostatic pressure resistance of only a few centimeters of water head. If the pressure rises higher the repellent effect is negated and “overpowered” and water will be able to penetrate into the concrete through the still open capillary system. In addition, new cracks will be left unprotected by hydrophobic materials and pose a risks for water ingress. In contrast, crystalline admixtures will re-activate in the presence of water (hydrophilic), form new crystals and “self-heal” new cracks in concrete.
Absorption testing is not recommended for crystalline admixtures. Due to their hydrophilic nature water is initially absorbed into the hardened concrete. This water will trigger the chemical reaction that forms the insoluble crystalline structures that will in turn seal all micro-cracks and concrete capillaries. Once the capillaries have been sealed, no further water will be able to penetrate into the concrete. Therefore absorption values obtained after several minutes/hours (depending on the selected standard) of testing may be misleading and should not be used to interpret the waterproofing performance of a hydrophilic product.
“The recommended and correct way to test the performance of crystalline admixtures (PRAH) are permeability tests. These tests apply water under pressure and will give a better indication of the performance of the product under hydrostatic conditions.”
Suitable and internationally accepted test standards include DIN 1048 pt. 5 (Testing concrete: Testing of hardened concrete), BS EN 12390-8 (Testing Hardened Concrete. Depth of Penetration of Water under Pressure) and ASTM D5084 (Standard Test Methods for Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Parameter).
Permeability tests observe the penetration of water under pressure into treated concrete samples. Depending on the applied standard, water is introduced into a hardened concrete sample, which has been cured for 28 to 35 days, under pressure (e.g. 5 bar) over a fixed amount of time (e.g. 3 days). Immediately after the pressure is released the water penetration into the sample is measured (e.g. in mm) by splitting the sample. Results of the treated sample are usually compared against a control sample.
These tests apply water under pressure and, contrary to absorption tests, are able to give an indication of the admixture’s performance under hydrostatic conditions. Since a lot of the water applied during this test is taken up by the crystalline reaction to form crystals, a true performance indication can be achieved by repeating the test cycle over several weeks (see 4 weeks test images below).
The construction industry has over 40 years of experience in the integral crystalline waterproofing field. Simply adding Penetron Admix, a crystalline waterproofing admixture, to concrete allows the construction industry to build economical and durable structures in a shorter timeframe, lasting up to 60 years longer.
When concrete is treated with the Penetron Admix, the concrete itself has the ability to self-heal and seal all hairline cracks, pores and capillaries within the concrete matrix when exposed to water. This results in a waterproof concrete element with the ability to withstand high hydrostatic pressure and chemical attack with a pH range of 3 to 11.
The challenge posed is that the method used to waterproof and protect concrete needs to be seen for an individual to believe that it is present.
Experiments & Results
The main objective of this report is to provide visual proof of the crystal growth inside the concrete matrix, which results in a decreased concrete permeability and overall increase in durability.
Cracked Penetron Admix containing concrete samples were cured in water for six months and examined under a microscope to verify the crystal growth. The images below were taken of the same sample and cracked area, but at different magnifications (x100, x500 and x1000). It is very clear that needle-like crystals formed within the crack, bridging and self-healing the crack. The crystals did not only grow in the cracked area, the crystalline growth is present within the entire concrete matrix, as well.