We hope the information presented here is helpful. It is based on data considered to be true and accurate that reflects our best understanding and knowledge, and is presented for the users consideration. We do not warrant results of actions based on any of the information contained. No statement, recommendation or suggestion is intended to infringe on any patent or copyright.

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Efflorescence is usually experienced as a white deposit on the surface of concrete building products. All types of concrete that contain cement are affected, including ready mix, precast, block, brick and pavers. Efflorescence is not a structural problem, strength and durability of elements is not affected. It does, however, negatively impact appearance.

The principal bad actor in efflorescence is calcium hydroxide, a slightly soluble salt found in cement which reacts with carbon dioxide in the air to form very insoluble calcium carbonate. The calcium hydroxide solution is drawn through the concrete matrix by capillary suction or wicking action to the surface of the concrete, where calcium carbonate is deposited as the water evaporates.

Conditions that aggravate efflorescence include:

  • Exposure to cold, wet weather during storage
  • Poor drainage and moisture control design in walls
  • Uncovered top courses on walls allowing water to enter the cores or cavity
  • Improper paver design or installation with poorly drained low areas that trap moisture
  • Exposure to large amounts of fertilizer or regular heavy sprinkling

The insolubility of calcium carbonate makes efflorescence hard to clean with water based techniques. Generally, an acid based cleaner must be used. Detailed removal tips and techniques are available for:



  • Interlocking Concrete Paver Institute (ICPI)
    • ICPI Tech Spec 5: Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement:

Not all geographic areas experience temperatures below 32°F (0°C). For those that do, extended exposure to freeze-thaw cycles is a major mode of deterioration in concrete products. As water freezes it expands around 9 percent and produces pressure in the capillary pores of the concrete. If the pressure exceeds the tensile strength of the concrete around it, the pore will expand and the adjacent concrete will weaken and potentially fail. Long term freeze-thaw exposure may extend the failure zone and cause systemic expansion, cracking and scaling.

A preventative for freeze thaw damage to wet cast concrete was developed in the mid 1900s. Air entrainment admixtures provide a network of air voids for the water to expand into, and remove the expansive strain on the matrix. Due to the manufacturing process, dry cast Manufactured Concrete Products have more open voids than wet cast and do not require additional air entrainment. Wet and dry cast products may be negatively affected by long term saturation in freezing conditions and designers should avoid this possibility.

To ensure acceptable long term performance, ASTM has developed Specifications and Test Methods to evaluate Concrete Masonry Unit and Paver durability when exposed to freeze-thaw action.

Over the years, compressive strength and absorption have been identified as critical performance indicators for freeze thaw durability. Lower absorption restricts the amount of moisture that is present in the concrete. Greater compressive strength ensures that the concrete matrix around the pores is strong enough to resist expansive forces.

Concrete Masonry Units (CMUs):

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Integral water repellents are polymerized chemical admixtures added to Concrete Masonry units (CMU) during the manufacturing process. The water repellent is incorporated into the concrete mix at the plant to ensure that each block has water repellent distributed throughout the concrete matrix.

RainBloc is typically used in single-wythe masonry construction for additional protection to water ingress. Single-wythe masonry walls can provide the performance of cavity wall construction in a cost-effective manner.

RainBloc is not impervious to moisture and it does not form a film on the masonry surface. RainBloc is not a vapor barrier, and the masonry remains breathable.

RainBloc is designed to perform for the life of the masonry unit .

Yes, there are no incompatibilities between RainBloc and post applied sealers which are often used to provide additional protection in a “belt and suspenders” approach.

RainBloc typically does not change the “paintability” characteristics of masonry, and therefore if untreated masonry can be painted, the same will apply to RainBloc treated units. Latex, acrylic latex, cementitious coatings and waterborne epoxies may all be used. Note that oil based paints (alkyls) are not recommended for exterior applications and should be carefully tested before application in any masonry construction.

Yes, RainBloc for Mortar is specifically designed for mortar applications, and contains additives to improve the workability and water repellency of the mortar. RainBloc for mortar does not affect the bond strength between the CMU and the mortar.

No, their formulations and functions are different and they cannot be interchanged.

Non-chloride accelerators may be used during winter months when faster set times are desired. Chloride accelerators are not recommended as they can react with steel reinforcement and cause corrosion of the steel.

To use an accelerator, simply replace a portion of the mix water with the recommended dosage rate of non-chloride accelerator.

RainBloc certified producers go through a rigorous certification process to ensure that
performance of their Block conforms to RainBloc standards for physical properties and water repellency. Certification must be renewed each year to ensure continued compliance.

Contact ACM Chemistries or your sales representative for a list of suppliers in your area.

ColorScape EverBold Pavers:

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ColorScape EverBold is a proprietary system that incorporates integral admixtures and in-line treatments. The ColorScape EverBold System works to enhance the original color depth of concrete pavers and extend color fastness or color durability over time. Paver physical properties and durability are also improved by increasing paver density and decreasing absorption.

The ColorScape EverBold System has been carefully optimized to synergize the performance of the integral and in-line treatments. Unlike color enhancement sealers or impregnations that are post applied, ColorScape EverBold is applied during the manufacturing process, so pavers start life protected and maintain that protection for years.

Paver colors are determined by the raw materials used in manufacturing e.g. sand, stone,
cement and supplementary cementitious materials such as fly ash and slag cement. Pigments are added to achieve the desired color hues and effects. Since pavers are made from natural materials that are variable , color consistency is carefully managed by paver producers.

Pigments are an important contributor to paver colors, however it is not pigment fading that causes most color failures. Pigment particles are held in the cementitious and fine aggregate paste blend that binds the coarser aggregates together. Over time through mechanical wear (foot or vehicular traffic), chemical wear from acid rain or cleaners or freeze thaw exposure, the fine particles on the surface of the paver may be worn away leaving a dusty residue and larger uncolored aggregates exposed, causing the paver to look faded.

Good quality pavers with high strength and low absorption will retain surface and color integrity for longer. Integral admixtures and in-line treatments can help to raise paver quality and preserve color depth and hues over time.

ColorScape EverBold pavers meet or exceed freeze-thaw durability and absorption conformance with ASTM C936 and CSA 231 when appropriate properly manufactured. Paver texture is not affected and pavers meet slip resistance coefficient of friction requirements per DCOF Acu-Test.

Concrete paver surfaces consist of a matrix of fine voids which may be penetrated by moisture, dirt and staining contaminants such as food, oils, deicing salts, leaves etc. ColorScape EverBold is applied during the manufacturing process, making pavers more resistant to common stains right from the start.

See the Video on ColorScape EverBold stain resistance for more information.

Efflorescence is a deposit of soluble salts, usually white, that may form on the surface of stone, brick, concrete or mortar. This occurs most often when moisture present in the materials reacts with calcium hydroxide in cement to form calcium carbonate. The calcium hydroxide/water solution is drawn through the concrete matrix by wicking action and calcium carbonate is left behind as water evaporates from the surface, leaving an unsightly residue.

Primary efflorescence in pavers usually occurs soon after manufacture when pavers are exposed to cold and wet. The worst efflorescence usually occurs in spring and autumn due to wet and slow evaporation conditions.

Secondary efflorescence occurs after installation and can be induced by poor moisture control design or incorrect installation that traps moisture. Pavers are often exposed to rain or frequent wet/dry cycles from sprinkler systems. If correct drainage is not applied, moisture will collect in low areas. Many landscape fertilizers contain chemicals that contribute to efflorescence. Certain bedding and joint sands contain high soluble alkali contents that can cause issues.

Efflorescence does not harm the pavers or impact physical properties. Left untreated, the white residue will usually slowly disappear by itself over the course of a year.

To minimize the potential for efflorescence designers may specify efflorescence controlling admixtures that limit the movement of water through the concrete matrix.

By improving the quality of the surface and the concrete matrix during the production process ColorScape EverBold reduces the occurrence of both primary and secondary efflorescence.

There is no complete preventative for efflorescence available at this time.

ColorScape EverBold improves resistance to acid rain which is an important contributor to paver color fading and general wear. See the acid rain resistance video which shows pavers subjected an acid rain resistance test.

To test acid rain resistance a concentrated muriatic acid solution is applied to untreated and ColorScap EverBold treated pavers. The untreated paver shows reaction with acid and etching after exposure for 2 minutes. The ColorScape EverBold treated paver shows minimal reaction and etching.

ColorScape EverBold pavers are not impervious to moisture and it does not form a film on the paver surface. ColorScape EverBold is not a vapor barrier, and the paver remains breathable.

With the increase in color richness and intensity of pavers using the ColorScape® EverBoldTM system, scuffs may be more noticeable than compared to pavers not using the system. Pavers using the system do not scuff easier than pavers not using the system. To help minimize the potential for scuffing we recommend the following:


  1. Use separator sheets between layers when cubing the product. Options include:
    1. Min ¼” thick, closed cell foam, sheet.
    2. Plastic mesh/grid sheet for smooth surface pavers (not recommended for textured pavers.
    3. Heavy geotextile fabric (landscape fabric).
  2. Place cubes of products on wood pallets to minimize the movement of pavers in the cube during handling/movement of cubes.

ColorScape EverBold is compatible with most post applied sealers, including polyurethane, acrylic and water based products. Silane/Siloxane based products are not recommended. Test in an inconspicuous area prior to application. Follow manufacturer’s instructions when using cleaning and sealing products

Pavers treated with ColorScape EverBold are protected during the manufacturing process, and have a natural matte appearance with deep color that lasts for years. If a wet-look is desired, pavers may be sealed after installation with appropriate sealers. Water and stain repellent sealers may also be applied to increase protection in a “belt and suspenders” approach.

Contact ACM Chemistries or your sales representative for a list of suppliers in your area.