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Historic Preservation - Technical Procedures

Spectitle:

Removing Moss Stains From Concrete

Procedure code:

0371029R

Source:

Hstrc Concrete: Investigation & Rpr/Pre-Conf Training - 1989

Division:

Concrete

Section:

Concrete Cleaning

Last Modified:

02/24/2012

Details:

Removing Moss Stains From Concrete



REMOVING MOSS STAINS FROM CONCRETE


THE CLEANING OR REMOVAL OF STAINS FROM CONCRETE MAY INVOLVE THE
USE OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON
ADJACENT MATERIAL, DISCOLOR THE CONCRETE OR DRIVE THE STAINS DEEPER
INTO POROUS CONCRETE.  USE THE PRODUCTS AND TECHNIQUES DESCRIBED
HERE ONLY FOR THE COMBINATIONS OF DIRT/STAIN AND CONCRETE SPECIFIED.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing moss stains
         from concrete using chemical solvents.

    B.   Safety Precautions:

         1.   DO NOT save unused portions of stain-removal
              materials.

         2.   DO NOT store any chemicals in unmarked containers.

         3.   EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY
              SOLVENT IS USED.  USE RESPIRATORS WITH SOLVENT
              FILTERS.

         4.   No use of organic solvents indoors should be
              allowed without substantial air movement.  Use only
              spark-proof fans near operations involving
              flammable liquids.

         5.   Provide adequate clothing and protective gear where
              the chemicals are indicated to be dangerous.

         6.   Have available antidote and accident treatment
              chemicals where noted.

    C.   See 01100-07-C for general project guidelines to be
         reviewed along with this procedure.  These guidelines
         cover the following sections:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   General Protection (Surface and Surrounding)

         These guidelines should be reviewed prior to performing
         this procedure and should be followed, when applicable,
         along with recommendations from the Regional Historic
         Preservation Officer (RHPO).


PART 2---PRODUCTS

2.01 MATERIALS

    NOTE:  Chemical products are sometimes sold under a common
    name.  This usually means that the substance is not as pure as
    the same chemical sold under its chemical name.  The grade of
    purity of common name substances, however, is usually adequate
    for stain removal work, and these products should be purchased
    when available, as they tend to be less expensive.  Common
    names are indicated below by an asterisk (*).

    A.   Ammonium Sulfamate:  

         CAUTION:  THE USE OF AMMONIUM SULFAMATE MAY BE DEPENDENT
         UPON REGIONAL, STATE OR LOCAL RESTRICTIONS.
         ENVIRONMENTAL CONDITIONS AND APPROPRIATENESS SHOULD BE
         REVIEWED.

         1.   Past use was a base for weed killers; Not now
              readily available; Substitute any brand weed killer
              solution.

         2.   Available from chemical supply house, construction
              specialties distributor, garden and lawn supply
              center.

         -OR-

         Copper Nitrate:

         1.   Other chemical or common names include Cupric
              Nitrate.  DO NOT USE THE COPPER NITRATE KNOWN AS
              CUPROUS NITRATE.

         2.   Potential Hazards:  TOXIC AND FLAMMABLE (WHEN IN
              CONTACT WITH ORGANIC SOLVENTS).

         3.   Available from chemical supply house, drugstore or
              pharmaceutical supply distributor, garden and lawn
              supply center, or hardware store.

         -OR-

         Copper Sulfate (CuSO45H20):

         1.   A sulfate of copper especially the normal sulfate
              that is white in the anhydrous form but blue in the
              crystalline hydrous form and that is often used as
              an algicide and fungicide.

         2.   Other chemical or common names include Cupric
              Sulfate; Blue stone*; Blue vitriol*; Roman
              vitriol*.

         3.   Potential Hazards:  TOXIC.


         4.   Available from chemical supply house, drugstore or
              pharmaceutical supply distributor, garden and lawn
              supply center, hardware store, swimming pool supply
              distributor, or water and sanitation supply
              distributor.

         -OR-

         Formaldehyde (CH2O):

         1.   A colorless pungent irritating gas used chiefly as
              a disinfectant and preservative and in synthesizing
              other compounds and resins.

         2.   Other chemical or common names include Formic
              aldehyde; Methanal; Methyl aldehyde; Oxomethane;
              Oxymethylene; Formalin*.

         3.   Potential Hazards:  TOXIC AND MODERATELY FLAMMABLE.

         4.   Available from chemical supply house, dairy supply
              distributor, drugstore or pharmaceutical supply
              distributor, photographic supply distributor (not
              camera shop), or printer's supply distributor.

         -OR-

         Sodium Hypochlorite (NaOCl):

         1.   An unstable salt produced usually in aqueous
              solution and used as a bleaching and disinfecting
              agent.

         2.   Other chemical or common names include Bleaching
              solution*; Household bleach*; Laundry bleach*;
              Solution of chlorinated soda*.

         3.   Potential Hazards:  CORROSIVE TO FLESH.

         4.   Available from chemical supply house, grocery store
              or supermarket, hardware store or janitorial supply
              distributor.

    B.   Chemicals for Sealing Concrete:

         1.   Magnesium Fluosilicate:

              a.   Other chemical or common names include
                   Magnesium silicofluoride.

              b.   Potential Hazards:  TOXIC.

              c.   Available from construction specialties
                   distributor (often sold under manufacturer's
                   brand name; the chemical name may appear on
                   the label).

         -OR-

         2.   Zinc Fluosilicate:

              a.   Other chemical or common names include Zinc
                   silicofluoride.

              b.   Available from construction services
                   distributor (often sold under a manufacturer's
                   brand name; the chemical name may appear on
                   the label).

         -OR-

         3.   Paints containing cuprous oxide or mercurous oxide.

2.02 EQUIPMENT

    A.   Stiff bristle brush (non-metallic)


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection:

         1.   Provide adequate wash solutions (i.e. water, soap
              and towels) before starting the job.

         2.   Whenever acid is used, the surface should be
              thoroughly rinsed with water as soon as its action
              has been adequate.  Otherwise it will continue
              etching the concrete even though the stain is gone.

3.02 ERECTION, INSTALLATION, APPLICATION

    NOTE:  DO NOT TRY MORE THAN ONE TREATMENT ON A GIVEN AREA
    UNLESS THE CHEMICALS USED FROM PRIOR TREATMENT HAVE BEEN
    WASHED AWAY.

    A.   To remove moss and related staining:

         1.   Use ammonium sulfamate and follow manufacturer's
              instructions for removing moss.

         -OR-

         1.   Mix one of the following:

              a.   Sodium Hypochlorite (laundry bleach, which
                   contains about 5% sodium hypochlorite, is
                   adequate).

              b.   Formaldehyde (1 part formalin [37%
                   formaldehyde solution] in 49 parts water).

              c.   Copper Nitrate (4 to 7 ounces by weight in 1
                   gallon of water).

              d.   Copper Sulfate (4 to 7 ounces by weight in 1
                   gallon of water).

         2.   Saturate the moss with the chemical using a stiff
              bristle brush.

         3.   Allow to sit in place about 7 days.  Reapply
              solution if it rains during the first 24 hours
              after application.

         4.   Brush off the dead vegetable growth.  The treatment
              should keep the concrete free of new growth for
              some time.

    B.   To seal the concrete (sealing the concrete may make it
         easier to clean in the future and, at the same time,
         provide some fungicidal action against moss growth):

         1.   Apply a solution of 7 ounces by weight of magnesium
              fluosilicate or zinc fluosilicate crystals in 1
              gallon of water.

         2.   Paints containing cuprous oxide or mercurous oxide
              (BOTH OF WHICH ARE TOXIC TO HUMANS) may also be
              applied to inhibit future growth.

                         END OF SECTION