Benifits to Concrete Under Acid Attack

BENEFITS TO CONCRETE UNDER ACID/CHEMICAL AGENT ATTACK


The susceptibility of Portland cement concrete to adverse agent contamination generally results from three inherent characteristics permeability, alkalinity, and reactivity. Degrees of permeability can vary in different concrete installations. Even extremely high quality concrete has some degree of permeability. Liquid penetration into concrete is oft en accompanied by a reaction with one or more of its constituents, such as cement, aggregates, or imbedded steel. Subsequent possible leaching of the concrete’s cement hydration compounds, or deposition of extraneous crystals, or crystalline reaction products can degrade concrete’s appearance, integrity, strength, and durability, ultimately causing its early failure.

The alkaline hydrated cement binder of concrete readily reacts with acidic substances. A reaction usually accompanied by extraneous formation or removal of concrete’s soluble reaction products, eventually resulting in its disintegration. The rate end extent of chemical attack are increased by an increase in aggressive agent concentration, in solution. Dry non-hygroscopic solids do not attack dry concrete, however, wet or moist reactive solids will attack it, as will aggressive liquids and solutions. Temperature also affects the rate of chemical attack indirectly since as the temperature rises, moisture content of concrete becomes reduced, making it drier, but however, more permeable to additional fluids. As temperature falls, it can sometimes cause sufficient normal shrinkage to create small open cracks, which allow even greater penetration of contaminants into concrete’s interior.

The extent of chemical attack depends greatly on concrete’s permeability, the ease with which liquids can travel through concrete’s pore systems. If concrete is very permeable, so that liquids can travel right through its thickness, calcium hydroxide will be leached out very quickly, leaving behind deposits of calcium carbonate, formed by reaction of calcium hydroxide with carbon dioxide. Calcium carbonate is whitish in color and, in most cases, makes its presence apparent by floating to the surface, in the form of efflorescence. Efflorescence is generally not harmful, however, extensive leaching of calcium hydroxide leaves concrete more vulnerable to chemical attack, since its pore void percentage is increased, also making it progressively weaker.

Many agents can attack concrete and destructively alter its chemical composition by means of reaction mechanisms which are partly or incompletely understood. However, these agents have to be able to penetrate into concrete’s interior, Densi-Proof™ prevents this. Densi-Proof™, where applied to a concrete’s surface, readily penetrates to its interior, to its surface porosity bottom; to its matrix top, where Densi-Proof™ reacts with concrete’s internal constituents, producing a 100% solids, insoluble barrier, within just seconds following the Densi-Proof™ application. Immediately, following barrier formation, the concrete becomes protected against further contaminant penetration past its surface porosity. Densi-Proof™, while still in solution form, due to its special molecular make-up, is the only liquid capable of penetrating this special barrier. NOTE: This unique Densi-Proof™ precipitated barrier should not be confused with temporary, soluble, weekly-linked, large pore, thixotropic gels, that are formed using sodium silicates, through free lime reactions, which has proven detrimental to long-range concrete integrity.

The unique barrier material produced from Densi-Proof™ consists of distinct spherically-shaped particles containing pore sizes significantly smaller than the treated concrete’s microporosity, allowing concrete to still breathe, while not allowing free water, moisture, or other liquids to pass into its interior. Free water, already present inside the concrete, prior to treatment with Densi-Proof™ becomes chemically tied-up in the Densi-Proof™ precipitated barrier, even participating in the barrier formation, rendering that internal water harmless to the concrete itself. Excess free water, if any, not utilized in barrier formation, is either purged out of the concrete or occupies the special barrier material porosity, where it is not free to migrate. Also, water which occupies the barrier’s porosity becomes postured in a stretched position due to the very small spine-shaped porosity of the specialty-formulated material. Since stretched water assumes density similar to that of ice, should a hard freeze occur this already stretched water does not further expand, therefore, it will not cause freeze damage to the concrete.

Furthermore, the special barrier material is able to absorb and chemically tie-up water / moisture because its molecules are water saturated only on their inner side, in precipitate form, therefore possessing residual valences which attract only substances that are hydrophilic, such as water or moisture, repelling hydrophobic substances, such as oil. Densi-Proof™ precipitated barrier particles have a surface film of bound water which can only be released at abnormally high temperatures. Subsequently, water or moisture content of the barrier material, even under extremely dry conditions, will never get lower than 6.5% of its total water capacity, unless baked out at temperatures of 115°C, or higher. However, should the unlikely event of complete dehydration of the special barrier material occur, such as involvement in a fire, this special barrier material will readily rehydrate, upon exposure to water or moisture. Also, the Densi-Proof™ precipitated unique barrier material is capable of dehydration without a significant loss of surface area inside concrete’s porosity, also should this material become filled with water to capacity, it becomes impervious to anything else, including water.

The most significant factor in Densi-Proof™’s ability to preserve concrete is that its barrier effectively hydrostatically stops liquids / pollutants (including undriven gases) from going into the Densi-Proof™ treated concrete’s interior, eliminating major sources of reactant material that may eventually destroy the integrity of its matrix component, concrete’s main strength component. Not only does Densi-Proof™ preserve concrete integrity, to extend its useful lifespan, but also works to preserve its imbedded steel. Densi-Proof™ has the unique ability to significantly enhance Portland cement concrete without altering its physical characteristics, nor does Densi-Proof™impair surface traction or bond quality, making Densi-Proof™ applicable to all concrete installations, whether traffic bearing or not. Densi-Proof™ improves past carbonation effects, if any.