CURE METHOD COMPARISONS
REASONS FOR CURING: The curing of concrete is probably the most important step in the development of high quality concrete. In order to obtain high quality concrete, the placement of an appropriate mix must be followed in a timely manner by curing in a suitable environment, during the early stages of strong initial hydration, generally as soon as is practical following the surface finish. Curing is a term given the procedures used to promote optimum hydration of plastic, or semi-plastic, Portland cement concrete, during its early development of strength. Curing normally consists of temperature control and moisture movement in or out of newly-placed concrete, since moisture movement ultimately affects its strength, permeability, and durability. However, the XtremecureT cure method takes curing to new parameters by also including ingredients that effectively enhance and accelerate strong initial hydration processes to a significant degree, resulting in production of additional hydration product, which in turn decreases concrete's total void percentages, and etc.

The past, or conventional, accepted objective, in concrete curing, is to retain as much of the original mix water, inside newly-placed concrete, as is possible, because the more water retained, the longer concrete initially strongly hydrates and continues to produce hydration product (C-S-H) subsequently, larger volumes of C-S-H gel, or hydration product, are generated, significantly improving finished concrete quality, especially when mix water pockets, or capillaries, become occupied to their fullest possible extent by products of hydration. However, fact is, in most cases, jobsite active curing ceases long before maximum possible hydration has taken place. Inadequate jobsite active curing will be a problem of the past where utilizing the XtremecureT cure method. Furthermore, prior to development, no practical curing method existed that could perform as well as the water ponding curing method. However, water curing requires continual monitoring of curing progression, and since curing time's duration varies greatly, due to many factors including temperature, degree of concrete protection, admixtures used, and etc., water ponding is often labor intensive, if performed properly.

Water Cure Method: For concrete installations with small surface / volume ratios, curing may be aided by oiling and water wetting forms, just prior to casting. After concrete is placed, forms should not be immediately removed, whenever practical, occasionally water wetting concrete and forms during hardening. However, should forms be removed while concrete is still at an early age, concrete should be water wetted and wrapped in polyethylene, or some other suitable material, until sufficiently hardened.

Large horizontal concrete surfaces such as parking decks, airport paving, highway slabs, and etc., present a more serious problem, however to prevent the surface from crazing, loss of water must be prevented while the concrete surface is adequately hardening so as not to be diluted or sustain damage from the water, when water curing. Since concrete is mechanically weak, while plastic, it may become necessary to suspend a covering over the surface. This type of protection is usually required only in hot dry weather, but may become necessary if trying to prevent rain from marring the surface of newly-placed plastic concrete. Once the concrete surface has sufficiently hardened, enough to receive water without damaging surface integrity, water curing can be provided by keeping the concrete in constant contact with water. This can be achieved using several techniques, used for water curing, such as spraying with water, using a water sprinkler, ponding or flooding with water, or perhaps covering the surface with wet sand, damp earth, sawdust or straw. Periodically wetted curing mats may be used or some other absorbent covering, such as wetted burlap, can be placed over the concrete. A continuous supply of water is naturally more effective than an intermittent one.

CURE METHOD COMPARSIONS

Impermeable Surface Membrane Cure Method: Another effective method for curing concrete is to seal the semi-plastic surface with an impermeable membrane material such as waterproof reinforced paper, or plastic sheeting. An impermeable membrane material will effectively prevent early evaporation of mix water, provided it isn't punctured or damaged, but doesn't allow water ingress, to replenish mix water, where needed to prevent too early self-desiccation of very low water to cement ratio concrete mixes. Impermeable surface membranes can be formed by using sealing compounds applied in liquid form, by hand or spray apparatus, after free surface water has disappeared, but before surface pores dry completely, so that compound can still be absorbed. There are primarily two basic types of liquid surface membrane curing compounds, wax-resin and all-resin. The wax-resin curing compound generally isn't suitable for concrete which is to be surface coated, since wax residue will remain adhered to the surface, hampering coating adhesion. The wax-resin curing compound is most commonly used on traffic bearing concrete's such as highway and airport pavement. The all-resin curing compounds are generally used to cure concrete where a surface treatment is planned, since it leaves no appreciable amount of surface residue. However, whenever wax-resin or all-resin compounds are used solely for curing purposes, a surface residue may exist for about 30 days, or more. If surface residue is not worn, washed, or blown away after this time, it can sometimes be removed using a stiff bristled brush. Even when a wax-free resin is specified to cure a concrete, which is to be surface treated, the contractor should still wash the surface using a solution of muriatic acid followed by a thorough rinsing with water, prior to the coat application, to ensure the best possible bonding quality. Alternatively, where utilizing the cure method, surface film / residue is not a problem, and acid washing is unnecessary to receive excellent surface bond quality. White pigmented curing agents are sometimes specified to reflect more ultraviolet rays, keeping temperature of newly-placed concrete lower through heat wave reflection, sometimes important during early curing, before concrete has reached sufficient strength to resist thermal stresses, produced by extreme temperatures. NOTE: XtremecureT can be ordered in white-pigmented form.

Resin type compounds have the potential to damage the environment. Wax-resin or all-resin compounds contain ingredients such as mineral spirits and hydrocarbon resin (usually coumaroneindene, derivatives of naptha, and coal tar), which are pollutants. In addition, wax-resin compounds have petroleum wax (usually paraffin wax). Until recent years, wax-resin and all-resin type curing compounds fulfilled over 90% of concrete curing requirements. However, in recent years, synthetic rubber solutions have grown popular as curing compounds, since they maintain a high moisture content, give dust-free characteristics to hardened concrete, and add a sealing surface film. Synthetic rubber solutions are usually butadiene-styrene or chlorinated rubber types, also containing ingredients that may pollute the environment, such as vinyl, xylol, naptha, and liquid chlorinated wax, plus their surface film is usually detrimental to surface traction and bonding quality, unless removed, usually by water or sand blasting the surface. Additionally, there are compounds based on sodium or potassium silicates which behave as curing and hardening compounds but have proven detrimental to the longevity of concrete's integrity, especially if reactive aggregates are a concern. XtremecureT is a one step cure method that contains no harmful ingredients, or volatile organic content. It provides the usual cure benefits normally associated with concrete curing, plus many additional benefits: Concrete cured with XtremecureT is extremely impermeable through the formation of smaller segmented porosity, based on the greatly enhanced hydration during curing. Tests have shown that XtremecureT cured concrete performs as well as, or better than water curing in relationship to durability, impermeability, freeze-thaw damage resistance, and strength.

Xtremecure Subsurface Membrane Cure Method: The XtremecureT cure method is the only method successfully utilizing the subsurface vapor-permeable membrane concept. It is applied using a non-atomizing low-pressure spray apparatus such as a pump-tank sprayer, motorized slurry pump, or alternatively by flooding the surface as concrete reaches its initial set, or as soon as is practical thereafter. For instance, where the concrete surface needs to be walked on for application, surface should be allowed time to sufficiently harden so as not to mar or imprint it during application. As XtremecureT is applied to surface finished concrete it readily penetrates beneath the surface, going out of sight (except pigment, where applicable), to its surface porosity bottom; to its matrix top, where within seconds, following application, a vapor-permeable, specially-formulated, colloidal silicate precipitate membrane is formed, immediately preventing moisture / water from exiting the plastic or semi-plastic concrete. Following subsurface membrane formation, water can only exit the concrete as a vapor gas. This aspect assures adequate moisture or water is available for the strong initial hydration processes, effectively sustaining a high humidity environment, for easier hydration product development. Length of time needed to complete the strong initial hydration processes depend on concrete mix's cement composition, fineness, and proportions. Even low water to cement ratio concrete, requiring at least an 80% humidity environment to prevent too early self-desiccation, will greatly benefit from this created environment. XtremecureT contains ingredients which deeply penetrate newly-placed plastic or semi-plastic concrete, providing to its mix water, still available for hydration, the ability to accelerate strong initial hydration processes to a significant degree, again dependant upon mix's cement composition, particle fineness, and richness. The concrete's strong initial hydration time period may or may not be extended by XtremecureT but, since concrete's strong initial hydration processes are accelerated, the actual hydration time achieved is by far more effective, producing greater quantities of C-S-H, or hydration product, in a shorter period of time. Strong initial hydration usually continues as long as moisture and space (capillary porosity) for hydration product is available. Generally, the more hydration product, or C-S-H, produced, the stronger more durable and impermeable the finished concrete will be. Therefore, XtremecureT not only provides concrete a superior cure, but also reinforces its C-S-H component, concrete's main strength component. Strengths are further increased by formation of more segmented porosity and lowered capillary void percentages. Subsequently, concrete becomes permanently internally sealed, effectively preventing pollutants from entering its matrix, preserving its integrity, yet still allowing the concrete to breathe. As a result of utilizing the XtremecureT cure method, concrete is more durable, more impermeable, more freeze-thaw damage resistant, more dust resistant, more abrasion resistant, more acid and chemical resistant, and easier to keep clean. XtremecureT subsurface vapor-permeable membrane consists of pores that are significantly smaller than concrete's micro-pores, forcing gases, such as radon gas, to seek other avenues of escape, instead of passing through the concrete.