Abstract:
Disclosed is a concrete curing blanket including an impervious layer, an absorbent layer and an acrylic glue configured to adhere to the impervious layer and absorbent layer while immersed in water during at least a prescribed period for curing concrete with an adherence strength that equals or exceeds an internal strength of the absorbent layer. Methods of making and curing concrete with same also are disclosed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Producing quality hydraulic concrete or cement requires proper curing. Curing increases concrete strength, hence structural value. Proper curing is necessary for producing water-tight, durable concrete. 
         [0002]    The most common hydraulic cement for construction purposes is Portland cement. Portland cement is a heat-treated mixture primarily of calcium carbonate-rich material, such as limestone, marl or chalk, and material that is rich in Al 2 SiO 2 , such as clay or shale. Portland cement comes in several varieties that are distinguished by such characteristics as the rate of acquiring strength during curing, the amount of heat of hydration generated, and resistance to sulfate attack. Other types of hydraulic cements include aluminous cement, chalcedony cement, which is made from amorphous quartz, and Roman cement, which combines burnt clay or volcanic ash with lime and sand. 
         [0003]    “Concrete” describes a mixture of stone, gravel or brushed rock and sand, referred to as “aggregate,” which is bound by a cement. As used herein, “concrete” includes reinforced concrete, concrete that contains organic or silica-based fibers or metallic wire, cable or rods as a reinforcing substance, and polymer-cement concrete that is bound with Portland cement and a polymerized monomer or resin system. Hydraulic concrete and cement are referred to herein as “concrete.” Additional information on the composition and characteristics of concrete may be found in Basic Construction Materials by C. A. Herubin and T. W. Narotta, third edition, Reston Book, Englewood, N.J., which is incorporated herein by reference. 
         [0004]    Curing involves chemical changes that result in setting and hardening. These chemical changes occur over a considerable period of time in the presence of water. Hydration is important in the curing of hydraulic concretes, i.e., concretes that are dependent on a hydration reaction for hardening, and concretes that are bound with hydraulic concretes. Ideally, concrete should be kept wet after it has set for as long a period as is practicable. This period generally ranges from 7 to 21 days. 
         [0005]    Maintaining an optimal amount of water in contact with curing concrete optimizes the strength and durability of the concrete. For example, if concrete is kept wet for the first ten days after setting, strength and durability thereof increase 75 percent over ordinary aging at dry surface conditions. As reported by Ken Hover in  Curing and Hydration: Two Half Truths Don&#39;t Make a Whole,  published in the summer 2002 edition of the Concrete News by L &amp; M Construction Chronicles, the more water that is made available to the concrete during curing, the better. 
         [0006]    To keep concrete hydrated, the concrete industry has come to rely on concrete curing blankets for covering wetted concrete and extending the duration of damp conditions on the curing surface thereof. Some concrete curing blankets have included burlap and cotton mats, wet rugs, moist earth or sand, sawdust and other coverings likely to act as a moisture barrier. Burlap-based blankets pose many problems, including hydrophillic greasiness; large voids that promote non-uniform concrete surface wetting; stiffness and non-resiliency that prevents conformity to surface irregularities; and fibers that snag on concrete surfaces, which may lead to undesired markings. Cotton mats tend to disintegrate well before the desired curing duration, leaving clumps of material stuck on the surface requiring refinishing. Some concrete curing blankets also have included moisture barriers, such as water-proof papers and plastic films. While films may help reduce evaporation, they do not cure problems associated with underlying absorbent layer. 
         [0007]    A recent concrete curing blanket, known in the industry as Ultracure™, avoids the issues described above with an absorbent layer of airlaid natural cellulose fibers latex or thermally bonded on an impervious backing, as described in U.S. Patent Application Publications 2005/0042957, 2006/0019064 and 2005/0214507, which are incorporated herein by reference. Because of its unusually absorbent and pliable properties, the Ultracure™ curing blanket also provides more moisture to the surface of curing concrete more uniformly than any other curing blanket. Because the smooth side of the airlaid layer, the surface formed on the wire or mesh during fabrication, is disposed against the concrete, the Ultracure™ curing blanket promotes a smooth finished surface on the concrete that major retailers are proud to display as primary flooring. 
         [0008]    As used herein, “airlaid” refers to a fibrous structure formed primarily by a process involving deposition of air-entrained fibers onto a mat, typically with binder fibers, and typically followed by densification and thermal bonding. In addition to traditional thermally bonded airlaid structures, those formed with non-tacky binder material and substantial thermally bonded, “airlaid,” according to the present invention, also includes co-form, which is produced by combining air-entrained dry, dispersed cellulosic fibers with meltblown synthetic polymer fibers while the polymer fibers are still tacky. 
         [0009]    “Airlaid” also includes an airformed web to which binder material is added subsequently. Binder may be added to an airformed web in liquid form, e.g., an aqueous solution or a melt, by spray nozzles, direction injection or impregnation, vacuum drawing, foam impregnation, and so forth. Solid binder particles also may be added by mechanical or pneumatic means. 
         [0010]    While the pliability of Ultracure™ curing blanket and its inherent tendency wick moisture therethrough promotes more uniform distribution of available water over a curing concrete surface, optimal curing may be defeated by an inadequate supply of available water from the start. Even though the clear, transparent or opaque backing of the Ultracure™ curing blanket permits viewing whether bubbles have formed, it remains difficult to know whether enough water is available throughout the surface. 
         [0011]    While effective for their intended purposes, thermally- and latex-bonded curing blankets are costly to manufacture from equipment and materials perspectives. Latex-bonded materials also may not be hydrophobic, which would lead to blanket layer breakdown well before the prescribed duration for curing concrete. 
         [0012]    What is needed is a concrete curing blanket that avoids thermal- and hydrophillic latex-bonding. 
       SUMMARY OF THE INVENTION 
       [0013]    The invention is a concrete curing blanket that avoids thermal- and hydrophillic latex-bonding. To that end, the invention is a concrete curing blanket including an impervious layer, an absorbent layer and an acrylic glue configured to adhere to the impervious layer and absorbent layer while immersed in water during at least a prescribed period for curing concrete with an adherence strength that equals or exceeds an internal strength of the absorbent layer. 
         [0014]    The invention provides improved elements and arrangements thereof, for the purposes described, which are inexpensive, dependable and effective in accomplishing intended purposes of the invention. Other features and advantages of the present invention will become apparent from the following description of the preferred embodiments which refers to the accompanying drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The invention is described in detail below with reference to the following figures, throughout which similar reference characters denote corresponding features consistently, wherein: 
           [0016]      FIG. 1  is a vertical cross-sectional detail view of an embodiment of a curing blanket constructed according to principles of the invention; 
           [0017]      FIG. 2  is an environmental perspective view of the embodiment of  FIG. 1 ; 
           [0018]      FIG. 3  is a schematic view of a method of curing concrete according to principles of the invention; 
           [0019]      FIGS. 4-10  are graphical representations of properties of the embodiment of  FIG. 1 ; 
           [0020]      FIG. 11  is a schematic view of a method of making a curing concrete according to principles of the invention; 
           [0021]      FIG. 12  is vertical cross-sectional detail view of the embodiment of  FIG. 1  on a surface drawn to a smaller scale; 
           [0022]      FIG. 13  is a plan view of the embodiment of  FIG. 1 ; 
           [0023]      FIG. 14  is a vertical cross-sectional detail view of overlapping trimmed embodiments of  FIG. 1 ; 
           [0024]      FIG. 15  is a partial plan view of an embodiment of a curing blanket constructed according to principles of the invention; and 
           [0025]      FIG. 16  is a partial cross-sectional detail view drawn along line XVI-XVI in  FIG. 15 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Referring to  FIG. 1 , an embodiment of a concrete curing blanket  10  constructed according to principles of the invention has an absorbent layer  15  disposed on an impervious layer  20 . A responsive layer  25  may be interposed between absorbent layer  15  and impervious layer  20 . Responsive layer  25  would exhibit a response that corresponds to one or more conditions related to curing concrete that aids in determining whether sufficient water is available for optimal curing. If available, concrete curing blanket  10  maintains the optimal amount of water in contact with an entire surface of curing concrete, which optimizes the strength and durability of the concrete when cured. 
         [0027]    Preferably, absorbent layer  15  is airlaid, as described above. Because airlaid hydrogen bonded materials tend to disintegrate with prolonged exposure to water, airlaid natural fiber mats have not been considered optimal for concrete curing. The invention overcomes this problem by incorporating natural cellulose material with synthetic and multibond fibers in the resultant airlaid structure. 
         [0028]    Absorbent layer  15  contains bi-component or multibond fibers, fluff pulp, ethylene vinyl acetate and latex. More specifically, absorbent layer  15  includes 5-50%, preferably 30%, synthetic bonding fibers. Synthetic fibers contribute as much as 3.8-4.25%, preferably 4%, by weight. Bi-component and multibond fibers are coaxial fibers having an inner component with a higher melting temperature than an encasing outer component. When heated, the outer component melts for bonding with other elements, while the inner component does not melt, thus lending integrity and strength to the bonded material. The inner and outer components may be selected from polypropylene, polyethylene or other compositions suitable for the purposes described. 
         [0029]    Absorbent layer  15  also includes 50-89%, preferably 70%, natural cellulose fluffed pulp fiber. The fluff pulp, preferably, is derived from southern softwood, northern softwood, southern hardwood, northern hardwood, kanaf or eucalypus fibers. These materials provide short fibers that offer great surface area for trapping and absorbing water. The fibers derived from protein based, cotton, agave, plant stalk (bast) fibers of other mats tend to be much longer, hence afford less surface area for trapping and absorbing water. These longer fibers also have waxes, resins and some lignin present that discourage entrapping water. These longer fibers are less absorbent and exhibit geometries that are not as favorable as the present cellulose from soft and/or hardwood fibers. Further, the pulp fibers of the present invention also tend to provide greater tensile strength than the fibers of other mats. 
         [0030]    The fluff pulp of absorbent layer  15  is obtained from a Kraft process, rather than mechanical pulping. Mechanical pulping does not produce a clean product, free of the waxes, resins, silicone, turpentine that are present in the virgin materials recited above. Bleached Kraft pulp provides optimal absorption capabilities by producing clean cellulose. The Kraft process produces a bulkier cellulose with a white absorptive component that prevents discoloration of a concrete surface in contact therewith. Discoloration commonly occurred with burlap materials. 
         [0031]    Ethylene vinyl acetate promotes great integrity and reduces dusting. 
         [0032]    The latex bonding agent is sprayed on natural fibers or part of the bi-component or multibond fibers aids in strengthening the adhesion among the bi-component or multibond fibers and other materials in absorbent layer  15 . The latex binders may contribute as much as 5-35%, preferably 20%, by weight. 
         [0033]    Referring also to  FIG. 2 , the unique composition of concrete curing blanket  10  enables it to wick moisture from oversaturated areas to dry areas. As edges  30  of concrete curing blanket  10  dry, concrete curing blanket  10  wicks moisture from more hydrated areas to edges  30  and vice versa. Concrete curing blanket equalizes the moisture saturation level therethrough. 
         [0034]    Another embodiment of absorbent layer  15  contains 5-20% super absorbent fibers. Super absorbent fibers are absorbent fibers coated with absorbent material. 
         [0035]    Preferably, impervious layer  20  provides a vapor barrier, but not a protection barrier. To this end, impervious layer  20  may include an extruded or coated polyethylene or polymer latex material or film as a vapor- and/or fluid-impervious backing. 
         [0036]    Absorbent layer  15  and impervious layer  20  may be thermally bonded in a basis weight ranging from 40 to 500 grams per square meter (gsm). Ideally, the latex material is a two-part manufactured composition that renders it insoluble in water. The water insolubility discourages disintegration of concrete curing blanket  10  or, more specifically, absorbent layer  15 , which would lead to imperfections in the finished surface of a concrete slab. Absorbent layer  15 , preferably, is spray coated, which lowers production costs. 
         [0037]    One part of the latex composition is a high-viscosity polymer filler agent, while the other part is a water resistant agent obtained by polymerization. A binder dispersed in water forms films by fusion of the plastic filler particles as the water evaporates during manufacturing or curing. 
         [0038]    Absorbent layer  15  and impervious layer  20  may be bonded with a special water resistant adhesive having a soft point of 210° F. 
         [0039]    Referring to  FIGS. 15 and 16 , preferably, absorbent layer  15  and impervious layer  20  are bonded with an acrylic glue disposed in strips  60  therebetween. The acrylic glue is formulated so that it does not require the heat required for thermal bonding. While the acrylic glue can be a kind of latex, it is formulated to be hydrophobic, so that it will not break down in the presence of water over time on a curing concrete slab. 
         [0040]    Strips  60  are configured to balance sufficient adhesion between absorbent layer  15  and impervious layer  20  to perform as a concrete curing blanket, as exemplified, but not limited by the description herein, and provide maximum hydration for a curing concrete slab. The acrylic glue should maintain sufficient adhesion to have a greater bond strength to impervious layer  20  and absorbent layer  15  after seven days of immersion in water than absorbent layer  15  has internal strength. In other words, absorbent layer  15  should exhibit fiber tear on impervious layer  20  when tested, as exemplified, but not limited by Table  3  below. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Peel Strength 
               
             
          
           
               
                   
                 Peel Strength in Newtons 
                   
               
             
          
           
               
                 Roll # 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 Average 
               
               
                   
               
             
          
           
               
                 1 
                 0.8 
                 0.9 
                 1.2 
                 1.1 
                 0.8 
                 1.3 
                 0.9 
                 0.7 
                 0.9625 
               
               
                 2 
                 0.8 
                 0.6 
                 0.9 
                 0.9 
                 0.9 
                 1.1 
                 0.9 
                 0.9 
                 0.8750 
               
               
                 3 
                 0.9 
                 0.5 
                 0.7 
                 0.4 
                 1.0 
                 1.2 
                 1.3 
                 1.0 
                 0.8750 
               
               
                 9 
                 1.5 
                 1.2 
                 1.3 
                 1.5 
                 1.4 
                 1.1 
                 0.9 
                 1.2 
                 1.2625 
               
               
                 15 
                 1.0 
                 0.4 
                 0.9 
                 0.9 
                 1.0 
                 1.2 
                 1.5 
                 0.7 
                 0.9500 
               
               
                 19 
                 1.1 
                 0.4 
                 0.7 
                 1.0 
                 1.0 
                 1.1 
                 1.3 
                 1.0 
                 0.9500 
               
               
                   
               
             
          
         
       
     
         [0041]    Since a hydrophobic acrylic glue retains little moisture, the sizing of and spacing between strips  60 , which may be regulated by a slotted blade or other suitable device or methodology, is critical. A preferred thickness  65  of strip  60  ranges from 1/16 to ⅜ inches. A preferred spacing  70  between strips  60  ranges from ¼ to 2 inches. 
         [0042]    Employing an acrylic glue as described above permits employing a lighter absorbent layer  15 , that is, a 85 gsm airlaid product rather than a 95 gsm product for a comparable thermal- or latex-bonded blanket, while providing just as much available water to the curing concrete surface. 
         [0043]    Alternatively, impervious layer  20  may provide for vapor and/or fluid transmission. To this end, impervious layer  20  may include a perforated film, preferably constructed of a polymer or metallic material. The number of perforations in impervious layer  20  may range from one to 500 per square foot. Each perforation has a diameter ranging from 0.001 mm to 0.1 mm. The perforations may define a pin hole, half moon hole, butterfly hole, full hole or other configuration suited for purposes described herein. 
         [0044]    The perforations provide for rewetting curing concrete, where concrete curing blanket  10  is adapted to cure concrete, and vapor transmission, where concrete curing blanket  10  is adapted to absorptive applications. Perforated embodiments of impervious layer  20  are especially suited for curing concrete highway constructions, pavements, bridges and the like. 
         [0045]    Impervious layer  20  may be UV enhanced and/or biodegradable. Impervious layer  20  may be opaque, with or without coloration, but preferably is clear or transparent. This allows for ready visual perception of water in concrete curing blanket  10  and on a slab surface, which realizes for owners and contractors tremendous labor savings in tending the curing slab and blanket to ensure that adequate water is present on all portions of a slab to be cured. Workers readily may see and take steps to eliminate bubbles or correct other non-uniformities with respect to contact between concrete curing blanket  10  to the surface of a curing concrete slab, or moisture provided thereby. 
         [0046]    A target caliper or thickness for concrete curing blanket  10  is 0.5-5.0 mm, preferably 1.80 mm. A target tensile strength for concrete curing blanket  10  is 1295-1350 g/50 mm, preferably 1300 g/50 mm. A target absorbency for concrete curing blanket  10  is 16.5-18.5 g/g, preferably 17 g/g. 
         [0047]    Responsive layer  25  is intended to give notice whether an appropriate amount of water is available for curing concrete. Accordingly, responsive layer  25  exhibits a response corresponding to one or more conditions related to curing concrete. The conditions include, inter alia, an amount of water, a pH level or a pH change. 
         [0048]    Of the many techniques that may be employed, preferably, responsive layer  25  is a metallized layer, preferably of aluminum having an optical density ranging from 0.05 to 10.0, that reacts, preferably within 21-48 hours, to the change in pH that occurs in the available water on curing concrete due to the hydration reaction. As curing concrete hydrates, it absorbs ions and increases the pH in the available water from about 11 to 14, which in turn reduces responsive layer  25 . The pH of cured concrete is about 12.5 or more. 
         [0049]    The invention is configured so that, without the concrete curing, the available water will not achieve sufficient alkalinity to react with, reduce or dissolve the metalized or pigmented coating of responsive layer  25 . In one embodiment of the invention, a clear impervious layer  20  is paired with a responsive layer  25  that is at least opaque or light reflective. As responsive layer  25  reacts, reduces or dissolves in the presence of water as described above, the non-translucence of responsive layer  25  becomes correspondingly light transmissive. Consequently, an appropriate amount of available water would allow a clear view of the curing concrete below, while an occluded view would signal an insufficiency of available water. Other embodiments of the invention provide for responses that manifest as color changes or other phenomena. 
         [0050]    In operation, areas of concrete curing blanket  10  in which the appearance has changed commensurate with reduction of responsive layer  25  could be understood as areas where the curing concrete is fully hydrated for optimal curing. On the other hand, areas of concrete curing blanket  10  in which the appearance has not so changed could be understood as areas where the curing concrete is not yet fully hydrated, thus in need of more water. Consequently, concrete curing blanket  10  provides a ready indicator, which, if timely heeded, would ensure that the entire curing concrete surface is fully hydrated for optimal curing. 
         [0051]    Referring to  FIGS. 2 and 3 , a method of curing concrete  100  according to principles of the invention includes a step  105  of wetting a target curing concrete surface C and a step  110  of disposing concrete curing blanket  10  on target curing concrete surface C with absorbent layer  15  nearest thereto. The method preferably includes a step  115  of re-wetting edges of concrete curing blanket  10  so that water wicks to all areas of concrete curing blanket  10 . The method also includes a step  120  of removing concrete curing blanket  10  from target curing concrete surface C after target curing concrete surface C is cured. 
         [0052]    In practice, prior to performing step  105  or step  110 , a manufacturer ships rolls  35  of concrete curing blanket  10  on pallets (not shown) to a site where concrete is to be poured. On each roll  35 , concrete curing blanket  10  has a width  40  defined by edges  30 . Each pallet contains approximately twelve rolls  35  that provide approximately 10,000 square feet of coverage. Each roll  35  is encased and protected with shrink wrap (not shown) to minimize exposure to contamination until concrete curing blanket  10  is applied to target curing concrete surface C during the wet cure process. The shrink wrapping allows concrete curing blanket  10  to be stored outside during construction. 
         [0053]    Step  105  involves misting or flooding target curing concrete surface C as specifications require. 
         [0054]    After removing the protective shrink wrap (not shown), concrete workers perform step  110  by slowly rolling concrete curing blanket  10  onto target curing concrete surface C. Properly aligning and rolling concrete curing blanket  10  reduces the possibility of forming wrinkles in concrete curing blanket  10  or trapping air thereunder. 
         [0055]    Once disposed on target curing concrete surface C, concrete curing blanket  10  becomes saturated with water and increases in weight dramatically. The weight increase allows for rolling out multiple adjacent lengths of concrete curing blanket  10 , preferably with an overlap of two to four inches, without having to lap, tape, weigh down or otherwise restrain adjacent edges  30  to maintain uniform, void-free coverage of target curing concrete surface C. Since the airlaid structure of concrete curing blanket  10  is so absorptive and takes longer to dry out, moisture, hence weight, dissipate slower, further eliminating the need to restrain edges  30 . 
         [0056]    For best results, water should be allowed to pond in front of roll  35  as it is rolled along target curing concrete surface C. 
         [0057]    In the unlikely event a wrinkle (not shown) occurs in concrete curing blanket  10  during application, the method may include a step  125  of eliminating a wrinkle in concrete curing blanket  10  which would be performed between step  110  and step  115 . Step  125  may involve cutting concrete curing blanket  10  across width  40  of the affected area with a razor. Three- to four-foot sections on each side of the wrinkled area are peeled away then reapplied to target curing concrete surface C by gently, simultaneously stretching and lowering the sections back onto the wet cure surface. 
         [0058]    Because concrete curing blanket  10  absorbs and retains significant amounts of water, concrete curing blanket  10  adheres to target curing concrete surface C like no other concrete curing blanket and insures a more complete, uniform wet cure and surface appearance that other concrete curing blankets. 
         [0059]    In the unlikely event a bubble (not shown) forms under concrete curing blanket  10  after application, the method may include a step  130  of eliminating an entrapped bubble. Step  130  involves applying a roller squeegee or a wide soft bristle push-squeegee to guide the bubble (not shown) to the nearest untapped edge  30 . Squeegee roller application ensures 100% contact between concrete curing blanket  10  and target curing concrete surface C. Removing entrapped bubbles in this manner is preferred for slab on grade/tilt up construction projects. 
         [0060]    Step  115 , preferably, involves gently spraying water around edges  30  of concrete curing blanket  10  in an amount sufficient for concrete curing blanket  10  to wick water to all areas thereof and providing 100 percent humidity to target curing concrete surface C, as recommended for a wet curing application. 
         [0061]    Step  120  involves folding concrete curing blanket  10  back onto itself in three- to four-foot sections until an entire concrete curing blanket section is folded. The foregoing is repeated until all of concrete curing blanket  10  disposed on target curing concrete surface C is folded into a removable condition. As concrete curing blanket  10  is intended for one-time use, once removed, folded concrete curing blanket  10  should be disposed of properly. 
         [0062]    Embodiments of concrete curing blanket  10  have been tested extensively. Samples of concrete curing blanket  10  measured approximately 8 by 12 inches and had a 1.0 mm/ply thickness. 
         [0063]    Table 1 summarizes results of a water vapor transmission and permeance test performed on some embodiments of concrete curing blanket  10  in general accordance with ASTM E96-00, “Standard Test Methods for Water Vapor Transmission of Materials” using the water method.  FIGS. 4-7  show the portion of data used to calculate results.  FIGS. 4 and 5  pertain to test samples oriented such that absorbent layer  15  was vertically superior to impervious layer  20 , defining a fibers up position, and  FIGS. 6 and 7  pertain to test samples oriented such that impervious layer  20  was vertically superior to absorbent layer  15 , defining a fibers down position. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Water Vapor Transmission and Permeance Data 
               
             
          
           
               
                   
                 Water vapor transmission 
                 Permeance 
               
             
          
           
               
                   
                 Si units 
                 inch-pound 
                 perm (grains/ 
               
               
                 Specimen 
                 (grams/ 
                 units grains/ 
                 h · sq 
               
               
                 identification 
                 h · sq m) 
                 h · sq ft 
                 ft · in. Hg) 
               
             
          
           
               
                 and orientation 
                   
                 average 
                   
                 average 
                   
                 average 
               
               
                   
               
               
                 Specimen 1 
                 0.040 
                 0.040 
                 0.057 
                 0.057 
                 0.14 
                 0.14 
               
               
                 fibers up 
               
               
                 Specimen 2 
                 0.040 
                   
                 0.057 
                   
                 0.14 
               
               
                 fibers up 
               
               
                 Specimen 3 
                 0.042 
                 0.037 
                 0.060 
                 0.053 
                 0.14 
                 0.13 
               
               
                 fibers down 
               
               
                 Specimen 4 
                 0.032 
                   
                 0.046 
                   
                 0.11 
               
               
                 fibers down 
               
             
          
           
               
                 Average 
                 0.040 
                 0.058 
                 0.13 
               
               
                   
               
             
          
         
       
     
         [0064]    For this test, sample material was cut into four 52 mm diameter circles and placed on anodized aluminum permeability cups manufactured by Sheen Instruments Ltd. Two specimens were placed in the fibers up position and two in the fibers down position. The specimens were allowed to equilibrate for seven days in a test room maintained at 73±0.60° C. and 50÷2% relative humidity (RH). The specimens then were sealed in the permeability cups over 6 mL reagent water (ASTM D1193 Type IV). A non-volatile, proprietary sealant was used to create a leak-free seal between the film and the cup faying surfaces. The specimens remained in the test room at 73±0.60° C. and 50±2% RH and were weighed in the room twice per week. The specimens were weighed until the weight change versus time was constant per ASTM E96. The referenced material meets the performance requirement for water vapor transmission rate of no more than 10 grams/m 2  in 24 hours (0.42 grams/hm 2 ) in ASTM C 171-03, “Standard Specification for Sheet Materials for Curing Concrete.” 
         [0065]    Results for Specimens  1  through  3  were similar, as shown on  FIGS. 4-6 . Specimen  4 , as shown on  FIG. 7 , developed a visible biological growth on the fiber side mid-way through the testing. Specimen  4  has lower water vapor transmission. The accuracy of the balance is 0.01 grams, therefore all data points fall on the horizontal grid lines. 
         [0066]    Another test measured the water retention of concrete curing blanket  10  in accordance with ASTM C156-98, “Standard Test Method for Water Retention by Concrete Curing Materials.” The test involved a composition of mortar containing by weight: 2,660 g concrete; 6,500 g standard sand; and 1,064 mL water to produce flow 35±5. The flow was 35.5% and water-to-concrete ratio was 0.4. Concrete curing blanket  10  met the performance requirement for water loss of no more than 0.55 kg/sq m in 72 hours per ASTM C171-97a, “Standard Specification for Sheet Materials for Curing Concrete.” 
         [0067]    The specific composition of concrete curing blanket  10  provides a thickness, MD dry tensile strength, CD dry tensile strength, CD wet tensile strength, absorbency rate, capacity, brightness, and caliper that allow concrete curing blanket  10  to lay completely flat on, provide increased surface-to-surface contact with, and promote desired, consistent coloration of curing concrete. MD dry tensile strength refers to the tensile strength of a dry sample in the direction of the fibers. CD dry tensile strength refers to the tensile strength of a dry sample transversely to the direction of fibers. CD wet tensile strength refers to the tensile strength of a wet sample transversely to the direction of fibers. Concrete cured with concrete curing blanket  10  are free of localized weaknesses and discolorations caused by bubbles or other contact discontinuities between the curing surface and a concrete curing blanket. Further, increased weight from absorption causes the saturated blanket to remain in place longer and require less attention. 
         [0068]      FIGS. 8-10  graphically describe, respectively, specific absorption, fluid capacity and tensile strength of various configurations of concrete curing blanket  10 . Materials exhibit two different tensile strengths: (1) yield, which is equivalent to the maximum amount of tensile stress the material can withstand yielding or stretching; and (2) failure, which is equivalent to the stress required to achieve material failure or tearing. Table 2, below, presents data averaged from three tests of various configurations of concrete curing blanket  10 . 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Preliminary Test Data 
               
             
          
           
               
                   
                   
                   
                 Pulp 
                 Pulp 
                 Pulp 
                 Pulp 
                 Burst 
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Basis 
                   
                 Up 
                 Up 
                 Down 
                 Down 
                 Index 
                 Tensile 
                   
                 % 
                 Capac- 
                 Capacity 
                   
                 Capacity 
               
               
                 Sample 
                 Wt. 
                 Caliper 
                 Mullen 
                 Mullen 
                 Mullen 
                 Mullen 
                 (kPa 
                 (N/5 
                 Tensile 
                 Elon- 
                 ity 
                 Index 
                 Capacity 
                 Retention 
               
               
                 Type 
                 (gsm) 
                 (mm) 
                 (psi) 
                 (kPa) 
                 (psi) 
                 (kPa) 
                 m2/g) 
                 cm) 
                 Index 
                 gation 
                 (g) 
                 (g/g) 
                 Retention 
                 Index 
               
               
                   
               
             
          
           
               
                 60gsm 
                 109 
                 0.389 
                 16 
                 110 
                 18.8 
                 130 
                 1.19 
                 62 
                 0.57 
                 11.64 
                 9.34 
                 2.38 
                 4.01 
                 1.02 
               
               
                 pulp sheet 
               
               
                 @ 30# poly 
               
               
                 60gsm 
                 129 
                 0.398 
                 20.5 
                 141 
                 22.4 
                 154 
                 1.2 
                 73 
                 0.57 
                 10.45 
                 8.54 
                 1.84 
                 4 
                 0.86 
               
               
                 pulp sheet 
               
               
                 @ 45# poly 
               
               
                 60gsm 
                 157 
                 0.296 
                 25.8 
                 178 
                 27.3 
                 188 
                 1.2 
                 95 
                 0.6 
                 8.65 
                 3.88 
                 0.69 
                 2.21 
                 0.39 
               
               
                 pulp sheet 
               
               
                 @ 60# poly 
               
               
                 100gsm 
                 151 
                 0.808 
                 28 
                 193 
                 35.7 
                 246 
                 1.63 
                 64 
                 0.42 
                 12.54 
                 21.99 
                 4.03 
                 6.49 
                 1.19 
               
               
                 pulp sheet 
               
               
                 @ 30# poly 
               
               
                 100gsm 
                 158 
                 0.79 
                 24.1 
                 166 
                 30 
                 207 
                 1.31 
                 69 
                 0.44 
                 12 
                 21.04 
                 3.7 
                 9.76 
                 1.71 
               
               
                 pulp sheet 
               
               
                 @ 45# poly 
               
               
                 100gsm 
                 201 
                 0.718 
                 30.3 
                 209 
                 37.7 
                 260 
                 1.3 
                 106 
                 0.53 
                 10.55 
                 18.72 
                 2.59 
                 7.54 
                 1.04 
               
               
                 pulp sheet 
               
               
                 @ 60# poly 
               
               
                 Non-woven 
                 305 
                 1.646 
                 237.5 
                 1636 
                 257.2 
                 1772 
                 5.82 
                 485 
                 1.59 
                 64.06 
                 17.36 
                 1.58 
                 1.34 
                 0.12 
               
               
                 poly w/ 
               
               
                 poly 
               
               
                 coating 
               
               
                   
               
             
          
         
       
     
         [0069]    Referring to  FIG. 11 , a method of making a concrete curing blanket  200  according to principles of the invention includes: step  205  of providing an impervious layer; step  210  of disposing an absorbent layer on the impervious layer; and step  215  of interposing between the impervious layer and absorbent layer a responsive layer that exhibits a response corresponding to one or more conditions related to curing concrete, as described above. 
         [0070]    Referring to  FIGS. 12 and 13 , current manufacturing techniques initially produce an embodiment a concrete curing blanket  10  as shown, with a portion  47  of impervious layer  20  that extends beyond absorbent layer  15  and/or responsive layer  25  (collectively indicated with reference character  50 ). If left in this untrimmed state and disposed on curing concrete according to method  100 , portion  47  would prevent the absorbent layer  15  of an overlapping segment of concrete curing blanket  10  from contacting the curing concrete and providing sufficient available water therealong for optimal curing. Consequently, a concrete slab cured with an untrimmed concrete curing blanket  10  would exhibit bands where the concrete did not cure as optimally. 
         [0071]    Accordingly, if needed to assure coextensiveness of absorbent layer  15 , impervious layer  20  and responsive layer  25 , method  200  should include a step  220  of trimming the concrete curing blanket so that the absorbent layer, impervious layer and responsive layer are substantially coextensive. 
         [0072]    Referring to  FIG. 14 , whether step  220  is required, portions of trimmed concrete curing blanket  10  would overlap as shown, without excess impervious layer  20  to interfere with the curing concrete C from contact by and water distribution from absorbent layer  15 . While a minimal gap  55  is shown, in practice, absorbent layer  15  swells and fills gap  55 , thereby providing a continuous, uniformly-distributing concrete curing blanket that indicates where appropriate hydration exists, therefore where optimal curing will occur. 
         [0073]    Steps  205  and  210  are described above, therefore discussed no further. 
         [0074]    Step  215  may involve applying the responsive layer to the absorbent layer or the impervious layer. For example, either of the absorbent layer or impervious layer could be metallized or spray coated with material appropriate for achieving the intended functions of the responsive layer. 
         [0075]    The invention is not limited to the particular embodiments described herein, rather only to the following claims.