Patent Grant
11740223
Concrete has been used as a construction material for more than a century. To ensure longevity of structures prepared from concrete, one must prepare the concrete using the correct water to binder ratio. The slump method is one of the most common methods for determining whether or not the water to binder ratio is proximate to the desired ratio. Unfortunately, the slump method does not provide an accurate assessment of the water to binder ratio. Therefore, the industry would benefit from an accurate assessment of the water to binder ratio. In particular, the industry would benefit from an assessment method that can be carried out at the construction site or where the mixture is created.
In one aspect, the present invention provides a method for determining the water to binder ratio in a fresh concrete mixture. In another aspect, the present invention provides a method for determining the water content of a fresh concrete mixture.
The method for determining the water content of a fresh concrete mixture begins with the step of providing a test sample of fresh concrete mixture. The fresh concrete mixture comprises binder, water and aggregates. The mass of test sample is determined. Additionally, the method provides for determining the volume of air in the test sample and the absolute volume of the test sample. Using the absorption capacity of the aggregates included in the fresh concrete mixture, the method provides for determining the mass of water contributed by the aggregates to the fresh concrete mixture. Typically, the test sample is formed into generally uniform thickness prior to heating under conditions which will remove all water from the test sample without decomposing the aggregates. Following removal of water from the test sample, the mass of the test sample is again determined and the mass of water removed from the test sample calculated. Finally, the mass of water in the fresh concrete is determined by subtracting the mass of water contributed by the aggregates in the test sample from the mass of water removed by heating the test sample.
The method for determining the water to binder ratio of a fresh concrete mixture begins with the step of providing a test sample of fresh concrete mixture. The fresh concrete mixture comprises binder, water and aggregates. The mass of test sample is determined. Additionally, the method provides for determining the volume of air in the test sample and the absolute volume of the test sample. Using the absorption capacity of the aggregates included in the fresh concrete mixture, the method provides for determining the mass of water contributed by the aggregates to the fresh concrete mixture. Typically, the test sample is formed into generally uniform thickness prior to heating under conditions which will remove all water from the test sample without decomposing the aggregates. Following removal of water from the test sample, the mass of the test sample is again determined and the mass of water removed from the test sample calculated. The mass of water in the fresh concrete is determined by subtracting the mass of water contributed by the aggregates in the test sample from the mass of water removed by heating the test sample. Finally, the water to binder ratio is determined by dividing the mass of water in the test sample of fresh concrete mixture by the mass of the binder in the test sample
The drawings included with this application illustrate certain aspects of the embodiments described herein. However, the drawings should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art with the benefit of this disclosure. In some instances, the term cement has a specific meaning, i.e. Portland Cement. For the purposes of this disclosure, the term binder will be used to represent those cementitious materials capable of undergoing a hydration reaction suitable for preparation of concrete structures.
This disclosure provides methods for determining, in the field, the water content and ultimately the water to binder ratio (w/cm) of concrete mixtures. In most cases, incorrect w/cm have an excess amount of water. In these instances, the resulting concrete structure will have decreased strength and stiffness, increased permeability, and will undergo excess shrinkage during drying. If the excess water produces as little as 0.01 increase in the w/cm ratio, the resulting decrease in strength can be as great as 103 kPa. As a result, structures prepared from this concrete mix will have shorter useful lifespans.
Increasing the w/cm ratio by 0.01 requires only the addition of 0.02 m3 of water per every 6 m3 of binder mix when using 335 kg/m3 of binder. The addition of excess water may occur in a variety of ways, including: leftover wash water, incorrect determination of aggregate moisture content and accidental increase in water to improve workability of the concrete. The method described herein provides the ability to field test the water content or w/cm prior to formation of the designed structure and adjustment of the binder/aggregate component to provide the desired final w/cm.
The described method requires less than 60 minutes to carryout. Typically, following preparation of the Test Sample, the method can be carried out in less than 20 minutes. The time required for performing the method is determined, in part, as described below by the heating mechanism used during the method. In general, use of a portable furnace will reduce the time necessary to perform the described method.
The method for determining the w/cm of a concrete mix will be first described in a stepwise manner and then described in connection with working examples. As this method will normally be practiced at a construction site or place of mixing concrete, the initial step of preparing a concrete mixture will typically occur at a remote location. However, preparation of the concrete mixture may also occur in a controlled environment such as a precast plant, factory, or at a laboratory.
Typical concrete mixtures will contain water, aggregate and a binder, i.e. cementitious component capable of undergoing a hydration reaction with water. Common binder components include, but are not limited to: calcium aluminate, calcium sulfate aluminate, Portland cement, fly ash, slag, silica fume, natural pozzolans and mixtures thereof.
After obtaining a volume of the concrete mixture, the concrete mixture must be formed into a sample suitable for testing. This material will be known as the Test Sample. To permit testing in the field and to reduce testing time, the volume of the Test Sample should be relatively small. In the practice of the present method, no more than 7000 cm3 will be required. In fact, the present w/cm test can be practiced with as little as 1200 cm3 of concrete mixture. Typically, Test Samples having volumes between about 1500 cm3 and about 6000 cm3 will be used to determine the w/cm. Preferably, the Test Sample will have a volume between about 1600 cm3 and about 1900 cm3. To promote uniformity in testing, the method utilizes a mold having a known mass to form the test volume into a Test Sample. If the mold is not suitable for the temperatures required in the test, then the Test Sample will be transferred to a Testing Container. Test results confirming the desired minimum and maximum sample volumes for the Test Sample are reported below after the test examples.
To provide accurate determination of the w/cm, the characteristics of the concrete mixture used to prepare the Test Sample must be either measured or calculated. The following table of variables provides the terms used in the equations provided below.
Following preparation of the Test Sample, the mass of the Test Sample in the mold is determined by subtracting the known mass of the mold from the total mass of the mold plus the Test Sample. Additionally, the volume of air in the Test Sample in the mold must be determined. Methods for determining the volume of air in a concrete sample are well known to those skilled in the art.
Two convenient methods are American Standard Test Method (ASTM) C231 which provides for the determination of the air content of freshly mixed concrete by the Pressure Method and ASTM C138 which provides a theoretical density calculation for the Test Sample based on the materials used to prepare the Test Sample. When using ASTM C231, a separate sample is usually tested, the percent air will be read from the gauge used during testing. Following determination of the percent air in the Test Sample, the volume of air can be readily calculated based on the known dimensions of the Test Sample.
When using ASTM C138, the air volume can be found by using the measured density of the Test Sample and calculating the theoretical density of the Test Sample. The measured density of the Test Sample is compared to the theoretical density as determined based on the components used to prepare the batch of concrete which produced the Test Sample.
The density of the Test Sample in the mold (Mold Density) can be found using the following formula:
Mold Density=(MoldFull−MoldTare)/VMold (Equation 1).
Where: MoldFull is the mass of the mold and Test Sample; MoldTare is the empty weight of the mold; and, VMold is the volume of the mold which equals the volume of the Test Sample.
The theoretical density of the Test Sample can be defined as: Theoretical Density=total Test Sample mass/Absolute Volume of the Test Sample (Air Free), where total Test Sample mass is determined as described above and is represented by:
Total Test Sample Mass=MBinder+MCoarse+MFine+MWater (Equation 2).
The Absolute Volume of the Test Sample (Air Free)=((MBinder)/(SGBinder×1000))+((MCoarse)/(SGCoarse×1000))+((MFine)/(SGFine×1000))+MWater/1000 (Equation 3).
For Equation 3 the masses are considered to be grams. For the theoretical density calculation in lb./ft3, the mass is replaced by batched weight and each 1000 is replaced by 62.4 lb./ft3.
Upon determination of the theoretical density, one can calculate the theoretical air content of the Test Sample by determining the percent difference between the theoretical density and the determined Test Sample density. This calculation is represented as:
Air Content (%)=((Theoretical Test Sample Density−Test Sample Density)/Theoretical Test Sample Density)×100 (Equation 4).
Following determination of the percent air in the Test Sample, the volume of air can be readily calculated based on the known dimensions of the Test Sample.
The Absolute Volume of the concrete batch mixture used to prepare the Test Sample, with air, must be determined to provide an accurate assessment of the w/cm (referred to Absolute Volume Batch). However, the mathematical expression of the Absolute Volume Batch can be written as:
Absolute Volume Batch=((MBinder)/(SGBinder×1000))+((MCoarse)/(SGCoarse×1000))+((MFine)/(SGFine×1000))+(MWater/1000)+(VBatch×(VAir/100)) (Equation 5).
For Equation 5 the masses are considered to be grams.
Because the w/cm test removes all water from the Test Sample, an accurate calculation of the w/cm requires knowledge of the absorption capacity of the aggregates used to prepare the Test Sample, i.e. the volume of water contributed by the aggregates. Additionally, coarse and fine aggregates absorb water differently. Therefore, different equations are needed to account for the difference in water absorption capacity. The following equation is used for coarse aggregates:
Coarse Aggregate Absorbed Water=(AbsCoarse/100)×MCoarse (Equation 6).
The following equation is used for fine aggregates:
Fine Aggregate Absorbed Water=(AbsFine/100)×MFine (Equation 7).
Thus, with knowledge of the absorbed water attributed to both fine and coarse aggregates in the concrete mix used to prepare the Test Sample, one can determine the Total Water Absorbed as reflected by the following:
Total Absorbed Water=Coarse Aggregate Absorbed Water+Fine Aggregate Absorbed Water (Equation 8).
Additionally, when more than one coarse or fine aggregate is used in the concrete mixture, their corresponding water absorption values will be added to the Total Absorbed Water value. Thus, the Total Absorbed Water for the batch of concrete mixture used to prepare the Test Sample can be determined by Equation 8.
Test Sample Density is calculated by taking the sum of the batched masses divided by the absolute volume of the batch. This can be shown mathematically as:
Test Sample Density=Total Test Sample Mass/Absolute Test Sample Volume (Equation 9).
This representation also corresponds to Test Sample Density=Eq. 2/Eq. 5. While the Test Sample Density generally corresponds to the value of Equation 1 divided by the known mass, the calculations described here uses all of the batch weights and provides a greater degree of accuracy. Additionally, one will normally compare the two values as a further check on accuracy of the determined Test Sample Density.
The process of removing water from the Test Sample will be explained in detail below. After establishing the mass and volume of the Test Sample in the mold, the Test Sample must be transferred to a Testing Container prior to removing water from the Test Sample. To ensure accurate determination of the w/cm, no more than 10 grams of Test Sample may remain in the mold after removal of the Test Sample. For the purposes of calculating water content or w/cm the mass of the Test Sample originally placed in the mold is used to obtain the volume of the Test Sample that is actually tested. This is calculated because some of the material may have been left within the mold. Thus, Test Sample Volume is represented by:
Test Sample Volume=((MoldFull−MoldEmpty)/(MoldFull−MoldTare))×VMold (Equation 10).
The total mass of water lost during the test corresponds to the difference between the mass of the Test Sample in the Testing Container (TC) and the mass of the Testing Container with the dry Test Sample. The total mass of water loss is represented as:
Water Loss Mass=TCfresh−TCDry (Equation 11).
The total mass of water lost during the test represents the total water in the Test Sample including the water contributed or absorbed by the coarse and fine aggregates. If the Test Sample is part of a larger batch, then a scale factor will aid in reducing the material weights of the larger batch to the volume of the Test Sample in the mold. This scale factor is identified as:
Volume Ratio=Test Sample Volume/Absolute Volume Batch (Equation 12).
Thus, Volume Ratio=Eq. 10 divided by Eq. 5. Multiplying the batch weight of a component by the Volume Ratio will represent the weight in the Test Sample for that component.
Thus, the Volume Ratio may be used to determine the weight of the binder, i.e. cement, in the Test Sample based on the corresponding Absolute Volume Batch used to prepare the Test Sample. Therefore, the amount of binder in the Test Sample can be determined by the following equation:
MoldBinder=Volume Ratio * MBinder (Equation 13)
Where MoldBinder is the mass of binder in the Test Sample. Further, if the Test Sample is a portion of a larger batch of concrete mixture, then the Volume Ratio will also be used to calculate the total water absorbed (MoldWaterAbs) in the Test Sample. The calculation of MoldWaterAbs is represented by:
MoldWaterAbs=Volume Ratio×Total Absorbed Water; or, (Equation 14)
MoldWaterAbs=Equation 12×Equation 8.
Having identified the variables and characteristics of the concrete mixture used to prepare the Test Sample, the method of testing to determine the w/cm can be described. Prior to preparing the Test Sample, the mass and volume of the empty mold to be used are recorded. The mold is filled with fresh concrete mixture to provide the Test Sample. After filling the mold, the mold with the Test Sample is weighed. Following weighing of the mold with the Test Sample, the Test Sample is removed from the mold and placed in a container suitable for heating (Testing Container). After emptying of the mold, the mold is weighed again to ensure that the final weight of the empty mold is within 10 g of the mold prior to filling with the concrete mixture. If the weight variance is within the 10 g tolerance, then the volume of the Test Sample can be determined by Equation 10.
The Test Sample in the Testing Container should have a uniform thickness. According to the present method, the Test Sample should be formed into a uniform thickness between about 6 mm and about 32 mm. The width and length of the Test Sample will be determined by the furnace or other heating device selected for use in the test. Typically, the Test Sample should have a thickness between about 6 mm and about 32 mm, a width between about 200 mm and about 300 mm and a length between about 350 mm and about 450 mm. Preferably, the thickness of the Test Sample will be between 15 mm and 23 mm.
The mass of the Testing Container and the Test Sample is recorded. Then, the Testing Container is placed within an oven or otherwise subjected to heating under a heating element or with the Testing Container sitting on the heating element. Typically, when heating the Testing Container in an oven, the oven will be preheated to a temperature between about 700° C. and about 900° C. More preferably, the oven will be preheated to a temperature between about 800° C. and 830° C.
The actual temperature of heating is not critical to the current method. Rather, complete loss of water is determined by weighing of the Testing Container with the Test Sample. Accordingly, use of a preheated temperature between 100° C. and 1400° C. will reduce the length of the time required to remove all water from the Test Sample. When operating at the higher temperatures, the sample will need to be removed before the aggregates decompose.
The Test Sample is considered to be dry, i.e. free of water, when the weight difference between successive two-minute readings is less than two grams. Upon determination of the complete loss of water based on the two-minute weight readings, the final mass of the Testing Container and Test Sample are recorded. Typically, when heating within an oven, the test time will require about 10 minutes to 20 minutes. More commonly, performing the test in an oven will require about 12 minutes.
When carrying out the test using one or two heating elements, the method does not have a time limit. Rather, the Testing Container can be left on or under the heating element(s) and subsequently weighed at any time after about 30 minutes. This allows other tasks to be performed during the testing and do not have to be immediately measured when all of the water is removed. This is discussed in more detail later in the document.
Following removal of water by heating, the w/cm can be calculated. The weight loss after heating represents the total water loss from the Test Sample, including absorbed water in the aggregates (fine and coarse). Thus, to determine the water content or w/cm the calculation must account for water that should be part of the aggregate. Total water loss mass minus the aggregate absorbed water (AbsCoarse+AbsFine) mass represents the adjusted water loss. Thus, the method for determining the w/cm will also provide the total water content and the adjusted water content in the Test Sample and provides the ability to determine the total water in the batch. The w/cm can then be determined by subtracting the MoldWaterAbs mass from the total water loss mass and dividing by Mold binder mass. Thus, the equation for the measured w/cm is:
Measured w/cm=(Water Loss Mass−MoldWaterAbs)/(MoldBinder) (Equation 15).
Equation 15 can also be represented by: Measured w/cm=(Eq. 11−Eq. 14)/Eq. 13. The measured w/cm is a result of the test method described above. The measured w/cm can be compared with the w/cm of the batch of concrete (Batch w/cm) used to prepare the Test Sample. The Batch w/cm is calculated by dividing the MWater by MBinder. The total water loss may also be a useful measure in this test as a method of quality control.
In an alternative embodiment, the method can be carried out using an oven with an integrated scale. When heating the Test Sample with an oven or other heating element having the ability to monitor Test Sample weight in real-time, the operating temperature can be increased to temperatures greater than the decomposition temperatures of the components making up the concrete in order to reduce testing time. By continuous monitoring of the Test Sample weight, one can determine the complete loss of water from the Test Sample prior to the individual components of the Test Sample undergoing decomposition due to excessive heat. The temperature and rate of thermal decomposition of concrete components are well known as evidenced by the following:
Additionally,
To determine the permissible time period for heating of a sample, a limestone 1 concrete mixture was tested within an oven at a temperature of 815° C. As reflected by
Thus, with knowledge of the decomposition time for the aggregate and other components within the concrete batch, one can determine the w/cm and water content at temperatures greater than the decomposition temperature of the concrete batch components. In order to practice the high temperature w/cm and/or water content analysis, a high temperature oven or other heating device and scales compatible with the same will be required. During heating to remove water from the Test Sample, the weight will be constantly monitored and recorded. As reflected by
The degree of hydration is a measure of the extent of the reactions between the cementitious materials and the water. The degree of hydration is defined as the ratio of the amount of reacted binder divided by the amount of binder added during mixing. The degree of hydration is a useful parameter because it indicates the amount of reaction that has taken place. Additionally, the degree of hydration corresponds to the amount of heat given off or the development of physical properties like the change in stiffness, strength, or decrease in porosity of the concrete. Further, the degree of hydration is proportional to the amount of water that has reacted with cement and is no longer available for reaction or evaporation. The water that is no longer available is known as bound water.
The most common techniques to determine the degree of hydration include measuring a parameter at a certain point in the reaction and comparing it to either the theoretical total amount or a measured amount from a mature sample. Some methods to do this include measuring: the total heat of hydration, the amount of chemically combined water, the amount of calcium hydroxide present in the paste, the specific gravity of the cement paste, the surface area of the cement paste, the amount of anhydrate cement present in the paste, the strength development or maturity, and the dielectric properties of the concrete. Other methods may also exist.
In this work, the degree of hydration will be determined by first estimating the total amount of heat released by the full reaction of the binder. The total heat of hydration for Portland cement can be quantified by the following equation:
Hcem=500×C3S+260×C2S+866×C3A+420×C4AF+624×SO3+1186×FreeCaO+850×MgO (Equation 16)
Where Hcem is the total heat of hydration of the binder (J/g). The other variables in Equation 16 are the weight ratio for each compound in the Portland cement binder. These compounds are abbreviated with cement chemistry shorthand where C3S is tricalcium sililcate, C2S is dicalcium silcate, C3A is tricalcium alumiate, and C4AF is calcium alumino ferrite. Thus, for example, as used in Equation 16, C3S represents the weight ratio of tricalcium sililcate. Other equations exist to determine the total heat of hydration for different binders that one skilled in the art will recognize and be able to apply in the described method.
The total heat of hydration can then be compared to the measured total heat at any given time during the reaction of the mixture to obtain the degree of hydration at that point in time. This can be expressed mathematically as:
Where H(t) is the cumulative heat of hydration released at time t (J/g) and Hcem is the total heat of hydration of the binder (J/g).
Test Results
The foregoing method has been tested using a combination of heating elements with one heating element located above the Testing Container housing the Test Sample and a second heating element under the Testing Container. This configuration of heating elements is referred to herein as Configuration 1. In the following test results, the heating element located above the Testing Container was operated at a temperature of about 700° C. The heating element on which the Testing Container rested was operated at its maximum output of 1500 Watts. The Testing Container had a diameter of 23 cm with a depth of 8 cm.
Configuration 1 was initially tested using 231 lab mixtures of concrete as reported in Table 1 below.
In Table 1, the average for the column Difference Batched and Measured was 0.001. Accordingly, very little difference exists, on average, between batched and measured w/cm. The average standard deviation for all measured w/cm for the 231 mixtures is 0.012 for w/cm between 0.36 and 0.48 for a variety of different materials. The average coefficient of variation (COV) for all the tests is 3.0%. Thus, the method for determining the w/cm of fresh concrete is highly accurate. Further,
Configuration 1 was also tested in the field. Table 2, provided below, contains the test results for the field tests. The standard deviation and COV values were based on two samples taken and tested per truck.
The data from Table 2 compares favorably to the data obtained from the laboratory test samples. In particular, the average standard deviation for Table 2 is 0.010 which is very close to the 0.012 standard deviation of Table 1. Further, the COV for Table 2 is 1.2% which is actually lower than the 3.0% obtained in Table 1. While the field testing used fewer samples, the results are clearly favorable and reflect the degree of accuracy necessary for use in the field to ensure the desired w/cm.
Table 3 below demonstrates the potential usefulness of the new method for testing the w/cm. In view of the lack of a testing method for fresh concrete, current specifications limit maximum slump of concrete to 18 cm over concerns of excess water. In this instance, batch samples from Trucks 6 and 7 experienced slump greater than the accepted limit. However, after testing both samples using the new field method for determining w/cm, the sample from Truck 7 was found to be within the acceptable w/cm range. Thus, the new method for testing the w/cm can reduce the number of rejected concrete loads while more accurately identifying those loads that fail to meet specifications.
Table 4 provided below provides the characteristics of the concrete for each sample Truck.
The method has also been tested by placing the Testing Container with Test Sample in an oven. The oven method is referred to as Configuration 2. The oven was set to operate at a maximum temperature of 815° C. For the purpose of the test results, a pan having a depth of 4.4 cm, a length of 22.9 cm and a width of 17.8 cm served as the Testing Container. The oven applied heat to the top and bottom of the Testing Container/Test Sample.
To evaluate Configuration 2, 133 samples were tested. For testing of Configuration 2, both pastes and concretes were evaluated. As reflected by Table 5, the concrete mixtures use Limestone 1 and Natural Sand 1.
As reflected by Table 5, the average standard deviation for all measured w/cm is 0.009 for w/cm having values between 0.30 and 0.60. The average coefficient of variation (COV) for all 133 tests is 1.8%. This shows the test is precise and accurate, regardless of the test setup.
Further evidence of the accuracy of the described method for determining the w/cm is provided in Table 6 and
To determine the desired minimum and maximum sample volume range suitable for the Test Samples multiple tests were carried out on Test Samples having a w/cm of 0.45. Nine samples of varying volumes were tested as reported in Table 7 below. Based on the results reported on Table 7, the disclosed method can be practiced on Test Samples having as little as 1200 cm3 and as much as 7000 cm3. In most instances, Test Samples will have volumes between about 1200 cm3 and about 6000 cm3. The preferred volume range may vary depending on the heating apparatus available and the Test Container used. However, preferred test volumes will generally be between about 1600 cm3 and about 1900 cm3. For comparison, the sample volume commonly used for the microwave oven test method is 694 cm3 according to AASHTO T318 test method.
Finally, for completeness of data, Table 8 provides analysis of the oxides in the binder used during the laboratory testing and Table 9 below provides information on the aggregates used during laboratory testing.
While Configurations 1 and 2 have been described for the heating portion of the described method, other configurations can be used to heat and remove water from the Test Sample. For example, Configuration 1 may be modified by removing either the heating element positioned above the Test Sample of the hot plate on which the Testing Container may be removed. Likewise, other oven configurations may be used in place of the oven described in Configuration 2.
Other embodiments of the present invention will be apparent to one skilled in the art. As such, the foregoing description merely enables and describes the general uses and methods of the present invention. Accordingly, the following claims define the true scope of the present invention.
The present application claims priority to U.S. Provisional Application No. 62/879,965 filed on Jul. 29, 2019.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5520730 | Barbour | May 1996 | A |
| 6347131 | Gusterson | Feb 2002 | B1 |
| 9278888 | Al-Mutlaq | Mar 2016 | B1 |
| 20130052452 | Lee | Feb 2013 | A1 |
| Number | Date | Country |
|---|---|---|
| 102016204332 | Oct 2017 | DE |
| 0376865 | Jul 1990 | EP |
| Entry |
|---|
| ASTM C566-13 “ Standard Test Method for Total evaporable Moisture content of aggregate by Drying” (Year: 2013). |
| Abrams, Duff A., Design of Concrete Mixtures, Structural Materials Research Laboratory, Lewis Institute, May 1919, pp. 1-25. |
| Concrete Manual—A Water Resources Technical Publication, U.S. Dept. of the Interior Bureau of Reclamation, 8th Edition, 1981, Reprinted 1988, pp. 34-39. |
| Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete, ACI Committee 211.1-91, American Concrete Institute Farmington Hills, 1991, pp. 1-38. |
| Bentz, Evan C., Probabilistic Modeling of Service Life for Structures Subjected to Chlorides, Materials Journal, Title No. 100-M44, Sep.-Oct. 2003, pp. 391-397. |
| Howdyshell, P.A., Revised Operations Guide for a Chemical Technique to Determine Water and Cement Concrete of Fresh Concrete, Construction Engineering Research Laboratory, Technical Report M-212, Apr. 1977, pp. 1-38. |
| Whiting, David et al., Laboratory Evaluation of Nuclear Gage for Measurement of Water and Cement Content of Fresh Concrete, ACI Materials Journal, Technical Paper, Title No. 96-M15, 1999, pp. 101-108. |
| Mancio, Mauricio et al., Instantaneous In-Situ Determination of Water-Cement Ratio of Fresh Concrete, ACI Materials Journal, 107(6), 2010, pp. 1-25. |
| Wei, Xiaosheng et al., Early Hydration Process of Portland Cement Paste by Electrical Measurement, Journal of Materials in Civil Engineering, 2006, pp. 99-105. |
| Standard Method of Test for Water Content of Freshly Mixed Concrete Using Microwave Oven Drying, American Association of State Highway and Transportation Officials (AASHTO), 2015, pp. 1-6. |
| Bickley, John et al., Preparation of a Performance-Based Specification for Cast-in-Place Concrete, RMC Research Foundation, Jan. 2006, pp. 14-18. |
| Standard Specification for Portland Cement, ASTM Int'l, C150/C150M-19a, 2019, pp. 1-10. |
| Standard Specification for Concrete Aggregates, ASTM International, C33/C33M-16, 2016, pp. 1-11. |
| Osmatka, Steven H et al., Design and Control of Concrete Mixtures, 14th Edition, Portland Cement Association, 2002, pp. 1-370. |
| Ley, Tyler M. et al., Determining the Air-Void Distribution in Fresh Concrete with the Sequential Air Method, Construction and Building Materials, 2017, pp. 723-737. |
| Standard Test Method for Total Evaporable Moisture Content of Aggregate by Drying, ASTM International, 2013, pp. 1-3. |
| Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete, ASTM International, 2017, pp. 1-6. |
| Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method, ASTM International, 2017, pp. 1-10. |
| Mehta, P. Kumar et al., Concrete Microstructure, Properties, and Materials, Third Edition, McGraw-Hill, 2006, pp. 1-684. |
| Standard Practice for Sampling Freshly Mixed Concrete, ASTM International, 2017, pp. 1-3. |
| Standard Practice for Making and Curing Concrete Test Specimens in the Field, ASTM International, 2017, pp. 1-6. |
| Standard Method of Test for Surface Resistivity Indication of Concrete's Ability to Resist Chloride Ion Penetration, AASHTO, TP95-11, 2011, pp. 1-9. |
| Standard Specifications, Oklahoma Dept. of Transportation (ODOT), 2009, pp. 1-805. |
| Standard Test Method for Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration, ASTM International, 2019, pp. 1-8. |
| Schindler, Anton K. et al., Heat of Hydration Models for Cementitious Materials, ACI Materials Journal, Title No. 102-M04, 2005, pp. 24-33. |
| Standard Test Method for Asphalt Content of Asphalt Mixture by Ignition Method, ASTM International, 2019, pp. 1-5. |
| Number | Date | Country | |
|---|---|---|---|
| 62879965 | Jul 2019 | US |
