FIELD OF THE INVENTION:

The present invention relates to a process and a device for preparing a dry concrete mixture.

BACKGROUND OF THE INVENTION

At the present time, for construction work involving a substantial volume of concrete, the contractor usually purchases ready mixed concrete which is prepared by a Supplier, the mixture being delivered in mixing trucks which agitate the plastic concrete in transit for direct pouring at the job. In other cases, the contractor purchases the sand, aggregate, and cement and mixes them together with water in suitable equipment at the job, then pours the concrete.

Also, are available dry concrete mixtures, which contain cement, sand, coarse aggregate and supplementary cementitious material and other additives in dry, mixed and packaged condition, so that the only thing the purchaser is required to do is to mix the contents of the package with water to obtain concrete.

Some of the materials used for preparing the dry concrete mixture may be in moist condition when shipped from the source of supply. Some of the materials may require washing with water to remove impurities before being taken up for preparing the dry concrete mixture.

By way of example, under normal conditions, the sand may contain uptol2 percent surface moisture by weight. Coarse aggregate (due to their large size) can retain as much as 2 percent surface moisture by weight. In addition to surface moisture, the particles also contain absorbed internal moisture, the amount of which varies from one material to another in accordance with the physical characteristics of the material and the prevailing environmental conditions. By way of example, natural limestone particles usually comprise approximately 1-2 percent of absorbed moisture by weight. Other materials vary from this plus or minus.

Presence of moisture (surface as well as internal) therefore presents a problem in preparing ready- mixed concrete (RMC) even though appropriate moisture corrections are adopted. This is usually so because the moisture contents measured in the aggregate stockpiles are never representative of the actual moisture contents of the material, at various locations of the stockpile. Hence, the corrections thus adopted are always misrepresentative. The system and process which allows production of ready- mix concrete in RMC plants can never guarantee the accuracy or precision to which such moisture corrections can be adopted. However, in the preparation of dry concrete mixture, the materials must be dried thoroughly before mixing and packaging, otherwise, the mixture will hydrate when the moist ingredients are combined with the cement. To summarize, the following challenges are faced while making the dry concrete mixture:

• Since the dry concrete mixture contains different materials, each material may contain different amount of moisture.

• Many of the materials (such as sand, gravel, fly ash, etc.) are procured from local sources and their moisture contents are subject to substantial variation, for example, substantial variation may be found between a first batch of the material and a second batch of the material.

• Many of the materials (such as sand, gravel, etc.) are hygroscopic in nature in that they absorb moisture from the environment. The material storage system may not be specially adapted to prohibit the materials stored therein from absorbing moisture from the environment. Thus, each material, based on factors such as the amount of time for which the material is stored, absorption capacity, the current environmental conditions, etc. may contain different amount of moisture. Because of the above, the quality of the product gets substantially affected.

While in the past, the materials were dehydrated prior to preparing the dry concrete mixture, a constant process of dehydrating was adopted. The constant process of dehydrating did not cater to the challenges mentioned above and because of the same, the process of producing the dry concrete mixture was effected in terms:

• as all raw materials will not have the same amount of moisture and same capability to absorb moisture if all raw materials are subjected to a constant heating process, it can lead to the partial disintegration of the raw material;

• the quality of the dry concrete mixture thus produced;

• the amount of energy consumed for producing the dry concrete mixture;

• the cost involved in producing the dry concrete mixture; etc.

Apart from the above, there has been a recommendation to measure the moisture level by providing an online moisture sensor system that continuously monitors changes in the moisture levels in the raw materials. However, such online moisture sensor systems are complicated, must be calibrated and checked regularly, and are expensive thus, increasing the overhead costs.

Further, even after completely dehydrating all the hygroscopic materials, they have a tendency to immediately start absorbing moisture from the environment, which increases over time. Hence, it is essential to determine the behavior of such materials, and a time limit under which the materials may be allowed to be stored in a temporary storage area after the dehydration process, before the packing of the individual material or the group of materials is completed in a moisture-proof packing system. Thus, there exists a need to provide a simple but accurate method for preparing and packaging of dry mix construction material to eliminate one or more disadvantages as mentioned above.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in a simplified format that is further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention and nor is it intended for determining the scope of the invention.

Broadly speaking, the present invention adopts a method of accurately estimating the moisture that may be absorbed in the raw material used for preparing e dry concrete mix. The estimation may be done prior to the process of preparation or during the process of preparation. Based on the estimated moisture content, the invention provides for controlling one or more parameters pertaining to the preparation of the dry concrete mixture and/or at least one parameter involved in the packaging of the dry concrete mixture.

In an aspect of the invention there is provided a process for preparing and packaging of dry mix construction material, said process comprising the steps of: determining a rate of moisture absorption of a raw material (MARx) used for preparing the dry mix construction material, the rate of moisture absorption being in relation to a prevailing environment condition; and controlling, based on the rate of moisture absorption thus determined, at least one parameter pertaining to preparing and packaging of dry mix construction material.

In an aspect of the invention, there is provided the process as described herein, wherein the rate of moisture absorption of the raw material (MARx) in relation to the prevailing environment condition is determined based on the closest match of the prevailing environmental condition with at least one pre stored environmental condition.

In an aspect of the invention, there is provided the process as described herein, wherein the rate of moisture absorption of the raw material (MARx) in relation to the prevailing environment condition is determined based on a mathematical prediction model.

In an aspect of the invention, there is provided the method as described herein, wherein based on a mathematical model, an expected amount of moisture content in the dry mix construction material is determined. In an aspect of the invention there is provided the method as described herein, wherein at least one parameter pertaining to preparing and packaging of dry mix construction material is controlled under any of the following conditions: if the expected amount of moisture content in the dry mix construction material (M) is above a corresponding preset threshold value; and/or if the moisture absorbed by a raw material (Rx) is above a corresponding preset threshold value.

The invention furthermore provides a device that may be used for preparing and packaging of dry mix construction material. The device comprises a moisture absorption rate determining module for determining a rate of moisture absorption of a raw material (MARx) used for preparing the preparing the dry mix construction material, the rate of moisture absorption being in relation to a prevailing environment condition. The device may additionally comprise a controlling module for controlling, based on the input from moisture absorption rate determining module, at least one parameter pertaining to preparing and packaging of dry mix construction material.

These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The detailed description is described with reference to the following figures. It should be noted that the description and figures are merely examples of the present subject matter and are not meant to represent the subject matter itself.

FIGURE 1 demonstrates a system 100 for controlling, based on the rate of moisture absorption, at least one parameter pertaining to preparing and packaging of dry mix construction material, in accordance with an example implementation of the present subject matter.

FIGURE 2 illustrates a process for preparing and packaging of dry mix construction material, in accordance with an example implementation of the present subject matter.

FIGURE 3 illustrates a process for determining the rate of moisture absorption of a raw material (MARx) used for preparing the preparing the dry mix construction material, in accordance with an example implementation of the present subject matter. FIGURE 4 illustrates a process for controlling at least one parameter pertaining to preparing and packaging of dry mix construction material, by determining the extent of moisture absorption, in accordance with an example implementation of the present subject matter.

FIGURE 5 depicts the rate of absorption of different raw materials at a temperature of 45°C and humidity of 30%, in accordance with an example implementation of the present subject matter.

FIGURE 6 depicts a device that may be used for preparing the dry mix construction material in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

Dry ready mixed construction material provides several advantages in construction work including providing quality control assurance and reducing the time taken to undertake construction work among others. The use of such ready to use materials saves construction companies from the task of procuring the separate components and designing and mixing them to form the construction mix.

In order for dry concrete mixes to be used effectively, an adequate amount of water needs to be added only at the time of preparation of the concrete which depends largely on the moisture content of components of the dry concrete mix. The moisture content varies among the concrete mix components and is also significantly affected by the prevailing atmospheric conditions. If the moisture content is estimated to be either lower or in excess of the determined absorption value of the aggregates/hygroscopic materials, it would alter the water-to-binder ratio as well as the aggregate/binder ratio of the concrete mix. Altering any of the above parameters affects the workability, pumpability, strength, and durability of the concrete mix.

Therefore it is necessary to estimate and control the moisture levels in the concrete components under the prevailing atmospheric conditions, in order to package the dry construction material with permissible moisture levels and prevent batch-to-batch variability.

The present invention relates to a process for determining the moisture levels in dry mix construction material and controlling the mixing and packaging parameters to ensure reduced moisture levels in the dry concrete mix.

For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are collected here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

The terms“dry concrete mix”,“dry construction mix”,“dry ready-mixed construction material”, “concrete” are to be used interchangeably.

The term “concrete” refers to a composition comprising cement, aggregates and optionally supplementary cementitious material.

The term“raw material” refers to the separate constituents of a concrete mix comprising cement, aggregates, and optionally supplementary cementitious material used to prepare the dry concrete mix.

The articles“a”,“an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

The terms“comprise” and“comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as“consists of only”.

Fig. 1 demonstrates a system 100 comprising components for preparing dry concrete mix. The system 100 comprises a computer 102 for controlling the process of weighing, mixing, and packaging the raw material 104 and/or the dry construction mix 112. The raw material 104 is mixed in the required proportions in the mixing unit 106 to obtain the dry construction mix 112 and then packaged in the packaging unit 108. In an example implementation, the computer 102 includes a processor(s) 110. The processor(s) 110 may be implemented as microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, the processor(s) 110 may fetch and execute computer-readable instructions stored in a memory coupled to the processor(s) 110 of the computer 102. The memory can be internal or external to the computer 110. The memory may include any non-transitory computer-readable storage medium including, for example, volatile memory (e.g., RAM), and/or non-volatile memory (e.g., EPROM, flash memory, NVRAM, memristor, etc.). The functions of the various elements shown in Fig. 1, including any functional blocks labeled as“processor(s)”, may be provided through the use of dedicated hardware as well as hardware capable of executing computer-readable instructions.

In accordance with the present invention, the raw materials 104 comprise the components required to prepare the dry mix construction material consisting essentially of cement, aggregate, and supplementary cementitious material. For example, raw material 1 includes aggregate comprising rock, sand, crushed stone, gravel, and combinations thereof. Raw material 2 includes cement comprising Ordinary Portland Cement (OPC), Portland Pozzolana Cement (PPC), Rapid Hardening Cement, Quick setting cement, Low Heat Cement, Sulphates resisting cement, Blast Furnace Slag Cement, High Alumina Cement, White Cement, Coloured cement, Air Entraining Cement, Expansive cement, Hydrographic cement, and combinations thereof. Raw material 3 includes aggregate comprising sand. Raw material 4 includes supplementary cementitious material comprising Fly Ash, Ground Granulated Blast Furnace Slag (GGBFS), silica fume, natural pozzolans, and combinations thereof.

In an example implementation of the present invention, the system 100 comprises an oven heater. The oven heater may be used to heat or remove moisture from raw materials 104. The oven heater may also be used to heat or remove moisture from the dry construction mix 112.

Fig 2 demonstrates the process steps for determining the rate of moisture absorption of raw material and controlling, based on the rate of moisture absorption thus determined, at least one parameter pertaining to preparing and packaging of dry mix construction material, in accordance with an implementation of the present invention. The rate of moisture absorption is dependent on the prevailing atmospheric conditions including temperature, and humidity among others. In one implementation, the rate of moisture absorption of the raw material 104 is determined based on the closest match of the prevailing environmental condition with at least one pre -stored environmental condition. This is exemplified in Fig. 5 which shows the data set for moisture absorption rate at various moisture levels at a temperature of 45°C. If the prevailing temperature and humidity conditions match at least one data point in the dataset, the corresponding rate of moisture absorption can be determined accordingly.

In another implementation of the present invention, the prevailing conditions are not present in a data set with the pre -determined absorption rate at specific environmental conditions. In such a case, the rate of moisture absorption of the raw material (MARx) in relation to the prevailing environment condition is determined based on a mathematical prediction model. The mathematical prediction model is based on at least two pre-stored values of rate of moisture absorption of the raw material, the two pre-stored values corresponding to two different environmental conditions, preferably two extremes, representing the highest and the least probable rates of moisture absorption, for a known set of raw materials.

The mathematical prediction model comprises best-fit interpolation model or a best-fit extrapolation model. The model comprises linear regression based prediction model, exponential regression-based prediction model, polynomial regression-based prediction model, logarithmic regression-based prediction model, power regression-based prediction model, and combinations thereof.

In accordance with the present invention, the rate of moisture absorption of the raw material for the prevailing conditions is determined by the closest match of the prevailing environmental condition with at least one pre-stored environmental condition or a mathematical prediction based model. The rate of moisture absorption is then used to calculate the moisture absorbed by the raw material 104 during the processing of the raw material 104 into dry construction mix 112 and the packaging of the dry construction mix 108. The moisture absorbed by a raw material is determined as:

Rx = (MARx* Tx) + Initial Moisture Content in the raw material;

wherein Rx is the moisture absorbed by a raw material;

MARx is the moisture absorption rate of the raw material; and

Tx is the time period for which the raw material will be processed.

In one implementation of the present subject matter, the initial moisture content of each raw material 104 is determined by moisture detection probes which may be controlled and analyzed using the computer 102. In another implementation, the initial moisture content is presumably zero in almost all cases in a dry mix concrete production operational system, since all hygroscopic materials are subject to dehydration, bringing them to bone dry conditions prior to packing and temporary storage. The initial moisture content may also be determined using standardized tests for determining moisture levels, calculating the (rate of moisture absorption x time exposed to prevailing moisture conditions), and estimating the water absorbed by subtracting the weight of the oven-dried raw material sample from the moisture absorbed raw material sample.

In accordance with the present invention, the expected amount of moisture content in the dry mix construction material is calculated using a mathematical model that is determined by:

M = [(W1*R1) + (W2*R2) + (W3*R3) + . + (Wn*Rn)]

wherein:

M is moisture in the dry construction material;

Rl is the moisture absorbed by raw material-l;

R2 is the moisture absorbed by raw material-2;

R3 is the moisture absorbed by raw material-3;

Rn is the moisture absorbed by raw material-n;

Wl is the weight of raw material-l in the dry mix construction material;

W2 is the weight of raw material-2 in the dry mix construction material;

W3 is the weight of raw material-3 in the dry mix construction material; and

Wn is the weight of raw material-n in the dry mix construction material. Fig. 4 illustrates the process steps for controlling at least one parameter pertaining to preparing and packaging of dry mix construction material. The moisture absorbed by the raw material 104 and the expected amount of moisture in the dry concrete mix are determined by the process steps as described herein. If the moisture content in the raw material 104 exceeds a preset threshold value, then at least one parameter pertaining to preparing and/or packaging the raw material 104 is controlled. If the expected amount of moisture in the dry concrete mix exceeds a preset threshold value, then at least one parameter pertaining to preparing and packaging the dry concrete mix is controlled, in accordance with an implementation of the present invention.

The moisture level in the dry concrete mix 112 or the raw material 104 is controlled by adjusting one or more parameters comprising: a time involved in preparing the dry concrete mixture; a time involved in packaging the dry concrete mixture; a time involved in transporting of the raw materials to a dry concrete mixture preparation location, a time involved in transporting the dry concrete mixture to a dry concrete mixture packaging location; a need to heat the dry mix construction material or a raw material for preparing the dry mix construction material; a need to heat the dry mix construction material or a raw material for preparing the dry mix construction material; a time period for heating the dry mix construction material or a raw material for preparing the dry mix construction material; and a temperature to which the dry mix construction material or a raw material for preparing the dry mix construction material is to be heated.

Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. The disclosure will now be illustrated with working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices, and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may vary.

In an example implementation, the raw materials comprising cement, crushed stone, sand, and fly ash are used to prepare the dry concrete mix. The prevailing conditions are determined to a temperature of 45°C and a humidity of 30%. The rate of humidity is then interpolated using linear regression based prediction model from the dataset as shown in Fig. 5. Once the rate of moisture absorption is determined for each raw material, the moisture absorbed by each raw material is determined from the mathematical formula:

Rx = (MARx* Tx) + Initial Moisture Content in the raw material;

wherein Rx is the moisture absorbed by a raw material;

MARx is the moisture absorption rate of the raw material;

Tx is the time period for which the raw material will be processed.

Rx for each of the raw materials is found not to exceed the threshold permissible moisture levels for each material and therefore parameters are not adjusted for the processing of the raw material.

The expected moisture content of the dry mix construct material is then calculated using the mathematical formula:

M = [(Wl*Rl) + (W2*R2) + (W3*R3) + . + (Wn*Rn)]

wherein:

M is moisture in the dry construction material;

Rl is the moisture absorbed by raw material-l;

R2 is the moisture absorbed by raw material-2;

R3 is the moisture absorbed by raw material-3;

Rn is the moisture absorbed by raw material-n;

Wl is the weight of raw material-l in the dry mix construction material;

W2 is the weight of raw material-2 in the dry mix construction material;

W3 is the weight of raw material-3 in the dry mix construction material; and

Wn is the weight of raw material-n in the dry mix construction material.

The expected moisture content of the dry mix construction material is determined to be higher than the threshold permissible moisture levels.

Therefore, the temperature to which the dry mix construction material is heated is extended to adjust for the increase in the moisture levels in the dry mix construction material.

Alternatively as a system correction, the time elapsed between the attainment of bone-dry condition of all the hygroscopic materials, to the time they are packed in moisture proof bags, either in isolation or in weighted average combination, is fine-tuned to such levels, that the combined moisture content does not exceed the threshold permissible moisture levels. This accounts for a thorough investigation of all the sub-processes involved in the total process and modifying them to a JUST IN TIME module. The corrective process may also be a combination of the above-mentioned processes.

Overall, the present invention provides a method whereby the quality, durability, and stability of dry construction material are substantial, improved, especially towards reaching zero standard deviation in the quality parameters. This is achieved by the precise calculation of the moisture levels in the raw material to prepare the dry construction mix and the expected moisture level in the dry construction mix. The precise calculation is obtained through the mathematical models of the present invention which correlate the prevailing atmospheric conditions with the rate of moisture absorption, to predict the expected rate of moisture absorption. Based on the moisture level findings, one or more parameters of the processing of the raw material into concrete and packaging of the dry concrete mix is adjusted to reduce the moisture levels.

Referring to Figure 6, there is illustrated a block diagram of a device 500 that may be used for preparing and packaging of dry mix construction material. The device 500 comprises a moisture absorption rate determining module 502 for determining a rate of moisture absorption of a raw material (MARx) used for preparing the preparing the dry mix construction material, the rate of moisture absorption being in relation to a prevailing environment condition; and a controlling module 504 for controlling, based on the input from moisture absorption rate determining module 502, at least one parameter pertaining to preparing and packaging of dry mix construction material.

In an embodiment of the invention, the device 500 further comprises an environmental condition sensing module 506 for determining the prevailing environmental condition.

In an embodiment of the invention, the moisture absorption rate determining module 502 may further include a storage device 508 storing thereupon plurality of pre-stored environmental conditions in mapped relation with rates of moisture absorption of the raw material (MARx); and a selection module 510 for selecting the rate of moisture absorption of the raw material (MARx) in relation to the prevailing environment condition based on a closest match of the prevailing environmental condition with at least one pre-stored environmental condition.

In another embodiment of the invention, the moisture absorption rate determining module 502 may further include a mathematical prediction model implementing module 512 adapted to determine the rate of moisture absorption of the raw material (MARx) in relation to the prevailing environment condition based on a mathematical prediction model.

In another embodiment of the invention, the mathematical prediction model implementing module 512 is adapted to implement a best-fit interpolation model or a best-fit extrapolation model. In another embodiment of the invention, the mathematical prediction model implementing module 512 is operatively coupled to a storage device 508 and is adapted to determine the rate of moisture absorption of the raw material (MARx) based on at least two pre-stored values of rate of moisture absorption of the raw material, the two pre-stored values corresponding to two different environmental conditions.

In another embodiment of the invention, the mathematical prediction model implementing module 512 is adapted to implement at least one of linear regression based prediction model, exponential regression-based prediction model, polynomial regression-based prediction model, logarithmic regression-based prediction model, and power regression-based prediction model.

In another embodiment of the invention, the device 500 may further comprise a calculating module 514 operatively coupled to the moisture absorption rate determining module 502 for determining an expected amount of moisture content in the dry mix construction material.

In still another embodiment of the invention, the calculating module 514 is adapted to calculate the expected amount of moisture content in the dry mix construction material based on:

M = [(W1*R1) + (W2*R2) + (W3*R3) + . + (Wn*Rn)]

wherein:

M is moisture in the dry construction material;

Rl is the moisture absorbed by raw material- 1;

R2 is the moisture absorbed by raw material-2;

R3 is the moisture absorbed by raw material-3;

Rn is the moisture absorbed by raw material-n;

Wl is the weight of raw material- 1 in the dry mix construction material;

W2 is the weight of raw material-2 in the dry mix construction material;

W3 is the weight of raw material-3 in the dry mix construction material; and

Wn is the weight of raw material-n in the dry mix construction material.

In another embodiment of the invention, the calculating module 514 is adapted to calculate moisture absorbed by a raw material based on:

Rx = (MARx* Tx) + Initial Moisture Content in the raw material

wherein Rx is the moisture absorbed by a raw material;

MARx is the moisture absorption rate of the raw material;

Tx is the time period for which the raw material will be processed. In another embodiment of the invention, the device 500 may further comprise a detecting nodule (516) for detecting the initial moisture content in the raw material.

In another embodiment of the invention, the controlling module 504 is adapted to control at least one parameter pertaining to preparing and packaging of dry mix construction material on basis of the expected amount of moisture content in the dry mix construction material.

In another embodiment of the invention, the controlling module 504 is adapted to control at least one parameter pertaining to preparing and packaging of dry mix construction material under any of the following conditions:

• if the expected amount of moisture content in the dry mix construction material (M) is above a corresponding preset threshold value; and/or

• if the moisture absorbed by a raw material (Rx) is above a corresponding preset threshold value.

In another embodiment of the invention, the at least one parameter pertaining to preparing and packaging of dry mix construction material is selected from a group comprising of:

a. a time involved in preparing the dry concrete mixture;

b. a time involved in packaging the dry concrete mixture;

c. a time involved in transporting of the raw materials to a dry concrete mixture

preparation location;

d. a time involved in transporting the dry concrete mixture to a dry concrete mixture packaging location;

e. a need to heat the dry mix construction material or a raw material for preparing the dry mix construction material;

f. a time period for heating the dry mix construction material or a raw material for preparing the dry mix construction material; and

g. a temperature to which the dry mix construction material or a raw material for

preparing the dry mix construction material is to be heated.

While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.