Description:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of construction materials engineering, and in specific relates to a zoning-controlled gradation process for producing concrete-grade fine aggregate from dredged sand through controlled blending with crusher dust to achieve particle size distribution compliant with IS 383 standards for structural concrete applications.
Background of the invention:
[0002] The rapid expansion of infrastructure and urban development has significantly increased the demand for fine aggregates used in concrete production. Conventionally, natural river sand has been widely used as a fine aggregate in structural concrete due to its suitable particle size distribution and compatibility with cementitious materials. However, excessive mining of river sand has resulted in environmental degradation, depletion of natural resources, and strict regulatory restrictions in many regions. Consequently, there is an increasing need to identify alternative sources of fine aggregates that can meet the grading requirements specified in IS 383 standards for concrete aggregates.
[0003] One potential alternative source is dredged sand obtained from seabed or harbor dredging operations. Such dredged sand is generated in large quantities during maintenance dredging activities intended to maintain navigational channels and port infrastructure. Despite its availability, dredged sand is generally considered unsuitable for structural concrete applications because it often contains irregular particle size distribution, excessive fine particles, and entrapped chlorides, which may adversely affect concrete performance and durability. As a result, dredged sand is typically discarded or used only for low-grade filling applications rather than structural concrete production because of high chloride content.
[0004] Although several attempts have been made to utilize alternative materials as fine aggregates in concrete, the existing approaches suffer from multiple technical limitations that restrict their effectiveness in transforming marginal materials into structurally reliable aggregates. One of the known approaches is disclosed in a prior art. IN202441095172A, which describes a method for producing fine aggregates by blending sea sand with crusher dust and evaluating the particle size distribution through sieve analysis. The method proposes blending ratios such as 70:30, 60:40, and 50:50 (sea sand to crusher dust) to obtain aggregates falling within the grading zones specified under IS 383 standards. However, the disclosed method primarily addresses the use of naturally occurring sea sand as the base material. Such sea sand generally exhibits relatively stable particle characteristics compared to dredged marine sand obtained from subsurface seabed deposits. Consequently, the approach does not address the technical challenges associated with dredged sand, which typically exhibits irregular particle size distribution, excessive fines, and variability in gradation, thereby limiting its suitability for structural concrete applications.
[0005] The above method generally relies on simple proportional mixing of materials rather than implementing a controlled gradation engineering framework. As a result, the particle size distribution of the blended material may not consistently achieve the cumulative percentage passing limits required to fall within Zone-II grading under IS 383, which is typically preferred for structural concrete. The absence of a systematic gradation control methodology therefore limits the ability of these approaches to convert marginal or low-grade sand resources into standardized fine aggregates.
[0006] Another approach disclosed in Indian Patent Application No. IN202541108715A focuses on producing sustainable concrete by partially replacing natural aggregates with recycled aggregates obtained from construction and demolition waste. While this approach contributes to environmental sustainability, the disclosed system primarily addresses the substitution of coarse aggregates rather than the gradation engineering of fine aggregates derived from unconventional materials such as dredged sand. Consequently, the method does not resolve the technical challenges associated with transforming dredged sand into concrete-grade fine aggregate.
[0007] In addition, several experimental studies reported in technical literature investigate the use of stone dust or crusher dust as a partial replacement for natural river sand in concrete. Although these studies demonstrate improvements in compressive strength and packing density under certain replacement levels, such approaches generally assume the presence of natural river sand as the primary fine aggregate, with crusher dust acting only as a supplementary material. These methods therefore fail to provide a systematic framework for upgrading dredged sand into standardized fine aggregate capable of satisfying structural concrete requirements.
[0008] Accordingly, the prior art suffers from several limitations, including the inability to effectively utilize dredged marine sand as a primary fine aggregate material, the lack of a controlled gradation engineering approach for modifying particle size distribution, and the absence of a process capable of reliably transforming dredged sand into IS 383 Zone-II compliant fine aggregate suitable for structural concrete applications. These limitations create a need for an improved process capable of redistributing particle sizes through controlled blending in order to convert dredged sand into structurally viable fine aggregate.
[0009] Therefore, there exists a need for an improved zoning-controlled gradation process capable of transforming dredged sand into concrete-grade fine aggregate by engineering particle size distribution through controlled blending with crusher dust. Such a process should enable the resulting aggregate to satisfy IS 383 Zone-II gradation requirements while maintaining structural performance characteristics suitable for concrete production.
Objectives of the invention:
[0010] The primary objective of the invention is to provide a zoning-controlled gradation process for transforming dredged sand into concrete-grade fine aggregate suitable for structural concrete applications.
[0011] The other objective of the invention is to provide a zoning-controlled gradation process for blending dredged sand with crusher dust to achieve particle size distribution compliant with IS 383 grading standards.
[0012] The other objective of the invention is to provide a zoning-controlled gradation process capable of redistributing particle size fractions of dredged sand to convert aggregates falling within Zone-III or Zone-IV grading into Zone-II compliant fine aggregates.
[0013] Another objective of the invention is to provide a zoning-controlled gradation process as a gradation optimization process that enhances particle packing density and inter-particle interlocking within blended aggregates to improve the mechanical performance of concrete.
[0014] The other objective of the invention is to provide a zoning-controlled gradation process for producing fine aggregates from dredged sand through controlled incorporation of crusher dust without requiring chemical treatment or complex material processing.
[0015] Yet another objective of the invention is to provide a zoning-controlled gradation process capable of improving compressive strength, split tensile strength, and flexural strength of concrete prepared using dredged sand-based aggregates.
[0016] Another objective of the invention is to provide a zoning-controlled gradation process as a sustainable and resource-efficient process for utilizing dredged marine sand generated from harbor and seabed dredging operations in structural concrete production.
[0017] Another objective of the invention is to provide a zoning-controlled gradation process that reduces reliance on natural river sand while enabling large-scale utilization of dredged sand in construction materials.
Summary of the invention:
[0018] The present disclosure proposes a zoning-controlled gradation process for converting dredged sand into structural fine aggregate for concrete. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.
[0019] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a zoning-controlled gradation process for converting dredged sand into structural fine aggregate for concrete.
[0020] The present disclosure provides a zoning-controlled gradation process for producing concrete-grade fine aggregate from dredged sand. The process involves obtaining dredged sand exhibiting a particle size distribution corresponding to Zone-III or Zone-IV grading as specified under IS 383 standards, and providing crusher dust having particle sizes passing a 4.75 mm sieve. The dredged sand and crusher dust are blended in 50:50, 60:40 and 70:30 proportions by weight, whereby the blending operation redistributes particle size fractions of the dredged sand. Through this controlled blending, the resulting material attains a continuous particle size distribution, thereby producing a blended fine aggregate having particle size distribution corresponding to Zone-II grading limits defined in IS 383, which is suitable for use as fine aggregate in concrete.
[0021] In certain embodiments, the dredged sand used in the process comprises marine dredged sand obtained from seabed deposits or harbor dredging operations. The crusher dust employed in the blending process comprises crushed rock fines exhibiting angular particle morphology, which assists in improving gradation characteristics and packing behavior of the blended aggregate.
[0022] The blending of dredged sand with crusher dust introduces intermediate particle size fractions that fill particle size gaps present within the particle size distribution of the dredged sand, thereby correcting gradation discontinuities. As a result, the blended fine aggregate exhibits a fineness modulus in the range of 2.29 to 2.90, which falls within the suitable range for concrete-grade fine aggregates.
[0023] Further, the redistribution of particle size fractions achieved through the zoning-controlled gradation blending reduces void ratio within the aggregate system and enhances particle packing density, thereby improving the overall gradation stability of the fine aggregate. The transformation of dredged sand into concrete-grade fine aggregate occurs without the use of chemical additives or chemical treatment, relying instead on controlled particle size redistribution.
[0024] In certain implementations, the blending of dredged sand and crusher dust is performed at a weight ratio of 50:50, which provides an optimized particle size distribution for achieving the desired gradation characteristics of the blended fine aggregate.
[0025] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0026] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.
[0027] FIG. 1 illustrates a flowchart of a zoning-controlled gradation process for producing concrete-grade fine aggregate from dredged sand, in accordance to an exemplary embodiment of the invention.
[0028] FIG. 2 illustrates a graphical representation of a particle size distribution curve of blended fine aggregate and various aggregate blends, in accordance to an exemplary embodiment of the invention.
[0029] FIG. 3 illustrates a graphical representation of compressive strength of blended fine aggregate and various aggregate blends, in accordance to an exemplary embodiment of the invention.
[0030] FIG. 4 illustrates a graphical representation of a split tensile strength of blended fine aggregate and various aggregate blends, in accordance to an exemplary embodiment of the invention.
[0031] FIG. 5 illustrates a graphical representation of a flexural strength of blended fine aggregate and various aggregate blends, in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
[0032] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.
[0033] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a zoning-controlled gradation process for converting dredged sand into structural fine aggregate for concrete.
[0034] According to an exemplary embodiment of the invention, FIG. 1 refers to a flowchart of a zoning-controlled gradation process for producing concrete-grade fine aggregate from dredged sand. The zoning-controlled gradation process provides a technical advancement by converting dredged sand from an inconsistent by-product into a standardized fine aggregate through zoning-controlled gradation. The zoning-controlled gradation process enables predictable particle size distribution which leads to improved packing density and better interfacial bonding between particles thus resulting in enhanced mechanical properties of concrete. The zoning-controlled gradation process creates economic benefits because it enables projects to use dredged materials at large scales while decreasing their dependence on natural river sand and maintaining structural strength.
[0035] According to another embodiment of the invention, the zoning-controlled gradation process for producing concrete-grade fine aggregate from dredged sand is disclosed. At step 102, dredged sand (DS) is provided as a base fine aggregate material, wherein the dredged sand comprises marine dredged sand obtained from seabed, river mouth, or harbor dredging operations. The dredged sand exhibits a particle size distribution corresponding substantially to Zone-III or Zone-IV grading limits as specified under IS 383 for fine aggregates, thereby indicating a relatively coarse or gap-graded particle distribution with insufficient intermediate size fractions. The dredged sand particles are generally rounded to sub-rounded in morphology due to natural hydraulic deposition processes.
[0036] At step 104, crusher dust (CD) is provided as a secondary fine aggregate component, wherein the crusher dust comprises crushed rock fines generated during mechanical crushing of rock materials. The crusher dust consists predominantly of angular and rough-textured particles and exhibits particle sizes substantially passing through a 4.75 mm sieve, thereby enabling the crusher dust to function as a filler material supplying deficient intermediate and fine particle size fractions.
[0037] At step 106, the dredged sand and the crusher dust are blended together in a predetermined dredged sand to crusher dust proportions of 70:30, 60:40 and 50:50 by weight respectively. The blending may be performed through mechanical mixing or batch mixing processes to ensure homogeneous distribution of both materials within the blended aggregate mass.
[0038] At step 108, the blending operation causes redistribution of particle size fractions present in the dredged sand through the incorporation of crusher dust particles. In particular, the crusher dust introduces intermediate and finer particle size fractions that fill particle size gaps present within the gradation curve of the dredged sand. As a result, the blended material exhibits a more continuous and well-graded particle size distribution, thereby reducing discontinuities within the gradation profile of the fine aggregate.
[0039] At step 110, a blended fine aggregate is obtained in which the overall particle size distribution conforms to Zone-II grading limits as defined under IS 383, thereby satisfying standard requirements for fine aggregate suitable for structural concrete applications. The blended aggregate demonstrates improved gradation continuity compared to the original dredged sand.
[0040] Further, the redistribution of particle size fractions achieved through blending results in reduced void ratio and enhanced particle packing density within the blended fine aggregate. The improved packing characteristics contribute to enhanced interparticle contact and improved mechanical behavior when the aggregate is incorporated into cementitious mixtures. In certain embodiments, the blended fine aggregate exhibits a fineness modulus in the range of approximately 2.29 to 2.90, indicating suitability for use as fine aggregate in structural concrete compositions.
[0041] Importantly, the zoning-controlled gradation transformation of dredged sand into standardized fine aggregate is achieved without the use of chemical additives, chemical stabilizers, or chemical treatment processes, thereby maintaining a purely physical modification approach based on particle size redistribution. In one preferred embodiment, the dredged sand and crusher dust are blended in an equal weight ratio of 50:50, which enables the resulting aggregate gradation to consistently fall within Zone-II grading limits under IS 383 while providing improved packing density and interparticle interlocking.
[0042] In one embodiment herein, the process aims to blend crusher dust and dredged sand to achieve Zone-II/Zone-III compliance as per IS standards for fine aggregate in M35 grade concrete making. The process aims to utilize the dredged sand in proportion with crusher dust greater than or equal to 50% in M35 grade of concrete. The M35 grade concrete with dredged sand and dredged sand-crusher dust blends as fine aggregate and tested at 28 days for compressive strength, split tensile strength, and flexural strength.
[0043] In one experimental embodiment, concrete mix design blends are prepared using dredged sand and dredged sand–crusher dust blends as fine aggregates for M35 grade concrete. Standard concrete mix proportions were prepared and cast into test specimens. The specimens were cured for 28 days and evaluated for mechanical properties including compressive strength, split tensile strength, and flexural strength according to standard testing procedures.
[0044] Table 1:
IS Sieve size (mm) DS (100%) DS (70%) + CD (30%) DS (60%) + CD (40%) DS (50%) + CD (50%) Zone-III Requirements as per IS 383 Zone-II Requirements as per IS 383
10 100.0 100.0 100.0 100.0 100 100
4.75 99.8 99.8 99.8 99.80 90–100 90–100
2.36 99.6 95.2 93.4 92.40 85–100 75–100
1.18 97.4 88.4 84.0 82.20 75–100 55–90
0.6 75.4 69.2 67.8 65.20 60–79 35–59
0.3 12.4 14.0 17.8 21.00 12-40 8-30
0.15 8.6 6.4 8.8 9.6 0-10 0-10
Fineness modulus (FM) 2.07 2.27 2.28 2.29 - -
Coefficient of curvature (Cu) 2.09 2.57 3.11 3.7 - -
Coefficient of curvature (Cc) 1.44 1.21 1.7 1.63 - -
Zone III III III II - -

[0045] Table 1 illustrates the gradation requirements specified under IS 383 and the corresponding gradation values obtained for various blends of dredged sand (DS) and crusher dust (CD).
[0046] According to another embodiment of the present invention, FIG. 2 illustrates a graphical representation 200 depicting the particle size distribution curves of blended fine aggregates formed using dredged sand (DS) and crusher dust (CD) in different blend proportions. The graphical representation 200 includes particle size distribution curves corresponding to 100% dredged sand, 70% DS + 30% CD, 60% DS + 40% CD and 50% DS + 50% CD blends. The gradation curves of these blends fall within the Zone-III grading limits as specified under IS 383, indicating that the resulting fine aggregate compositions correspond to the relatively finer grading range suitable for concrete applications.
[0047] Further, the gradation characteristics demonstrate a progressive modification in particle size distribution upon incorporation of crusher dust. In particular, the coefficient of uniformity (Cu) for the blends increases from approximately 2.09 to 3.11, indicating a gradual broadening of the particle size distribution. Similarly, the fineness modulus (FM) increases from about 2.07 to 2.28, confirming a controlled increase in the overall fineness of the blended aggregate while still remaining within the acceptable range for fine sand. Additionally, the coefficient of curvature (Cc) values for the blends lies within the range of approximately 1.21 to 1.70, which falls within the acceptable limits for well-graded aggregates. These values indicate a balanced and symmetrical particle size distribution around the mean particle size of the fine aggregate, thereby confirming the absence of gap grading within the blended material.
[0048] The gradation curves further demonstrate that the incorporation of crusher dust introduces intermediate particle size fractions that effectively fill voids present in the original dredged sand gradation. Consequently, the particle size distribution becomes more continuous and better graded. Notably, the progressive addition of crusher dust enables a transition in aggregate classification from Zone-III towards Zone-II grading limits under IS 383, which highlights the technical significance of the blending process. This transition indicates that the blending of dredged sand with crusher dust effectively modifies the gradation characteristics of the material, improves particle packing behavior, and results in a higher grading classification suitable for structural concrete applications.
[0049] According to another embodiment of the invention, FIG. 3 refers to a graphical representation 300 of compressive strength of blended fine aggregate and various aggregate blends. In one experimental embodiment of the present invention, the compressive strength of blended fine aggregate was observed to increase progressively with increasing proportions of crusher dust in the fine aggregate blend. This improvement in strength is attributed to the enhanced gradation and packing characteristics of the blended fine aggregate. The measured compressive strength values ranged from 42.67 MPa to 49.78 MPa. The lowest compressive strength of 42.67 MPa was recorded for the concrete mix containing 100% dredged sand, indicating that dredged sand used alone does not provide an optimal particle packing structure for strength development.
[0050] When crusher dust was incorporated at 30% by weight with 70% dredged sand, the compressive strength increased to approximately 47.70 MPa, demonstrating improved particle interlocking and packing density within the fine aggregate matrix. Further enhancement was observed for the blend containing 60% dredged sand and 40% crusher dust, which achieved a compressive strength of about 48.44 MPa, indicating a progressive improvement in mechanical performance with increased crusher dust content.
[0051] The blend comprising 50% dredged sand and 50% crusher dust exhibited the highest compressive strength of approximately 49.78 MPa, thereby identifying this proportion as an optimum mix ratio among the investigated compositions. The results confirm that the controlled blending of dredged sand with crusher dust improves gradation continuity, reduces void spaces within the aggregate matrix, and enhances the overall compressive strength of concrete.
[0052] According to another embodiment of the invention, FIG. 4 refers to a graphical representation 400 of a split tensile strength of blended fine aggregate and various aggregate blends. In another experimental embodiment of the present invention, the split tensile strength of concrete exhibited a systematic trend similar to that observed for compressive strength, thereby confirming that the gradation and composition of the fine aggregate blend significantly influence crack resistance and internal bonding within the concrete matrix. The measured split tensile strength values ranged from approximately 3.11 MPa to 3.47 MPa.
[0053] The concrete mix containing 100% dredged sand recorded the lowest split tensile strength of about 3.11 MPa, indicating that dredged sand alone does not provide an optimal particle packing structure or sufficient interparticle interlocking required for improved tensile performance. Upon incorporation of crusher dust into the dredged sand matrix, a gradual increase in split tensile strength was observed. In particular, the blend containing 70% dredged sand and 30% crusher dust achieved a split tensile strength of approximately 3.26 MPa, while the blend containing 60% dredged sand and 40% crusher dust exhibited a further improved split tensile strength of about 3.33 MPa.
[0054] The highest split tensile strength of approximately 3.47 MPa was obtained for the blend comprising 50% dredged sand and 50% crusher dust, thereby identifying this composition as the optimum blend among the investigated proportions. These results indicate that the addition of crusher dust enhances the gradation continuity and particle interlocking within the fine aggregate system, which in turn improves tensile strength and resistance to crack propagation in the resulting concrete.
[0055] According to another embodiment of the invention, FIG. 5 refers to a graphical representation 500 of a flexural strength of blended fine aggregate and various aggregate blends. In another experimental embodiment of the present invention, the flexural strength of concrete prepared using dredged sand (DS) and crusher dust (CD) as blended fine aggregates was evaluated. The measured flexural strength values ranged from approximately 7.65 MPa to 8.24 MPa. The concrete mix containing 100% dredged sand exhibited the lowest flexural strength of about 7.65 MPa, indicating relatively lower resistance to bending stresses due to sub-optimal particle packing and reduced interparticle interlocking.
[0056] The incorporation of crusher dust into the dredged sand matrix resulted in a progressive improvement in flexural performance. In particular, the blend comprising 70% dredged sand and 30% crusher dust achieved a flexural strength of approximately 7.90 MPa, while the blend containing 60% dredged sand and 40% crusher dust further increased the flexural strength to about 8.19 MPa. The highest flexural strength of approximately 8.24 MPa was obtained for the blend comprising 50% dredged sand and 50% crusher dust, thereby identifying this composition as the optimum blend for enhancing bending resistance of the concrete. The results indicate that the incorporation of crusher dust improves particle size gradation and packing density within the fine aggregate system, thereby enhancing the flexural performance of the resulting concrete.
[0057] In one embodiment herein, the process establishes that dredged sand can be transformed into concrete-grade fine aggregate through controlled blending with crusher dust. The analysis of particle size distribution showed that the combination of dredged sand and crusher dust resulted in a zone change from Zone-III to Zone-II with 50% DS+50%CD satisfying the Zone-II gradation. The 50% DS+50% CD mix has coefficient of uniformity (Cu) of 3.7 and fineness modulus of 2.29 while maintaining coefficient of curvature within the range of 1 to 3, which demonstrate that the achieved gradation is conducive for better packing.
[0058] The concrete made with 100% dredged sand showed the lowest compressive strength of 42.67 MPa, split tensile strength of 3.11 MPa and flexural strength of 7.65 MPa which demonstrated that dredged sand functions as a poorly graded and mechanically weak fine aggregate when used in its natural state. The addition of crusher dust as a partial replacement for dredged sand brought about a progressive improvement in compressive strength which increased from 42.67 MPa for 100% DS to 49.78 MPa for 50% DS+ 50% CD, split tensile strength increased from 3.11 MPa (100% DS) to 3.47 MPa (50% DS+ 50% CD) and flexural strength increased from 7.65 MPa (100% DS) to 8.24 MPa (50% DS+ 50% CD).
[0059] The highest strengths in compression, tension and flexure of 49.78 MPa, 3.47 MPa and 8.24 MPa respectively are obtained for the concrete with 50% DS +50% CD as fine aggregate among the crusher dust-dredged sand blends considered in the study. 50% DS+ 50% CD blend satisfied Zone-II gradation of IS 383 for fine aggregate to be utilized in concrete and hence, yielding highest mechanical properties compared to concrete mixes of 70% DS+30% CD and 60% DS +40% CD blends as fine aggregate. The zoning-controlled gradation framework enables large-scale utilization of dredged materials in infrastructure projects while maintaining structural performance of concrete.
[0060] The experimental investigation clearly demonstrates that dredged sand often discarded for engineered use can be transformed and used as fine aggregate after blending with crusher dust. This shows a sustainable alternative to natural river sand addressing the disposal problems of dredged sand and reduction of fine aggregate scarcity. The present invention also provides environmental benefits by enabling the utilization of dredged sand generated during harbor and seabed dredging operations. This reduces disposal challenges and minimizes dependence on natural river sand extraction.
[0061] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, the zoning-controlled gradation process for converting dredged sand into structural fine aggregate for concrete is disclosed. The zoning-controlled gradation process for transforming dredged sand into concrete-grade fine aggregate is suitable for structural concrete applications. The zoning-controlled gradation process for blending dredged sand with crusher dust achieves particle size distribution compliant with IS 383 grading standards.
[0062] The zoning-controlled gradation process is capable of redistributing particle size fractions of dredged sand to convert aggregates falling within Zone-III or Zone-IV grading into Zone-II compliant fine aggregates. The zoning-controlled gradation process as a gradation optimization process enhances particle packing density and inter-particle interlocking within blended aggregates to improve the mechanical performance of concrete. The zoning-controlled gradation process for producing fine aggregates from dredged sand through controlled incorporation of crusher dust without requiring chemical treatment or complex material processing.
[0063] The zoning-controlled gradation process is capable of improving compressive strength, split tensile strength, and flexural strength of concrete prepared using dredged sand-based aggregates. The zoning-controlled gradation process as a sustainable and resource-efficient process for utilizing dredged marine sand generated from harbor and seabed dredging operations in structural concrete production. The zoning-controlled gradation process reduces reliance on natural river sand while enabling large-scale utilization of dredged sand in construction materials. The blending of dredged sand and crusher dust reduced the chloride concentration of the fine aggregate.
[0064] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.
, Claims:CLAIMS:
I / We Claim:
1. A zoning-controlled gradation process for producing concrete-grade fine aggregate from dredged sand, comprising:
providing dredged sand exhibiting particle size distribution corresponding to Zone-III or Zone-IV grading under IS 383; providing crusher dust having particle sizes passing a 4.75 mm sieve; blending the dredged sand and the crusher dust in a weight ratio of dredged sand to crusher dust between 50:50 and 70:30; redistributing particle size fractions of the dredged sand through the blending such that the blended material exhibits continuous particle size distribution; and obtaining a blended fine aggregate having particle size distribution corresponding to Zone-II grading limits defined in IS 383.
2. The zoning-controlled gradation process as claimed in claim 1, wherein the dredged sand is marine dredged sand obtained from seabed or harbor dredging operations.
3. The zoning-controlled gradation process as claimed in claim 1, wherein the crusher dust comprises crushed rock fines exhibiting angular particle morphology.
4. The zoning-controlled gradation process as claimed in claim 1, wherein blending of dredged sand and crusher dust introduces intermediate particle size fractions that fill particle size gaps within the particle size distribution of the dredged sand.
5. The zoning-controlled gradation process as claimed in claim 1, wherein the blended fine aggregate exhibits fineness modulus in the range of 2.29 to 2.90.
6. The zoning-controlled gradation process as claimed in claim 1, wherein the redistribution of particle size fractions reduces void ratio and improves particle packing density within the blended fine aggregate.
7. The zoning-controlled gradation process as claimed in claim 1, wherein the zoning-controlled gradation transformation of dredged sand into fine aggregate occurs without chemical additives or chemical treatment.
8. The zoning-controlled gradation process as claimed in claim 1, wherein the weight ratio of dredged sand to crusher dust is 50:50.