DefinePK

Research Objective

To quantitatively examine the Khairabad Limestone of Paleocene age through physical, chemical, mineralogical, engineering, and mechanical tests to evaluate its aptness as aggregate material for construction purposes.

Methodology

The study involved collecting fresh rock samples from Khairabad Limestone, preparing them according to ASTM D75 standards, and crushing them into various sizes. Standard engineering tests (AASHTO, ASTM, BS, NHA) were conducted at the engineering geology laboratory of the Institute of Geology, University of the Punjab, Lahore. These tests included Los Angeles Abrasion, Aggregate Impact, Aggregate Crushing, Soundness, Sieve Analysis, Coating and Stripping of Bitumen, Specific Gravity and Absorption, Unit Weight, Flakiness and Elongation, and Petrographic Analysis for Alkali-Silica Reaction (ASR) and Alkali-Carbonate Reaction (ACR). Results were compared with international standards.

Methodology Flowchart

                        graph TD
    A[Sample Collection from Khairabad Limestone] --> B[Sample Preparation: Crushing];
    B --> C[Engineering Tests];
    C --> C1[Los Angeles Abrasion];
    C --> C2[Aggregate Impact];
    C --> C3[Aggregate Crushing];
    C --> C4[Soundness Test];
    C --> C5[Coating and Stripping];
    C --> C6[Specific Gravity and Absorption];
    C --> C7[Unit Weight];
    C --> C8[Flakiness and Elongation];
    C --> C9[Petrographic Analysis ASR/ACR];
    C1 --> D[Data Analysis & Comparison with Standards];
    C2 --> D; C3 --> D; C4 --> D; C5 --> D; C6 --> D; C7 --> D; C8 --> D; C9 --> D;
    D --> E[Evaluation of Aptness as Aggregate];
    E --> F[Conclusion: Suitable Aggregate Resource];                    

Discussion

The Khairabad Limestone, excluding its basal argillaceous part, is characterized by hard and tough physical properties, making it an excellent source for aggregate. Petrographic analysis confirms its composition of calcite with minor amounts of dolomite, quartz, clay, and iron oxide, and importantly, a lack of deleterious minerals that could cause ASR or ACR. The engineering test results consistently fall within or below international standards, indicating high strength, durability, and resistance to weathering and crushing. The limestone's accessibility via road and proximity to a railway station further enhances its potential for large-scale aggregate preparation and supply.

Key Findings

Khairabad Limestone exhibits suitable physical, chemical, mineralogical, engineering, and mechanical properties for use as aggregate. Key test results include: Los Angeles Value (26.59%), Aggregate Impact Value (13.91%), Aggregate Crushing Value (12.84%), Soundness Value (1.84%), Coating and Stripping of Bitumen (96.4%), Specific Gravity (2.7), Water Absorption (0.83%), Unit Weight (1.65 g/cm3), and Total (elongation + flakiness) Index (22.78%). Petrographic analysis revealed negligible reactive components, indicating no ASR or ACR potential. The investigated reserve is vast and thick enough to supply aggregate for local and national megaprojects.

Conclusion

Khairabad Limestone is a highly durable and suitable aggregate resource in the Western Salt Range, Pakistan. Its favorable mineralogical, chemical, physical, and mechanical properties, coupled with its lack of ASR and ACR potential, make it an excellent material for various construction applications, including concrete mix design, mortar, bound and unbound pavements, and buildings. The lower argillaceous part of the reserve should be avoided for mining.

Fact Check

1. Los Angeles Value: The average Los Angeles Value obtained was 26.59%, which is below the maximum allowable limit of 40% for road base coarse, 35% for concrete, and 50% for granular sub-base as per AASHTO T-96.
2. Soundness Test Value: The average soundness test value was 1.841%, which is significantly less than the maximum limit of 12% required for high-quality aggregate, indicating good resistance to weathering.
3. Aggregate Crushing Value: The average aggregate crushing value was 12.84%, which is well below the limit of 45% (and especially below 30% for concrete work) set by AASHTO and ASTM, indicating high resistance to crushing.

Mind Map