Cement and Concrete Mix 2022-2023 PDF
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Uploaded by WellKnownElbaite5416
2022
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Summary
This document is a past paper on cement and concrete mix, covering topics such as physical tests on cement, concrete, miscellaneous construction materials, and asphaltic materials. It includes key points, important numbers, and formulas related to cement and concrete.
Full Transcript
overage of Exam: C 1. Physical Test on Cement a. Normal COnsistency b. Time of Setting c. Autoclave Expansion d. Aircontent 2. Concrete 3. Miscellaneous Construction Materials a. Concrete Masonry Unit b. Reinforcing Stee...
overage of Exam: C 1. Physical Test on Cement a. Normal COnsistency b. Time of Setting c. Autoclave Expansion d. Aircontent 2. Concrete 3. Miscellaneous Construction Materials a. Concrete Masonry Unit b. Reinforcing Steel Bar c. Reinforced Concrete Culvert Pipe 4. Asphaltic Materials CEMENT AND CONCRETE MIX 2022-10-06 1 14 Normal Consistency (1) ased on the provided documents, here are summarized key points and important numbers B that can assist in your examination preparation related to cement and concrete: General Concepts and Definitions 1. Composition of Concrete by Weight: ○ Cement: 14% ○ Aggregates: 80% (Coarse 50%, Fine 30%) ○ Water: 6%. 2. Composition by Volume: ○ Cement: 10% ○ Aggregates: 70% ○ Water: 15% ○ Air: 5%. 3. Hydration: ○ Heat of hydration depends on cement's chemical composition. ○ Critical temperatures: Drying: 425°C Calcining: 875°C Clinkering: 1400–1480°C. Portland Cement Types and Compositions 1. Types of Portland Cement: Type I (Normal): General use. ○ ○ Type II (Moderate Sulfate Resistance): Lower heatof hydration. ○ Type III (High Early Strength): Rapid setting; usefulfor early strength gain. ○ Type IV (Low Heat): Used in massive structures likedams. ○ Type V (Sulfate Resistant): Designed for high sulfateareas. 2. Principal Cement Compounds: ○ Tricalcium Silicate (C3S): Early strength (40–60%). ○ Dicalcium Silicate (C2S): Long-term strength. ○ Tricalcium Aluminate (C3A): Reacts quickly, least sulfate resistant. ○ Tetracalcium Aluminoferrite (C4AF): Limited contribution to strength. . Chemical Composition: 3 ○ Oxides: CaO: 60–65% SiO2: 10–25% Al2O3: 5–10% Fe2O3: 2–4% ○ Compounds: C3S, C2S, C3A, and C4AF are critical. Testing Standards and Procedures 1. Normal Consistency Test: ○ Requires 10 ± 1 mm penetration using the Vicat apparatus. ○ Normal water content: 25–35%. 2. Setting Time: ○ Initial Set: Time before paste loses fluidity. ○ Final Set: Time when paste resists defined pressure. 3. Autoclave Expansion Test: ○ Measures cement soundness by detecting volume stability. 4. Compressive Strength Test: ○ Indicates maximum load-bearing capacity. 5. Normal Consistency Formula: ○ 6. \text{Normal Consistency} = \frac{\text{Mass of Water}}{\text{Mass of Cement}} \times 100 ] Example: For 190 mL water and 650 g cement: ○ 7. = \frac{190}{650} \times 100 = 29.2% , \text{(rounded to nearest 0.5%)} ]. Practical Considerations 1. Storage: ○ Store cement in moisture-proof, weatherproof conditions. ○ Shelf life: Retest if stored over 6 months. 2. Pozzolans: Natural: Volcanic materials like ash. ○ ○ Artificial: Fly ash from coal combustion. 3. Uses of Pozzolans: ○ Improve durability and resistance to chemical attacks. ○ Reduce heat of hydration. Key Numbers for Quick Reference 1. Water-Cement Ratios: ○ Low ratio (0.25–0.35): Thick cream consistency. ○ High ratio: Fluid mix. 2. Temperature for Testing: ○ Air: 23 ± 4°C. ○ Mixing water: 23 ± 2°C. 3. Specific Gravity: ○ Not a quality indicator but useful in mix design. 4. Heat of Hydration: ○ C3S: High heat, quick set. ○ C2S: Low heat, slow set Normal Consistency Formula Summarized Notes with Important Numbers 1. Autoclave Expansion of Hydraulic Cement (ASTM C151): P urpose: Determines soundness by assessing delayed expansion due to hydration of CaO or MgO. Specification: Maximum autoclave expansion = 0.8%. Equipment: ○ Molds (Gauge Length = 250 mm). ○ Temperature: 23.0 ± 2.0°C; Humidity: ≥ 95%. ○ Autoclave Pressure: 2.4 MPa (350 psi) ± 5%. Computation Formula: Sample Results: ○ Expansion of +0.40% and -0.08% calculated from respective lengths. 1. Autoclave Expansion of Hydraulic Cement (ASTM C151) Purpose: D etermines the soundness of cement by measuring delayed expansion due to hydration of calcium oxide (CaO) or magnesium oxide (MgO). Specification Requirement: Maximum allowable autoclave expansion: 0.8%. Key Equipment: M olds: Conforming to Practice C490 with a gauge length of 250 mm. Moist Cabinet/Room: Temperature: 23.0 ± 2.0°C, Relative Humidity: ≥ 95%. Autoclave Machine: ○ Pressure: 2.4 MPa (350 psi) ± 5%. ○ Equipped with automatic controls, thermometer, and vent valve. Computation Formula: Where: : Length before autoclaving (mm). : Length after autoclaving (mm). : Gauge length (250 mm). Sample Results: 1. Expansion: ○ Initial length: 3.861 mm. ○ Final length: 4.867 mm. ○ Expansion: +0.40%. 2. Shrinkage: ○ Initial length: 1.023 mm. ○ Final length: 0.821 mm. ○ Expansion: -0.08%. 2. Time of Setting of Hydraulic Cement (ASTM C191): P urpose: Measures initial and final setting times using the Vicat needle. Specifications: Initial setting time: Minimum 45 minutes. ○ ○ Final setting time: Maximum 375 minutes. Key Criteria: ○ Initial set: Penetration = 25 mm. ○ Final set: Penetration = 0 mm. Environmental Conditions: ○ Temperature: 23.0 ± 2.0°C; Humidity: ≥ 95%. Formula for Initial Setting Time: Sample Result: Initial setting time = 132 minutes. Purpose: D etermines the time required for cement paste to reach initial and final set using the Vicat needle. Specifications: Initial Setting Time: Minimum 45 minutes. Final Setting Time: Maximum 375 minutes. Key Criteria: Initial Set: Penetration = 25 mm. Final Set: Penetration = 0 mm. Environmental Conditions: T emperature: 23.0 ± 2.0°C. Relative Humidity: ≥ 95%. Computation Formula for Initial Setting Time: Where: : Time of last penetration > 25 mm. : Time of first penetration < 25 mm. : Penetration reading at. : Penetration reading at. Sample Calculation: Penetration results: ○ Last penetration > 25 mm: Time = 124 min, Penetration = 27 mm. ○ First penetration < 25 mm: Time = 139 min, Penetration = 23 mm. Using the formula: 3. Air Content of Hydraulic Cement Mortar (ASTM C185): P urpose: Measures air content to verify compliance with air-entraining properties. Requirements: ○ Maximum air content for Type I cement: 12%. Batch Proportions: ○ Cement: 350 g, Sand: 1400 g, Water: 285 mL (Flow = 87.5% ± 7.5%). Key Equipment: ○ Flow Table (7.2–7.8 inches), Mixer (Slow: 140 ± 5 rpm, Medium: 285 ± 10 rpm), Measure (Volume: 400 ± 1 mL). Computation: Air Content Reported Air Content: 4%. Purpose: Verifies compliance with air-entraining or non-air-entraining requirements. Specification Requirement: Maximum air content for Type I cement:12%. Batch Proportions: Cement:350 g. S and:1400 g. Water: Determined by flow test (Required Flow =87.5%± 7.5%). Key Equipment: M easure: Cylindrical, volume400 ± 1 mL. Flow Table: Conforming to C230/C230M (Flow = 7.2–7.8inches). Mixer: ○ Slow Speed:140 ± 5 rpm. ○ Medium Speed:285 ± 10 rpm. Weighing Devices: Precision evaluated for a totalload of2000 g. Computation Formula: Where: : Theoretical mass/unit volume =2.201 g/cm³. : Actual mass/unit volume =2.114 g/cm³. Sample Results: Air Content:4%(Reported to nearest 1%). Asphaltic Materials D efinition: Dark brown to black cementitious materialcontaining bitumen. History Highlights: ○ 3200–540 B.C.: Used in Mesopotamia for masonry and waterproofing. ○ 1870: First asphalt pavement laid in Newark, NJ. Key Grades: ○ Penetration (AASHTO M-20): AC 40-50, AC 60-70, AC 85-100. ○ Viscosity (AASHTO M-226): AC-2.5, AC-5, AC-10, AR-10, AR-20. Tests on Asphalt: ○ Penetration Test: Measures consistency. ○ Ductility Test: Indicates adhesive properties. ○ Flash Point: Safe heating temperature. ○ Viscosity: Fluidity measurement. Applications: ○ Prime/Tack Coat, Roofing, Waterproofing, Road Base. Concrete Masonry Units (CMU) Specifications: ○ ASTM C-90: Load-bearing units. ○ ASTM C-129: Non-load-bearing units. Testing Requirements: ○ One quality test for every 10,000 units or fraction. ○ 3 specimens for compressive strength; 3 for moisture content. Compressive Strength: ○ Calculation: Max Load (N)/Net Area (mm2)\text{Max Load (N)} / \text{Net Area (mm}^2\text{)}Max Load (N)/Net Area (mm2). Moisture Content & Absorption: ○ Uses an oven-dried method for measurement. ○ Formulas: Reinforcing Steel Bars Types: ○ Deformed: With protrusions. ○ Plain: Smooth surface. Grades: ○ Grade 280: Sizes 10–19 mm. ○ Grade 420: Sizes 10–57 mm. Testing: ○ Yield Strength: Minimum 275 MPa. ○ Tensile Strength: Minimum 480 MPa. ○ Elongation: Minimum 12% elongation. ○ Mass Variation: Must not exceed ±6% of nominal weight. ○ Phosphorus Content: Maximum 0.06%. Acceptance Criteria: ○ Retests allowed for results within close range of specifications. ○ Overweight bars are not grounds for rejection. Important Notes and Key Numbers for Examination Asphaltic Materials Definition: ○ A dark brown to black cementitious material containing bitumen, used for its cementing and waterproofing properties. History Highlights: ○ 3200–540 B.C.: Used in Mesopotamia for masonry andwaterproofing. ○ 1870: First asphalt pavement laid in Newark, NJ. 1926 onwards: Petroleum asphalt production increased significantly. ○ Key Grades and Specifications: ○ Penetration (AASHTO M-20): AC 40-50, AC 60-70, AC 85-100. ○ Viscosity (AASHTO M-226): Original: AC-2.5, AC-5, AC-10. Residue: AR-10, AR-20. ○ Performance Grades (AASHTO MP1): PG 46, 52, 58, 64, 70, 76, 82 (temperature grades specified). Testing: ○ Penetration Test: Measures consistency. ○ Ductility Test: Determines stretching ability withoutbreaking. ○ Flash Point Test: Identifies safe heating temperature. ○ Viscosity Test: Assesses fluidity and flow characteristics. Applications: ○ Binder, waterproofing, roofing, prime coat, tack coat, and seal coat. Concrete Masonry Units (CMU) Specifications: ○ ASTM C-90: Load-bearing concrete masonry units. ○ ASTM C-129: Non-load-bearing concrete masonry units. Testing Requirements: ○ One quality test for every 10,000 units or fraction thereof. ○ Specimen Breakdown: 3 specimens for compressive strength. 3 specimens for moisture content and absorption. Compressive Strength: ○ Significance: Indicates structural suitability. ○ Calculation: Net Area Compressive Strength = Moisture Content & Absorption: ○ Significance: Determines water resistance and absorptioncapability. ○ Steps: Measure and record mass as sampled. Oven-dry specimen to constant weight and record as dry mass. Saturate specimen for 24 hours and record as wet mass. Weigh submerged specimen and record as immersed mass. ○ Formulas: Moisture Content (%) = Absorption (kg/m³) = Reinforcing Steel Bars Types: ○ Deformed Bars: Surface has lugs/protrusions. ○ Plain Bars: Smooth surface. Grades: ○ Grade 280: Sizes 10–19 mm. ○ Grade 420: Sizes 10–57 mm. Key Properties: ○ Yield Strength: Minimum275 MPa. ○ Tensile Strength: Minimum480 MPa. ○ Elongation: Minimum12%. ○ Mass Variation: Must not exceed±6%of nominal weight. ○ Phosphorus Content: Maximum0.06%. Testing Procedures: ○ Yield Strength: ○ Tensile Strength: ○ Elongation: Acceptance Criteria: No rejection due to being overweight. Retests allowed if results are within close margins of specifications.
