Materials Engineer Pre-Accreditation Comprehensive Study Guide

Concrete Materials and Properties

• Lean Concrete Strength and Dimensions

  • Minimum Compressive Strength: The minimum compressive strength required for lean concrete is $1,500\,psi$.
  • Procedural Note: Materials engineers must also be familiar with the minimum thickness requirements for lean concrete applications.

• Concrete Classes and Applications

  • Rubble Concrete and Slope Protection: The concrete class specifically designated for use in Rubble Concrete and Concrete Slope Protection is Class B.
  • Mechanically Stabilized Earth (MSE) Retaining Walls: Item 515 for MSE Retaining Walls utilizes Class A concrete.
  • Underwater Deposition: The class of concrete used specifically for deposition under water is Class Seal.

• Cement Cementitious Materials and Proportions

  • Cement Content for Class B: For Class B concrete, the required cement content per cubic meter is $9.5\,\text{bags}$.
  • Fly Ash Admixture: In Item 311 (PCCP), fly ash may be used as a mineral admixture but is limited to a maximum of $20\%$ partial replacement of Portland cement.
  • Effects of Fly Ash:
    • Improves concrete workability.
    • Increases concrete durability.
    • Leads to longer setting and curing times.
    • Exception: It does not increase the heat of hydration; it is typically used to reduce it.

• Physical Handling and Storage of Cement

  • Stacking Limits: To prevent the bursting of bags in the bottom layers, cement bags must be stacked no more than $12\,\text{layers}$ high, or to a maximum total height of $4.5\,m$.

• Concrete Testing and Quality Requirements

  • Strength Level Satisfaction: Concrete strength is considered satisfactory if the average of all sets of 3 consecutive strength test results equals or exceeds the specified strength ($f'c$), and no individual result is deficient by more than $15\%$ of the specified strength.
  • Core Sampling Adequacy: Representative cores (at least 3) are considered adequate if the average strength of the cores is at least $85\%$ of the specified strength and no single core is less than $75\%$ of the specified strength.

Bituminous and Asphalt Materials

• Asphalt Types and Composition

  • Rapid Curing Cut-back Asphalt: This is composed of asphalt cement combined with gasoline.
  • Asphalt Cement Alternative Name: Commonly referred to as Hot Asphalt.
  • Emulsifying Agents: Added to emulsified asphalt primarily to make water and asphalt combine effectively.

• Construction Procedures and Requirements

  • Bituminous Prime Coat (Item 301): This consists of preparing and treating an aggregate base course.
  • Item 302 Bituminous Tack Coat / Item 303 Seal Coat: Standard applications for emulsified and cutback asphalts.
  • Asphalt Mixing and Workability: The workability of an asphalt mix is highly dependent on the temperature of the asphalt mix.
  • Joint Sealing: The most appropriate penetration grade of asphaltic material for sealing Portland Cement Concrete Pavement (PCCP) joints is no more than 90.
  • Temperature Measurement: To determine the temperature of a delivered asphalt mix, an armored stem thermometer must be inserted to a minimum depth of $6\,\text{inches}$.

• Asphalt Pavement Compaction and Finishing

  • Rolling Speed: For both vibratory and static modes during asphalt construction, the rolling speed should be maintained between $3\text{ - }5\,km/hr$.
  • Tolerance: The minimum requirement for asphalt pavement thickness acceptance is $-5\,mm$.
  • Opening to Traffic (Item 734 SMA): Newly paved sections of Stone Mastic Asphalt must remain closed to vehicular traffic until the temperature cools to the atmospheric temperature of $40\text{ - }50\,^\circ C$.

• Asphalt Testing Protocols

  • Flash Point: Measures the tendency of asphalt to form a flammable mixture with air; identifies the safe working temperature limit to prevent fire.
  • Marshall Stability Test: Used to measure the resistance to deformation of a bituminous mixture.
  • Spot Test: Used to determine if the asphalt was overheated during the manufacturing process.
  • Cutback Asphalt specific tests: Includes the Float Test, Kinematic Viscosity, Flash Point, and Water Percent.

Soils and Aggregates

• Classification and Physical Properties

  • Plasticity Index (PI) Calculation: If Plastic Limit ($PL$) is $23$ and Liquid Limit ($LL$) is $35$, then $PI = LL - PL = 35 - 23 = 12$.
  • Fineness Modulus (FM): If the summation of percent retained from Sieve $3/8"$ to No. 100 is $287\%$, the FM is $2.87$.
  • Plastic Limit Test: The soil thread must begin to break at a diameter of $3.2\,mm$.

• Compaction and Earthworks

  • Compaction Curve: Graphing the Maximum Dry Density ($MDD$) and Optimum Moisture Content ($OMC$) forms a Parabolic curve.
  • Modified Proctor Test (AASHTO T-180): Utilizes a drop height of $18\,\text{inches}$.
  • Aggregate Layer Thickness: The maximum compacted thickness per layer for aggregate subbase and base courses is $200\,mm$. For a total thickness of $50\,cm$, the material must be placed in 3 layers.
  • California Bearing Ratio (CBR): Involves forcing a plunger into the sample to a depth of $2.5\,mm$.
  • Field Density Test (FDT) Frequency: For a $1,500\text{ - square meter}$ area of base course, $5$ sets of tests are required per layer.

• Quality and Gradation

  • Abrasion Loss: The maximum allowed percentage of abrasion loss for paving coarse aggregate is $40\%$.
  • Non-compliant Grading: If an aggregate sample passes all quality tests except for grading, the material should be processed again by blending.
  • Abrasion Sieve: The sieve size used for sieving materials discharged from an abrasion machine is No. 12.

Pavement Features and Highway Items

• Drainage and Slope Protection

  • Weep Holes: Spaced at not more than $2.0\,meters$ center-to-center in a staggered manner. They must be at least $50\,mm$ diameter PVC or other approved pipe material.
  • Riprap Stones: For Class A stones in riprap and grouted riprap, the weight must vary between $30\,kg$ to $70\,kg$.
  • Subsurface Drainage and Waterproofing: Geotextiles (Item 714) are used for hydraulic filters, erosion control, and as waterproofing/stress-relieving membranes.

• Traffic Markings and Signs

  • Traffic Paint Application: Applied at a rate of $0.33\,Liter/sqm$. Drying time (to be free from cracking) is $15\text{ - }30\,\text{minutes}$.
  • Glass Beads for Paint: Added at a rate of $500\,\text{grams/liter}$ of paint. The refractive index must be between $1.5\text{ - }1.6$.
  • Reflective Sheeting Brightness: When totally wet by rain, brightness shall not be less than $90\%$ of the specified table values.
  • Reflectorized Thermoplastic Rubble Strips: The height of these strips is $5\text{ - }13\,mm$.
  • Reflective Pavement Studs: Must support a vertical load of $10\,KN$ during testing.

• Road Surface and Quality

  • International Roughness Index (IRI): The acceptable IRI value for national primary roads is not more than 3 m/km.
  • Pavement Width: Base and subbase courses are compacted with an extension of $0.50\,m$ on each side, making the carriage way $1.00\,m$ greater than the design width.

Structural Materials and Specialized Repairs

• Steel Reinforcement (Rebars)

  • Splice Limits: Not more than $1/4$ of the bars may be spliced in the same cross-section unless specified.
  • Phosphorus Content: Acts as a ferrite strengthener after carbon; increases yield and tensile strength; improves atmospheric corrosion resistance.
  • Color Coding: Grade 275 rebars are identified by the color Green.
  • Weight: The weight of a $3\text{ - }meter$ long rebar with a $16\,mm$ diameter is approximately $4.75\,kg$.

• Carbon Fiber Sheet (CFS) and Repair

  • Minimum Tensile Strength: $3,400\,N/mm^2$.
  • Adhesion Testing: Executed via direct pull-off tests. Failure at the bond line at a tensile stress below $1.373\,MPA$ is cause for rejection.
  • Procedural Note: Familiarize with minimum pull-offs, Young’s modulus, lap length, and density of CFS.

• Shotcrete

  • Compressive Strength: Minimum required is $13.8\,MPA$.
  • Curing: Must be cured uninterrupted for at least $7\,\text{days}$.

• Grout and Miscellaneous Items

  • Non-Shrink Grout: Must be placed within $30\,\text{minutes}$.
  • Gabions: Dimensions must not differ by more than $\pm 5\%$ from ordered size. Fabrication of coconut geonets (Item 622) uses fibers $12\text{ - }24\,\text{microns}$ in diameter.

Sampling and Quality Assurance Protocols

• Sampling Frequencies

  • Piles: Integrity Testing must be conducted on at least $25\%$ of the total number of piles.
  • Concrete Coring: Average of 3 cores is required per specific lot size.
  • Bituminous Pavement Cores: Required every $250\,\text{linear meters}$ per lane.
  • Reinforced Concrete Pipe Culverts (RCPC): For a lot of 250 pieces, $5\,\text{samples}$ are taken for testing.
  • Aggregate Base Course: For $45,250\,\text{cubic meters}$, $31\,\text{quality tests}$ are required.
  • Hot-Dip Galvanized Coating: For articles with a surface area greater than $100,000\,mm^2$, the average of 3-specimen thickness grades is recorded.

• Instrumentation and Permits

  • Nuclear Density Gauge: High-technology equipment containing a radioactive source used to read in-place density or moisture content.
  • Chemical Procurement: Permits for laboratory chemicals like sodium hexametaphosphate are obtained from the PDEA.
  • Laboratory Authorization: Contractor Materials Engineers handling DPWH projects are generally not allowed to perform testing at DOST laboratories without specific authorization.

Standard Specifications (Buildings and Flood Control)

• Item 1000: Termite Control Work

  • Cordoning Method: Used when there is no visible evidence of termite infestation.
  • Application Rate: When infestation is present, the working solution is applied at a rate of $24\,Liters$ per square meter.

• Item 1704: Embankment (Flood Control)

  • Suitable Materials: Soils with a Liquid Limit ($LL$) less than 75 and Plasticity Index ($PI$) less than 50. Soils with a density of $800\,kg/m^3$ or lower are considered unsuitable.

• Item 1013: Corrugated Roofing

  • Wind Pressure: Each roof in position must be able to withstand wind pressure up to $250\,km/h$.

• Underwater Construction

  • Tremie: A large metal hopper and pipe system used to distribute freshly mixed concrete over an underwater site.