Quality Assurance

Quality Assurance of Concrete

1. Physical Properties of Aggregates

1.1 Fine Aggregate (River Sand and Crushed Sand)

  • Fine Aggregate (River Sand and Crushed Sand)
    • Sieve analysis test (ASTM C 136)
    • Surface moisture test (ASTM C 70)
    • Organic impurities test of fine aggregate (ASTM C 40)
    • Bulk density test (ASTM C 29)
    • Specific gravity and absorption test (ASTM C 128)
    • Clay lump and friable particles test (ASTM C 142)
    • Material finer than 75μm (No.200) sieve test (ASTM C 117)
  • Coarse Aggregate (River Shingle and Crushed Stone)
  • Sieve analysis test (ASTM C 136)
  • Bulk density test (ASTM C 29)
  • Specific gravity and absorption test (ASTM C 127)
  • Flat and elongated particles test (ASTM D 4791)
  • Clay lump and friable particles test (ASTM C 142)
  • Material finer than 75μm (No.200) sieve test (ASTM C 117)

Testing for physical properties of every incoming batch aggregate are done not only at internal laboratory according to standard method and procedure but also external third party laboratory as specified interval. Nominal maximum size of 9.5 mm and 19 mm coarse aggregate are commonly available for general mix proportion and nominal maximum size of 25 mm and 37.5 mm can be applied as project required.

2. Cement
  • Physical Properties of Ordinary Portland Cement
    • Compressive strength of hydraulic cement mortar test (ASTM C 109)
    • Normal consistency of hydraulic cement (ASTM C 187)
    • Setting time test of hydraulic cement by Vicat Needle (ASTM C 191)
    • Fineness of hydraulic cement by Air-Permeability Apparatus (ASTM C 204)
    • Soundness test (BS EN 196-3)

Type-1 Ordinary Portland Cement is mainly used in concrete production. Apache cement manufactured by Shwe Taung Cement is widely used in most of concrete mix proportions. Cement mortar test are regularly performed for every incoming cement in internal laboratory. Monthly physical quality testing of current using cement is done in order to assure the quality. Also, chemical properties of each batch cement can be available from cement test certificate of manufacturer/supplier. Cement stored at warehouse over three months is retested for use in production.

3. Water
  • Ground water
    • pH value
    • Chloride 
    • Sulphate
    • Total alkalinity 
    • Total solid

Water analysis test is conducted at external laboratory at every six months. Usually, water is kept in clean and free from undesirable particle, injurious amount of sewage, oil, acid and other deleterious matters.

  • Cool water

Cool water can be available and applied for concrete temperature purpose as special requirement of construction projects.

4. Admixture
  • Retarder
  • Superplasticizer 
  • High range water reducing admixture (polycarboxylate ether polymer base)
  • Air- Entrained admixture
  • Waterproofing admixture
  • Slump retention admixture

Most of chemical suppliers are Grace, Sika and BASF. Quality assurance certificate of each incoming batch can be available from chemical supplier. Specific gravity test of every incoming chemical admixture is done as an internal quality checking.

5. Concrete
  • Testing of Fresh Concrete
    • Workability/ Slump test (ASTM C 143)
    • Unit weight test (ASTM C 138)
    • Air content test by pressure (ASTM C 231) 
    • Temperature test of fresh concrete (ASTM C 1064)
    • Concrete setting test (ASTM C 403)
  • Concrete sampling (ASTM C 172)
  • Concrete specimen making and curing
    • At Laboratory condition (ASTM C 192)
    • At Field condition (ASTM C 31)

Every batch of concrete supplied will be mixed thoroughly and performed required fresh concrete tests before delivery to construction sites. Slump test and specimen making will be responsible of concrete supplier.  Six number of cube or cylinder specimens are collected per 100 cubic meter or as per customer site requirement.

  • Testing of Hardened Concrete
    • Compressive strength test

In order to monitor and control concrete quality, in- house concrete specimens are tested compressive strength at the age of 3 days, 7 days and 28 days or as required.

  • Acceptance Criteria of Concrete (ACI 318)
    • Every arithmetic average of any three consecutive strength tests equals or exceeds specified strength fc’.
    • No strength test falls below specified strength fc’ by more than 3.5 MPa when fc’ is 35 MPa or less or by more than 0.10 fc’ when fc’ is more than 35 MPa.
6. Calibration

Batching load cells and all testing equipment will be calibrated by external labs or in-house labs at appropriate intervals.

7. Quality Control Documentation
  • Incoming Quality Check List for Cement and Cementitious Materials
  • Incoming Visual Check List for Fine Aggregate
  • Incoming Visual Check List for Coarse Aggregate
  • Incoming Quality Check List for Chemical Admixture
  • Visual Check List for Mixing Water
  • QC Check List At Plant
  • QC Check List On Site
  • Concrete Trial Mix Record and Report
  • Screening Machine Daily Checklist and Operating Record
  • Compressive Strength of Concrete Specimen
  • Daily In-house Compression Test Pass Fail Record
  • Test Record for Rebound Number of Hardened Concrete
  • Compressive Strength of Cement Mortars Cube Specimens
  • Test Record for Surface Moisture in Fine Aggregate
  • Test Record for Evaporable Moisture Content
  •  Sieve Analysis of Fine and Coarse Aggregate
  • Test Record for Bulk Density of Aggregate

Ready-Mixed Concrete

Available Concrete Products

  • Ordinary Concrete
  • Air- Entrained Concrete
  • Temperature Control Concrete
  • High Early Strength Concrete
  • High Strength Concrete
  • Waterproofing Concrete
  • Self-Compacting Concrete
  • Slump Retention Concrete
  • Under Water Concrete
  • Pervious Concrete