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General Mix Concrete Quality Control: |
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1 - General Introduction
1 - General Introduction
The implementation of a proper Quality Control procedure with reliable and adequate instruments along with a professional team, can build a sound assurance to the ready mix as to its compliance with the technical national and international standards like ASTM, BS, ACI, Libnor and others.
This will strengthen the confidence and the mutual success between General Mix concrete and the clients.
Our Quality Control Policy covers all the aspects related to the production of reliable, sound and state of the art concrete going through all the levels of concrete production, transportation, pumping, site sampling and lab testing.
Each of these levels implements a different category of quality assurance program based on : • Material source and consistency • Laboratory instruments and equipments • Competence of the laboratory team • Production and handling • Follow up for the conformance to the general standards 2 - Quality Control Procedures
2 - Quality Control Procedures
2.1 Material Sampling (ASTM D-75)
All samples are identified upon sampling with the following information: • Material • Source – Date • Delivery Ticket number 2.1.1 Aggregates (ASTM C-33) Sampling and Testing of aggregates is conducted as per the list of tests and frequency. Every delivery is subject to a visual inspection before unloading. Any change in gradation, color or contamination presence will be detected, recorded and informed to the Technical dept. for corrective actions. Stockpiles are visually inspected biweekly for any non-conformity and to assure that no segregation is occurring. 2.1.2 Cement (ASTM C-150) Each daily delivery is subject to sampling for test analysis. Each sample is labeled and stored for a minimum period of one month in the lab store. Cement tests are conducted at least once per month as per the list of tests and frequency. Whenever any suspicion arises in the cement quality, the related sample will be subject to relative tests for assessment and evaluation. 2.1.3 Admixture (ASTM C-494) Each admixture delivery is subject to conformity tests (density and soild content). Each sample is labeled and stored for a minimum of 15 days in the lab store. If any changes in the color or density of the admixture are noted upon receipt of new shipment, the admixture supplier and the Technical department are notified for the corrective actions. Admixture dispensers are checked by the operators on a daily basis for the proper functioning and pump ability. The admixtures is regularly agitated by the use of circulation pumps in order to reduce the possibility of sedimentation 2.1.4 Mixing water (ASTM C-94) The mixing water pumped from the wells is tested for acceptance on a routine basis at least every 3 months. 2.2 Plants Equipments 2.2.1 Batching Plants The mechanical operation of the batching plants is regularly checked for any break down while the scales zeroing is checked daily. The weigh scales are calibrated every one month by a certified firm and these are subject to internal calibration on a monthly basis. 2.2.2 Truck mixers and pumps: Our well equipped mechanic shop ensures the proper functioning of the equipments for a consistent concrete supply with the least accidents. Our equipments are thoroughly checked on monthly basis along with a normal daily checking. 2.3 Concrete Production Control 2.3.1 Batching Aggregates moisture tests are conducted twice per day to ensure the water quantity added to the mix and establish a consistent slump and yield before concrete is supplied to site. The process for concrete production is issued via a fully computerized system which shows the actual materials quantities in the mix. The operator is a well trained technician for identifying any noticeable change in the mix ingredients. Mix design is not modified without immediate notification of plant management, laboratory and technical Dept. 2.3.2 Concrete workability During concrete supply, the drivers are well trained to monitor and report the slump loss or increases in water demand. Trial mixes are consistently checked for evaluating the slump loss during concrete supply. In case of late delivery due to traffic or any delay that could occur on site, the drivers are trained to estimate the slump and to adjust accordingly by using the adequate admixture quantity. This will be applied in accordance with the client/consultant approval. 2.3.3 Transportation and pumping All concrete transit mixers and pumps are calibrated, capacity controlled and mechanically tested for reliability and failure risk elimination while performing their duties. Concrete volume delivered is checked on a routine basis for yield calculation .Rouring control and delivery quality assurance is being scheduled and controlled for technical compliance. A qualified team of pumping will coordinate with the client to ensure the quickest and proper pumping facilities on site using the appropriate extensions and scaffolding needs. 2.3.4 Site Testing During concrete pouring, a mobile laboratory is being allocated for cylinders sampling as agreed with the client/consultant for the number of samples. The technician on site is well experienced personnel capable of solving general concrete problems related to slump loss, concrete workability and proper pouring. 3 - Company's Liability and Third Party Assistance.
3 - Company's Liability and Third Party Assistance.
The Company’s liability in respect of defects in the goods includes failure to comply with the specifications, such specifications having been given to and accepted by the Company in full at the time of enquiry is limited to the cost of removal and replacement. The Company can only accept such liability where the Purchaser can establish that:
• No extra water in excess of the amount recommended or any other material has been added to the product without the prior agreement of the Company • The sample tested has been taken during discharge from the Company’s vehicle or from a central mixer in the case of goods collected from the Company’s plants, in accordance with the relevant clauses of ASTM C-172. • All sampling, making, curing and testing of specimens has been carried out in accordance with the relevant clauses of ASTM C-172 and C-31 and tested in our laboratories (free of charge) or in a certified laboratory (all external tests will be borne by the Purchaser). The tests will take place in any of the following laboratories to be selected by the Purchaser upon its requirements that tests be made: - Laboratory of American University of Beirut - Laboratory of Institute for Scientific Research - Laboratory of Ecole Superieure d’Ingenieurs de Beyrouth - Laboratory of Advanced Construction Technology Services (ACTS) • Test results have been interpreted in accordance with ASTM C-39 or any other specification previously accepted in writing by the Company. • References to compressive strength in the specification shall unless otherwise agreed refer to compressive strength obtained from concrete cylinders, made, Cured and tested in accordance with ASTM C-39. • The Purchase has notified the Company within 40 days from the date of delivery of the goods of their failure to comply with the specification. • The Company has been given an opportunity of investigating any alleged defect and of making representations as to any remedial action to be taken. If the defect in goods should have been revealed by examination on delivery, the Company’s responsibility in respect of such defect shall be limited to the delivery of a fresh supply of goods. Under no circumstances will the Company accept responsibility or liability for the workmanship of the Purchaser’s employees or subcontractors. 4 - Control of NonConforming Product
4 - Control of NonConforming Product
• Company's product (Ready mix concrete) conformity is assured by computer software control and regular machine calibration and product testing
• Company's inventory control system (on site storage areas) prevents nonconforming materials from being used • Nonconforming, not-approved goods are marked visibly and stored in a separate location in the storage area • When parts show nonconformance during assembling, these are returned to the storage area and destroyed or reworked • Suspect materials (such as asphalt or concrete) are tested in the laboratory or sent to specialized laboratories for validation, and refused if laboratory reports show the materials as non-conforming • Test cylinders of concrete are clearly marked and stored in a protected area in the Laboratory • Results of all non-conforming goods and products are filed. 
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