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|Title||Quality Function Deployment (QFD): A Method for Improving Concrete Characteristics Made From Recycled Aggregate Concrete (RAC)|
This study aims at developing a procedure for integrating the Quality Function Deployment (QFD) method as an effective design tool into recycled concrete ready mix concrete industry improvement; design, and prioritizing Engineering characteristic for concrete mix. The significance of this work lies in its attempt to provide some performance data of Recycle aggregate Concrete (RAC) made in Gaza Strip so as to draw attention to possible use of Recycled Concrete Aggregate (RCA) in ready mix concrete industry. This work is limited to the development of a suitable concrete mix design that satisfies the requirements of mix proportion in the plastic stage using Recycled Concrete Aggregates (RCA) and then to determine the strength and permeability of such concrete mix when exposed to stressing at different ages: 7, 28 for compressive strength, 28 days for flexure, split strength and 120 days for water penetrations. Moreover, it involves a comparative study of the strength and permeability of four concrete mixtures at various water cement ratio and Traditional Mix Approach (TMA) and Two Stage Mix Approach (TSMA) to specify which the best mix fit on economical and technical requirements. During the mix design, Quality Function Deployment (QFD) identified which components were the most critical to fulfilling customer requirements. As the products cost is analyzed, the QFD analysis could be used to support decisions to require a higher level of quality, and therefore a higher cost per unit quantity, for certain components. The biggest benefit of QFD analysis occurs when integrated into the mix design. As the final design is completed and refined, critical RAC specifications were made more stringent to reduce or eliminate the failure concrete sample. In practice, four replacement ratios (0.00, 030, 0.50, and 0.70) of the recycled aggregate, reduction of water cement ratio from 0.55-to-0.45-to-0.35 and cement content (330 kg/m3, 350 kg/m3 and 380 kg/m3) were considered to determine their effects on the improvement physical properties of the RAC and to obtain an acceptable quality of concrete with maximum utilization of recycled aggregate in place of natural aggregate using TMA,159 samples were prepared and measurements of compressive strength, splitting strength, flexure strength at 28days. In addition, the mix method was refined using TSMA with the same conditions and construct 135 samples and avoiding 30% replacement for water depth penetration test because it was not achieve economical requirements. Due to the laboratory test which is performed to ensure and prove the developmental shift on workability, strength and permeability of new concrete mix (RCA mix), it can be clearly seen that the permeability and the strength of the RCA concrete is very dependent on the properties of the RCA aggregate, percent substitutions, w/c and mixing method. According to the results of this study, concrete incorporating very well graded RCA replacing 50% of NCA and with accepted properties showed satisfactory results regarding water permeability and strength comparing with those of the standard concrete mixes, and consequently, it is recommended that the RCA concrete according to the final design proportions (with RCA replacing 50% of NCA) can be used as a sustainable material in structural applications and produced concrete structure grade B250- B300-B350 at w/c 045, 0.45 and 0.35 respectively, and can be widely used in construction works with optimum cost and water depth penetration less than 3cm (low permeability) due to using TSMA.
|Publisher||the islamic university|
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