Proportioning manufactured sand in flowable concrete

Manufactured sand has started to be used in concrete due to its availability and low cost. However, it has different shape properties, gradations, and mineralogy in comparison to the natural sand, and these differences can impact the performance of the concrete. This work quantifies the shape properties of manufactured sands and natural sands using sophisticated tests such as the AIMS II and more practical lab tests such as the Uncompacted Voids Content (ASTM C1257 -Method A). A correlation between these two measurements is presented. Next, concrete mixtures are proportioned with different amounts and gradations of manufactured sand at a variety of paste volumes, and their influence on the concrete workability is measured. Adjustments are also made to the Tarantula Curve Mixture Design tool to accommodate the different characteristics of manufactured sands in a concrete mixture for flowable concrete that must be finished. Further, this work investigates the impacts of manufactured sand on the pumping pressures. The workability and pumping pressure for three different manufactured sand sources and one natural sand are compared. Recommendations are made for the usage of manufactured sand in pumpable concrete mixtures. Also, the fine sand content and the combined uncompacted voids content of blended fine aggregates (natural sand and manufactured sand) are shown to be significant for concrete pumpability. Further, suggested changes are made to the fine sand content minimum limit on the Tarantula Curve to be 27% to keep pumping pressures manageable

Quantitative Evaluation in the Box Test and Evaluation of Field Mixtures by the Tarantula Curve

In this research project, a proposed evaluation technique of the surface voids concentrations in the Box Test was introduced. This was done by the development of a point count template that can allow critical surface voids to be identified and the evaluation to be more systematic. This method showed reliable results with low variability and can be considered as a useful tool in the Box Test surface voids assessment. Vibrators consolidate the concrete by removing unwanted air voids from its matrix. Frequency of a vibrator is one of the key parameters that impacts the vibration effort. An investigation was made to determine the effect of changing the vibrator’s frequency on the consolidation degree of concrete in terms of the amount of surface voids concentrations by the use of the Box Test. Results showed that a reduction in the frequency level could dramatically increase the surface voids concentrations at the sides of a Box Test sample. Finally, the Tarantula Curve, which is a new aggregate gradation technique that gives recommendations of aggregate gradations used in designing concrete mixtures. Hundreds of field mixtures that were made and placed and utilized in different states were compared to the suggested recommendations. Results showed that there were high agreement between the evaluated aggregate gradations and the Tarantula limits.Civil Engineerin