Concrete Mix Design - Report Example

Material technical report Module title: Module code: ------ Assignment: Value: ------ Assignment Tutor: ------- Student Name: ----- ID: ------ Submission date: ------ Executive summary The aim was to design concrete mix using BRE method and compare compression strength of cylinder and cubes from the mix. There was also comparability of their workability, elastic modulus, Load rates and Hardened concrete density test. The result indicated that the cylinder had better workability test and elastic modulus; however cubes had better hardened concrete density. The graph showed that the as the load increases deflection increases as the same rate. Table of Contents Material technical report 1 Module title: 1 Value: ------ 1 Executive summary 2 List of tables and figures 4 Introduction 5 Experimental method 5 Results 6 Casting and sample testing 6 RC Beam test 8 Discussion 11 Conclusion 12 References 13 List of tables and figures Table 1: results spreadsheets 7 Table 2: load, deflection and Demec reading 8 Table 3: Plot strain distribution 9 Introduction The durability of a structure depends on the strength of concrete as well as the ability of the cement to deflect in case there is a load applied to it. This is done by looking at the tensile strength and elastic modulus. Load-bearing capacity is done using deflection which is measured by compressive strength of the cubes and cylinders in the experiment. Its use help increase in-situ strength of concrete giving an ultimate design and reduce the expected weight as well as allow concrete design mix to strengthen. In addition, the effect of the concrete design mix will have a strong structure in regard to reducing the effect of the exerted weight. The report therefore forms a basis for interesting skepticism that allows one to re-evaluate the unifying theme of the concrete design mix. It will also be instrumental in ensuring that the concrete mix design is stable despite the many weather conditions that could subjected to it. Experimental method In order to achieve useful 28-day compressive strength we need a 50% fine aggregate that can passing at 600 sieve and coarse aggregate of 10mm. This will enable concrete mix design is used to maintain its’ strength has remained a marvel to modern architecture and architects have modified its’ characteristics to create various works. The cubes cast mould was of 100mmX100mmX100mm while the cylinder had radius of 50 and a height of 200mm. the experiment involved only three cubes and three cylinders. The concrete was mixed and poured to each moulds for cylinder and cube and vibrated to ensure concrete was compact and was allowed 24hours to to stick together before removing them. Results After carrying out experiment, the results of compressive test split tensile test, flexural test, RCPT and deflection test and analyzed and discussed in below. Casting and sample testing The following table shows results of casting and sample testing; Input by: Group number Design specification Characteristic strength (N/mm2) 20 Target slump 50 Target slump flow (mm) 600 Mix design used Cement (kg) 50 PFA(kg) 2 Water(kg) 10 Fine aggregate (kg) 30 Coarse aggregate (kg) 30 Trial mix Superplasticiser (g) 50 VMA(g) 50 Actual water used(kg) 9 Workability tests Slump(mm) 20 Slump flow(mm) d1 d2 L box (mm) H1 H2 V funnel flow time(s) 12 Hardened concrete density test Cubic mass(kg) 33.737 0.32006 0.34671 Cylinder mass(kg) 0.23739 0.17463 0.19393 Concrete density (kg/mm3) 500 500 500 Strength tests Curing time & regime(days cured in water or air) 28 28 28 Schmidst hammer rebound number R, angle, 25 26 27 Ultrasonic pulse time() 46 45.3 45 Pulse transmission length(mm) 22.1 23.4 22.8 Cube maximum load(kN) 66.37 66.37 66.37 Cylinder maximum load(kN) 66.37 66.37 66.37 Load rates Cube (N/mm2/s) 3.05 3.01 2.99 Cylinder (N/mm2/s) 3.886 3.827 3.801 Calculated strengths Cube compressive strength((N/mm2) 6.63 6.63 6.63 Cube strength()rebound hammer(N/mm2) 6.73 6.83 6.93 Cube strength(ultrasound)(N/mm2) 7.23 7.23 7.63 Cylinder compressive strength((N/mm2) 8.45 8.45 8.45 Calculated elastic modulus Compression (cube) ( kN/mm2 ) 27 26.2 24.65 Compression (cube-ultrasound) (kN/mm2 ) 25 24 25 Compression (cylinder) (kN/mm2 ) 27.23 26.75 26 Table 1: results spreadsheets Density of sample = = = 1118.1kg/m3 Load rates for cubes= = = 3.05 N/mm2/s Load rates for cubes= = =3.01 N/mm2/s Load rates for cubes= = = 2.99 N/mm2/s Load rates = = = 3.886 N/mm2/s Load rates = = = 3.827 N/mm2/s Load rates = = = 3.801 N/mm2/s Cube compressive strength((N/mm2) = = = 6.63 N/mm2 Figure 1: PFA and cement content The relationship cube strength is achieved and looking at the destructive and non-destructive tests, it will be noted that there is much difference in the strengths of the two. However cube has high compressive strength as opposed to cylinder. In this cement is seen the main unifying factor. A high strength material can be achieved at desirable concrete mix. The desirable part thickness depends on cement content and on PFA content for high strength. RC Beam test Tabular form –load, deflection and Demec reading Load Deflection 1 2 3 4 5 0 0 0 0.072 0.077 -0.325 -0.064 3 0.15 -0.011 0.063 0.055 -0.314 0.092 6 0.59 -0.028 0.055 0.051 -0.308 0.110 9 0.83 -0.047 0.046 0.063 -0.290 0.141 12 1.15 -0.079 0.042 0.073 -0.268 0.200 15 1.46 -0.085 0.040 0.091 -0.239 0.254 18 1.79 -0.106 0.035 0.104 -0.211 0.309 21 2.09 -0.125 0.028 0.119 -0.177 0.366 24 2.38 -0.147 0.023 0.131 -0.155 0.413 27 2.68 -0.164 0.017 0.138 -0.128 0.462 30 2.98 -0.189 0.011 0.155 -0.106 0.509 31 3.15 32 3.22 33 3.33 34 3.50 35 3.63 Table 2: load, deflection and Demec reading Load vs mid-span deflection Figure 2: Load vs mid-span deflection The graph above shows that an increase in the load leads to an increase in deflection. This will continue until a breaking point of 66.37kN is reached. However, it is a linear relationship up to 35kN. Plot strain distribution Load Deflection Strain 1 2 3 4 5 0 0 0 0 0.072 0.077 -0.325 -0.064 6 0.59 -0.028 0.055 0.051 -0.308 0.110 12 1.15 -0.079 0.042 0.073 -0.268 0.200 18 1.79 -0.106 0.035 0.104 -0.211 0.309 24 2.38 -0.147 0.023 0.131 -0.155 0.413 30 2.98 -0.189 0.011 0.155 -0.106 0.509 Table 3: Plot strain distribution Figure 3: Strain distribution From the chart above it is observed can be noted that when load increases to certain point when it changes to uniformity point decreases, the bending is increased for the same load. The graph indicates that the shear stress cases deformation and different positions of the beam. The measurement of the strain in opposite sides of the section is not identical according to the plotted graph Load verses maximum compression Figure 4: Load verses maximum compression Discussion Casting and sample testing However cube has high compressive strength as opposed to cylinder. In this cement is seen the main unifying factor. A high strength material can be achieved at desirable concrete mix. The desirable part thickness depends on cement content and on PFA content for high strength. Mix Redesign The experiment involved the flow workability test and the load test was done. The calculated strain were both negative and positive values. The modulus elasticity of the beam appears to change in the opposite direction of the deflection. The results showed that changes in load will have an similar effect on deformation RC beam with theory where deflection is said to be proportional to the limit of modulus elasticity some of the result obtained provided figures which were not consistent with universally accepted values. This is associated with errors during recording, measuring and calculating. Conclusion From the experiment Compressive strength of both cylinder and cubes a minimal difference is minimal. The compressive strength of cylinder is however better by at least 8.23% while calculated elastic modulus for the cube was higher than that of the cylinder. The load rates were seen to be lower cubes than in cylinder concrete mix. The breaking point as well as strain distribution behavior is predicted for RC beam at a given at 90 degrees indicated that result is no similar with theoretical value. It assumed that the stress to be proportional to the strain. In case of load is applied to the equation as seen above such as force the shear- strain will be subject to breaking point. References Bentz, E. C. et al, 2006. “Simplified Modified Compression Field Theory for Calculating Shear Strength of Reinforced Concrete Elements”, ACI Structural Journal Bungey, J. & Madandoust, R. 2004. Strength variation in lightweight concrete beams. Cem Concr Res., Francis A., 2013. “Mechanical properties of self curing”, Indian journal of emerjing trends in engineering and development, vol. 2 pp. 641 - 647. Mindess, S., Young, J.F, & Darwin, D. 2003. Concrete . New York: Prentice Hall. Ponikiewski, T., 2013. “Flexural behaviour of self-compacting concrete reinforced with different types of steel fibers” Construction and Building Materials Vol. 47 pp. 397–408. Ranjbar, M., Hosseinali Beygi, M., Nikbin, I., Rezvani, M. & Barari, A. 2011. Evaluation Of The Strength Variation Of Normal And Lightweight Self-Compacting Concrete In Full Scale Walls. Materials and technology Ravikumar M., Selvamony, K., Gnanappa, S. 2009. “Development of high strength self compacted self curing concrete with mineral admixtures”, ARPN J Eng, Vol. 3, pp. 103-108. Tsartsari and Byars, 2002. Ultra-high-strength concrete using conventional casting. Concrete Read More