The Material and Fundamentals in Production and Design of Material - Assignment Example

1.0 Introduction and Objectives The production process of concrete is seen as a very important aspect in terms of quality control in many projects where construction is involved. Formation of concrete involves cement hydration (ASTM C 702-98, 2003).aggregates, water and cements are the three components of concrete where cement serves as the bonding agent. Ordinary Portland cement is in common use in a country like the UK (Babor, et al, 2009). Portland cement is compost of calcium and aluminium silicates that are formed through heating and fusion of limestone and shale. The formation of stiff building material is as a result of water and calcium silicates reacting with fine fibres or crystals being formed and being cemented together. The hydration process is greatly affected by the amount of water. Addition of too little amount of water may be a hindrance to the hydration process where the optimal strength may not be attained , on the other hand excessive water results to void formation that results to low density and thus low strength (Murdock, L. J. and Brook, K. M., 1979). It is from this that water content of the mix is one of the basic steps when it comes to concrete design and control process. Normally structural concrete design is from characteristic design strength (Naik, 2005). In this experiment mix details were given and this have been used to come up with the design mix. The objective of the experiment was to introduce the material and some fundamentals in production and design of material. The calculation involved in the experiment were as follows NB: 1 N mm-2 = 1Mpa Aims and objectives The aim of the experiment is to investigate and validate the theory that is associated with concrete mix design and to use Pulverised Fly Ash (PFA) as partial cement replacement. The objectives are 1. Designing and batching a normal concrete trial mix using BRE method with PFA as a partial replacemet with the mix being modified to come up with a self compacting concrete (SCC). 2. Performing standard workability tests and reporting the outcome 3. Casting several concrete samples and performing standard tests on the samples to establish mechanical properties of the hardened concrete 4. Re-designing the trial mix using the observed workability and strength results 5. Undertaking analysis of the concrete results for all mixes used in the experiment by the module cohort and drawing conclusions on the efficacy of using PFA as a partial cement replacement and self-compacting concrete to improve the sustainable use of concrete in practice. 6. 1.2 Experiment procedure Coarse aggregate, the fine aggregate and cement were dry mixed thoroughly with care being taken to avoid production of dust. Water was added gradually as the concrete was being mixed to a point where the mix was of uniform colour and consistency. A slump test was done for each of the three mixes with the first step being the placing of the cone on a tray and securing it in place. A representative sample of concrete was obtained and the cone was filled in three layers with each layer being tampered 25 times. Surplus concrete was struck off to ensure that concrete was level with the top of the cone. About 5 to 10 seconds was taken as the cone was being carefully lifted straight up, the cone was then inverted and placed next to the mound of concrete. The tamping bar was laid across the top of the inverted cone in a way that it passed across the top of the concrete mound at its highest point. The distance between the underside of the bar and the highest point the concrete was measured to the nearest 5mm, this being the measure of slumping in the concrete. The concrete was then returned to the original tray and was mixed with the remaining concrete. The 100mm standard cube mould was filled in three equal layers and compacting each of the layers with at least 25 strokes using a tamping bar. Surplus concrete was removed and the top surface was levelled using a trowel and the concrete was then left for 7 days. The corresponding mould numbers were recorded in a table against the appropriate mix After the seven days the samples were retrieved from the curing tank. The dimensions of the cubes were measured, their masses were recorded and their volumes and densities were calculated with the data being entered into a table. One cube for each water cement ratio cube samples was saturated in the vacuum apparatus under a close supervision of the laboratory supervisor or technician. The specimens were placed in a vacuum chamber which was evacuated for 10 minutes. The chamber was then flooded with water that saturated the specimens and upon 10 minutes lapse the specimens were removed. The surplus water was wiped off, the specimens were then weighed and their saturated masses recorded in a table. 1.3 Calculations Characteristic strength : 20Mpa Target age : 28days Type of cement = CEM1 class 52.5 Coarse aggregate: 10mm maximum size, uncrushed Fine Aggregate = 50% passing 600µm sieve Specific gravity Cement = 3.15 Fine Aggregate = 2.61 Coarse Aggregate (10mm) = 2.66 Minimum Cement =400 kg / m3 Maximum water cement ratio = 0.45 1.4 Mix Calculation: – Target Mean Strength = 20+ ( 5 X 1.65 ) = 28.25 Mpa Selection of water cement ratio:- Assume water cement ratio = 0.4 Calculation of water Approximate water content for 10mm max. Size of aggregate = 208 kg /m3 (As per Table 2 ). Calculation of cement content Water cement ratio = 0.4 Water content per cum of concrete = 208 kg Cement content = 208/0.4 = 520 kg / m3 Calculation for C.A. & F.A. Volume of concrete = 1 m3 Volume of cement = 520 / (3.15 X 1000) = 0.1650 m3 Volume of water = 208 / (1 x 1000) = 0.208 m3 Total volume of other materials except coarse aggregate = 0.208 + 0.1650 = 0.373 m3 Volume of coarse and fine aggregate = 1 – 0.373 = 0.627 m3 Volume of F.A. = 0.7016 X 0.33 = 0.2315 m3 (Assuming 33% by volume of total aggregate) Volume of C.A. = 0.7216 – 0.2315 = 0.4901 m3 Therefore weight of F.A. = 0.2315 X 2.61 x 1000 = 604.215 kg/ m3 Say weight of F.A. = 604 kg/ m3 Therefore weight of C.A. = 0.4901 x 2.655 X 1000 = 1301.2155 kg/ m3 Say weight of C.A. = 1301 kg/ m3 Density = (208+520+604+1301)/1=2633 km/m3 Changes with admixture As plasticizer is proposed we can reduce water content by 20%. Now water content = 208 X 0.8 = 166.4 kg /m3 Cement content = 166.4/0.4 = 416 kg / m3 Volume of cement = 416 / (3.15 x 1000) = 0.1320 m3 Volume of water = 166.4 / (1 x 1000) = 0.1664 m3 Volume of Admixture = 4.994 / (1.145 x 1000) = 0.0043 m3 Total volume of other materials except aggregate including admixture = 0.1320 + 0.1664 +0.0043 = 0.3027 m3 Total weight of aggregate =1- 0.3027 m3=0.6973 m3 Volume of F.A. (with admixture included) = 0.6973 x 0.33 = 0.2301 m3 (Assuming 33% by volume of total aggregate) Volume of C.A.(with admixture) = 0.6973 – 0.2301 = 0.4672 m3 Therefore weight of F.A. (with admixture) = 0.2301 x 2.61 X 1000 = 600.561 kg/ m3 Say weight of F.A. = 600 kg/ m3 Therefore weight of C.A.(with admixture) = 0.4672 x 2.655 x 1000 = 1240.416 kg/ m3 Say weight of C.A. = 1240 kg/ m3 Density= 166.4+416+600+1240.4+4.994=2427.794kg/m3 1.5 Results Table 2 Sample Mould type Slump(mm) Cubecross-sectional area (mm2) Cube volume Cube mass(kg) Cube density Average compressive strength (Nmm-2) Average cube density (mm3) (m3) 1 1 wet 40 10000 1000000 0.001 2.281 2281 33.73 1771.3 2 dry 10000 1000000 0.001 1.2616 1261.6 2 1 wet 45mm 10000 1000000 0.001 2.2923 2292.3 32.006 1775 2 dry 10000 1000000 0.001 1.2577 1257.7 3 1 wet 40 10000 1000000 0.001 2.2837 2283.7 34.671 1770 2 dry 10000 1000000 0.001 1.2563 1256.3 Sample Mould number Slump(mm) Cubecross-sectional area (mm2) cylinder volume Cube mass(kg) Cube density Average compressive strength (Nmm-2) Average cube density (mm3) (m3) 1 1 wet 45 7854 1570800 0.00157 3.6225 2307.325 23.73 1797.2 2 dry 7854 1570800 0.00157 2.0206 1287.006 2 1 wet 40 7854 1570800 0.00157 3.5902 2286.752 17.46 1781.27 2 dry 7854 1570800 0.00157 2.0030 1275.796 3 1 wet 55 7854 1570800 0.00157 3.8442 2448.535 19.39 1872.99 2 dry 7854 1570800 0.00157 2.037 1297.452 1.6 Ultrasonic test results The modulus of elasticity is given by the relationship Where  represents the Poisson’s ratio,  is density of specimen and  is the longitudinal wave velocity for the sample materials From the experiment  is determined from and from the calculated densities  is obtained by choosing appropriate Poisson’s ratio. After obtaining E the relationship  By using this procedure the following were the concrete strength for the cubical and cylindrical samples Table 3: Strength for cubical samples Sample Strength 1 22.1 2 23.4 3 22.8 Table 4: Strength for cylindrical samples Sample Strength 1 23.739 2 17.463 3 19.393 1.7 Discussion From the mix calculation it has been seen that with admixture the water content maybe reduced by up to 20%. The wet density of a mix with admixture is seen to have a lower density compared to that without admixture. Usually this lower density is supposed to be taken care of by increasing the amount of cementious materials by about 10%. From the results it was seen that the cubical samples had higher strength compared to the samples with cylindrical sections. This could be an indication that in a cylindrical sections the cross sectional area is smaller and thus failure occurs at a lower load. The results also indicated that samples with higher strength had higher slump value. This could be an indication that the samples with higher strength had higher cement and high cement increased workability of the mix which resulted to a higher slum value. Conclusion This experiment has shown that it is possible to come up with a concrete mix of the desired strength. To achieve this it is required to come up with several mixes and to make adjustment in the desired direction. References ASTM C 702-98(2003), “Standard Practice for Reducing Samples of Aggregate to Testing Size.” ASTM C 637-98a (2003), “Standard Specification for Aggregates for Radiation-Shielding Concrete.” Babor, D., Plian, D. and Judele, L. (2009) “Environmental Impact of Concrete”, Publicat de Universitatea Tehnică „Gheorghe Asachi” din Iaşi Hansen, T. C. and Narud, H. (1983) “Strength of Recycled Concrete Made from Crushed Concrete Coarse Aggregate”, Concrete International, Vol. 5, Iss. 1, pp 79–83. Laskar, A. I. (2009) “Correlating slump, slump flow, vebe and flow tests to rheological parameters of high-performance concrete”, Materials Research, Vol. 12, Iss. 1, pp. 1516–1439. Logic Sphere (n.d.) “Slump Test”, visited on 31-03-2010, available at: http://logicsphere.com/products/firstmix/hlp/html/work5xd0.htm Murdock, L. J. and Brook, K. M. (1979) “Concrete Materials and Practice”, 5th edition, London, Edward Arnold Ltd. Naik, T. R. (2005) “Sustainability of Cement and Concrete Industries”, Presented and Published at the Global Construction: Ultimate Concrete Opportunities, Dundee, Scotland. Available at: http://www4.uwm.edu/cbu/Papers/2004%20CBU%20Reports/CBU-2004-15.pdf, visited on 15/04/2010. Read More

The tamping bar was laid across the top of the inverted cone in a way that it passed across the top of the concrete mound at its highest point. The distance between the underside of the bar and the highest point the concrete was measured to the nearest 5mm, this being the measure of slumping in the concrete. The concrete was then returned to the original tray and was mixed with the remaining concrete. The 100mm standard cube mould was filled in three equal layers and compacting each of the layers with at least 25 strokes using a tamping bar.

Surplus concrete was removed and the top surface was levelled using a trowel and the concrete was then left for 7 days. The corresponding mould numbers were recorded in a table against the appropriate mix After the seven days the samples were retrieved from the curing tank. The dimensions of the cubes were measured, their masses were recorded and their volumes and densities were calculated with the data being entered into a table. One cube for each water cement ratio cube samples was saturated in the vacuum apparatus under a close supervision of the laboratory supervisor or technician.

The specimens were placed in a vacuum chamber which was evacuated for 10 minutes. The chamber was then flooded with water that saturated the specimens and upon 10 minutes lapse the specimens were removed. The surplus water was wiped off, the specimens were then weighed and their saturated masses recorded in a table. 1.3 Calculations Characteristic strength : 20Mpa Target age : 28days Type of cement = CEM1 class 52.5 Coarse aggregate: 10mm maximum size, uncrushed Fine Aggregate = 50% passing 600µm sieve Specific gravity Cement = 3.

15 Fine Aggregate = 2.61 Coarse Aggregate (10mm) = 2.66 Minimum Cement =400 kg / m3 Maximum water cement ratio = 0.45 1.4 Mix Calculation: – Target Mean Strength = 20+ ( 5 X 1.65 ) = 28.25 Mpa Selection of water cement ratio:- Assume water cement ratio = 0.4 Calculation of water Approximate water content for 10mm max. Size of aggregate = 208 kg /m3 (As per Table 2 ). Calculation of cement content Water cement ratio = 0.4 Water content per cum of concrete = 208 kg Cement content = 208/0.

4 = 520 kg / m3 Calculation for C.A. & F.A. Volume of concrete = 1 m3 Volume of cement = 520 / (3.15 X 1000) = 0.1650 m3 Volume of water = 208 / (1 x 1000) = 0.208 m3 Total volume of other materials except coarse aggregate = 0.208 + 0.1650 = 0.373 m3 Volume of coarse and fine aggregate = 1 – 0.373 = 0.627 m3 Volume of F.A. = 0.7016 X 0.33 = 0.2315 m3 (Assuming 33% by volume of total aggregate) Volume of C.A. = 0.7216 – 0.2315 = 0.4901 m3 Therefore weight of F.A. = 0.2315 X 2.61 x 1000 = 604.

215 kg/ m3 Say weight of F.A. = 604 kg/ m3 Therefore weight of C.A. = 0.4901 x 2.655 X 1000 = 1301.2155 kg/ m3 Say weight of C.A. = 1301 kg/ m3 Density = (208+520+604+1301)/1=2633 km/m3 Changes with admixture As plasticizer is proposed we can reduce water content by 20%. Now water content = 208 X 0.8 = 166.4 kg /m3 Cement content = 166.4/0.4 = 416 kg / m3 Volume of cement = 416 / (3.15 x 1000) = 0.1320 m3 Volume of water = 166.4 / (1 x 1000) = 0.1664 m3 Volume of Admixture = 4.994 / (1.145 x 1000) = 0.

0043 m3 Total volume of other materials except aggregate including admixture = 0.1320 + 0.1664 +0.0043 = 0.3027 m3 Total weight of aggregate =1- 0.3027 m3=0.6973 m3 Volume of F.A. (with admixture included) = 0.6973 x 0.33 = 0.2301 m3 (Assuming 33% by volume of total aggregate) Volume of C.A.(with admixture) = 0.6973 – 0.2301 = 0.4672 m3 Therefore weight of F.A. (with admixture) = 0.2301 x 2.61 X 1000 = 600.561 kg/ m3 Say weight of F.A. = 600 kg/ m3 Therefore weight of C.A.(with admixture) = 0.4672 x 2.655 x 1000 = 1240.

416 kg/ m3 Say weight of C.A. = 1240 kg/ m3 Density= 166.4+416+600+1240.4+4.994=2427.794kg/m3 1.5 Results Table 2 Sample Mould type Slump(mm) Cubecross-sectional area (mm2) Cube volume Cube mass(kg) Cube density Average compressive strength (Nmm-2) Average cube density (mm3) (m3) 1 1 wet 40 10000 1000000 0.001 2.

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