The Modification of Concrete Structures - Lab Report Example

CONCRETE LAB REPORT By Concrete structures are liable to modification and improvement to enhance their performance and durability during their service life. The main reason for the adjustments change use new and better design standards deterioration the effects the steel exposure poor natural disaster such earthquakes and In such conditions, two possible solutions are put forward: replacement or retrofitting. Full structure replacement might have determinate disadvantages such as high costs for material and labor, reduced environmental effects and inconveniences due to the interruption of the functions of the structure such as traffic problems. If possible, it is advisable to upgrade a structure by retrofitting. Fly ash is commonly utilized in the manufacture of the concrete pavement mixtures, with the auxiliary levels. The replacement typically ranges from 10% to corresponding 20% of the underlying total cementitious material. Nevertheless, the specifications are commonly based on the empirical approximations that lack appropriate engineering examination. The effort decrease the carbon footprint related to the cement production severe effect the environment coupled the eventually concrete performance numerous transportation sectors have expressed interest utilizing relatively higher quantities the fly the concrete infrastructure While the prevailing high volumes fly ash, concrete is balanced to manufacture to produce durable concrete regardless of the underlying predicaments (Choo & Newman, 2003, pp. 123-167). For the recent years, the development of a strong and durable glue has resulted in a technique that which has considerable influence in the in structure upgrading. It involves sticking steel or fiber polymer plates to the concrete. The plates then act compositely with the concrete and help to carry the load. Aims and objectives The primary purpose of the experiment to perform an investigation to examine the theory linked with a mix design of concrete and the design and analysis of reinforced concrete beams. Below are the objectives of the experiment; 1. The method used was batch and Design, which was a standard concrete mix while using the BRE method. A self-compacting concrete was then achieved through the combination of PFA being a replacement for the cement. 2. A standard workability test was carried out, and the results were reported as bellow. 3. A variety of concrete samples were casted, and standard tests performed to examine the mechanical properties of the resulting hardened concrete. 4. Re‐designing of the non‐Self Compacting trial mix was carried out by the use of the using the strength and workability results observed. 5. All mixes in by in resulting of SCC to of in. 6. On the reinforced concrete casting, fabrication and loading test were carried out. 7. The deflection performance of the load on the RC beam predicted theoretical point of view were compared with the results, which were obtained, conclusions were drawn on the shortcomings of the established theory.. Experimental procedure Preparation of mix design was carried out by the individual students then compared to the results of other group members. Inconsistencies were investigated and resolved in order to ensure a well mix design before commencing the laboratory session. It was important for groups to earn as many marks as possible in the assessment sheet. Health and Protection risk administration within laboratory activities Long hair and loose clothes could be caught in the machine, in the lab in which the overhead crane operates. The moulds of the concrete are normally heavy, especially when full thus require taking special care of not dropping them. Moreover, an individual ought not to try to carry a whole mini‐beam mould individually (Choo & Newman, 2003, pp. 123-167). Noise generated by the vibrating table is excess hence requires wearing ear defenders in case a person uses it much more. The lab assistance or a trained staff member should authorize the use of lab. Minimize skin contact with cement and washing all splashes in the lab after usage. The water from the curing tank are normally very alkaline thus it is advisable to wear gloves when performing the experiment and washing of hands after getting in contact with the water was also of necessity. Precautions that were observed during the experiment The lab equipment should not be used without the authority of the staff or the authority of lab attendant. Closed footwear with reinforced tie cap ought to be presented in the lab. Moreover, proper attire should be observed including glove wear especially in the casting area. The safety laboratory goggles must be worn at all time in the casting area. Trial mix designing of a trial mix of 0.035 m3 was done for the following specification. Strength property was taken from Table 1 Duration for the test1: 28 days Percentage of faculty: 5% Slump flow was taken from Table 1, and 100mm target slump was assumed for the process. Cement required class 52.5 of CEM1 Coarse aggregate: uncrushed 10 mm maximum size of fine aggregate of 50% The process was last for days designed the students even though some tests were performed different times. The mix was to have some powdery content of around 500kg/m3 that involved the use PFA. The powdery content was assumed to have developed 30% of the tensile strength of the same amount of cement to a maximum equivalent proportion of 40% PFA. Reinforced compacting beam Testing Lab usually four weeks after casting of the slump but do vary based on the rota (Choo & Newman, 2003, pp. 123-167). The experimental set up the beam was performed as demonstrated in the appendix, demec was recorded at zero, and deflection gauge readings were taken. The points of demec deflection were recorded, and the loads were applied at 1/3 span position and the measurement of the deflection were carried out at midspan. Loading was carried out in equal measurements of 3kN until 30kN was loaded. Every load increment the deflection and the demec readings were taken Results and analysis Reinforced Compacting beam test Testing was carried out to examine the increase strength and stiffness o the reinforced R C-beams. Every beam was tested to failure with the use of four points loading (Newman & Choo, 2003, pp. 178-234). The applied load and during testing, vertical deflection, web and of the structural steel and strain in the internal reinforcing steel were all recorded, and comparison was carried out between the observed values and the theoretical data. Even though too much work has been achieved with the use of PFA laminates in retrofitting there exist an urge for further model refinement and further parameter studies (Mamlouk & Zaniewski, 2013, pp. 123-145). From the prevailing literature as mentioned above review, it can be concluded that the interface zone has been modeled with linear or in 2D with non-linear models. The present study comprises a 3D cohesive model, which is believed to reflect the behavior of retrofitted beams better. Theoretical versus the observed measurements Specimen designation Theoretical ultimate load Measured ultimate Percentage difference C1 14600 16310 +11.7 C2 14400 17780 +23.5 C3 14500 16280 +12.3 E1 28500 29310 +2.8 E2 27900 30400 +9.0 E3 29600 30320 +2.4 W1 29600 28700 -2.8 W2 29200 28010 -4.1 W3 29600 30320 +2.4 Hardened concrete design Cube 1 mass in (kg) 2.2284 Cylinder1mass in (kg) 3.5337 Cube 2 mass in (kg) 2.2669 Cylinder 2 mass in (kg) 3.5343 Cube 3 mass in (kg) 2.2577 Cylinder 3 mass in (kg) 3.5401 Casting and sampling Due to the practical use of retrofitting, the structure is often damaged at the time of retrofitting. To take account of this, the beams in the experimental study as well as in the simulations were pre-cracked before retrofitting. It is undertaken prior to connection with retrofitting in shear or investigation of influence of PFA length (Newman & Choo, 2003, pp. 178-234). Researchers reported on different failure modes. It is important to understand under that circumstances a certain failure mode will occur. To contribute to this understanding, a parametric study of the influence of CFRP stiffness and width is included in this simulation work. Workability Test Crash (mm) 75 L-box H1 (mm) 103 Crash drift d2 (mm) 750 slump flow d1(mm) 700 L-box H2(mm) 85 V-funnel drift duration (s) 12.6 Concrete properties Items Self compacting concrete Water binder ratio 25-40 Air content 4.5-6.0 Compressive strength (28 days) 40-80 Comprehensive strength (91 days) 55-100 Tensile strength (28 days) 2.4-4.8 Elastic modulus 30-36 Shrinkage strain 600-800 Wet mass Dry mass Wet mass Cube 1(kg) 2228.4 1210.4 Cube 2 (kg) 2266.9 1232.5 Cube 3(kg) 2257.7 1223.7 Cylinder1(kg) 3533.7 1933 Cylinder2(kg) 3534.3 1940 Cylinder3(kg) 3540.1 1934.7 Concrete mix design Maximum strength (compressive); fc=, where p is the peak load and A, is the cross-sectional are of the cylinder. Maximum tensile strength; Ft=2P/πdL, where P is the peak load under the tensile testing while L and d are the length and diameter respectively. Estimate f the compressive modulus elasticity; Et=4500, where fc is the comprehensive strength of the concrete while Ec concrete modulus of elasticity is referred as the slope of a line connecting the origin and the point corresponding to 0.4fc. Discussion The figures did vary. It was because of the frictional forces acting on the load and the surface of the specimen with an aim of restraining the specimen from experiencing expansion (Choo & Newman, 2003, pp. 123-167). The ration between the specimen length and diameter decreases resulting in considerable error in the experiment since it will result in higher comprehensive strengths while these of the rubber or lubrication between the loading plate and the specimen often induces lateral stress at the other end of the specimen resulting in vertical splitting and reduction of apparent strength. Specimen size is also a source of error in the experiment by the fact that an increase in size of the specimen is accompanied with an element that will fail at a small load (Mamlouk & Zaniewski, 2013, pp. 123-145). Since stirrups were spaced center to center with dimensions that are of 3-4 multiples, the cost of the experiment was low Compressive strength reduced with the corresponding increase of the fly content and reduces more when the load is least (Newman & Choo, 2003, pp. 178-234). However, the underlying compressive strength accomplished was relatively higher for the prevailing substitutions of the 20-40%, reaching a minimum of 3000psi. For the mixture possessing Class F fly as, plastic viscosity coupled with the corresponding yield stress escalated with the accumulative fly ash content. Nevertheless, the trend was limited due to the small alterations of the plastic viscosity and yield stress in the changeability of the underlying test. Finding the necessary Properties of Geopolymer Concrete like Compressive Strength, Split Tensile Strength, Flexural Strength and Static Modulus of Elasticity for both sand and M-sand, Rigorous trial-and-error method was adopted (Mamlouk & Zaniewski, 2013, pp. 123-145). Mix re-design required specimen; 1. One beam 2. 4no. 100mm cubes 3. four no. 100mm*200mm cylinders In summation, the thesis BEEN method was followed, and the experimental data varied with theoretical data. It was therefore summarized that, for the development of cracks in the region resulted from a high localized bond stress in the steel which in the overall effect magnified the shear stress resulting in diagonal cracks showing a clear failure by the stirrups. Longitudinal cracks occurred bellow on the side plates and later developed into vertical cracks that extended up to the end of the plate. The jacketed beams too reached a full stress capacity. References Choo, B. S., & Newman, J. (2003). Advanced concrete technology. Oxford, Butterworth- Heinemann. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=195066. Newman, J., & Choo, B. S. (2003). Advanced Concrete Technology, 1-4 (Four- Volume Set). Burlington, Elsevier. http://public.eblib.com/choice/publicfullrecord.aspx?p=477360. Mamlouk, M. S., & Zaniewski, J. P. (2013). Materials for civil and construction engineers. Teychenné, D. C., Erntroy, H. C., & Franklin, R. E. (1997). Design of normal concrete mixes. London, Constructions Research Communications. Jirásek, M., & BažAnt, Z. P. (2002). Inelastic analysis of structures. Chichester, West Sussex, England, Wiley. Read More