Construction and Substances Spark Multiplication Blocks Aid Properties - Lab Report Example

Labe experiments Name Institution Date Experiment 1 Abstract The characteristics of flame propagation outline the nature of cables when they are exposed under fire. When they are burned, they my exhibit smoke which may either be toxic. In the construction industry, cables are used in virtually all buildings. They are used in the transmission of power and other functions. When they are loaded, they may experience heat hat may cause them to cause fire. This calls for proper mitigation strategies that would ensure that the set standards are attained in the manufacturing of the cables. This paper height a lab experiment conducted on the propagation of flame in cables. A thermocouple used in the experiment to records the temperature of the cable that was being heated by the Bunsen burner. Introduction Testing the electric cable ensures that its physical and chemical properties are ascertained. This would aid in determining the level of resistance of a given cable. . Ideally, they are not normally the elements that cause fire, but they are involved to a large extent on the effects they have after being burnt. They may release the toxic substances that may affect the adjacent rooms. Various cables are made of materials such as nylon and plastic in which then they are exposed to fire, they furl the fire to promote the combustion process. The fire retardant cables are designed so as they can be used in fire situations. This is utilized in scenarios where the flames may spread where there are long route cables. This makes it important to use the in the survival of cables due to the low cost. 2Procedure 2.1Apparatus Thermocouple Gas burner Digital reader Clamp Figure 1 The set up of the apparatus 1. One metre cable was placed into the top and bottom of the clamp to make sure they are tight. 2. A line of 20 mm distance was marked right from the top edge of the bottom clamp so as the allowance distance was set to be 420 mm. 3. The Bunsen burner was set to a flame height of about 125mm leaving the inner core to be blue Place a filter paper underneath the cable. 4. The thermocouple was set such that, it touches the top and the bottom of the wire while ensuring the data logger is functioning. 5. The flame was impinged at 45 degrees at the 20mm. 6. The flame was left impinged on the cable for duration of 60 seconds. 7. The temperatures of the thermocouples were recorded after every 15 8. The cables were observed to ascertain whether the cables had burned from top clamp or whether the droplets that emanate from the cable had ignited the paper. 9. The process was repeated with a second sample of a different cable. 10. The angle and he slope were inclined 45 degrees for the remaining samples. This was done by having the widest part from their bottom while observing their behaviour. 3 Results measurements Straight or angled Length of flame propagation Filter paper Observation Temperature readings Sample 1(Grey wire) straight 180 Small amount of black debris 57/57 57/57 Sample 2 (Blue wire) straight 270 Very small quantities of debris 30/30.5 Sample 3(Grey wire) angled 170 Small amount of black debris 35/35.5 35/35, Sample 4(Blue wire) angled 250 No debris 21/22 22.5/22.5 The results indicate tthat, the green and the yellow stripped cable did not meet the vertical test criterion. The PVC which was white placed ata n angle of 45 derees passed the test. On the other hand, the longest burnt length was exeperineced in the nylon cable that was placed ina a vertical position. The cables used in instrumentation, and power 4 Discussions From the experiment , it was apparent that, the blue cable has a lower resistance as compared to the grey one. Additionally, the angled position makes it easier to ignite the flame as opposed to the straight ones. Additionally, the cables that had yellow and green stripped nylon and 7 core (Vertical had a rising top temperature and took a lot of time to make the test to fail. The orientation also makes the cables to burn steadily. Cables that were oriented at 45 degrees as indicated in the second and fourth graphs exhibited steady increase in the temperatures. The main causes of the electric cable heating are associated with the; excess withdrawal of currents, poor insulation and wrong connections. These factors contribute to electric cable heating. In order to avert wrong connections o cables, the cables have codes that are used universally. They define the destination where the cables have to be used. The common colour codes include yellow and greeb=n thatrepresnts ground, brown or black that represents line voltage and blue or white that are used for general purpose. In a constructions site, presence of hanging cables or necked wires poses as great danger towards causing fire in cables. The overhead and underneath cables may be cut down during the construction process. This calls for proper process during construction process. N order to deal with electric fires, class C of fire extinguishers have to be used. These may involve he halon , carbon dioxide extinguisher or the dry chemical extinguishers. In order to prevent the electric fires, the cables have to be properly insulated and ground all the appliances. Additionally, personal protective equipments have to be used so as to avoid exposure to he wires. The unit for measuring electric current passing through a cable is the ampere. It is vital as it would determine whether a given cable can withstand a given current. In the building process, the electrical cables constitute of serious hazards as, when the resistance id very hight, it would cause overheating that may lead to fires. Additionally hia may also damage the electronic equipments. Conclusion From the experiment, it is evident that the nature in which the cable is oriented may have an impact on its flame propagation. It affected theime taken for burning. This calls for proper measures to be utilised while handling electric cables. References CousinS, K., 2000. Polymers for wire and cable: changes within an industry; a Rapra industry analysis report. Shawbury, RAPRA Technology. Troitzsch, 2004. Plastics flammability handbook: principles, regulations, testing, and approval. Munich, Hanser [u. Abstract Use of Bricks and blocks play a vital role in the construction industry. This works by the aspect of capillary action that exhibits in these materials. In the scenario where proper building process has not been adhered to, there might be cases of dampening as well as actions of frost, efflorescence and emergence of sulphate that may pose as a threat to the building. The engineering brick mainly used in construction include the Facing bricks, thermilite and the engineering brick. His experiment highlights the experiment process conducted on the bricks and blocksto determine their properties. Part A absorption of water by capillary actions/suction 1 Introduction Lab experiment performed on the performance of bricks and blocks aid to determine their properties. Small pores lead to high rate of suction whereas an increase in the number of pores leads to high rate of absorption. This experiment measures the capillary actions in the masonry by using the mass of the samples the have been placed in water. The initial rate of absorption acts as an important factor in determining the bond that exists in a given brick. His would aid in determination of the nature of the motor that would be utilised. The effects of suction may affect the layers of blocks during construction. Te size of the materials determines the porosity of a given material. It affect the porosity of a given brick or block Material that exhibit large grains have a higher porosity as compared to those that have low grains. The graded grains exhibit low porosity that would prevent the absorption of water. Hypothesis There exists a relationship in the porosity of the brick and block with the size of grains. Theree is a relationship between the amount of water absorbed and the number of pores. Method Materials Rag Weighing machine. Stop watch stand 1. The specimen of the facing brick, engineering brick and the thermalite block were selected. 2. The specimens were weighed. 3. The height, width and depth of the samples were measures using a ruler. Supports were placed at the bottom then filled with water in a dish that covered a depth of about 5mm. 4. Sample was placed on the supports then; the timer was started and left for about one minute. 5. The specimen was later removed from the dish, wiped off with a damp cloth. Its weight was measured then was recorded while the timer was still running. 6. The same support was used while the specimen was replaced that exposed the same surface of water while. The settings were adjusted after 10 minutes. The sample at an interval of 10 minutes as the water level was adjusted accordingly. 3 Results Table 1 sample measurements Measurement Thermilite block Engineering block Facing block Length 24 cm 21.4 cm 17.5 cm Height 9.7 cm 6.9 cm 6.3 cm Width 9.7 cm 10.4cm 10.5 cm Area 232.8cm2 49.86cm2 183.75 cm Table 2 water absorption by capillary Thermalite block Specimen Themalite block Mass dry 1251.8 Area 232.8cm2 Time(Min Mass when weighed after every min Cumulative mass of water absorbed Mass of water absorbed per minute Square root of time 1 1271.8 20 20 1 2 1279.8 48 28 1.41 3 1284.8 81 33 1.73 4 1289.4 118.6 37.6 2 5 1294.0 160.8 42.2 2.24 6 1297.2 206.2 45.4 2.45 7 1300.4 254.8 48.6 2.65 8 1303.2 306.2 51.4 2.83 9 1305.4 359.8 53.6 3 10 1308.3 416.2 56.4 3.16 Table 3 water absorption by capillary Engineering brick Specimen: Engineering Brick Mass dry (g): 2347.4 Area (cm2): 49.86 cm2 Time (minutes) Mass when weighed (g) Cumulative Mass of water absorbed (g) Mass of water absorbed per minute (g) Time (min0.5) 1 2349.2 1.8 1.8 1 2 2350 4.4 2.6 2 3 2350.6 7.6 3.2 3 4 2350.6 10.8 3.2 2 5 2351.2 14.6 3.8 5 6 2351.4 18.6 4 6 7 2352.0 23.2 4.6 7 8 2352.2 28 4.8 4 9 2352.4 33 5 3 10 2353.0 37.6 4.6 10 Specimen Engineering block Mass dry 3228.72 Area 215 Time Mass when weighed after every min Cumulative mass of water absorbed Mass of water absorbed per minute Square root of time 1 3229.27 0.55 0.55 1 2 3229.42 0.7 0.15 1.41 3 3229.67 0.95 0.25 1.73 4 3229.61 0.89 -0.06 2 5 3229.74 1.02 0.13 2.24 6 3229.94 1.21 0.2 2.45 7 3230.03 1.31 0.09 2.65 8 3229.73 1.16 -0.15 2.83 9 3229.73 1.01 -0.15 3 10 3229.99 1.27 10.26 3.16 Table 4 water absorption by capillary facing brick Specimen: Facing Brick Mass dry (g): 2761.0 Area (cm2): 183.75 cm2 Time (minutes) Mass when weighed (g) Cumulative Mass of water absorbed (g) Mass of water absorbed per minute (g) Time (min0.5) 1 2762.4 1.6 1.6 1 2 2762.6 3.2 1.6 2 3 2762.6 4.8 1.6 3 4 2762.6 6.4 1.6 2 5 2762.8 8.2 1.8 5 6 2762.6 9.8 1.6 6 7 2762.8 11.6 1.8 7 8 2762.8 13.4 1.8 4 9 2762.8 15.2 1.8 3 10 2762.8 17 1.8 10 Specimen facing brick Mass dry 1983.61 Area 217.26 Time Mass when weighed after every min Cumulative mass of water absorbed Mass of water absorbed per minute Square root of time 1 1990.6 6.99 6.99 1 2 1993.89 10.28 3.29 1.41 3 1996.7 13.3 3.02 1.73 4 1999.35 15.74 2.44 2 5 2001.55 17.74 2 2.24 6 2003.73 20.12 2.38 2.45 7 2005.73 22.12 2 2.65 8 2007.79 24.18 2.06 2.83 9 2009.91 26.3 2.12 3 10 2011.97 28.36 2.06 3.16 4 Discussion Evidently, the engineering block exhibited least amount of water that was absorbed. This makes it the mostly used type of brick that is utilised in the sewers or ground works. The size of the particles affects the nature in which they absorb water. A high rate of initial absorption was exhibited in bricks such as the thermalite die to presence of wide pores. Conclusion Engineering block exhibits the lowest rate of initial absorption making it vital to retain the amount of water that is found in the bricks. This makes it important to select the appropriate type of bricks used for construction at different site. B. Comparative water absorption of Brick and block materials 1 Introduction This experiment aims to find out the rate of water absorption in relation to the pores of a given masonry sample. This enables he aspects of durability and resistance to be studied effectively. This experiment also tries to find out the variation in water absorption rate in various sampes as regards to porosity in the block and bricks 2 Method 1. The same samples used previously in part A were used in this experiment. 2. The same weights were also used. of samples from part a that were recorded in part A were also recorded. 3. The samples were saturated using a vacuum saturation apparatus in which they were evacuated for ten minutes. Later on, the chamber was flooded with water that saturated the specimens. After 10 minutes had elapsed, the specimen were removed. 4. The water which was surplus wiped off then, the masses of the samples were recorded. 5. The volume for the specimens was also determined. 3 Results Table 5 Water absorption brick and block Specimen Thermalite Block Engineering Brick Facing Brick Bulk volume (cm3) 232.8cm3 233.26cm3 183.75cm3 Mass dry (g) 1251.8g 2347.4g 2761g Mass saturated (g) 1308.2g 2353g 2762.8g Mass of water absorbed (g) 56.8g 5.6g 1.8g Volume of water absorbed (cm3) 0.0568cm3 0.00056cm3 0.00018cm3 Water absorption porosity (by volume %) 2.3% 0.02% 0.0000097% Percentage water absorption (by mass %) 4.53% 0.2% 0.06% Specimen Thermalite Block Engineering Brick Facing Brick Bulk volume (cm3) 232.8cm3 233.26cm3 183.75cm3 Mass dry (g) 1251.8g 2347.4g 2761g Mass saturated (g) 1308.2g 2353g 2762.8g Mass of water absorbed (g) 56.8g 5.6g 1.8g Volume of water absorbed (cm3) 0.0568cm3 0.00056cm3 0.00018cm3 Water absorption porosity (by volume %) 2.3% 0.02% 0.0000097% Percentage water absorption (by mass %) 4.53% 0.2% 0.06% Specimen Thermalite Block Engineering block Facing brick Bulk volume (cm3) 2258.16 1535.664 1159.6095 Mass dry (g) 642 3228.72 1983.61 Mass saturated (g) 676.53 3229.99 2011.97 Mass water absorbed (g) 44.16 1.27 28.38 Volume of water absorbed (cm3) 0.29 0.78 0.035 Water absorption porosity (by volume %) 0.02245 0.056 0.002497 Percentage water absorption (by mass %) 0.0531 0.0393 1.43 Table 6 water absorption of brick block properties Specimen Initial rate of absorption (g/cm2) Water absorption co- efficient (A) gcm-2 min-0.5 Volume Cm3 Thermalite 0.0698 0.0571 2258.16cm3 Engineering block 0.0026 4.75 1535.664 Facing brick 0.0322 2.889 1159.6095cm3 24 9.7 9.7= 2258.16cm3 (b)Engineering brick 21.46.9.4= 1535.664 cm3 (c) Facing brick 17.53 6.3 10.5= 1159.6095cm3 5 Discussions The nature and size of pores have a great effect to the way particles absorb water. Larger grains leads to hih porosity of materials. This indicates that there is a relationship between thye porosity of a given block and the size of the grains. Additionally, the number of pores would also affect the nature in which the particles absorb water. The rate of moisture ensures that th bricks are able to reduce the suction to a reasonable value soa s it may be able to overcome consitions that may be adverse. Part C Answers to questions 1. Graphs Figure 1 cumulative mass of water absorbed (g) against square root of time of thermalite brick Figure indicating the cumulative mass of water absorbed (g) against square root of time of engineering brick Figure indicating the cumulative mass of water absorbed (g) against square root of time of facing brick 2 Initial rate of absorption It is defined as the the amount of water that a given material would absorb in one minute ina given bed of bricks 3 Definition of Capillary action and the effect on the pore size This is a situation in which water rises through the small given pores. The adhehise forces that exists between a given substance and ater molecules that ensure hat this process is possible. The initial rate of absorption is greatly influenced by the size of pores. Small pores have a low rate of initial absorption and capillary action while, large pores would exhibit high rate of absorption as well as high rate of capillary action 4 The type of brick with lowest initial rate of absorption The engineering brick had the lowest initial rate of absorption with a value of g/cm2. 5 How does initial rate of absorption affect the bond between bricks and the mortar? The bond between the brick greatly affects the rate of absorption. This ensures there is proper bonding that exists in the mortor and the cement. Nippling from the joints occurs when excess water has been absorbed leading to depreciation. This actions hinders the next layer from bonding effectively. The bricks would tend to float on the motor in the scenario where More water is absorbed by the mortor. 6 The brick that absorbed most of the water during the absorption through capillary From the experiment, the thermalite brick absorbed most of the water via capillary action. This was by a value of 34.13g 7 Water absorption is an important factor in the durability of a brick. State two adverse conditions that could arise from excess water in bricks In case there is excess absoption of water, there might effect suchs as Crumbling of bricks due to freezing and effect of efflorescence. 8 Suitable bricks for the following listed functions (a) Above ground external wall- Thermalite bricks (b) Below ground works or sewers- Engineering bricks (c) Internal above ground walls- Facing bricks References Sherwyn, S., 2008. Building and Construction. Wellington: New Zealand Law Society, Family Law Section and Property Law Section. Van, E., 2000. Construction materials for civil engineering. Kenwyn: Juta. THERMAL CONDUCTIVITY AND HEAT TRANSFER IN METALS Conduction of a metallic solid is attributed to the random motion of the electrons found in a metal. It is apparent that the electrons in the already hotter part possess a higher kinetic energy than the colder part and thus distribute up a fraction of this kinetic energy to the atoms which are cold therefore resulting in heat transfer from hot surface to the cooler parts. Some heat transfer can also be attributed to the inter-atomic vibrations(Tritt, 2004).Thermal conductivity in metals cannot be directly measured the way it is done when it comes to conduction of electricity. Two methods can be used when considering thermal conductivity and they consists of transient and steady state techniques. In overall, when applying steady state technique measurement should be carried if the temperature of the material being measured is not subject to vary with change in time. This is done to make it easy specifically for the process of signal analysis. When it comes to transient techniques there is performance of a measurement carried out specifically during the process of heating up and it is a bit complicated but again the advantage is that measuring can be quickly carried out. Taking metals into consideration, thermal conductivity roughly trails electrical conductivity in accordance to the law of Weidmann-Franz. In case there is existence of discrepancies in temperature at various locations of the metal conduction of heat occurs. The temperature dissemination in a metal is commonly a task of location working together with time and is in agreement per the Boltzmann transport equation. It should be noted that it is at room temperature that the process of electron conduction in metal possess a more superior way for the free path greater than the phonons. It is for this motivethat the heat conduction in metals can be considered to be principally due to the electrons. Thermal conductivity in metals includes energy in transfer within the metal and exclusive of any motion of the metal as a whole. Metals generally are better thermal conductors compared to non-metals reason being that the same free and mobile electrons which take part in electrical conduction similarly take part in the heat transfer. In case of metals, The whole process of thermal conductivity is generally higher compared to non-metals. Relatively it can be ascertained that the metals which are considered best electrical conductors are correspondingly among the best thermal conductors. At any random temperature both electrical and thermal conductivities are proportionate but contrastingly increase in temperature consequently increases thermal conductivity while in difference decreases the electrical conductivity. The behavior can be justified in the law of wiedemann-Franz. The speed of heat transfer is dependent on the gradient of the temperature together with the thermal conductivity of the metal. Algebraic techniques can also prove to be useful when calculating heat conduction across wall which is plane but when concentrating on geometries the transfer of heat must be stated by assistance of a thermal gradient. Abstractly the process of thermal conductivity can be literally taken as the base for the middle-dependent characteristics which interrelate the rate at which is lost per unit area to temperature change.In relation to thermal conductivity, the function of a mathematical gradient can be defined as a derivative of direction which points towards the course of the maximum rate of variation of the function. Heat transfer direction will be opposite to the gradients temperature because the net transfer of energy is from a relatively higher temperature to a lower temperature. This direction of extremely concentrated heat transfer will be perpendicular to the temperature surfaces which are equal and adjacent to the heat source (Wang, 2005). Heat Flow between Unequal Amounts of Liquid There is necessity in science to project the flow of energy and subsequently measure the flow of heat in unequal amounts of liquid. Given that energy is not visible special equipments are often required to perform this. This study approximates the flow of heat as it is impacted by different variables. In this experimentation, water of unequal volumes are used to determine if the temperature regulatesautomatically to the median in relation to the two original temperature interpretations. If the substances are the similar, as they are in this setting, the outcomes can he projected (Tritt, 2004). There is anadvantageofpredicting this equilibrium temperature through the calculation of the quantity of heat energy that is shiftedfrom one flask to alternative by usage of the following formula: Q = mCT Whereby; Q = heat energy in calories m = the mass of the water in gram C =specific heat of the water T = the temperature change of the water (Difference in T = Tfinal- Tinitial). THE EFFECTS OF WATER: CEMENT RATIO UPON THE COMPRESSIVE STRENGTH OF CONCRETE Concrete is one of the most useful materials that is used in the process of civil engineering and construction works. Concrete is a compound that could be utilized solely or mixed with other materials e.g. steel or perhaps with the materials locally obtained like the fibers from the oil palm tree and this will depend upon many reasons such as the design of the structure being constructed. Concrete could be described as an artificial resultant material from an accurately-measured mixture of water, cement and any aggregate which could be inform of either fine and coarse sand and even gravel. This takes after the container’s shape and even form work if toughened therefore forming a solid bulk when subjected to an appropriate humidity and temperature among other required conditions. In tension, it can be noted that concrete is weak and brittle but then again it has a compressive power which ranges from approximately ten to thirteen times superior than tensile(Kleger, 1994). . In most ordinary structural designs, the contractors always neglect the tensile strength of concrete. In contrast, the tensile strength of concrete is commonly taken into consideration when it comes to construction of structures which are anticipated to contain liquids. A typically good, standard and ideal concrete whether pre-stressed, reinforce or even plain is expected to be strong to contain and bear super-imposed masses along its predicted life line. Other properties in relation to a good concrete include; durability, cracking, cavitations, impermeability and surface wear among others. The density and the compression power of a concrete is always determined through performance of compression test upon the concrete cylinders or blocks with standard sizes. The compression strength of a concrete is partly affected by the relative percentage of cement and aggregates either fine or coarse but even so water – cement ratio is a very significant factor. For production of a concrete with a maximum strength there is a specific optimum amount of water needed. The workability and the ease to work with concrete is also dependent on the quantity and the quality of water used. The application of water below the optimum required level is likely to turn the setting to be tough therefore decreasing the workability. Relatively, when water is used beyond or exceeding the optimum amount, there will be decline in strength and subsequent shrinkage. This therefore implies that the best water-cement ratio is dependent on a specific concrete mix. It is significant to indicate that weight, compressive strength and density of concrete relatively decreases with subsequent increase in water cement ratio. Nevertheless, compressive power increases with age as the number of curing days continue to elapse. In present days, due to construction of hydraulic structures like the dams, the issue of concrete durability has turn out to be a very critical element of hydraulic structures. The key agenda in this regard is the resistibility of concrete against abrasion which has a relationship with water, cement and the subsequent formation of crystalline particles. According to Abrams classic law, the strength of concrete is basically dependent upon the strength of cement paste and relatively the ability of the paste is dependent on its dilution thus increases with cement content and reduction in water content (Kleger, 1994). The relationship between strength and water/cement ratio of concrete In the above expression it is not only the volume of water taken into account but also the volume of air as it indirectly means that the air fills voids in the concrete and is considered when approximating the strength of the concrete. It is evident that Cement: Water ratio can be used if the concrete is vibrated to attain a superior strength. If the cement: water ratio is lower than the practical limits the power of the concrete swiftly cascades as a result of air voids introduction. Experiment A: What causes corrosion? The nails in labels 1 and 3 have no observable changes but the nail in label 3 had begun to show signs of a brown coating on its surface. Reason: the contents of label 2 contained both water and oxygen from the atmospheric air and thus a clear indication that for corrosion to occur both water and oxygen must be present. Experiment B: Corrosion of dissimilar metals Analysis 1. Metal Electrode Potential E0(v) magnesium -2.36 aluminium -1.67 zinc -0.76 iron -0.44 nickel -0.24 lead -0.13 2. Corrosion is the damaging attack in metals by either electrochemical or chemical reactions with its surroundings to form either pure elements, oxides or other compounds. 3. Experimental Data Anodic (more reactive) Water electrolyte Acidic electrolyte Alkaline electrolyte 1. Mild steel Zinc Lead 2. Zinc Aluminium Mild steel 3. Aluminium Lead Brass 4. Lead Stainless steel Copper 5. Brass Mild steel Stainless steel 6. Copper Brass Zinc 7. Stainless steel Copper Aluminium Cathodic (less reactive) 4. When a metal is placed in an electrolyte, an interface is created between the metal and the electrolyte which is called an electrode. In this interface neither electrons in the metal nor negative ions in the solution cross the interface. There is the tendency of metal ions to diffuse from the electrode to the electrolyte which is counter balanced by the potential difference across the interface, creating Nernst equilibrium. 5. How the tested metals may be used in the industry Zinc- it can be used to coat other metal e.g. steel to protect them from corrosion for example the galvanized iron sheets for roofing Mild Steel- can be used in making of mild steel pipes, rods, bars and sheets as they can withstand high temperatures and chemical resistant. Aluminum –can be used in cladding, windows, skylights, gutters, door frames and roofing due to its corrosion resistant and light weight. Lead- it is not advisable to use in construction due to its harmfulness to health Copper- it can be in roofing, cladding, and plumbing because it is water proof. Due to its light weight, it can also be used in freestanding structures. Lightning rods and roofs are made of copper. It is also used in electricity transmission lines, and electronic gadgets Brass- it can be used in decoration because of its bright gold-like appearance, applications in areas where low friction is required such as locks, gears, bearings, ammunition, and valves. Also can be used for plumbing and electrical applications.. Stainless steel- can be used in cladding, construction of Handrails and balustrading, drainage and rainwater goods and roofing 6. Why copper and brass have similar reactivity This is because brass is an alloy of copper and zinc, so they have similar properties. 7. Galvanic cells Galvanic cells are built by electrically connecting two strips of different metal at one end, the other end being immersed in an electrolyte of a suitable choice. This will create a potential difference between the two strips this forming a galvanic cell. 8. 3 ways in which the corrosion of metals used in the construction industry can be minimized or avoided Metal coatings Use of plastics in place metals Use of metal alloys 9. “Cathodic Protection” and “Sacrificial Anode”. Cathodic protection This is the application of an electric current externally to the surface of the metal that is to be protected against corrosion such that it becomes a cathodic area such that a net positive current penetrates to all areas of the metal including those that were initially anodic. Sacrificial anode This is a highly active metal that is used to protect a less active metal from corrosion. They are created from metal alloys with more a more negative electrochemical potential than the metal it will be used to protect from corrosion. Normally, the sacrificial anode will be eaten up instead of the metal it is protecting thus it is called a sacrificial anode. 10. Effect of change of pH on corrosion The pH of the electrolyte is a critical characteristic which determines the rate of corrosion of any substance. In addition, the influence of the pH depends upon the type of metal that undergoes corrosion. The corrosion rate of gold, platinum and the noble metals are unaffected by the pH of the electrolyte. However, aluminum, zinc and lead depict an up surge in their corrosion rate in both acidic and basic electrolytes. This is because aluminum, zinc and lead form hydroxide precipitates that are insoluble and form coatings and prevent corrosion but they dissolve in electrolytes that are purely alkaline or acidic hence no protective layers are formed to prevent corrosion. The rate of corrosion of iron, nickel, cadmium and magnesium are such they form soluble compounds in acidic electrolytes but form protective layers in neutral and alkaline electrolytes. Thus these elements undergo corrosion in acidic electrolytes and are unaffected with the increase of the pH from acidic to alkaline state. Experiment 6 1. Grading chart. Particle size (mm) Percentage passing (%) 10 100 5 97.84 2.36 65.3 1.18 53.8 0.0006 44.5 0.0003 33.7 0.00015 9.7 PERCENTAGE BY MASS PASSING Coarse Percentage Medium Percentage Fine Percentage 5 to 45 30 to 70 55 to 100 BS Sieve Mass on sieve (g) (Column a) Cumulative mass retained (g) (Column b) % retained (column c) % passing (column d) 5.00 mm a2 13.0g b2 13.0g C2 2.16% d2 97.84% 1. According to the table above indicating the percentage by mass passing and the results obtained from the 5mm sieve the tested sample is graded as fine 2. The percentage occupied by the fine and coarse aggregate occupy in a concrete mix is 60 -75 % 3. A well graded aggregate in respect of aggregates that are used in concrete refers to a mixture that includes a range from minimum particle size to the maximum particle size specifications with the aim to cover most voids. A well graded aggregate retains a reasonable amount of aggregate on each sieve and offers a more economical mixture in comparison to one that is poorly graded. It also, in most cases, appears to contain an optimum amount of cement and water. A well grade aggregate is simpler in placement, compacting as well as in finishing. 4. The physical properties of concrete aggregate include the following; Surface texture The surface texture helps in the development of the bond that brings together the cementing material and the aggregate particle. Strength and elasticity Strength offers assistance to the aggregate in standing crushing as well as pulling forces whereas elasticity offers the stretch that is desired in the aggregate. Both strength and elasticity raises the stability of the compact material and lowers the disintegration rate. Absorption and permeability The absorption assists the particles of the aggregate to enhance the liquid take in ability whereas permeability facilitates the passage of liquid through the particles of the aggregate. 5. Aggregate sizing affects concrete properties such as the content of cement, strength and water demand. Aggregate grading is important in concrete production in that is determines the distribution of granular material particles among a variety of sizes. 6. The chloride salts corrodes the reinforcing bar that is within the concrete and therefore affects the concrete as a whole by lowering its strength. 7. The high silt content reduces the expansion temperature and also changes the physical properties of the concrete and this brings about variation in the crushing strength on the concrete. 8. Chloride limits are as follows; Precast Concrete has a maximum chloride content of 0.6% Reinforced Concrete has a maximum chloride content of 0.15% Plain Concrete has a maximum chloride content of 2% 9. Aggregates are used in concrete for the following reasons; For purposes of adding reinforcement to concrete They offer stability that is dimensional They influence abrasion resistance and hardness 10. Materials passing a 75μm sieve are defined finer silt particles Experiment 8 1. For each of the samples tested the level of the effects of ignition is as follows based on the scale shown below; Up to 35mm – Low radius effects of ignition 40-75mm Medium radius effects of ignition 80 and over High radius effects of ignition 1) Sample 1- Medium radius effects of ignition 2) Sample 2- Medium radius effects of ignition 3) Sample 3- Medium radius effects of ignition 4) Sample 4- Medium radius effects of ignition 5) Sample 5- Medium radius effects of ignition 6) Sample 6- Medium radius effects of ignition 2. The orientation of the sample did not affect the rate of flame spread. 3. A graph showing time to ignition 4. Diagrams illustrating the effects of ignition 5. Importance of this test Hot metal nut method testing on floor textile is very important and useful especially in the field of fire engineering design. This is because it assists in the establishment of the level of contribution of condition that are hazardous by the materials that are used in floor making. This test also plays an important role in determining whether certain textile used in floor making poses dangers to the users of the structure so as to develop safety measures appropriately. The hot metal nut method testing on floor textile enlightens the designers concerning the behaviour of smoke and flame in relation to several flooring textiles. This information is useful to both the textile designers as well as the textile users. Following the evaluation and analysis of the results obtained from this test, it becomes possible and much easier to put in place safety precaution measures that are aimed at preventing the occurrence of fire outbreaks in the structures that uses such textiles in floor making. Read More

The common colour codes include yellow and greeb=n thatrepresnts ground, brown or black that represents line voltage and blue or white that are used for general purpose. In a constructions site, presence of hanging cables or necked wires poses as great danger towards causing fire in cables. The overhead and underneath cables may be cut down during the construction process. This calls for proper process during construction process. N order to deal with electric fires, class C of fire extinguishers have to be used.

These may involve he halon , carbon dioxide extinguisher or the dry chemical extinguishers. In order to prevent the electric fires, the cables have to be properly insulated and ground all the appliances. Additionally, personal protective equipments have to be used so as to avoid exposure to he wires. The unit for measuring electric current passing through a cable is the ampere. It is vital as it would determine whether a given cable can withstand a given current. In the building process, the electrical cables constitute of serious hazards as, when the resistance id very hight, it would cause overheating that may lead to fires.

Additionally hia may also damage the electronic equipments. Conclusion From the experiment, it is evident that the nature in which the cable is oriented may have an impact on its flame propagation. It affected theime taken for burning. This calls for proper measures to be utilised while handling electric cables. References CousinS, K., 2000. Polymers for wire and cable: changes within an industry; a Rapra industry analysis report. Shawbury, RAPRA Technology. Troitzsch, 2004. Plastics flammability handbook: principles, regulations, testing, and approval.

Munich, Hanser [u. Abstract Use of Bricks and blocks play a vital role in the construction industry. This works by the aspect of capillary action that exhibits in these materials. In the scenario where proper building process has not been adhered to, there might be cases of dampening as well as actions of frost, efflorescence and emergence of sulphate that may pose as a threat to the building. The engineering brick mainly used in construction include the Facing bricks, thermilite and the engineering brick.

His experiment highlights the experiment process conducted on the bricks and blocksto determine their properties. Part A absorption of water by capillary actions/suction 1 Introduction Lab experiment performed on the performance of bricks and blocks aid to determine their properties. Small pores lead to high rate of suction whereas an increase in the number of pores leads to high rate of absorption. This experiment measures the capillary actions in the masonry by using the mass of the samples the have been placed in water.

The initial rate of absorption acts as an important factor in determining the bond that exists in a given brick. His would aid in determination of the nature of the motor that would be utilised. The effects of suction may affect the layers of blocks during construction. Te size of the materials determines the porosity of a given material. It affect the porosity of a given brick or block Material that exhibit large grains have a higher porosity as compared to those that have low grains. The graded grains exhibit low porosity that would prevent the absorption of water.

Hypothesis There exists a relationship in the porosity of the brick and block with the size of grains. Theree is a relationship between the amount of water absorbed and the number of pores. Method Materials Rag Weighing machine. Stop watch stand 1. The specimen of the facing brick, engineering brick and the thermalite block were selected. 2. The specimens were weighed. 3. The height, width and depth of the samples were measures using a ruler.

Supports were placed at the bottom then filled with water in a dish that covered a depth of about 5mm. 4. Sample was placed on the supports then; the timer was started and left for about one minute. 5.

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