道路工程材料(申爱琴版)-作业-集料水泥(英文版).docx

Assignment for Road Engineering Materials Chapter 1 & Chapter 2Name： Class ： NO. ： SCHOOL OF HIGHWAY COLLEGECHANGAN UNIVERSITYOCTOBER 31, 2013Chapter one Aggregate1. Here are two kinds of stone, and the test results are shown in following table. Which kind of stone has better performance?Solution: Step 1, the porosity of these two stone can be calculated as the following formula:n=1-dt100%And the nA=0.07 nB=0 .Step 2, the value saturation-water coefficient of A stone is 0.75, which is higher than the B stones, 0.65.Step 3, the higher porosity of stone is, the better water absorption gets and the worse frost resistance is. So is the saturation-water coefficient. From what has been mentioned above, the stone A apparently gets a higher porosity of stone and saturation-water coefficient, so the stone A is worse at frost resistance. Conclusion: stone B has better performance.2. Please describe the difference between strength indexes of stone and aggregate, and the test methods.Solution:a) The major strength index for stone is uniaxial compressive strength. The result of measuring uniaxial compressive strength test is represented as resilient modulus R=PA with triaxial chamber with external LVDTs and load cell. And the prepare sample can be cube (in road engineering) or cylinder (in bridge engineering).b) The major strength index for aggregate is crushing value. And the test method is in the below.Procedure to determine Aggregate Crushing Valuei)The aggregates passing through 12.5mm and retained on 10mm IS Sieve are oven-dried at a temperature of 100 to 110oC for 3 to 4hrs.ii) The cylinder of the apparatus is filled in 3 layers, each layer tamped with 25 strokes of a tamping rod.iii) The weight of aggregates is measured (Weight A).iv) The surface of the aggregates is then leveled and the plunger inserted. The apparatus is then placed in the compression testing machine and loaded at a uniform rate so as to achieve 40t load in 10 minutes. After this, the load is released.v) The sample is then sieved through a 2.36mm IS Sieve and the fraction passing through the sieve is weighed (Weight B).vi) Two tests should be conducted. Aggregate crushing value = (B/A) x 100%.3. Please describe the classification of aggregate from deferent perspectivesSolution：Solution:Notification: There is some other types of aggregate by different standardsl Crashed gravell Crushed sandl Stone chipl Fillerl Slag4. There are two kinds of aggregate, and the test results are shown in following table. Please describe the difference of the performance of these two kinds of aggregate.Solution: The lower crushing value is, the better anti-crushing performance aggregate gets. And so is the Los Angeles abrasion ration. So, the aggregate B has a better anti-crushing and anti-crushing and abrasiveness performance.The higher polishing value is, the better anti-slip performance aggregate gets. So, the aggregate A has a better anti-slip performance.5. Please describe the definition, the test and the calculation methods of densities of aggregate, and give the rank of different densities.Solution:a) True density:Definition: the mass of a unit volume of the impermeable portion of material, including the solid and impermeable pore.Test: Le Chatelier flask methodCalculation method: s=msvsb) Apparent density: Definition: the mass of a unit volume of the impermeable portion of material, including the solid and impermeable pore.Test: Wire basket methodsCalculation method: a=msvs+vnc) Bulk density: Definition: the mass of a unit volume of material under natural status, including solid, permeable and impermeable pores.Test: Wire basket methods for coarse aggregate Flask method for fine aggregateCalculation method: b=msvs+vn+vid) Stacking density：Definition: dry mass per unit volume of aggregate under some stacking methods.including：Loose density, Tamping density, Compaction density Calculation method: =msvs+vn+vi+vfRank: sab6. The gradation curves of three kinds of aggregate are show in right Fig. Please judge the gradationcategories, and the structure of asphaltmixture consisted of these aggregateSolution:Gradation A is the gap gradation. One or more intermediate particle sizes aggregates are missing. Gradation B is the continuous gradation. The particles distribute on each sieve size from the large to small.Gradation C is the open gradation. The particles distribute on larger sieve size.7. Discuss the differences between gradation and fineness modulus of fine aggregate Have sand A and sand B, which have the same fineness modulus, the same gradation?Solution: Gradation, the particle sizes and size distribution, refers to the proportion by mass or weight of aggregate particles distributed in special particle-size ranges, not only to individual fine and coarse aggregate , but also to the combined or mixed aggregateFineness modulus, a value which statistically represents the coarse or fine condition of fine aggregate, is statistically determined by the percentage of coarse aggregateSo, the different gradation can have the same fine modulus, and the same fine modulus may not represent the same gradation.Sand A and sand B can have the same the same fineness modulus but not the same gradation.8. Sieving test results of 500g sand are shown in table. Please fill the blank, and calculate the fineness modulus.Solution:sieve size（mm)9.54.752.30.15Panmi(g)020154011512515530ai(g)04382325316Ai(g)04715386394100Pi(g)100969385623760The fineness modulus:f=A2.36+A1.18+A0.6+A0.3+A0.15-5A4.75100-A4.75=2.0529. The passing percentages of four aggregates are listed in the Tab.9.1 and the gradation limit are shown in Tab.9.2. Please use the graphic method and linear programming method to determine the proportions in mixed aggregate according to the mid-value of gradation limits, and calculate the composite gradation.Table 9.1Table 9.2Solution:Linear programming methodThe gradation can be designed by the Excel macro, linear programming, as long as some constraints are correctly set.Here is the gradation design sheet.Designed values of gradation are the numbers with the blue background. They are proportions of different components which are simulated by linear programming.With the assumed amount of four aggregates, the composite values can be calculated and they are displayed in the sheet. And next is the gradation curveThere are four lines in this illustration. From the legend, it can be known that the purple one, composite gradation, is always between the upper limit of gradation and lower limit of gradation and approaching the middle value of gradation. So, the design of composition gradation is qualified.Graphic method：The gradation is illustrated in the attached graph.10. The shape and surface texture of aggregate particles are important for both cement concrete and hot mix asphalt.(1)For preparing PCC, would you prefer round and smooth aggregate or rough and angular aggregate? Briefly explain why.(2)For preparing HMA, would you prefer round and smooth aggregate or rough and angular aggregate? Briefly explain why.Solution:(1) For PCC, the round and smooth aggregate particles are desirable to improve workability. Because the angular aggregate will be more difficult to work in place and easier to be fractured. Besides, aggregate with a rough texture are more difficult to compact into a dense configuration than smooth aggregate. (2) For asphalt mixture, angular and rough aggregate Particles are desirable to improve workability. Because angular aggregate produce bulk materials with higher stability than round aggregate and the roughness of aggregate surface plays an important role in the way of aggregate compacts and bonds with binder materials. 11. A sample of coarse aggregate from a stockpile has the following properties:Mass of wet aggregate=5298gMass of oven dry aggregate=5216gMass of aggregate in water=3295gMass of SSD aggregate=5227Determine:(a)The bulk & apparent specific density(b)The moisture content and absorption of stockpile aggregateSolution：Known: ma=5216g,mf=5227g,mw=3295g,m1=5298ga) The apparent specific densitya=mama-mw=2.72The bulk specific densityf=mamf-mw=2.70b) The absorption contentwx=mf-mama100%=0.21%The moisture contentwx=m1-mama100%=1.57%Chapter two Portland Cement1. Briefly describe the hardening process of lime. Solution: The hardening process of lime comprises two parts, recrystallization and carbonification.Part 1: Recrystallization CaOH2 + nH2O = CaOH2nH2O The reaction product has some strength by the crystal and shows some cementing properties.Part 2: CarbonificationCa(OH)2 + CO2 = CaCO3The reaction product is insoluble, showing better water stability. And it makes material denser and higher strength.2. Discuss the reason of the generation of under-burnt lime and over-burnt lime. Explain the harms of over-burnt lime to concrete structure, and how to eliminate the harm.Solution:a) Under-burnt limeGeneration reason:When fire heat in limekiln is not even or raw material size is over large, some product may become “under-burnt lime” which is considered as residue. It will reduce actual content of active ingredient.b) Over-burnt limeGeneration reason: If firing process is over heat or over time, some product may become“burned lime”.Harms:Because some expansion from “burned lime” in volume will still take place during application process and in service stage, it will result in cracking and plaster flaking.Elimination:Immersing the burnt lime in the slaking pool for several weeks so that those unslaked grain can get totally slaked. (陈伏)3. What ingredients are used for the production of Portland cement? What is the role of gypsum？Solution:Production of Portland cement starts with two basic raw ingredients: a calcareous material and an argillaceous material.The calcareous material is a calcium oxide, such as limestone, chalk or oyster shells.The argillaceous material is a combination of silica and alumina that can be obtained from clay, shale, and blast furnace slag.Besides, there are some other adjustable materials such as diatomite (SiO2), magnetite (Fe2O3), alumina (Al2O3), etc and gypsum and activity mixtures.Gypsum plays a role as a retarder to regulate the setting time of the cement in the concrete and a control amount of gypsum can prevent some side-effect.4. What are P.I, P.II, P.O, P.S, P.P, P.F shorted for? Solution:P.P means Portland-pozzolana cement;P.F means Fly-ash Portland cement;P.I. and P.II. mean Portland cement;P.O. means Ordinary Portland cement;P.S. means Portland slag cement.Notation: In America, the P.I. stands for normal type Portland cement while P. II. means moderate sulfate resistance type Portland cement. And they two type are inseparable in China.5. What are the four mineral compounds in Portland cement? How do the chemical compounds contribute to the hydration, strength and other properties? Solution:The four mineral compounds in Portland cement are tricalcium silicate (3CaOSiO2), dicalcium silicate (2CaOSiO2), tricalcium aluminate (3CaOAl2O3), tetracalcium aluminoferrite (4CaOAl2O3Fe2O3).The chemical components contribution of hydration can be summarized in the following table.More specifically, the relationship can be reflected by inequalities.Hydration speed:C3AC3SC4AFC2SHydration heat:C3AC3SC4AFC2SEarly strength:C3SC3AC4AFC2SPost strength:C3SC2SC3A C4AF6. What are the primary chemical reactions during the hydration of Portland cement?Solution:C3S hydration:C2S hydration:C3A hydration: In water without gypsum In water with gypsum After the gypsum exhaustedC4AF hydration:Its similar to C3A.7. Describe the corrosion and prevention of cement stone?Solution:1) The corrosion of cement stone includes:Calcium hydroxide dissolved lost in fresh water;Erosion of sulfate;Erosion of magnesium salt;Erosion of carbonate.2) The ways to prevent cement from corrosion includes:a) Choosing right type cement which produces less amount calcium hydroxide Ca(OH)2 during process of hydration, such as Portland slag cement;b) Selecting cement with less content of C3A;c) Improving construction technology and denseness of cement;d) Painting of waterproof coating on cement surface.8. Why should we determine the water requirement of normal consistency of cement?Solution:There are two reasons about that: Setting time or soundness is measured only under the condition of normal consistency Normal consistency expresses a state that cement pastes shows the same consistency.9. Define the initial and final setting time, and briefly describe the test methods.Solution: Definition Initial setting time The initial setting time is the interval between the mixing of the cement with water and the time when the mix begins to lose plasticity, stiffening to a certain degree. It marks roughly the end of the period when the wet mix can be molded into shape Final setting time The final setting time is the interval between the mixing of the cement with water and the time when the mix completely lose plasticity. It represents the point at which the set cement has acquired a sufficient firmness to resist a certain defined pressure. Test method A sample of cement paste is prepared with water required for normal consistency Maintained in 30min Penetration is repeated in every 5s near the initial setting The initial setting time is when the distance between the test needle and the bottom is 4mm1mm Penetration is repeated in every 15min near the final setting The final setting time is when the distance between the test needle and the surface is 0.5-1mm10. What is the strength grade of Portland cement, and how to determine the strength grade of a given Portland cement?Solution:Strength grade of Portland cement is classified by the compressive strength and flexural strength of the required curing day. The “MPa” is used to represent the strength grade. Portland cement has three strength grade