1、Assignment for Road Engineering MaterialsChapter 1 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 resis
2、tance 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 (
3、3CaOSiO2), dicalcium silicate (2CaOSiO2), tricalcium aluminate (3CaOAl2O3), tetracalcium aluminoferrite (4CaOAl2O3Fe2O3).The chemical components contribution of hydration can be summarized in the following table.Assignment for Road Engineering Materials Chapter 1 Erosion of sulfate;Erosion of magnes
4、ium salt;Erosion of carbonate.2) The ways to prevent cement from corrosion includes:a) Choosing right type cement which produces less amount calcium 2 2 2(3)(CaOSinHxCaOSiyHxCaO222 )(Hii OAlCaOAlCaOHAlCa 232232232 81947)( 32413()141422342aSalaSHAAA41323421HFtOlCOAssignment for Road Engineering Mater
5、ials Chapter 1 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: Set
6、ting 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 initi
7、al 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
8、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 c
9、onsistency 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
10、 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
11、“MPa” is used to represent the Assignment for Road Engineering Materials Chapter 1 & Chapter 212strength grade. Portland cement has three strength grade and six types, i.e. 42.5, 42.5R, 52.5, 52.5R, 62.5, 62.5R.The measuring method of strength grade of a given Portland cement is ISO method. The proc
12、ess are preparing the standard 4040160specimen with and and then measuring the flexural =13 =0.5strength and compressive strength with enough curing days (3 days or 28 days) at the standard curing requirements.11. Please analyze the volume unsoundness of Portland cement. What effects does volume uns
13、oundness bring to structures?Solution:The volume unsoundness of Portland cement means the ability to retain volume of cement paste after setting.Lack of soundness (unsoundness) is attributed to excessive amount of free lime or magnesia (-CaO, -MgO) and extra-gypsum.12. There are two batches of Portl
14、and cement from Plant A and Plant B, and their mineral compounds are given in the following table. Please compare their differences about strength development and hydration heat features, and discuss the reasons. Solution:The Portland cement from plant B may have a higher hydration heat and lower st
15、rength development. By contrast, The Portland cement from plant A may have a lower hydration heat and higher strength development.The amount of plays a dominate role in the hydration heat. And there is 3more in the Portland cement of plant B. So, it may have a higher hydration 3heat.The mount of plays a dominate role in the strength development. And there 3is more in the Portland cement of plant A. So, it may have a higher hydration 3Assignment for Road Engineering Materials Chapter 1 & Chapter 213heat.
