問題一覧
1
The dividing line between coarse and fine aggregate is
4.75 mm
2
The objective of concrete mix design is to proportion mix ingredients such that the resulting concrete
is economical , meets target durability , meets workability requirement
3
has lower amount of CSH gel , more porous , is weaker
4
A concrete mix design represents
the weight of water, cement, coarse and fine aggregates, and admixtures for a given volume of concrete
5
What are the essential compounds formed as a result of OPC hydration?
C3S2H8 and CH
6
The global annual production of steel is
is less than that of concrete and wood.
7
The main reason why aggregates are incorporated into concrete is
economical
8
The hydration of C3A is expansive and does not stop even when space is not available
True
9
True
10
False
11
The unit of fracture toughness is
MPa (m)^1/2
12
Wood characteristics of interest for construction includes the broad classes of
visual characteristics , durability characteristics, fire characteristics , environmental characteristics , basic physical characteristics , mechanical characteristics
13
When designing structures, the plastic yielding failure mode is preferred over the brittle fracture failure mode.
True
14
The growth portion of a tree is
the cambium
15
It is important to measure the moisture content of aggregates because
it introduces additional amount of water brought into a concrete mix, if wet, it varies depending on weather exposure condition, it removes some amount of water which otherwise is meant for cement hydration, if partially dry, it is used to adjust the amount of mix water in order to keep the water to cement ratio at target value in the concrete mix design
16
it is made up of different phases, including aggregates, cement and interface
17
increases with the rate of loading
18
The wall panels for the building shown in the video are
16 inch thick solid wood
19
Drying shrinkage increases rapidly below the fiber saturation point (FSP).Drying shrinkage increases rapidly below the fiber saturation point (FSP).
True
20
Cell walls of wood is made up of long molecular chains of (C6H1005)n.
True
21
Clear wood refers to wood
with no defects , along grain
22
The MAS appropriate for a job is determined by
the size of dorm work, the locally available aggregate size, the spacing between rebars
23
Fatigue responds to load cycle amplitude as well as the initial length of crack.
true
24
The specific strength of parallel-to-grain wood is competitive to that of high strength steel
True
25
Air entrainment
should only be used if necessitated by freeze-throw durability consideration
26
Compare to that in the perpendicular direction, the compressive strength of wood in the parallel direction
can be several times
27
Aggregates are size graded for the purpose of
reduce cement paste , enhance durability , economy, enhance workability
28
True
29
Wood properties are anisotropic in
drying shrinkage , compressive strength , tensile strength
30
The annual carbon emission of steel making is
is about the same when compared with that of concrete manufacturing.
31
A reinforced concrete column has to be designed for a structure in California where earthquakes are a major concern. The column reinforcement should withstand a load of at least 270 kips (1 kip = 1000 |b). You are the site engineer and asked to make one of the following choices for re-bars. What is the best choice among the following?
3 x Number 10 - grade 75 bars
32
Type C fly ash involves both pozollanic reaction and hydration reaction
True
33
The specific stiffness of parallel-to-grain wood is better than that of high strength steel
True
34
The coefficients of thermal expansion of steel and concrete are
about the same
35
The mositure content of aggregates can be obtained by
the weight difference between the stock pile weight and the SSD
36
Cement hydration involves the following ingredients reacting with water;
calcium silicate compounds
37
The three most common categories of chemical admixture used in concrete are
plasticizing admixture , air-entraining agent , set-controlling admixture
38
A well-designed concrete should have fresh properties that allows it to be
castable without segregation of ingredients , easy to finish , pumpable
39
Water in wood dries out in the cell wall first, before water is evaporated from the lumin.
False
40
The annual global production (tonnes/year) of the three materials, in order, is
concrete > wood > steel
41
Cell walls of wood is made up of 70% crystalline cellulose and about 30% amorphous lignin.
True
42
The absorption capacity of aggregates can be obtained by using
the weight difference between the OD and the SSD weight
43
True
44
For fatigue failure, the critical crack length refers to
the length of crack when the stress intensity factor reaches the fracture toughness.
45
The tensile strength of a steel
the same as its compressive strength.
46
Fresh concrete should
have no segregation of ingredients, including bleeding , be capable of being finished properly , uniform within a batch and between batches , be easily mixed and transported , completely filled the formwork , have the ability to be fully compacted
47
high wind , loss of water by evaporation shortly after the casting of concrete in a structure
48
Under microscope, CH appears
platelets
49
enhances workability of concrete by dispersing cement particles more uniformly in the mix water. , physically keeps cement particles apart from each other for a longer time by coating particle surfaces with long-chain polymers. , neutralizes the polar attractions among cement grains.
50
Caution should be used in applying chemical admixture in concrete because excessive amount can lead to
undesirable amount of chloride , undesirable strength loss, undesirable slump
51
What are the most essential raw ingredients fed into a cement kiln to produce Portland Cement clinker?
limestone and clay
52
Pervious concrete
is used to enhanced water drainage through concrete slabs and reduce runoff in cities , is obtained using a concrete with no fines
53
Drying shrinkage is highest in the longitudinal direction of wood.
False
54
Higher w/c ratio gives rise to smaller amount of capillary pores
False
55
The specific gravity for most pozzolans
is lower than the SG of cement
56
Some disadvantages of wood as a construction material include its being
susceptible to fire damage, susceptible to insect damage, susceptible to dimensional change under varying humidity, susceptible to fungi attack
57
The slump test is appropriate for fresh property testing of
most concrete mix except those design for self-consolidation
58
Segregation of aggregates in concrete may occur due to
insufficient fines, high SG of coarse aggregates , angular, rough coarse aggregates
59
For quality control of concrete, the following properties are measured for fresh concrete
air content , unit weight , slump
60
True
61
increases with w/c ratio
62
Welded wire mesh is
mainly used for crack control., reduce labor due to elimination of tying rebars., more suitable for thin section concrete structures
63
The most used construction material by volume are
Concrete>timber>steel
64
Hydration of cement involves
the difusion of calcium ions into the mix water between cement grains, the filling up of space occupied by mix water , the formation of calcium-silicate-hydrate(CSH) and calcium hydroxide(CH)
65
Compared with normal concrete, the magnitude of drying shrinkage of lightweight concrete is typically
higher
66
What is the particle size of Type I OPC cement grains?
15 micron on average and can be up to 50 micron
67
The fineness of cement grain
governs the early age of compressive strength , governs the amount of heat of hydration , governs the long term compressive strength , governs the water demand for hydration
68
Under flexural load of clear wood, a crack from the tension side may bifurcate because
the microstructure of wood reduces the resistance to crack propagation in the along-grain direction.
69
Prior to conducting concrete mix proportioning, it is necessary to collect job parameters, including
the dimensions of the structural element and reinforcement details , the climatic condition of where the construction/structural element is located , the type of element such as slab, beam, column to be constructed , the required 28-day compressive strength
70
The tensile strength of clear parallel-to-grain wood can reach
150 Mpa
71
The strength of wood is influenced by
the presence of seasoning defects., the slope of grain, the presence of bark pockets., the presence of tension and compression wood.
72
Low alloy steel has alloying elements 10-20%.
False
73
ASTM standards are used for concrete testing for the purpose of
standardizing test method , standardizing specimens preparation procedure , standardizing specimen size and shape , standardizing to allow comparison of test data conducted by different laboratories
74
Hardwood is stronger than softwood
False
75
Sample of concrete for quality control at the construction site should
be tested within 5 minutes after collection , be taken from a full stream of concrete coming off the chute from a ready-mix truck
76
Evaporable water can be found in the lumin and bounded water in the cell wall of wood.
True
77
Comparing the Young's modulus of wire fabrics,
Grade 75 = Grad 60 = Grade 40
78
For control quality control, concrete samples are typically made
by collecting representative concrete material at the job site
79
The specific strength of parallel-to-grain wood is competitive to that of high strength steel
True
80
The workability of fresh concrete is measured using
ASTM C231, the slump test
81
The numbering system on aggregate sieves indicate
the number of meshes per linear inch
82
The workability of concrete is
fresh property of concrete relating the ease which it can be mixed, placed, consolidated and finished , good when the concrete can be compacted with minimum energy and without segregation
83
Steel has a carbon content more than 2%.
False
84
The stress field at the tip of a sharp crack is
singular
85
Grading of aggregates is quantified by
sieving of aggregates using sieves with a range of hole sizes, weighting the amount of aggregates left on each sieve
86
can develop longer over time due to mineral admixtures. , can be determined using cylinders aged to 56 days. , can develop faster due to use of fine particles or Type III cement.
87
CaOH crystals looks like
platlets
88
Among all engineering materials, which is used the most by volume and weight?
Concrete
89
The MAS suitable for a particular concrete job is determined by
the minimum clear spacing between reinforcing bars or between bars and framework, the concrete mixing and placing equipment , the thickness of concrete slab, the smallest dimension between sides of concrete formwork
90
Wood properties are anisotropic inWood properties are anisotropic in
tensile strength, drying shrinkage, compressive strength
91
Under microscope, CSH appears
gel like , crumbled paper
92
compressive strength
93
Optimal air content for durability should be in the range of
4-10%
94
55 GPa
95
In addition to hardness enhancement, Manganese is added to increase weldability.
True
96
Workability of fresh concrete is influenced by
water content , time and temperature , aggregate grading, shape and roughness, cement characteristics , admixtures
97
Rebar size 11 means bars with nominal diameter of
1 3/8 in
98
The temperature in the blast furnace in the making of steel is
about 1600C