TECHNOLOGY OF CIVIL WORKS

1. What should contain a technological chart (control tag)?

Description of the technological process;

Characteristic sketches that describe the erection stages involved in the process in

a logic order;

Necessary resources for works achievement: raw materials, equipment,

manpower;

Works inspection;

Works acceptance;

Bill of quantities, works duration

2. What are the steps to follow in order to trace a building?

- Finding the special topographical grid and verification of tracing landmarks of the

topographical grid as position and structural integrity

- Tracing of the construction axes

- Rigger construction or trestles positioning for each structure axis

- Axes marking on riggers (both main and secondary axes)

- Foundations tracing

- Vertical alignment

2. How can be checked the formwork horizontality and verticality?

Checking verticality can be done using spirit level or plumb. Plumb line is used mounted

on a balance blade, with a sign traced on the lower arm at a distance equal to the one

between end of lead wire and the upper arm. Formwork is vertical when the plumb line

coincides with the sign on the lower arm.

Horizontality check can be achieved with spirit level , by placing it on the track and

noticing that the air bubble level to be drawn between two landmarks on the glass tube. If

the surface is not horizontal bubble is moving towards the higher side.

4. What are the main technical requirements to be met by concrete aggregates?

To come from strong rocks, that ensure grain self resistance greater than the concrete

one

Granules are well sized, and the ratio between the three dimensions after the

rectangular directions of grain to be b / a ≤ 0.66, c / a ≤ 0.33

It is preferable to use gravel aggregates – rounded shape. In the case of aggregate

crushing – that have rough surface –a larger amount of water and cement is necessary

to obtain the same workability.

The maximum size of grain used to be correlated with the minimum cross section of

the building element and the distance between the reinforcement bars.

Aggregates used must be characterized by a continuous curve of grain.

5. What rules will be considered and what measures will be taken for concreting in

cold weather conditions?

During preparation of concrete: o ratio Water / Cement reduction o heating the aggregates and water o adding anti-freeze additives

During concrete transport: o Using a fast and cold insulated vehicles for transport o Avoiding a large transport distances

o Checking of vehicles

o During concrete pouring:

- Foundations pits to be protected against freezing. The construction joints

should be avoided, or if not possible, cleaned and heated when resume

pouring

- Poured concrete heating with steam / hot air or with metal electrodes

embedded in concrete, etc.

6. What are the main rules to be followed in carrying out technological joints

position in case of cast in place concrete structures?

Working joints are determined taking into account the following rules:

o Areas of minimum effort

o Thickness of the element to be poured

o Dimensions of the surface to be poured

o Contractions direction

Problema tehnologie

For the foundations plan attached, find the duration of concrete pouring in foundations when the site is equipped with two rod vibrators, one for site use and one for backup.

It is required to draw the compaction scheme for the studied case. Concrete used: C12/15 with L2 workability Rod vibrator characteristics:

- Rod diameter: 60 mm d1 = 60mm, r1=30 mm - Rod length: l = 575 mm - Maximum vibrations amplitude in the air: A1 = 1.8mm - Vibrations frequency: n = 2800 vibr/min

Optimum vibrations range from the point of productivity: 0.07 0.12 mm

35 400 400 35

35

350

350

35

35 35

70

35 35

70

35 35

70

35

35

70

35

35

70

35

35

70

-1.20

-1.20

-1.20

-1.2

0

-1.2

0

-1.2

0

CTN=-0.10m

Table 1: damping coefficient of vibrations in fresh concrete b and minimum amplitudes

Amin

Vibr. frequency

b[cm-1] Amin[mm]

Concrete workability

L1 L2 >L3 L1 L2 >L3

2800 0.18 0.10 0.77 0.10 0.014 0.006

4500 0.16 0.09 0.06 0.07 0.010 0.004

6000 0.14 0.08 0.05 0.02 0.004 0.0025

7000-12000

0.13 0.07 0.04 0.01 0.003 0.002

Table 2: Compaction duration for rod vibrators

Concrete workability

Compaction duration t1 [sec]

L1

l18045

L2

l4025

>L3

l205

Solution Finding the span range (r0) for rod vibrator.

From table. 1, for L2 si n=2800 vibr/min b=0.1 cm-1; Amin = 0.014 mm

It is chosen r2 = 40 cm mm077.0e40

38.1e

r

rAA 3401.01r2r

2

11

A(0.07; 0.12)mm r0 = 40 cm Finding the distance (l1) between 2 successive positions of rod vibrator.

01 r5.1l 405.0l1 mm60l1

Finding distance (l2) to the excavation edge.

021 r5.0ld2 405.0l62 2 l2 [12; 20] cm

Finding the thickness of vibrated concrete layer (δ).

cm105l

l4

3

cm1055.57

5.574

3

cm5.525.47

cm43

δ ≤ 43 cm Compaction scheme

R40

R40

R40

R40

R40

R40

R40

R40R

40

R40

l2=

20

l1=

60

l1=

60

l2=20 30 l2=20

l2=20 l1=60 l1=60 l1=60 l1=60

l2=

20

30

l2=

20

A

A

Section A-A

Stage 1

20 30 20

40

11

0

Stage 2

20 30 20

40

11

0

35

Stage 3

20 30 20

40

11

0

35

35

5..

.10

5..

.10

Compaction duration

Acc. to table 2, for L2 l

4025t1

sec28

5.57

4040t1

Hour average productivity of the rod vibrator

e

21

20lexp k

tt

3600r2P

where t1 = 8 10 sec (necessary duration to move the rod

vibrator between 2 successive positions)

h

m48.88.0

1028

36004.02P

32

lexp

Concrete volume necessary for the continuous foundations (according to the

foundation plan)

31 m333230.310.170.0370.710.170.0V

Volume of fresh concrete necessary to be poured in foundations

312 m47

70.0

33

K

VV

Works duration in order to erect the continuous foundation

hours648.8

47

P

Vt

lexp

2