19-08-2014, 02:31 PM
DEVELOPMENT OF MIX DESIGN FOR PUMP CONCRETE USING LOCAL MATERIAL PROJECT REPORT
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Abstract
This paper presents the result of mix design developed for pump concrete.
Pump concrete is that concrete whose slump is 125mm or more. Pump concrete can
be placed in areas that are difficult or impossible to reach by other placement
methods. Pumping often results in manpower and equipment cost and time. Pump
concrete generally has little more sand and little less stone than normal concrete so
it can be smoothly pumped from a distant place. Pump concrete needs more cement
per cubic meter to achieve the right strength .In this research work a mix design for
pump concrete is developed using local materials. Seven sets of cylinders are made
with seven mix ratios. Each set contains nine cylinders; three are tested after three
days, three after 7-days and three cylinders after 28-days. The mix ratios 1:0.5:1.5,
1:0.6:1.2, 1:1:1.5, 1:1:2, 1:1.5:3, 1:2:4 and 1:2.25:4.5 are used to obtain maximum
compressive strength with different water cement ratios. The water cement ratio
varies between 0.37 to 0.67.Superplasticizer was used as admixture in the concrete.
The main purpose of using super plasticizer is to produce flowing concrete with
slump in the range of 150mm to 180mm.The ability of super plasticizers is to
increase the slump of concrete depends on factors such as the type, dosage and
time of addition of super plasticizer, water cement ratio and the nature or amount of
cement .It is found that maximum compressive strength is achieved at 0.37 water
cement ratio with slump of 150mm.The ratio at which the maximum strength is
achieved is 1:0.6:1.2.It is observed that this method of mix design for pump concrete
is very useful and beneficial for contractors and practicing engineers working in
construction industry
Introduction
ACI defines pumped concrete as concrete that is transported through hose or pipe by means
of a pump. Pumping concrete through metal pipelines by piston pumps was introduced in the United
States in Milwaukee in 1933. This concrete pump used mechanical linkages to operate the pump and
usually pumped through pipelines 150 mm or larger in diameter.Many new developments have since been made in the concrete pumping field. These include
new and improved pumps, truck mounted and stationary placing booms, and pipe line and hose that
with stand higher pumping pressure. As a result of the innovations concrete placement by pump has
become of the most widely used practices of the construction industry.
Pumping may be used for most concrete construction but in especially useful where space for
construction equipment is limited. A steady supply of pump able concrete is necessary for satisfactory
pumping [1]. A pump able concrete, like conventional concrete, requires good quality control i.e.
uniform, properly graded aggregate materials, uniformly batched and mixed thoroughly [2]. Concrete
pumps are available with maximum output capacities ranging from 15 to 250 yd3
/hr. Maximum volume
output and maximum pressure on the concrete cannot be achieved.
Simultaneously from most concrete pumps because this combination requires too much
power. Each foot of vertical reduces the horizontal pumping distance about 3 to 4 feet because three
to four times more pressure is required per foot of vertical rise than is necessary per foot of horizontal
movement.
Pumped concrete moves as a cylinder riding on a thin lubricant film of grout or mortar on the
inside diameter of the pipe line [3, 4, 5]. Before pumping begins, the pipeline interior diameter should
be coated with grout. Depending upon the nature of material used, this initial pipe line coating mixture
may or may not be used in the concrete placement. Once concrete flow through the pipe line is
established, the lubrication will be maintained as long as pumping continues with properly proportional
and consistent mixture.
Concrete pumping is so established in most areas that most ready mixed concrete produces
can supply a concrete mixture that will pump readily if they were informed of the concrete pump
volume capacity and its pressure capability, pipeline diameter and horizontal and vertical distance to
be pumped.
Experimental Program
The experimental work has been carried out to develop mix design for pump concrete. Three
basic ingredients were used in this experimental work. The coarse aggregate was collected from
Margallah Hills and the type used was “CRUSHED” having maximum size (3/4”) 20mm. The fine
aggregate was Lawrancepure sand. Ordinary Portland cement was used as binding material.
The maximum size of angular coarse aggregate was limited to one third of the smallest inside
diameter of the pump. For well rounded aggregate, the maximum size should be limited to two fifth of
these diameters. The grading of sizes of coarse aggregate was done according to the requirements of
ASTM C33 which is shown in table – 2
The properties of fine aggregate or sand play a much important role in the proper training of
pump able mixes. Together with cement and water, the fine aggregate provides the mortar or fluid
which conveys the coarse aggregate in suspension, thus rendering a mixture pump able.
Result and Discussion
The properties of coarse aggregate and fine aggregate have most important role in the
development of pump concrete. The maximum size of angular coarse aggregate was limited to one
third of the smallest inside diameter of the pump. The maximum size of round aggregate should be
limited to two fifth of the diameter of the pumps otherwise blockage of the pumps will take place. The
fine aggregate combines with cement and water and provides the mortar or fluid which conveys the
coarse aggregate in suspension which increase the pump ability of concrete mix. With the increase in
cement content the compressive strength of concrete was increased. The maximum strength of mix
ratio (1:0.6:1.2) at 0.38 water cement ratio shows good results for pumping concrete. The fineness
modulus of fine aggregate plays important role in pump ability of concrete. The fineness modulus of
2.76 gives good results for pump ability of concrete.
Conclusion
In this research work local material of Pakistan was used to develop pump able concrete.
Properties of fresh and hardened concrete were examined. The conclusions are as follows:
1. The slump from 150 to 180 mm is most suitable for pumping of concrete. When the flow of
concrete is over 200 mm the coarse aggregate will separate from mortar and paste which
causes pipeline blockage. Overly wet mixes shows excessive bleeding.
2. The maximum compressive strength was achieved at 1:0.6:1.2 mix ratio.
3. The density of concrete at which the maximum strength achieved is 2262 kg/m3
.