CHAPTER-1:
INTRODUCTION
1.1 GENERAL:
The concrete is best martial for all the civil engineering structure like Building, Dams, Road etc. The concrete is major role in civil engineering structure. The development of new technology in the material science is progressing rapidly in last few decide. A number of research are carried out for improve the performance of concrete as compare to the strength and durability for economic point of view as well as safety purpose. In congested the reinforcement design the concreting After short time casting of any big concreting work like slab, road payment, dam etc that time concrete is in plastic or semi plastic state. Due to hit of hydration same cracks are developing. This cracks are known as plastic shrinkage of concrete. In the summer or dry months of the year it is by no means scarce to find cracks appearing on the surface of the concrete within a short duration of its placing. Plastic cracking is very divergent from the cracks which come on account of thermal movement. They notice to roughly follow their straining element, eg. Changing the concrete section. After casting of concrete up to 24 hours cracking may become problematic are very difficult to pleasing properly. The lack of proper compaction the honey combing effect are produce and decrees the strength of concrete. When the use of self compacted concrete this difficulty are reduce because there are no need to vibration or compaction in any concrete structure. It can destruction the aesthetics of the concrete section and decrease the durability and serviceability by facilitating the entrance of unhygienic material. The Plastic shrinkage cracking are developing most of large concreting surface area such as in slab and floor. The moisture is removed in the concrete, the surface concrete decrement, resulting in tensile stresses in the weak material. To prevent cracks in concrete reduce water content & proper concrete mix design, curing, compaction etc.
1.2-SELF COMPACTED CONCRETE:
Self compacting concrete is a latest type of concrete that developed in Japan. It is not require manually compaction . It is able to free flow on congested reinforcement area. It has also able to dropped from a specified height without segregation . Owing to the fact that it does not require vibration to compact, it is useful for reducing the concrete placing costs, and prevention of health hazards resulting from vibrations.
Self-compacted concrete has been considered as a vast development in construction in all our world since its first developed in Japan. The flowing -bility of the concrete is the main property of Self compacted concrete so that it can be placed under its self-weight without compaction and vibration. The Self compacted concrete of high fluidity without segregation or bleeding during the transporting or placing of the concrete , the use of high powder content, super plasticizers (SP) and viscosity modifying admixtures (VMA) seems to be a very good solution. However, the cost of this type of concrete is much more than normal vibrated concrete. The use of Fly ash and ground granulated blast-furnace slag or other west matrial it can be decrease the material cost and increase the flow-ability concrete.
Various studies have shown that mineral supplements have been mostly used as a supplementary for Ordinary Portland cement in many applications because of its advantageous properties which include the cost-decrising, heat-reducing , decrease in permeability and increase in chemical resistance. Congested reinforcement has more innovative design , more complex shape of RCC member, thinner section are possible to reduce bleeding problems and proper compaction in very danced reinforced areas. Selfcompacted concrete has high Fluidity that prevents segregation. Self-compacted concrete is also known as Self-consolidated concrete. The self-compacted concrete has relatively high powder content. In Self-compacted concrete the ratio of fine to coarse aggregates is more.
1.3 History of SCC:
Self-compacted concrete it was not developed until the 1980’s in Japan. The Self compacted concrete was first developed in 1988 by Professor Okamura to increase the durability properties of concrete structures. The rate of demand this type of concrete work was due to shortage of skilled construction labors in Japan. The first prototype was introduced in 1988 by K. Ozawa from the Tokyo University. At the year 2000, It was become more popular use in Japan for the precast concrete product and ready mixed concrete. There are main three properties that affecting to the fresh concrete of Self-compacted Concrete it is the passing ability of concrete, filling ability of concrete, Andthe segregation resistance of concrete respectively. Self-compacted concrete is also referred As the Self consolidated concrete that was developed in Japan. Self-consolidated concrete has a high performance materials design to flow in to the formwork under its self-weight without any vibration and compaction. The durability of any concrete structures it can be increased by using Self consolidation concrete. Since then, the various experiments has been carried out and the Self-compacted concrete has been used in various civil engineering structures in Japan and Europe, for big construction companies. Experiments for establishing a rational mix-design method and self-compacting ability of the testing methods have been carried for making it a standard concrete. To construct a various durable concrete structures the effectively compaction is required by skilled construction labors. However, the gradually decreasing in the number of skilled labors in the construction industry has led to decrease in the quality of construction work. Solution for achieving the durable concrete structures, independent of the quality of construction work, is the use of the Self compacted concrete, which can be compacted into every corner of a formwork, purely by means of its self-weight and without the need of vibrating compaction (Fig 1.1)
Self-compacted concrete
Skilled Construction Labours
(Decreasing) (In the future)
Durable Concrete Structures
Fig. 1.1: Necessity for Self-Compacted Concrete (SCC):
1.4 Definition:
“A concrete which can flow and fill each and every single part and corner of the formwork, even within congested reinforcement area , simply method for its own particular weight and no need to vibration or any other type of compaction machine it’s called self-compacting concrete. It is give flexibility of superb passing ability, filling capacity, and segregation resistance.
1.5 Applications of Self compacting concrete:
The using of self-compacting concrete is very useful for all development applications, where the specified area of interest are important to get a decent concrete quality. Particularly in very heavy reinforced design and concrete member like bridge or abutments, metro or road tunnel linings or tubing segments, where there is difficult to build the any structure, self-compacting concrete is effectively suggested. A standout amongst the most exceptional applications in the country of self-compacting concrete, Japan is the Yokohama Landmark Tower and Akashi Kaikyo Bridge. Since the improvement of the model of SCC in 1988, the utilization of Self compacting concrete in development industry has steadily expanded.
1.6 Advantages:
Increasing quality of concrete and decreasing of onsite repairs.
Faster construction work.
Reduce overall costs.
Facilitation of introduction of automation into concrete construction.
Improve health condition and safety is also achieve through elimination of handling of vibrators.
It is also useful for reducing environmental noise loading on and around a site
Better surface finishing.
Easy placing.
Use at thin concrete sections.
Use in any congested are there for no limitation in reinforcement design.
Improve durability of concrete structures.
Ease of placing than reduced cost of equipment and labor cost.
The high resistance to external segregation and the mixture self compacting ability allow the elimination of air bubbles and honey combing effect.
1.7 Limitation of SCC:
Cost –
when the use of self compacted concrete the cost of concrete is much more high as compare to the conventional concrete. Because super-plasticizer and Viscosity modified
Agent are costly which utilized as a part of SCC is higher.
Careful curing at early ages –
In hardened properties of Self consolidation concrete depends generally on curing at early ages.
Non availability of standards and codes-
since the development of self concrete no codes and principles are accessible for
especially in India for the improvement.
Required rounded aggregate –
It is required for rounded aggregates that are not effectively available in local market.
1.8 Aim and objectives of project:
? To evaluate the fresh properties such as Passing ability and filling ability of SCC by
using regional sand 0% ,10% ,20%,30% and fly Ash 25% replacement of cement.
? To evaluate the harden properties such as compressive strength ,Split tensile Strength
and Flexural test of SCC with use of regional sand 0% ,10% ,20%,30% and fly Ash
25% replaced by binder material.
? To evaluate the durability Acid attack with H2So4 and HCL solution of SCC with use
of regional sand 0% ,10% ,20%,30% and fly Ash 25% replaced by binder material.
1.9 Problem Specification:
? There is no availability of IS: Code for mix design.
? There is no specific mix design for SCC.
? Trial error is more comparing to conventional concrete.
? It is totally dependent on assumption.
? No specific guideline is provided for SCC.
CHAPTER 2
Experimental Materials
2. INTRODUCTION
The properties and the detail of the all kind of material to be used in the concrete mix design are as given bellow.
Cement
Coarse aggregate
Fine aggregate
Water
Super plasticizer
Viscosity modification agent
2.1 CEMENT
In the most common sense of the word, cement is a binder, a substance that sets and hardens independently, and it can bind other materials together. The very important use of cement is the production of mortar and Concrete the bonding of natural or artificial aggregates to form a strong building material that is durable in the face of normal environmental effects. Concrete should not be confused with cement, because the term cement refers to the material used to bind the aggregate materials of concrete. Concrete is a combination of cement, aggregate and water.
Figure 1: Ultratech Cement (OPC)
Table 2 Properties of Cement
PROPERTIES A VALUE FOR OPC USED IN THIS STUDY STANDARD VALUE FOR OPC
Specific Gravity 3.15 –
Standard Consistency 31.5% –
Initial Setting Time (min) 48 >30
Final Setting Time (min) 225 <600
Fineness by Dry Sieving 8 % <10 %
Soundness (mm) 2 <10
COMPRESSIVE STRENGTH (N/mm2)
3-Days 27.33 >27
7-Days 38.06 >37
28-Days 53.63 >53
Source: As Per Company Details
COARSE AGGREGATE
Figure 2: Coarse Aggregate
The largest proportion of the aggregate was used to manufacture concrete (36%), with a further 10% used to manufacture the cement that is also used in the concrete. Used in roads was the second largest category (26%), while 20% of aggregates were used in other construction uses & fills and another 2% were used for railway ballast.
Aggregates are the most mined material in the world. Aggregates are a component of composite materials such as concrete and asphalt concrete; the aggregate serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and road side edge drains.
Aggregates are also used as base material under foundations, roads, and railroads. In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniform properties (e.g. to help prevent differential settling under the road or building), or as a low-cost extender that binds with more expensive cement or asphalt to form concrete.
SPECIFIC GRAVITY OF AGGREGATE
PROCEDURE
About 2kg of the aggregate sample is washed thoroughly to remove fines, drained and then placed in the wire basket and immersed in distilled water at a temperature between 22 to 320C with a cover of at least 50 mm of water above the top of the basket
Immediately after the immersion the entrapped air is removed from the sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per second. The basket and the aggregate should remain completely immersed in water for a period of 24±0.5 hours afterwards.
The basket and the sample are then weighed while suspended in water at a temperature of 22 to 32?C. The weight is noted while suspended in water (W1) g.
The basket and the aggregate are then removed from water and allowed to drain for a few minutes, after which the aggregates are transferred to one of the dry absorbent clothes.
The empty basket is then returned to the tank of water, jolted 25 times and weights in water (W2) g.
The aggregates placed in the dry absorbent clothes are surface dried till no further moisture could be removed by this clothe.
Then the aggregate is transferred to the second dry cloth spread in a single layer, covered and allowed to dry for at least 10 minutes until the aggregates are completely surface dry. 10 to 60 minutes drying may be needed. The surface dried aggregate is then weighed W3 g.
The aggregate is placed in a shallow tray and kept in an oven maintained at a temperature of 110C for 24 hours. It is then removed from the oven, cooled in air tight container and weighed W4 g.
Sample of aggregate = 16mm retain about 2.5 to 3 kg aggregate
SAMPLE WEIGHT (gm)
EMPTY WEIGHT OF WIRE MESH BUCKET IN SUBMERGE CONDITION 724.50
SUBMERGE WEIGHT
3096
AIR DRY AGGREGATE WEIGHT 3735
OVEN DRY AGGREGATE
3678.5
WATER ABSORPTION OF AGGREGATE
As mention above in cl.3.3.2
BULK DENSITY OF AGGREGATE
PROCEDURE:
Take the weight of empty measure (W)
Fill the measure with aggregates sample for about one third height and tam evenly with 25 strokes of the rounded end of the tamping rod
Add a similar quantity of aggregate as second layer and tamp it evenly with 25 strokes.
Fill the measure with a third layer of aggregate up to over following and tamp it with 25 strokes
Strike off the surplus aggregate using the tamping rod as a straight edge.
Take the weight (w1)
Empty the measure and fill it again to over flowing by means of a shovel, the aggregate being discharged from a height not exceeding 5 cm above the top of the measure.
Level the surface of the measure and weight it (w2).
OBSERVATIONS AND CALCULATIONS:
Table of observations for Bulk Density
Sample State Sample Type Wt. of container Volume of
container Wt. of container
+
wt. of agg. Wt. of agg. Bulk density
(Kg) (m3) (Kg) (Kg) (kg/m3)
LOOSE Fine 5.7 .0035 10.60 4.9 1400
Coarse 7.45 .0053 15.3 7.85 1481
COMPACTED Fine 5.7 .0035 11.15 5.45 1557
Coarse 7.45 .0053 16.20 8.75 1651
Increase in Bulk Density (Fine aggregate) = 11.21 %
Increase in Bulk Density (Coarse aggregate) = 11.48 %
FINE AGGREGATE (SAND)
Figure 3: Fine Aggregate
Source: Sltiet, Rajkot
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand is silica (silicon dioxide, or SiO2), usually in the form of quartz.
ISO 14688 grades sands as fine, medium and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm.
SIEVE ANALYSIS OF SAND
Determination of quantitative size distribution of particles of soil down to fine-grained fraction.
Procedure:
Take a suitable quantity of oven dried soil. The mass of soil sample required for each test depends on the maximum size of material.Clean the sieve to be used and record the weight of each sieve and the pan.Arrange the sieves to have the largest mesh size at the top of the stack. Pour carefully the soil sample into the top sieve and place lid over it.Place the sieve stack on the mechanical shaker, screw down the lid, and vibrate the grit sludge sample for 10 minutes.Remove the stack and re-weight each sieve and the bottom pan with the soil sample fraction retained on it.Initial mass of soil sample taken for analysis (kg) = 1000gms
Table 3.5 Observation Table
SIEVE SIZE (MM) MASS OF SIEVE (G) MASS OF SIEVE + soil (G) SOIL RETAINED (G) PERCENT RETAINED (%) CUMULATIVE PERCENT RETAINED (%) PERCENT FINER (%0
4.75 mm 366 440 74 7.4 7.4 92.6
2.36 mm 317 382.5 65.5 6.55 13.95 86.05
2 mm 335.5 344 8.5 0.85 14.8 85.2
600 µm 357.5 790 432.5 43.25 58.05 41.95
425 µm 355 666.5 311.5 31.15 89.2 10.8
300 µm 285.5 311 25.5 2.55 91.75 8.25
150 µm 320 395.5 75.5 7.55 99.3 0.7
75 µm 335 341 6 0.6 99.99 0.01
Pan 286 287 1 0.1 100 0
Total 1000gms 100% 474.44 Fitness Modules = % Retain100 = 474.44100S0, the Finesse Modules of sample is 4.74, Zone – III.
DETERMINATION OF SPECIFIC GRAVITY: SAND
Procedure
Wash, dry and weight the Pycnometer. Place about 10 g of sand sample in the Pycnometer. Weight the bottle with the sand. Add sufficient desired water to cover the sand, and connect the bottle to a vacuum pump to remove all entrapped air. Disconnect the pump and fill the bottle with water up to the calibration mark.
Clean the exterior surfaces of the bottle Pycnometer with dry cloth, and weight the bottle with the contents. Empty the bottle and clean it. Fill it with distilled water up to the mark and record its weight.
Table 3.6 Observation table
TEST NO 1 2 3
Mass Of Pycnometer, W1 (G) 256 256 256
Mass Of Pycnometer + Grit Sludge, W2 (G) 470 522 581
Mass Of Pycnometer + Grit Sludge +Water, W3 (G) 1148 1171 1221
Mass Of Pycnometer + Water, W4 (G) 1016 1016.5 1016.5
Specific Gravity 2.60 2.38 2.59
2.3 Super plasticizer:
The most important admixtures are the super plasticizers (high range water reducers), used with a water reduction greater than 20%.Admixture conforming to IS 9103. Admixture is most important constitute of self-compacting concrete to achieving flowability and passing ability. In this experimental study, Chryso fluid optima S830
Fig 4 SUPER PLASITICIZER
Colour Light brown
Specific
gravity
Near1.01 g/cm3
pH >6
Chloride
content
< =0.10 by mass
Table 1.6: Property of superplasticizer
The principal consideration of the proposed method is to fill the paste of binders into voids of the aggregate framework piled loosely. The loose unit weight of the aggregate is according to the shoveling procedure of ASTM C29, except discharging the aggregate at a height of 30 cm above to the top of the measure. Usually, the volume ratio of aggregate is about 52–58%, in other words, the void in the loose aggregate is about 42–48% according to ASTM C29. The strength of SCC is provided by the aggregate binding by the paste at hardened state, while the workability of SCC is provided by the binding paste at fresh state. Therefore, the contents of coarse and fine aggregates, binders, mixing water and SP will be the main factors influencing the properties of SCC. With the proposed method, all we need to do is to select the qualified materials, do the calculations, conduct mixing tests and make some adjustments, and SCC with good flowability and segregation resistance can be obtained with self-compacting ability as specified by the JSCE (Table 1). The procedures of the proposed mix design method can be summarized in the following steps.
2.1. Step 1: calculation of coarse and fine
aggregate contents
Step 2: calculation of cement content
Step 3: calculation of mixing water content required
by cement
Step 4: calculation of mixing water content needed
in SCC
Step 5: calculation of SP dosage
Step 6: adjustment of mixing water content needed
in SCC
Step 7: trial batches and tests on SCC properties
Step 8: adjustment of mix proportion
CHAPTER :3
Methodology
3 Methodology
(1) Batching
(2) Mixing
(3) Transporting
(4) Placing
(5) Curing
3.1 Batching:
The measurement of materials for making self-compacting concrete is known as batching. There are two methods of batching
(I) Volume batching
(ii) Weight batching
Volume batching:
Volume batching is not a good method for proportioning the material. The Volume of moist material in a loose condition weights much less than the same volume of dry compacted material therefore volume batching are not used for general purpose.
Weight Batching:
Batching by weight is more accurate and leads to more uniform proportioning and quality of concrete. For important concrete structure weight batching system should be adopted.
Fig. 5 Weight Batching
3.2 Mixing:
The aim of mixing of concrete is to produce a homogenous and uniform coloured SCC. This means that the different constituted material of concrete be uniformly distributed throughout the concrete mass. There are two methods adopted for mixing concrete:
(i) Hand mixing
(ii) Machine mixing
Hand Mixing:
Hand mixing is practiced for small scale unimportant concrete works. As the mixing cannot be thorough and efficient, it is desirable to add 10 per cent more cement to cater for the inferior concrete produced by this method.
Machine Mixing:
Mixing of concrete is almost invariably carried out by machine, for reinforced concrete work and for medium or large scale mass concrete work. Machine mixing is not only efficient, but also economical, when the quantity of concrete to be produced is large. Various type of concrete mixture available foe mixing of concrete such as follow Batch mixers, continuous mixers etc.
3.3 Casting:
It is not enough that a self-compacting concrete mix correctly designed, batched, mixed and transported; it is also importance that the concrete must be placed in systematic manner to yield optimum results.
? Concrete is poured in the mould of cube size 150mm×150mm×150mm.
? For cylinder size is 150mm diameter and 300mm depth.
? For Beam size is 100mm x 100mm x 500mm.
? No compaction is given by vibration or Tamping rod in SCC.
fig 6 cube casting
3.4 Curing of concrete:
Concrete hardens is due to chemical reactions between OPC and water. Concrete derives its strength by the hydration of cement content. The hydration of cement is not a momentary action but a process continuing for long time. The rate of hydration is fast to start with, but continues over a very long time at a decreasing rate. The quantity of the product of hydration and consequently the amount of gel formed depends upon the heat of hydration. After 72 hours of casting the specimens is to be demoded and is transferred to the curing tank, wherein they will allow curing for 7 and 28 days before testing.
Chapter 4
METHOD OF TEST
1. Slump flow test
The slump flow test is used assess the horizontal free flow of self compacting concrete in the absence of obstructions. The test method is based on the test method for determining the slump
2. V Funnel Test
V funnel test on self compacting concrete is used to measure the flowability. But the flowability of concrete is affected by its other properties as well which may affect the flowability of the concrete during testing.
3. L Box Test
This test assesses the flow of the concrete and also the extent to which it is subjected to blocking by reinforcement.
4. U Box Test
U Box test is used to measure the filing ability of self compacting concrete. U box test was developed by the Technology Research Centre of the Taisei Corporation in Japan. Some time the apparatus is called a “box shaped” test.
5. Fill Box Test
Fill box test is also known as ‘Kajima test’ is used to measure the filling ability of self compacting concrete with a maximum aggregate size of 20 mm.
Slump flow test
Assessment of Slump Flow Test
This is a simple, rapid test procedure, though two people are needed if the T50 time is to be measured. It can be used on site, though the size of the base plate is somewhat unwieldy and level ground is essential.
It is the most commonly used test, and gives a good assessment of filling ability. It gives no indication of the ability of the concrete to pass between reinforcement without booking, but may give some indication of resistance to segregation.
It can be argued that the completely free flow, unrestrained by any foundries, is not representative of what happens in concrete construction, but the test can be profitably be used to assess the consistency of supply of supply of ready-mixed concrete to a site from load to load.
Equipment for Slump Flow Test
The apparatus is show in figure;
o Mould in the shape of a truncated cone with the internal dimensions 200 mm diameter at the base, 100mm diameter at the top and a height of 300 mm.
o Base plate of a stiff non-absorbing material, at least 700mm square, marked with a circle marking the central location for the slump cone, and a further concentric circle of 500mm diameter
o Trowel
o Scoop
o Ruler
o Stopwatch(optional)
Fig. 8: Accessories for Flow cone Flow table Slump test
Fig. 9 Slump flow test and T 50 cm test
Procedure of Slump Flow Test on Self Compacting Concrete
About 6 liter of concrete is needed to perform the test, sampled normally. Moisten the base plate and inside of slump cone, place base plate on level stable ground and the slump cone centrally on the base plate and hold down firmly.
Fill the cone with the scoop. Do not tamp, simply strike off the concrete level with the top of the cone with the trowel.
Remove any surplus concrete from around the base of the cone. Raise the cone vertically and allow the concrete to flow out freely.
Simultaneously, start the stopwatch and record the time taken for the concrete to reach the 00mm spread circle (This is the T50 time).floatable test, might be appropriate.
The T50 time is secondary indication of flow. A lower time indicates greater flow ability. The Brite EuRam research suggested that a time of 3-7 seconds is acceptable for civil engineering applications, and 2-5 seconds for housing applications.
In case of severe segregation most coarse aggregate will remain in the centre of the pool of concrete and mortar and cement paste at the concrete periphery. In case of minor segregation a border of mortar without coarse aggregate can occur at the edge of the pool of concrete. If none of these phenomena appear it is no assurance that segregation will not occur since this is a time related aspect that can occur after a longer period.
V Funnel Test
Assessment of test
Though the test is designed to measure flowability, the result is affected by concrete properties other than flow. The inverted cone shape will cause any liability of the concrete to block to be reflected in the result if, for example there is too much coarse aggregate.
High flow time can also be associated with low deformability due to a high paste viscosity, and with high inter-particle friction. While the apparatus is simple, the effect of the angle of the funnel and the wall effect on the flow of concrete is not clear.
Equipment
o V-funnel
o Bucket (±12 liter)
o Trowel
o Scoop
o Stopwatch
Fig 10: V Funnel test Apparatus
Procedure flow time:
About 12 liter of concrete is needed to perform the test, sampled normally. Set the V-funnel on firm ground. Moisten the inside surface of the funnel. Keep the trapdoor to allow any surplus water to drain. Close the trap door and place a bucket underneath.
Fill the apparatus completely with the concrete without compacting or tamping; simply strike off the concrete level with the top with the trowel.
Open within 10 sec after filling the trap door and allow the concrete to flow out under gravity. Start the stopwatch when the trap door is opened, and record the time for the complete discharge (the flow time). This is taken to be when light is seen from above through the funnel. The whole test has to be performed within 5 minutes.
Procedure flow time at T5 minutes:
Do not clean or moisten the inside surface of the funnel gain. Close the trapdoor and refill the V-funnel immediately after measuring the flow time. Place a bucket underneath.
Fill the apparatus completely with concrete without compacting or tapping, simply strike off the concrete level with the top with the trowel.
Open the trapdoor 5 minutes after the second fill of the funnel and allow the concrete to flow out under gravity.
Simultaneously start the stopwatch when the trap door is opened and record the time discharge to complete flow (the flow time at T5 minutes). This is to be taken when light is seen from above through the funnel.
Assessment of test:
This is a widely used test, suitable for laboratory and perhaps site use. It asses filling and passing ability of SCC, and serious lack of stability (segregation) can be detected visually. Segregation may also be detected by subsequently sawing and inspecting sections of the concrete in the horizontal section.
Unfortunately there is no arrangement on materials or dimensions or reinforcing bar arrangement, so it is difficult to compare test results. There is no evidence of what effect the wall of the apparatus and the consequent ‘wall effect’ might have on the concrete flow, but this arrangement does, to some extent, replicate what happens to concrete on site when it is confined within formwork. Two operators are required if times are measured, and a degree of operator error is inevitable.
Equipment for L Box Test
o L box of a stiff non absorbing material
o Trowel
o Scoop
o Stopwatch
Procedure of L Box Test
About 14 liter of concrete needed to perform the test, sampled normally. Set the apparatus level on firm ground, ensure that the sliding gate can open freely and then close it.
Moisten the inside surface of the apparatus, remove any surplus water, fill the vertical section of the apparatus with the concrete sample.
Leave it stand for 1 minute. Lift the sliding gate and allow the concrete to flow out into the horizontal section. Simultaneously, start the stopwatch and record the time for the concrete to reach the concrete 200 and 400 marks.
When the concrete stops flowing, the distances ‘H1’ and ‘H2’ are measured. Calculate H2/H1, the blocking ratio. The whole has tom performed within 5 minutes.
Chapter 5
TESTING REPORT
Result of Compressive Strength
M-30 Normal 10% 15% 20%
7 days 28 days 7 days 28 days 7 days 28 days 7 days 28 days
1. 19.00 33.73 25.00 34.25 25.30 36.76 27.87 38.19
2. 18.4 37.84 27.27 38.96 27.50 39.40 28.23 40.92
3. 19.3 37.17 26.50 38.42 27.02 39.17 27.75 39.65
Results Of Compressive Strength Test
