CENTURION UNIVERSITY OF TECHNOLOGY AND MANAGEMENT LAB MANUAL CONCRETE STRUCTURE LAB. Department of civil engineering 1st EDITION

CENTURION UNIVERSITY OF TECHNOLOGY AND MANAGEMENT LAB MANUAL CONCRETE STRUCTURE LAB Department of civil engineering 1st EDITION JTANI,RAMACHANDRAPUR,BHUBANESWAR,752050

CONCRETE STRUCTURE LAB LAB MANUAL (FOR B.TECH PROGRAMME) Name : Branch : Roll No. : Registration No. : Group : DEPARTMENT OF CIVIL ENGINEERING CENTURION INSTITUTE OF TECHNOLOGY JATNI, BHUBANESWAR

Laboratory Manual for CONCRETE STRUCTURE LAB [PCCE-3108] First Release, July 2012. Compiled by: Dr. Ramakanta Panigrahi [Professor] & Ms. Shubhashree Behera [Asst Professor] Department of Civil Engineering Centurion Institute of Technology, Jatni, Bhubaneswar All rights reserved. No part of this manual may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise (except for the internal use of CUTM students during the laboratory work as directed by the faculty in-charge), without prior written permission of the HOD, Department of Civil Engineering, Centurion Institute of Technology, Bhubaneswar.

ABSTRACT The concrete structural laboratory is an opportunity for civil engineering students to investigate behavior of concrete in a controlled experimental setting, and to acquire hands-on knowledge of practical testing. Planning and facilitation of concrete structural laboratories is a challenging search for learning about concrete behavior, and optimizing both student and faculty time in the learning process. The balancing act also includes consideration of: Emphasis on learning by students, who will not work in the sites versus learning of concepts that will be the foundation of future construction work. Use of sophisticated modern automated equipment versus the manual devices still commonly used in many commercial laboratories, Benefits of test simulation software versus real testing, and Integrating laboratory work into the course learning versus allowing students to direct the learning independently. This invited paper for the session on concrete structural Engineering Education wrestles with these issues and others, providing suggestions for how faculty may choose to set priorities in making choices about the design and implementation of learning in the area of construction work. Dr. Ramakanta Panigrahi HOD, Department of Civil Engineering, Centurion Institute of Technology, Bhubaneswar.

TABLE OF CONTENTS Exp. No. Name of the Experiments Date of submis sion Page No. Checkend by Evaluatio n Result (10 point scale) 1 Workability test of Concrete by Slump test 2 Workability test of Concrete by compaction factor test 3 Workability test of Concrete by flow table test \ 4 Cube test of concrete (Nominal mix) 5 Cylinder test for concrete (Nominal mix).determination of axial stress, longitudinal strain, lateral strain and Poisson s ratio, plotting of stress-strain curve and determination of modulus of elasticity. 6 Split tensile strength test of concrete 7 Prism test for determining modulus of rupture of concrete 8 Design of Concrete Mix (As per Indian Standard Method) 9 Failure of RC beams in bending by two point and one point loading 10 Failure of RC beam under shear with shear reinforcement 11 Failure of RC beam under shear without shear reinforcement

COURSE OBJECTIVES: To verify geotechnical engineering theory on real specimens Student learning outcomes: The student will demonstrate the ability to: a) Identify when theory applies and when theory is limited by simplifying assumptions b) Identify reasons why actual measurements will differ from theoretical calculations To learn to run an experiment Student learning outcomes: The student will demonstrate the ability to: a) Perform pre-laboratory calculations to estimate experimental parameters, outcomes and Limits b) Develop an organized and meaningful data sheet c) Use software tools to reduce and analyze data d) Organize a team to share responsibilities for operating equipment and collecting data To learn to use testing equipment and measurement instrumentation Student learning outcomes: The student will demonstrate the ability to: a) Use the laboratory equipment correctly and safely to perform all experiments To learn to write a laboratory report Student learning outcomes: The student will demonstrate the ability to: a) Write experimental objectives and procedures b) Present results in an organized and clear manner c) Draw graphs and figures to summarize key findings d) Put together a complete report including tables of contents, references and appendices

EXPERIMENT NO.1 AIM OF THE EXPERIMENT: To determine the workability of fresh concrete by slump test. APPARATUS REQUIRED: 1- Weights and weighing device. 2- Tools and containers for mixing, or concrete mixer. 3- Tamper ( 16 mm in diameter and 600 mm length) 4- Ruler 5- Slump cone which has the shape of a frustum of a cone with the following dimensions: Base diameter 20 cm Top diameter 10 cm Height 30 cm Materials thickness at least 1.6 mm SLUMP CONE APPARATUS MATERIALS REQUIRED: i) Cement ii) Coarse aggregate iii) Fine aggregate (sand) iv) water

PROCEDURE: i) The internal surface of the mould is thoroughly cleaned and applied with a light coat of oil. ii) The mould is placed on a smooth, horizontal, rigid and non-absorbent surface. iii) The mould is then filled in four layers with freshly mixed concrete, each approximately to one-fourth of the height of the mould. iv) Each layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed evenly over the cross-section). v) After the top layer is rodded, the concrete is struck off the level with a trowel. vi)the mould is removed from the concrete immediately by raising it slowly in the vertical direction. vii) The difference in level between the height of the mould and that of the highest point of the subsided concrete is measured. viii) This difference in height in mm is the slump of the concrete. OBSERVATIONS AND CALCULATIONS: Slump= Height of the mould- highest point of the specimen being tested Sl.No. W/CRatio Slump(mm) RESULTS: The slump value of concrete is CONCLUSION: Signature

EXPERIMENT NO. 2 AIM OF THE EXPERIMENT: To determine the workability of fresh concrete by compacting factor test. APPARATUS REQUIRED: i) Compacting factor apparatus, which consists of a holder fixing two conical hoppers and a cylinder at the base. ii) Trowels, Graduated cylinder of 100ml capacity, electronic weighing balance and tamping rod. iii) Tools and containers for carrying and mixing the materials. MATERIALS REQIURED: i) Cement ii) Coarse aggregate iii) Fine aggregate (sand) iv) water COMPACTIN FACTOR APPARATUS PROCEDURE: i) The sample of concrete is placed in the upper hopper upto the brim. ii) The trap-door is opened so that the concrete falls into the lower hopper. iii) The trap-door of the lower hopper is opened and the concrete is allowed to fall into the cylinder. iv)the excess concrete remaining above the top level of the cylinder is then cut off with the help of plane blades. v) The concrete in the cylinder is weighed. This is known as weight of partially compacted concrete. vi)the cylinder is filled with a fresh sample of concrete and vibrated to obtain full compaction. The concrete in the cylinder is weighed again. This weight is known as the weight of fully compacted concret

OBSERVATIONS AND CALCULTIONS: Compacting factor =Weight of partially compacted concrete/ Weight of fully compacted concrete Weight of empty cylinder (W1) = ---------kg Sl.No. W/C Ratio Wt. Of partially compacted concrete(w2- W1)Kg Wt. Of fully compacted concrete(w3- W1)Kg C.F = W2 - W1/ W3 W1 RESULTS: The compaction factor of the given sample of concrete is CONCLUSION: Signature

EXPERIMENT NO. 3 AIM OF THE EXPERIMENT: To determine the workability of fresh concrete by flow table test. APPRATUS REQIURED: i) Mould: The mould shall made of a smooth metal casting in the form of the frustum of a cone with the following internal dimensions. A base 250mm in diameter, upper surface 170mm in diameter and height 120mm, the base and the top shall be open and at right angles to the axis of the cone. The shall be provided with handles. ii) iii) Flow table: flow table shall conform to the design as shown in fig. And shall be mounted on and bolted to a concrete base having a height of 400 to 500mm and weighing not less than 140 kg. A tamping bar, Tools and containers for mixing and weighing device FLOW TABLE APPARATUS PROCEDURE: The apparatus consists of flow table about 76cm. in diameter over which concentric circles are marked. A mould made from smooth metal casing in the form of a frustum of a cone is used with the following internal dimensions. The base is 25cm. in diameter upper surface 17cm. in diameter and height of the cone is 12cm. 1. The table top is cleaned of all gritty material and is wetted. The mould is kept on the center of the table, firmly held and is filled in two layers.

2. Each layer is rodded 25 times with a tamping rod 1.6cm in diameter and 61cm long rounded at the lower tamping end. 3. After the top layer is rodded evenly the excess of concrete which has overflowed the mould is removed. 4. The mould if lifted vertically upward and the concrete stands on its own without support. The table is then raised and dropped 12.5cm 15times in about 15 seconds. 5. The diameter of the spread concrete is measured in about 6 directions to the nearest 5mm and the average spread is noted. The flow of concrete is the percentage increase in the average diameter of the spread concrete over the base diameter of the mould. 6. The value could range anything from 0 to 150 per cent. A close look at the pattern of spread of concrete can also give a good indication of the characteristics of concrete such as tendency for segregation. OSERVATIONS AND CALCULATIONS: The flow of the concrete shall be recorded as the percentage increase in diameter of the spread concrete over the base diameter of the moulded concrete, calculated from the following formula: Flow (percent) = (spread diameter in mm - 250/250) * 100 RESULT: Flow (percent) of the concrete is = CONCLUSION: Signature

EXPERIMENT NO. 4 AIM OF THE EXPERIMENT: To determine the compressive strength of cube concrete specimens. APPARATUS REQUIRED: i) Cue moulds 150mm size, weighing machine, mixer, tamping rods ii) Compressive testing machine. PROCEDURE: 1- Prepare a concrete mix as mentioned in with the proportions suggested Such as: 1: 2: 4 with w/c = 0.6 by mechanical mixer. 2- Prepare three testing cubes; make sure that they are clean and greased or oiled thinly. 3-Metal moulds should be sealed to their base plates to prevent loss of water. 4-Fill the cubes in three layers, tamping each layer with (35) strokes using a tamper, square in cross-section with 2.54 cm side and 38.1 cm length, weighing 1.818 kg. 5- While filling the moulds, occasionally stir and scrape together the concrete remaining in the mixer to keep the materials from separating. 6- Fill the moulds completely, smooth off the tops evenly, and clean up any concrete outside the cubes. 7- Mark the specimens by a slip of paper on which is written the date and the Specimen identification. Leave the specimens in the curing room for 24 hours. 8- After that open the moulds and immerse the concrete cubes in a water basin for 7 days. 9- Before testing, ensure that all testing machine bearing surfaces are wiped clean. 10-Carefully center the cube on the lower platen and ensure that the load will be applied to two opposite cast faces of the cube. 11-Without shock, apply and increase the load continuously at a nominal rate within the range of ( 0.2 N/mm2.s to 0.4 N/mm2.s ) until no greater load can be sustained. On manually controlled machines, as failure is approached, the loading rate will decrease, at this stage operate the controls to maintain, as far as possible, the specified loading rate. Record the maximum load applied to each cube. OBSERVATIONS AND CALCULATIONS: Specimen no. 1 2 3 Average load Load in Newtons on cube Cube strength = Average load ------------------------------------------------- = -------- N/mm² Area of cross section of cube specimen RESULTS: The average compressive strength of cube = -------- N/mm² Signature

EXPERIMENT NO. 5 AIM OF THE EXPERIMENT: To determine the splitting tensile strength of cylindrical concrete specimens. APPARATUS REQUIRED: 1. Weights and weighing device. 2. Tools, containers and pans for carrying materials & mixing. 3. A circular cross-sectional rod (φl6mm & 600mm length). 4. Testing machine. 5. Three cylinders (φ150mm & 300mm in height). 6- A jig for aligning concrete cylinder and bearing strips. PROCEDURE: 1. Prepare three cylindrical concrete specimens following same steps as test No.3 2. After moulding and curing the specimens for seven days in water, they can be tested. 3. Two bearings strips of nominal (1/8 in i.e 3.175mm) thick plywood, free of imperfections, approximately (25mm) wide, and of length equal to or slightly longer than that of the specimen should be provided for each specimen. 4. The bearing strips are placed between the specimen and both upper and lower bearing blocks of the testing machine or between the specimen and the supplemental bars or plates. 5. Draw diametric lines an each end of the specimen using a suitable device that will ensure that they are in the same axial plane. Centre one of the plywood strips along the centre of the lower bearing block. 6. Place the specimen on the plywood strip and align so that the lines marked on the ends of the specimen are vertical and centered over the plywood strip. 7. Place a second plywood strip lengthwise on the cylinder, centered on the lines marked on the ends of the cylinder. 8. Apply the load continuously and without shock, at a constant rate within, the range of 689 to 1380 kpa/min splitting tensile stress until failure of the specimen. 9. Record the maximum applied load indicated by the testing machine at failure. Note the type of failure and appearance of fracture. OSERVATIONS AND CALCULATIONS: Calculate the splitting tensile strength of the specimen as follows: T = 2P/Ld Where: T: splitting tensile strength, N/mm² P: maximum applied load indicated by testing machine, N L: Length of the specimen, mm d: diameter of the specimen, mm RESULT: Split tensile strength= --------- N/mm² Signature

EXPERIMENT NO. 6 AIM OF THE EXPERIMENT: To determine the compressive strength determination of compressive strength of cylindrical concrete specimens. APPARATUS REQUIRED: 1- Weighing device. 2- Tools and containers and pans for mixing, or mixer. 3- A tamper (circular in cross-section) (16 mm in diameter and 600 mm in length). 4- Compressive testing machine. 5-Three cylinders (150mm in diameter and 300mm in height). Procedure: 1- Prepare a concrete mix as mentioned in with the proportions suggested Such as: 1: 2: 4 with w/c = 55% by mechanical mixer. 2- The cylinder also must be clean, lightly oiled, well fixed with the base. 3- Filling the specimens will be also in three layers, rodding each layer by (25) strokes using the circular section rod. 4- Trowel off surplus concrete from the top of moulds. 5- Mark the specimens by a slip of paper on which is written the date and the Specimen identification. Leave the specimens in the curing room for 24 hours. 6- After that open the moulds and immerse the concrete cubes in a water basin for 7 days. 7- Before testing, ensure that all testing machine bearing surfaces are wiped clean. 10-Carefully center the cylinder on the lower platen and ensure that the load will be applied to two opposite cast faces of the cube. 11-Then the load is applied continuously, uniformly and without shock The rate of loading should be 250KN/minute for cylinder. The load is increased till the specimen fails. Record the maximum load taken by each specimen during test. Also note the failure and appearance of cracks. OBSERVATIONS AND CALCULATIONS: Specimen no. 1 2 3 Average load Load in Newtons on cylinder Cylinder strength = Average load ------------------------------------------------- = -------- N/mm² Area of cross section of cylinder specimen RESULTS: The average compressive strength of cylinder = -------- N/mm² Signature

EXPERIMENT NO. 7 AIM OF THE EXPERIMENT: To determine the quantities of aggregate and water for a concrete mix in accordance with Indian standard recommended guide lines. THEORY: Design of concrete mixes involves determination of the proportions of the given constituents, namely, cement, fine aggregates, coarse aggregates, water and admixture, if any, which would produce concrete possessing specified proportions both in fresh and hardened states with the maximum overall economy. Workability is specified as the important property of concrete in the fresh state and for hardened state compressive strength and durability are important. The mix design are generally carried out for a particular compressive strength of concrete with adequate workability so that fresh concrete can be properly placed and compacted to achieve the required durability. The proportioning of concrete mixes is accomplished by the use of certain relationships established from experimental data which afford reasonably accurate guide to select the best combination of ingredients so as to achieve the desirable properties. APPARATUS REQUIRED: i) Weighing balance ii) Measuring cylinder iii) Trowels iv) Moulds v) Tamping rod vi) Vibration table vii) Universal testing machine PROCEDURE: (i) The 28 days target mean strength ( fck ) is first calculated from the following formula: fck = fck + 1.65 S----------------------------------- (1) The value of Standard deviation S (if not available from the construction site) can be assumed as given in Table: 1, depending on the quality control expected to be exercised as given in Table: 4. TABLE-1 Suggested Values of Standard Deviation Grade of concrete Standard deviation for different degree of control (N/mm2) Very good Good Fair M10 2.0 2.3 3.3 M15 2.5 3.5 4.5 M20 3.6 4.6 5.6 M25 4.3 5.3 6.3 M30 5.0 6.0 7.0 M35 5.3 6.3 7.3 M40 5.6 6.6 7.6

M45 6.0 7.0 8.0 M50 6.4 7.4 8.4 M55 6.7 7.7 8.8 M60 6.8 7.8 8.8 Table - 2 DEGREE OF QUALITY CONTROL EXPECTED UNDER DIFFERENT SITE CONDITIONS Degree of Conditions of Production Control Very Good Good Fair Fresh cement from single source and regular tests, weigh batching of all materials, aggregates supplied in single sizes, control of aggregate grading and moisture content, control of water added, frequent supervision, regular workability and strength tests, and field laboratory facilities. Carefully stored cement and periodic tests, weigh batching of all materials, controlled water, graded aggregate supplied, occasional grading and moisture tests, periodic check of workability and strength, intermittent supervision, and experienced workers. Proper storage of cement, volume batching of all aggregates, allowing for bulking of sand,, weighbatching of cement, water content controlled and occasional supervision and tests. For concrete containing admixtures (retarders) characteristic strength (fck) should be enhanced to take into account loss of strength due to retarder. Enhanced value of characteristic strength should be used in the above formula. (ii) The water cement ratio for the target mean strength us chosen from fig. 1 The water cement ratio so chosen is checked against the limiting water cement ratio for the requirements of durability given in table 3 and adopts the lower of the two values.

TABLE 3 MINIMUM CEMENT CONTENT & MAX. WATER CEMENT RATIO REQUIRED IN CEMENT CONCRETE TO ENSURE DURABILITY UNDER SPECIFIED CONDITIONS OF EXPOSURES Exposure Plain concrete R.C. Concrete Minimum cement content Maximum water cement Minimum cement content Maximum water cement ratio ratio Mild 220 kg/mᵌ 0.7 250 kg/mᵌ 0.65 Moderate 250 kg/mᵌ 0.6 290 kg/mᵌ 0.55 Severe 310 kg/mᵌ 0.5 310 kg/mᵌ 0.45 Note: 1. When the maximum water-cement ratio can be strictly controlled, the cement content may be reduced by 10 percent 2. The minimum cement content is based on 20mm aggregate. For 40mm aggregate, it should be reduced by about 10 percent ; for 12.5 mm aggregate, it should be increased by about 10 percent (iii) The air content ( amount of entrapped air) is estimated from table.4 for the maximum size of aggregate used. Nominal maximum Size of coarse aggregate (mm) TABLE -4 Approximate Air Content Entrapped air (% of volume of concrete) 10 3.0 20 2.0 40 1.0 (iv) For the desired workability, the quantity of mixing water per unit volume, of concrete and the ratio of fine aggregate to total aggregate by absolute volume are to be estimated from table 5 and 6. Depending upon the nominal maximum size and type of aggregate.

Table 5 Approximate Sand and Water Content per Cubic Meter of Concrete for Grading Up to M35 Nominal Maximum Size of Aggregate mm Water Content Per Cubic Meter Of Concrete kg Sand As Percentage Of Total Aggregate By Absolute Volume 10 208 40 20 186 35 40 165 30 Table 6 Approximate Sand and Water Content per Cubic Meter of Concrete for Grading above M35 Nominal Maximum Size of Aggregate mm Water Content Per Cubic Meter Of Concrete kg Sand As Percentage Of Total Aggregate By Absolute Volume 10 200 28 20 180 25 (v) For other conditions of workability, water-cement ratio, grading of fine aggregate, and for rounded aggregate, certain adjustments in the quantity of mixing water and fine to total aggregate ratio are to be made as per table 7

Table 7. Adjustment of Values in Water Content and Sand Percentage for Other Condition Change In Conditions Stipulated For Tables Adjustment Required In % Sand In Total Water Content Aggregate For sand conforming to grading Zone III or Zone IV of Table 4, IS: 383-70 0 +1.5% for Zone I -1.5% for Zone III -3% for Zone IV Increase or decrease in the value of compacting factor by 0.1 Each 0.05 increase or decrease in water-cement ratio ±3% 0 0 ±1% For rounded aggregate -15 kg -7% (vi) (vii) The cement content per unit volume of concrete may be calculated from the free water-cement ratio and the quality of water per unit volume of concrete. The cement content is also calculated shall be checked against the minimum cement content requirements of durability (Table 2) and the greater of the two values adopted. With the quantities of water and cement per unit volume of concrete and the ratio of fine to total aggregate already determined, the total aggregate content per unit volume of concrete may be calculated from the following equations: V = [W + C + 1 fa ] 1/1000. (2) Sc P Sfa

V = [W + C + 1 ca ] 1/1000.. (3) Sc 1 P Sca Where V = absolute volume of fresh concrete, which is equal to gross volume (m 3 ) minus the volume of entrapped air W = mass of water (kg) per m 3 of concrete C = mass of cement (kg) per m 3 of concrete Sc = specific gravity of cement P = ratio of fine aggregate to total aggregate by absolute volume Fa = total mass of fine aggregate and coarse aggregate (kg) per m 3 of concrete Sca = specific gravity of saturated surface dry fine aggregate and coarse aggregate respectively. (viii) Determine the concrete mix proportions for the first trial mix. (ix) Prepare the concrete using the calculated proportions and cast three cubes of 150 mm size and test them wet after 28-days moist curing and check for the strength. (x) Prepare trial mixes with suitable adjustments till the final mix proportions are arrived at. OBSERVATINS AND CALCULATIONS: Characteristic strength(fck) = Level of quality control (refer table.2) = Value of standard deviation adopted, S = Mean target value, ft (using equation 1) = Water cement ratio (i) for mean target strength = (ii) For durability requirement = Water cement ratio adopted lower value from (i) and (ii) = Type of cement = Grading of fine aggregate = Type of coarse aggregate = Nominal size of coarse aggregate, mm = Specific gravity of cement, Sc = Specific gravity of saturated surface dry fine aggregates, Sca = Specific gravity of saturated surface dry fine aggregates, Sfa =

Percentage of entrapped air = Water content per cubic metre of concrete, W (kg) = Before adjustment = After adjustment = Ratio of fine aggregate in total aggregate by absolute volume, p = Before adjustment = After adjustment = Cement content per cubic meter of concrete, c (kg) = From water cement ratio = From durability requirements = Total fine aggregate per cubic meter of concrete, fa (kg) = Total fine aggregate per cubic meter of concrete, ca( kg) = Mix proportion by weight = Desiganation of specimen Load in kg after 28 days Strength in kg/cm² Strength in N/mm² 1 2 3 Avearge Average compressive strength of concrete = --------- N/mm² RESULT: The mix proportions is Signature

EXPERIMENT NO. 8 AIM OF THE EXPERIMENT: To determine the flexural strength (modulus of rupture) of concrete of given proportions. THEORY: When concrete is subjected to bending, tensile and bending compressive stresses and in many cases, direct shear stresses are developed. The most common plain concrete structure subjected to flexure is a highway pavement and the strength of concrete for pavements is commonly evaluated by means of bending test. Flexural test intended to give the flexural strength of concrete in tension. The flexural test is also more easily carried out and may even be more convenient than the crushing test use in field, since in this test much smaller loads are required. APPARATUS REQUIRED: i) Steel prism moulds of size 100mm x 100mm x 500mm ii) Flexural strength testing machine iii) weighing machine, mixer, tamping rods PROCEDURE: i) Prepare a concrete mix as mentioned in with the proportions suggested Such as: 1: 1.5: 3 with w/c = 0.6 by mechanical mixer. ii) Prepare three testing prisms; make sure that they are clean and greased or oiled thinly. iii) Metal moulds should be sealed to their base plates to prevent loss of water. iv) Fill the prism mould in two layers, tamping each layer with 100 times using a tamper, square in cross-section with 2.5 cm side and 40 cm length, weighing 1.818 kg. v) While filling the moulds, occasionally stir and scrape together the concrete remaining in the mixer to keep the materials from separating. vi) Fill the moulds completely, smooth off the tops evenly, and clean up any concrete outside the prisms vii) Mark the specimens by a slip of paper on which is written the date and the Specimen identification. Leave the specimens in the curing room for 24 hours. viii) After that open the moulds and immerse the concrete prisms in a water basin for 28 days. Specimens shall be tested immediately on removal from water while they are in wet condition. The dimensions of each specimens shall be noted before testing. ix) The bearing surfaces of the supporting and loading rollers shall be wiped clean and any loose sand or other material removed from the surface of the specimens where they are make contact with the rollers. The specimen shall then be placed in the machine in such a manner that the load shall be applied to the upper most surface as cast in the mould, along two lines spaced 200mm 0r 133mm apart. The axis of the specimens shall be carefully aligned with the axis of the loading device. No packing shall be used between the bearing surfaces of the specimens and the rollers. The load shall be applied without shock and increasing continuously at a rate such that the extreme fibre stresses increases at 0.7 N/mm²/mint that is at a rate of loading of 4KN/mint for 150 mm specimen and at a rate of 1.8KN/ mint for the 100mm specimens. The load shall be increased until the specimen fails and maximum load applied to the specimen during the test shall be recorded. The appearance of the

fractured faces of concrete and any unique features in the type of failure shall be noted. OBSERVATIONS AND CALCULATIONS: Specimen no. 1 2 3 Average load Load in Newtons on cube The flexural strength of specimen shall be as the modulus of rupture and shall be calculated as follows: σ = ρa /bd²--------- (1) σ = 3ρa/bd²-------- (2) Where a equals the distance between the line of fracture and the nearer support, measured on the centre line of the tensile side of the specimen in mm. Equation (1) is applicable when a is greater than 133mm for 100mm specimen. Equation (2) is applicable when a is less than 133mm but greater than 110mm for 100mm specimens. b= measured width in mm of the specimen d= measured depth in mm of the specimen p= maximum load in N (kg) applied to the specimen If a is less than 110mm for a 100mm specimen, the Results of the test shall be discarded. RESULT: The average flexural strength (modulus of rupture) of prism specimen.. N/mm² Signature