IRC SP-62-2014 Guidelines for Design and Construction of Cement Concrete Pavements for Low Volume Roads PDF

 IRC:SP:62-2014 GUIDELINES FOR DESIGN AND CONSTRUCTION OF CEMENT CONCRETE PAVEMENTS FOR LOW VOLUME ROADS ( First Revision Published by: INDIAN ROADS CONGRESS Ka...

 IRC:SP:62-2014 GUIDELINES FOR DESIGN AND CONSTRUCTION OF CEMENT CONCRETE PAVEMENTS FOR LOW VOLUME ROADS ( First Revision Published by: INDIAN ROADS CONGRESS Kama Koti Marg, Sector-6, R.K. Puram, New Delhi-110 022 January, 2014 Price : ^ 600/- (Pius Pacl 150 CVPD, a default value of ten percent of the values obtained from Equation 3.1 may be considered for cumulative fatigue analysis as illustrated later. In case the road is expected to carry a large volume of very heavy trucks on a regular basis, spectrum of axle loads may have to be considered to avoid damage to pavements and design concept of IRC:58 may be used. 3.5 Characteristics of the Subgrade The strength of subgrade is terms of modulus of subgrade reaction, k, which expressed in is determined by carrying out a plate bearing test, using 750 mm diameter plate according to 18:9214-1974. In case of homogeneous foundation, test values obtained with a plate of 300 mm diameter, k may be converted to give k determined using the standard 750 mm dia. plate by the following correlation: 3.2 Since, the subgrade strength is affected by the moisture content, it is desirable to determine it soon monsoon. Stresses in a concrete pavement are not very sensitive to minor after the variation in k values and hence its value for a homogeneous soil subgrade may be obtained from its soaked CBR value using Table 3.1. It can also be estimated from Dynamic Cone Penetrometer also as described in IRC:58. Table 3.1 Approximate k Value Corresponding to CBR Values Soaked subgrade CBR 2 3 4 5 7 10 15 20 50 k Value (MPa/m) 21 28 35 42 48 50 62 69 140 The minimum CBR of the subgrade shall be 4. 4  !RC:SP:62-2014 3.6 Sub-Base 3.6.1 A good compacted foundation layer provided below a concrete pavement quality is commonly termed as subbase. It must be of good quality so as not to undergo large settlement under repeated wheel load to prevent cracking of slabs. The provision of a sub-base below the concrete pavement has many advantages such as: i) It provides a uniform and reasonably firm support ii) It supports the construction traffic even if the subgrade is wet iii) It prevents mud-pumping of subgrade of clays and silts iv) It acts as a leveling course on distorted, non-uniform and undulating sub- grade v) It acts as a capillary cut-off 3.6.2 Sub-base types 3.6.2.1 Traffic up to 50 CVPD 75 mm compacted Water Bound Macadam Grade thick (WBM lll)/Wet Mix Macadam III (WMM) may be provided over 1 00 mm granular subbase made up of gravel, murrum or river bed material with CBR not less than 30 percent, liquid limit less than 25 percent and Plasticity Index less (PI) less than aggregates are not available within a reasonable cost, 150 mm 6. If of cement/lime/lime-flyash treated marginal aggregate/soil layer with minimum Unconfined Strength (UCS) of 3 MPa at 7 days with cement or at 28 days with lime/lime-flyash may be used. The stabilized soil should not erode as determined from wetting and drying test (IRC:SP:89). 3.6.2.2 Traffic from 50 to 150 CVPD 75 mm thick WBM lll/WMM layer over 00 mm of granular material may be used as a subbase. 1 Alternatively, 100 mm thick cementitious granular layer with a minimum unconfined strength (UCS) of 3 MPa at 7days with cement or 28 days with lime/lime-flyash over 100 mm thick cementitious naturally available materials with a minimum UCS of 1.5 MPa with cement at 7 days or with lime or lime-flyash at 28 days may be provided. 3.6.2.3 Traffic from 150 to 450 CVPD 150 mm thick WBM lll/WMM over 100 mm of granular subbase may also be used. Alternately, 100 mm of cementitious granular layer with a minimum UCS of 3.0 MPa at 7 days with cement or at 28 days with lime or lime-flyash over 00 mm of cementious layer with naturally 1 occurring material with a minimum UCS of 1.5 MPa days with cement or at 28 days at 7 with lime or lime-flyash. Cementitious marginal aggregates may be much cheaper than WBM/WMM in many regions having acute scarcity of aggregates. The granular subbase and WBM layers should meet the requirement of MORD Specifications, Section 400(34). Quality of subbases varies from region to region and past 5 IRC:SP:62-2014 experience on performance of concrete pavements in different regions is tlie best guide for the selection of the most appropriate subbases. 3.6.2.4 Commercially available IRC accredited stabilizers with no harmful leachate also may be used if found successful on trials. 3.6.3 Effective modulus of subgrade reaction over granular and cement treated subbases For the granular subbases, the effective k value may be taken as 20 percent more than the k value of the sub-grade shown in Table 3.1. For the cementitious subbases, the effective k value may be taken as twice that of the subgrade. Recommendations for estimated of effective modulussubgrade reaction over granular or cemented subbase are given in of Table 3.2. Reduction in stresses in the pavement slab due to higher subgrade CBR is marginal since only fourth root of k matters in stress computation but the loss of support due to erosion of the poor quality foundation below the pavement slab under wet condition may damage the it seriously. The GSB layer with fines passing 75 micron sieve less than 2 percent can act as a good drainage layer and addition of 2 percent cement by weight of total aggregate will make non-erodible. Most low volume roads with concrete pavements in built up area having it WBM over GSB have performed well even under adverse drainage conditions. Table 3.2 Effective k Values Over Granular and Cementitious Subbases Soaked CBR 2 3 4 5 7 10 15 20 50 k Value over granular subbase 25 34 42 50 58 60 74 83 170 (thickness 150 to 250 mm), MPa/m k Value over 150200 mmto 42 56 70 84 96 100 124 138 280 cementations sub base MPa/m It should be ensured that embankment, the subgrade and the subbase shall be well compacted as per MORD specifications (34) otherwise heavy wheel loads may displace the subbase under adverse moisture condion leading to cracking of the unsupported concrete slab. 3.7 Concrete Strength Since concrete pavements fail due to bending stresses, it is necessary that their design is based on the flexural strength of concrete. Where there are no facilities for determining the flexural strength, the mix design may be carried out using the compressive strength values and the following relationship: =...3.3 f, 0.7t, where, ff = flexural strength, MPa f = characteristic compressive cube strength, MPa 6  IRC:SP:62-2014 For Low volume suggested that the 90 day strength may be used for design roads, it is since concrete keeps on gaining strength with time. The 90 day flexural strength may be taken as 1.10 times the 28 day flexural strength or as determined from laboratory tests. 90 day compressive strength is 20 percent higher than the 28 day compressive strength. Heavy traffic may be allowed after 28 days. The concrete mix should be so designed that the minimum flexural strength requirement in the field is met at the desired confidence level. For rural roads, the tolerance level (accepted proportion of low results), can be taken as 1 in 20. The normal variate, Z^, for this tolerance level being 1.65, the target average flexural strength is obtained from the following relationship: S = S^+Za a...3.4 where, S = target average flexural strength, at 28 days, MPa = characteristic flexural strength, at 28 days, MPa Zg = normal variate, having a value of 1.65, for a tolerance factor of 1 in 20 a = expected standard deviation of field test samples, MPa; Table 3.3 gives the values of expected standard deviation of compressive strength. Table 3.3 Expected Values of Standard Deviation of Compressive Strength Grade of Concrete Standard Deviation for Different Degrees of Control, MPa Very Good Good Fair M 30 5.0 6.0 7.0 M 35 5.3 6.3 7.3 M 40 5.6 6.6 7.6 Flexural strength can be derived from the Equation 3.3. For pavement construction for rural roads, it is recommended that the characteristic 28 day compressive strength should be at least 30 MPa and corresponding flexural strength (third point loading) shall not be less than 3.8 MPa. 3.8 Modulus of Elasticity and Poisson's Ratio The Modulus of Elasticity, E, of concrete and the Poisson's ratio may be taken as 30,000 MPa and 0.15 respectively. 3.9 Coefficient of Thermal Expansion The coefficient of thermal expansion of concrete, a, may be taken as: a = 10 X 10-^ per °C. 7 IRC:SP:62-2014 3.10 Fatigue Behaviour of Concrete Pavement For most rural roads, fatigue behaviorbecause of low volume of commercial is not important vehicles. In case a rural road forms a connecting link between two important roads or if the road connects several villages, there can be significant amount of traffic consisting of buses and trucks due to agriculture, construction and social activities, and fatigue behavior of pavement slab may be considered in such cases. Fatigue equations of IRC:58 cannot be used because they are valid for 90 percent reliability. Following fatigue equation (MEPDG, Appendix III, IRC:58) for 60 percent reliability is recommended rural village roads. ^^-2.222 log., N =... 3.5 ^ 0.523 Where is fatigue pavement subjected to stresses caused by the combined effect life of a of wheel load of 50 kN and temperature gradient. If the number of heavy vehicles are large, fatigue analysis should be done for the spectrum axle load recommended in IRC:58. Influence of light commercial vehicles is negligible. Occasional heavy loads may not affect the pavements since the subgrade is weak only during certain period in the monsoons/post monsoon periods and only worst value of subgrade strength is considered in design. Concrete also keeps on gaining strength with time. SR = stress ratio defined as: - flexural stress due to wheel load and temperature SR — flexural strength 4 DESIGN OF SLAB THICKNESS 4.1 Critical Stress Condition Concrete pavements are subjected due to a variety of factors and the conditions to stresses which induce the highest stress in the pavement should be considered for analysis. The factors commonly considered for design of pavement thickness are traffic loads and temperature gradients. The effects of moisture changes and shrinkage, being generally opposed to those of temperature and are of smaller magnitude, would ordinarily relieve the temperature effects to some extent and are not normally considered critical to thickness design. For the purpose of analysis, two different regions in a pavement slab edge and corner are considered critical for pavement design. Effect of temperature gradient is very less at the corner, while it is much higher at the edge. Concrete pavements undergo a daily cyclic change day and opposite of temperature differentials, the top being hotter than the bottom during the is the case during the night. The consequent tendency of the pavement slabs to curl upwards (top convex) during the day and downwards (top concave) during the night, and restraint offered to the curling by self-weight of the pavement induces stresses in the pavement, referred to commonly as curling stresses. These stresses are flexural in nature, being tensile, at bottom during the day, (Fig. 4.1) and at top during night (Fig. 4.2). As the restraint offered 8  V IRC:SP:62-2014 any section of the slab would be a function of weight of the slab, is obvious that to curling at it corners have very little of such restraint. Consequently the temperature stresses induced in the pavement are negligible in the corner region. Tension at bottom Stresses at the Fig. 4.1 Tensile Fig. 4.2 Tensile Stresses at Bottom Due to Curling During Day the Top Due to Curling During Night The corner tends bend like a cantilever; giving rise to tension at the top while the tension to is at bottom in case for edge loading. Deflections due to wheel loads are larger at the corner causing displacement of weaker subgrade resulting in loss of support under repeated loading and consequent corner breaking. A shorter transverse joint spacing imparts safety to a panel due to load sharing by the adjacent slabs because of better load transfer across the transverse joints since dowel bars are not recommended in low volume roads except near a permanent structure. Wheel load stresses for interior loading are lower than those due the edge and corner loading. For low volume roads carrying a low volume of traffic, heavy vehicles are not frequent and the chance that highest axle load when the temperature gradient also is highest is will act likely to be of rare occurrence. The maximum tensile stresses in the edge region of the slab will be caused by simultaneous occurrence of wheel loads and temperature differentials. This would occur during the day at the bottom in case of interior and edge regions. 4.2 Calculation of Stresses 4.2.1 Edge stresses 4.2.2.1 Load stresses at edge Fig. 4.3 shows a slab subjected to a load through a dual wheel set of a commercial vehicle applied at the edge region. Fig. 4.3 Wheel Load at Pavement 9 IRC:SP:62-2014 Widely validated and accepted Westergaard's equation (15) for edge loading is recommended for the computation of edge stresses caused by single or dual wheel at the edge 4.22 MPa and hence the design is unsafe. If the joint spacing is 2.5 m, the stress = 3.64 MPa and hence the design is safe for 170 mm slab For the joint spacing of 3.75 m, increase the thickness to 180 mm the computed stress = 3.89 MPa, and hence the design is safe. 36  IRC:SP:62-2014 Adopt 180 mm with 3.75 m joint spacing for granular subbase It can thus be seen that 1 70 mm slab is safe for 2.50 m joint spacing while 1 80 mm is needed for 3.75 m spacing Cemented subbase Temperature curling stresses can be reduced by adopting a lower joint spacing while wheel load also reduces marginally by decreasing the spacing K = 70 MPa/m for 150/200 mm cementitious subbase Trial thickness = 170 mm for 3.75 m joint spacing Stress = 4.15 MPa < 4.22 MPa, hence safe Designers have to consider all the factors in selecting the joint spacing. Saw cutting or plastic strips can be used to create shorter joint spacings. Cost and convenience will determine the adoption of the types of joints. It is necessary to provide a non-erodible subbase to avoid lack of subgrade support Pavement design for traffic = 200 CVPD Fatigue fracture of concrete should be considered for design. Total of wheel load and temperature stresses are considered in fatigue analysis. Since concrete keeps on gaining strength even after 90 days, there is residual strength even though fatigue analysis indicates end of pavement life Design life = 20 years The entire computation is shown in the excel sheet. Every designer can develop his/own spread sheet for the computation since the approach is simple. Assume a thickness of 200 mm and a joint spacing of 4 m over 250 mm GSB The cumulative fatigue damage is 193.31. Hence it is unsafe. It should be less than 1 Assume a joint spacing of 2.5 m. The pavement is still unsafe safe since the cumulative fatigue damage is 2.49. Take thickness = 220 mm for 4.00 joint spacing. Pavement is still unsafe since the cumulative fatigue damage = 9.62 Consider a joint spacing of 2.50 m The pavement is safe since cumulative fatigue damage is 0.01 A designer can exercise various options of joint spacing using the spread sheet and adopt the thickness and transverse joint spacing according his/her resources. 37 IRC:SP:62-2014 Appendix II (Refer Clause 4.2.1.2) 2.1 Analysis of Stresses Caused by Non-Linear Temperature Distribution The temperature distribution across the slab thickness is usually non-linear though linearity has been assumed in thickness design in earlier versions of IRC:SP:62 and IRC:58. The actual temperature variation across the depth of a pavement (Fig. 11-1 a) can be taken as the sum of a uniform and a nonlinear temperature variation. The nonlinear variation can be further approximated by bilinear variation and the temperature variation can be split as shown in Figs. 11-1 (b), (c) and (d). The total stress due to thermal-loading condition is obtained by adding algebraically the bending stresses due to the linear temperature and the nonlinear temperature part. Fig. 11-2 (Venkatasubramanian 1964) shows temperature measurements made at the surface, 1/4^^ depth, the mid depth, the 3/4^^ depth and at the bottom for a 203.2 mm thick slab. The measurements were made at Kharagpur in Eastern India. When the surface of the concrete has its maximum or minimum daily temperatures, the temperature difference between the surface and the mid depth can be more than double the difference between the mid depth and the bottom. Similar observations were reported by Croney and Croney (1991). In the present analysis it is considered that the temperature difference between the top surface and the mid depth is double that between mid depth and the bottom during the day hours when the traffic is higher on low volume roads. (a) (b) (c) (d) Fig. 11-1 Components of Nonlinear Temperature Distribution during Day Time The due total stress to thermal-loading condition is obtained by adding algebraically the bending stresses due to linear temperature part which extends through full depth of slab and linear temperature part which extends only to top half of the slab. Temperature fC) Fig. 11-2 Temperature Variation (°C) in a 203.2 mm Concrete Slab March 30-31, 1963 38  IRC:SP:62-2014 From the and others (Venkatasubramanian 1964, Choubane et.al 1993) can be Fig. 11-2 it observed that the difference in temperature between surface and underface of the slab is higher during day time as compared to the difference at night. During night time this difference is approximately half of that during day time. It can also be observed that during day time the temperature variation is highly nonlinear as compared to night time variation. The slab with the linear temperature variation extending to the full depth of the slab is analyzed by Bradbury's theory. The linear temperature variation over half the depth of the slab causes internal bending stresses in the pavement and was analyzed by using classical plate bending theory. 2.2 General Plate Bending Theory Formulation If the plate is subjected to the action of tensile or compressive forces acting in the x and y direction and uniformly distributed along the sides of the plate, the corresponding bending moment is equal to M = D — o w T^\^ —wV o 11=1 where, Eh' D = 11-2 12(1-^1^) 6M Bending Stress, c = 11-3 IF 2.3 Day and Night Time Curling During the day time, the upper half of the slab will tend to bend due to linear temperature distributionbetween the top and the middle surface but lower half will have no effect and it remains in its original position (horizontal) if free to do so and consequently the upper and the lower halves will tend to have different radii of curvature as shown in Fig. 11-3. The reverse is the trend during the night hours as shown in Fig. 11-4. Fig. 11-3 Bending of Upper and Lower Halves of Slab When Free to Bend 39 IRC:SP:62-2014 M Fig. 11-4 Bending of Upper and Lower Halves of Slab When Free to Bend The real slab is a monolithic mass and will curl up or warp down as one unit with a common radius of curvature of — (Figs. 11-5 and 11-6) and internal stresses will be set up due to internalbending moments M as shown in Figs. 11-3 & 2-4 to annul the different curvatures of the upper and the lower parts. This causes compressive stresses at the top and the bottom and tensile stresses at mid depth during day time and tensile stresses at top and bottom and compressive stresses at mid depth during night time. The values of stresses can be approximately estimated from geometrical compatibility as shown below. C Fig. 11-5 Tensile and Compressive Stresses due to Internal Bending Moments During Day Time Fig. 11-6 Tensile and Compressive Stresses due to Internal Bending Moments During Night time a) In the interior close to the center, the bending moment is given as... 18 Since curvatures in the two directions are equal, M = 0—^(1+^1)... 19... 20 40  IRC:SP:62-2014 b) Along the edge, the bending moment is given as d''w M = D... 21 6M EaA, Edge Stress, a =... 22 For a = 10 -^ E = 30,000 MPa, |j = 0.15, = 0.0767 (Compressive at the bottom) If the temperature differential is 3A^, Bradbury's equation is used for the computation of curling stresses for 2 and the compressive curling stress is subtracted to obtain the net curling stresses. The compressive curling stresses for various temperature differentials are shown in Table 1-1. Table 1-1 Nonlinear Part Temperature Stresses, Daytime Temperature Difference °C Edge Curling Stresses, Interior Curling Stresses, MPa (Compressive) MPa (Compressive) 8 -0.20 -0.23 13 -0.33 -0.38 17 -0.43 -0.44 21 -0.53 -0.61 41 IRC:SP:62-2014 Appendix III (Refer Clause 1.2) SELF-COMPACTING CONCRETE 1 INTRODUCTION A constant strive to improve performance and productivity led to the development of Self- Compacting Concrete (SCO). Traditionally Placed Concrete (TPC) mix is compacted with the help of external energy inputs from vibrators, tamping or similar actions. On the other hand, SCC mix has special performance attributes of self-compaction/consolidation under the action of gravity. For mould ability, a concrete mix irrespective of being TPC or SCC should have the ability to fill the formwork as well as encapsulate reinforcing bars and other embedment in fresh state maintaining homogeneity. case of TPC, In is it achieved by means of ensuring a minimum level of slump at fresh state and placing it with the help of external energy. However, a fresh SCC mix shall have appropriate workability under the action of its self-weight for filling all the space within form work (filling ability), passing through the obstructions of reinforcement and embedment (passing ability) and maintaining its homogeneity (resistance to segregation). High deformability can be achieved by appropriate employment of super plasticizer, maintaining low water powder and Viscosity Modifying Agent (VMA), if needed. These are the basics ratio to achieve the flowability and viscosity of a suspension to achieve self-compacting properties. The rheological characteristics of fresh concrete mix is not only necessary for workability to achieve desired mould ability but they also help in achieving desired in-situ strength and durability attributes at the hardened state. The difference between the SCC and TPC exists in the performance requirements during fresh state; not much in terms of performance requirements in hardened state such as strength and durability. The advantages of SCC are enhanced productivity, and reduction of costly labour and noise discomfort at construction Improved surface finish and quality of hardened concrete as site. well as improvement of working condition are few of the great potentials of SCC. Usage of higher dosages of fly ash in SCC enhances its flow ability which in turn reduces the usage of costly chemical admixtures. The SCC is, therefore, another option considering these properties for rigid pavement dense compacted concrete of village road noting the fact that a in line and level is a prime requirement for village road. Minimum efforts in vibration mean an ordinary screed is enough to get surface in line and level to obtain a dense concrete. SCC can thus be a solution for rigid pavement of village roads. While the material cost of SCC has generally been higher than conventional concrete, but due to development of new admixtures, the differential cost is much reduced. Marginal increased initial cost compensated to a great extent considering such advantages as reduction in is construction time and a higher ultimate durability of the structure and may finally become it cost effective. Standard manual/guidelines for usage of SCC in India are not available, but 42  IRC:SP:62-2014 they are available in developed countries as cited in references and a working detail is given in the following. 2 TERMS AND DEFINITIONS For the purposes of this publication, the following definitions apply: Mineral Admixtures Pozzolanic materials conforming to relevant Indian Standards may be used, provided uniform blending with cement is ensured. Finely-divided inorganic material used in concrete in order to improve certain properties or to achieve special properties. This publication refers to pozzolanic materials defined in IS 456-2000 as: Mineral Admixtures. Chemical Admixture Material added during the mixing process of concrete in small quantities related to the mass of cementitious binder to modify the properties of fresh or hardened concrete. Binder The combined cement and mineral admixture. Filling Ability The ability of fresh concrete to flow into and fill all spaces within the formwork, under its own weight. Flow Ability The ease of flow of fresh concrete when unconfined by formwork and/or reinforcement. Fluidity The ease of flow of fresh concrete. Mortar The fraction of the concrete comprising paste plus those aggregates less than 4.75 mm. Paste The fraction of the concrete comprising powder, water and air, plus admixture, if applicable. Passing Ability The ability of fresh concrete to flow through tight openings such as spaces between steel reinforcing bars without segregation or blocking 43 IRC:SP:62-2014 Powder (Fines) Material of particle size smaller than 0.125 mm (125 |j) Note : It includes fractions in the cement, cement additives as flyash, silica fumes and aggregate specially crushed sand Robustness The capacity of concrete to retain its fresh properties when small variations in the properties or quantities of the constituent materials occur Self-Compacting Concrete (SCC) Concrete that is able to flow and consolidate under its own weight, completely fill the formwork even in the presence of dense reinforcement, whilst maintaining homogeneity and without the need for any additional compaction. Segregation Resistance The ability of concrete to remain homogeneous in composition while in its fresh state Slump-Flow The mean diameter of the spread of fresh concrete using a conventional slump cone Thixotropy The tendency of a material (e.g. SCC) to progressive loss of fluidity when allowed to rest undisturbed but to regain its fluidity when energy is applied Viscosity The resistance to flow of a material (e.g. SCC) once flow has started. Note : In SCC it can be related speed of flow T^^^ in the Slump-flow to the test or the efflux time in the V-funnel test described in the Annexures III-1 and III-2 Viscosity Modifying Admixture (VMA) Admixture added to fresh concrete to increase cohesion and segregation resistance. 3 RHELOGY PROPERTIES 3.1 Rheology Self-compaction of fresh concrete is described as its ability to fill the formwork and encapsulate reinforcing bar/available space only through the action of gravity while maintaining homogeneity. The achieved by designing the concrete to have suitable inherent ability is rheological properties. SCC can be used in most applications where traditionally vibrated concrete is used. 44  IRC:SP:62-2014 Rheology is the study of flow and deformations of all forms of matter. The basic property influencing the performance of the fresh concrete in casting and compaction is its rheological behavior. Rheology has thus been central in the development of SCC. Rheology of concrete, mortar as well as paste is important for understanding the behavior and optimisation processes. 3.2 Workability In workability terms, self-compactability signifies the ability of the concrete to flow after being discharged from the pump hose, a skip or a similar device only through gravity to fill intended spaces in formwork to achieve a zero-defect and uniform-quality concrete. Self-compactability in a fresh state property can be characterized by three functional requirements: Filling Ability Resistance to Segregation Passing Ability 3.2.1 Filling ability SCC must be able to deform or change its under its self-weight. The meaning shape very well of the filling ability includes both the flow, in terms of how far from the discharge the concrete can flow (deformation capacity), and the speed with which it flows (velocity of deformation). Using the slump flow measurement, the deformation capacity can be evaluated as the final flow diameter of the concrete measured after the concrete has completely stopped deforming. The velocity of deformation can in the same method be evaluated as the time it takes the concrete to reach a certain deformation. To achieve a good filling ability, there should be a good balance between the deformation capacity and velocity of deformation. 3.2.2 Resistance to segregation Concrete should not show tendency to segregate during movement. SCC should not have any of the following segregation parameters in either flowing or stationary state; > Bleeding of water > Paste and aggregate segregation > Coarse aggregate segregation leading to blocking > Non-uniformity in air-pore distribution To avoid the segregation of water from the solids, it is essential to reduce the amount of movable water in the mixture. Movable water can be reduced by using low water content and low W/P. (Water/Powder) It is also possible to use powder material (Materials having size less than 0.125 mm (125 micron) with high surface area since more water can be retained on the surface of the powder material. Segregation resistance between water and solids can also be improved by increasing the viscosity of water through the use of VMA. 45 IRC:SP:62-2014 The other categories can be solved by having a paste phase which is capable of segregation of carrying the aggregate particles. This can be done by increasing the cohesion between the paste phase and aggregate phase through the use of low w/p or by using VMA. 3.2.3 Passing ability For sec with excellent filling ability & segregation resistance, blocking will occur in the following conditions: > The maximum size of the aggregate is too large > The content of large-sized aggregates is too high The blocking tendency is increased if the concrete has a tendency for segregation of coarser aggregate particles. Thus blocking can occur even if the maximum aggregate size is not excessively large. 4 SPECIFICATION 4.1 General The filling ability and stability of self-compacting concrete in the fresh state can be defined by four key characteristics. Each characteristic can be addressed by one or more test methods: Characteristic Preferred test method(s) Flowability Slump-flow test Viscosity (assessed by rate of flow) T^^^ Slump-flow test or V-funnel test Passing ability L-box test Segregation Segregation resistance (sieve) test The above tests are fully described in EN 12350-2. Since the SCC is intended to be used for rigid pavement for roads and the roads are in grades and camber, the acceptable values of parameters will have to be fixed by trials and carrying out field observations. Slump flow of 400 mm and V cone of 8 seconds if observed would meet the requirement for village roads as seen by several experiments. Slump Flow & V-funnel test methods for SCC are described in Annexures III-1 and III-2 4.2 Segregation Resistance Visual observations during the Slump flow test and/or measurement of the T^^^ time can give additional information on the segregation resistance. There should not be any visible signs of segregation. 5 CONSTITUENT MATERIALS 5.1 General The constituent materials for SCC are the same as those used in traditional vibrated concrete conforming to IS:456. 46  IRC:SP:62-2014 5.1.1 Minimum Cement The requirements conforming to IS:456 of the minimum cement content durability for the given exposure conditions should be adhered to. 5.2 Mineral Admixtures 5.2.1 General Due to the fresh property requirements of SCC, inert and pozzolanic/hydraulic additions are commonly used to improve and maintain the cohesion and segregation resistance. The addition will also regulate the cement content in order to reduce the heat of hydration and thermal shrinkage. The additions are classified according to their reactive capacity with water: Pozzolanic Fly Ash conforming to Grade 1 of IS:3812(Part-1) Silica fumes Rice husk ash Metakaoline having fineness between 700 - 900 m^/kg Hydraulic GGBS conforming to IS: 12089 5.2.2 Fly ash Flyash has been shown to be an effective addition for SCC providing increased cohesion and reduced sensitivity to changes in water content. However, high levels of fly ash may produce a paste fraction which is so cohesive that it can be resistant to flow. Fly ash conforming to IS:381 2 (Part-1 ) 2003 shall be used. Some of the important requirements of fly ash are listed below: Sr. No. Requirement Limit 1 Total Sulpher as SO, (%) Max 5.0 2 Total Chloride (%) Max 0.05 3 LOI (%) Max 5.0 4 Fineness (m^/kg) Min 320 5 Particles retained on 45 m IS sieve Max 34 5.3 Aggregates Normal-weight aggregates should conform to IS:383 and meet the durability requirements of IS:456. All normal concreting sands are suitable for SCC. Both crushed or rounded sands can be used. The amount of fines less than 0. 1 25 mm is to be considered as powder and is very important for the rheology of the SCC. A minimum amount of fines (arising from the binders and the sand) must be achieved to avoid segregation. 47 IRC:SP:62-2014 5.3.1 Coarse aggregate Coarse aggregates conforming to IS:383 are appropriate for the production of SCC. 5.3.2 Fine aggregate/sands The influence of fine aggregates on the fresh properties of the SCC is significantly greater than that of coarse aggregate. Particles size fractions of less than 0.125 mm should be include the fines content of the paste and should also be taken into account in calculating the water powder ratio. The high volume of paste in SCC mixes helps to reduce the internal friction between the sand particles but a good grain size distribution is still very important. Many SCC mix design methods use blended sands to match an optimized aggregate grading curve and this can also help to reduce the paste content. Some producers prefer gap-graded sand. 5.4 Admixtures High range water reducing admixtures conforming to IS:9103 are an essential component of SCC. Viscosity Modifying Admixtures (VMA) may also be used to help reduce segregation and the sensitivity of the mix due to variations in other constituents, especially to moisture content. 5.4.1 Superplasticiser/high range water reducing admixtures The admixture should bring about the required water reduction and fluidity but should also maintain its dispersing effect during the time required for transport and application. The required consistence retention will depend on the application. High efficiency Poly carboxylate based high range water reducer having a consistent performance should be used. 5.4.2 Viscosity modifying admixtures Admixtures that modify the cohesion of the SCC without significantly altering its fluidity are called Viscosity Modifying Admixtures (VMA). These admixtures are used in SCC to minimize the effect of variations in moisture content, fines in the sands or its grain size distribution, making the SCC more robust and less sensitive to small variations in the proportions and condition of other constituents. 5.5 Mixing Water Water conforming to IS:456 should be used in SCC mixes. 6 BASIC MIX DESIGN There no standard method for SCC mix design and many academic institution and company is dealing with admixtures, ready-mixed concrete, precast concrete etc. have developed their own mix proportioning methods. 48  IRC:SP:62=2014 Mix designs often use volume as a key parameter because of the importance of the need to fill the voids between the aggregate particles. Some methods try to fit available constituents to an optimized grading envelope. Another method is to evaluate and optimize the flow and stability of first the paste and then the mortar fractions before the coarse aggregate is added and the whole SCC mix tested. Table III-1 Typical Range of SCC Mix Composition for M30 to M40 Grade of Concrete Constituent Quantity (kg/m^) Quantity (Ltrs/m^) Water 155-175 155-175 Powder 375 - 600 Fine Aggregates 40 - 60% of the total Aggregate weight Coarse Aggregates 750- 1000 270 - 360 w/p (water/paste volume) 0.76 to 1.0 Cement 240 to 290 kg Fly ash 160 to 210 Kg Paste Volume 34 to 38% Water/Binder (cement + flyash) Max 0.4 Mix proportion for aggregate as per 18:10262 gives good guidelines for the quantity of aggregate which can be followed. Several experiment of mix design can be done and upper and lower bound of aggregate size curves established by series of trial mixes for M30 to M40 grade of concrete. A range of mix composition is given in Table III-1. The upper and lower limits and the typical combined grading in a trial are shown in Table III-2 and Fig. III-1. Table III-2 Combined Gradation of Aggregate for Mix Design of M30 to M40 Grade of Concrete IS Sieve 20 mm 10 mm Crushed Natural Combined Recommended Recommended sand sand (as adopted upper limit lower limit in lab trial) % age 20 mm 97.25 100 100 100 99.03 95 100 10 mm 1.13 95.75 100 100 64.65 50 70 4.75 mm 0.02 0.40 91.65 100 48.63 35 55 2.36 mm 0.00 0.28 62.35 100.00 33.06 25 45 1.18 mm 0.00 0.00 39.90 100.00 21.15 15 35 0.600 mm 0.0 0.0 27.40 100.00 14.52 10 30 0.300 m 0.00 0.00 19.95 100.00 10.57 3 15 0.150 m 0.00 0.00 13.50 100.00 7.16 6.00 0 0.075 0.00 0.00 8.30 0.00 4.4 4.5 0 49 IRC:SP:62-2014 Gradation curve 0.1 1 10 100 IS Sieves Fig. III-1 Upper and Lower Limits of aggregate gradations and Combined gradation for SCC Trial mixes-Several mixes can be evolved for M 30 grade of concrete and typical proportion trial of various ingredients are given in Table III-3 can form the basis for different trials Table III-3 Quantities of Materials for Trial Mixes Ingredient Trial 1 kg/Cubic Meter Trial 2 kg/Cubic Meter Cement 260 270 Fly ash 200 180 Crushed sand (0 to 4.75 mm) 988 893 5 to 10mm Coarse aggregate 221 384 10 to 20 mm coarse aggregate 664 473 Water 165.6 171 w/c 0.36 0.38 Special admixture 0.8% 0.9% 8 CURING Curing is important for all concrete but especially so for the top-surface of elements made with SCC. These can dry quickly because of the increased quantity of paste, the low water/fines ratio and the lack of bleed water at the surface. Initial curing should therefore commence as soon as practicable after placing and finishing in order to minimise the risk of surface crusting and shrinkage cracks caused by early age moisture evaporation. 50  IRC:SP:62-2014 Test Methods TESTING FRESH CONCRETE SLUMP-FLOW TEST : - Introduction The slump-flow diameter is a test to assess the flowability and the flow rate of self-compacting concrete in the absence of obstructions. It is based on the slump test described in EN 1 2350-2. The result is an indication of the filling ability of self-compacting concrete. 1 Scope This document specifies the procedure for determining the slump-flow diameter for self- compacting concrete. The test is not suitable when the maximum size of the aggregate exceeds 40 mm. 2 Principle The fresh concrete is poured into a cone as used for the IS:9103 slump test. The largest diameter of the flow spread of the concrete and the diameter of the spread at right angles to it are then measured and the mean is the slump-flow. 3 Apparatus The apparatus shall be in accordance with EN 12350-2 except as detailed below: 3.1 Baseplate, made from a flat plate with a plane area of at least 900 mm x 900 mm on which concrete can be placed. The plate shall have a flat, smooth and non-absorbent surface with a minimum thickness of 2 mm. The surface shall not be readily attacked by cement paste or be liable to rusting. The construction of the plate shall be such as to prevent distortion. The deviation from flatness shall not exceed 3 mm at any point when a straight edge is placed between the centres of opposing sides. The centre of the plate shall be scribed with a cross, the lines of which run parallel to the edges of the plate and with circles of 200 mm diameter and 500 mm diameter having their centres coincident with the centre point of the plate. See Fig. 1. 3.2 Rule, Graduated from 0 mm to 1000 mm at Intervals of 1 mm. 3.3 Stop Watch, Measuring to 0.1 s. 3.4 Weighted Collar (Optional), Having a Mass of at Least 9 kg. Note : the weighted collar allows the test to be carried out by one person. 51 IRC:SP:62-2014 Fig. 1 Base Plate Reference Clause 4.1 4 TEST SAMPLE The sample shall be obtained in accordance with IS: 11 99. 5 PROCEDURE Prepare the cone and base plate as described in EN 12350-2. Fit the collar to the cone if being used. Place the cone coincident with the 200 mm circle on the base plate and hold in position by standing on the foot pieces (or use the weighted collar), ensuring that no concrete can leak from under the cone. Fill the cone without any agitation or rodding, and strike off surplus from the top of the cone. Allow the cone to stand for not more than 30 filled s; during this time remove any spilled concrete from the base plate and ensure the base plate is damp all over but without any surplus water. Lift one movement without interfering with the flow of concrete. Without the cone vertically in disturbing the base plate or concrete, measure the largest diameter of the flow spread and record as to the nearest 10 mm. Then measure the diameter of the flow spread at right angles to d to the nearest 10 mm and record as d to the nearest 10 mm. Check the concrete spread for segregation. The cement paste/mortar may segregate from the coarse aggregate to give a ring of paste/mortar extending several millimetres beyond the coarse aggregate. Segregated coarse aggregate may also be observed in the central area. Report that segregation has occurred and that the test was therefore unsatisfactory. 6 TEST RESULT The slump-flow is the mean of d^ and d^ expressed to the nearest 10 mm. 7 TEST REPORT The test report shall include: a) Identification of the test sample; b) Location where the test was performed; c) Date when test performed; d) Slump-flow to the nearest 10 mm; e) Any indication of segregation of the concrete; 52  IRC:SP:62-2014 f) Time between completion of mixing and performance of the tests; g) Any deviation from the procedure in this document. The report may also include: 1) The temperature of the concrete at the time of test; j) Time of test. TESTING FRESH CONCRETE V-FUNNEL TEST : - 2 Introduction The V-funnel test is used to assess the viscosity and filling ability of self-compacting concrete. 1 SCOPE This document specifies the procedure for determining the V-funnel flow time for self -compacting concrete. The test is not suitable when the maximum size of the aggregate exceeds 20 mm. 2 PRINCIPLE A V-shaped funnel is filled with fresh concrete and the time taken for the concrete to flow out of the funnel is measured and recorded as the V-funnel flow time. 3 APPARATUS 3.1 V-funnel, madedimensions (tolerance ± 1 mm) in Fig. 1, fitted with a quick to the release, watertight gate at its base and supported so that the top of the funnel is horizontal. The V-funnel shall be made from metal; the surfaces shall be smooth, and not be readily attacked by cement paste or be liable to rusting. 3.2 Container, to hold the test sample and having a volume larger than the volume of the funnel and not less than 12 liters. 3.3 Stop watch, measuring to 0.1 s. 3.4 Straight Edge, for Striking off Concrete Level with the Top of the Funnel '-^ I 1 hinged trapdoor Fig. 1 V-Funnel 53 IRC:SP:62-2014 4 TEST SAMPLE A sample of at least 12 Itrs shall be obtained. 5 PROCEDURE Clean the funnel and bottom gate, the dampen all the inside surface including the gate. Close the gate and pour the sample of concrete into the funnel, without any agitation or rodding, then strike off the top with the straight edge so that the concrete is flush with the top of the funnel. Place the container under the funnel in order to retain the concrete to be passed. After a delay of (10 ± 2) s from filling the funnel, open the gate and measure the time t^, to 0.1 s, from opening the gate to when it is possible to see vertically through the funnel into the container below for the first time, t^ is the V-funnel flow time. 6 TEST REPORT The test report shall include: a) Identification of the test sample; b) Location where the test was performed; c) Date when test performed; d) V-funnel flow time (tj to the nearest 0.1 s; e) Time between completion of mixing and performance of the tests; f) Any deviation from the procedure in this document. The report may also include: h) The temperature of the concrete at the time of test; i) Time of test. REFERENCES 1. IS: 11 99, Testing fresh concrete - Part 1: Sampling. 2. EN 9103, Testing fresh concrete - Part 2: Slump test. 54