Mechanical and deformational properties, and shrinkage cracking behaviour of lightweight concretes

MECHANICAL AND DEFORMATIONAL PROPERTIES, AND SHRINKAGE CRACKING BEHAVIOUR OF LIGHTWEIGHT CONCRETES DANETI SARADHI BABU NATIONAL UNIVERSITY OF SINGAPORE 2008 MECHANICAL AND DEFORMATIONAL PROPERTIES, AND SHRINKAGE CRACKING BEHAVIOUR OF LIGHTWEIGHT CONCRETES DANETI SARADHI BABU (B.Tech., JNTU; M.S. (by Research), IITM) THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2008 ACKNOWLEDGEMENTS I would like to express my gratitude and sincere appreciations to my supervisor Associate Professor Wee Tiong Huan for his inspiring, invaluable and untiring guidance and help in all the matters. I also wish to thank Dr. Tamilselvan S/O Thangayah for his comments and kind advises in finalising my thesis. I gratefully acknowledge and admire the generosity and infinite patience shown by them in all matters. My gratitude is also extended to my examiners Associate Professor Tan Kiang Hwee and former Associate Professor Mohamed Maalej for their support and helpful recommendations to improve the research work during the PhD qualifying examination presentation. I would also like to thank Associate Professor Tam Chat Tim and Professor Balendra, T for serving on my committee. The valuable suggestions and encouragement given by them has helped me immensely. The research reported in this thesis was part of the more comprehensive R&D program entitled “Development of high strength lightweight concretes with and without aggregates” jointly funded by Building and Construction Authority of Singapore (BCA) and National University of Singapore (NUS). The research scholarship and support from NUS is gratefully acknowledged. I am highly thankful to my colleagues Dr. Lim, Kum, Dr. Kannan, Dr. Rafique, Mathi, Lim Sun Nee, Kong Ruiwen, and friends Dr. Nagi Reddy, Dr. Pavan Kumar, Dr. Chava, Dr. Rajan, Niranjan, Vijay, Uma, PineGrove group and others for their valuable help, encouragement and suggestion during my research work. I wish to express my thanks to the staff of the Structural and Concrete Laboratory, namely, Mr. Lim, Sit, Ang, Choo, Koh, Ow, Yip, Kamsan, Ong and Mdm. Tan Annie are greatly appreciated. Last but not least, the work is devoted to my loving parents - Ramaswamy and Varahalamma, Wife – Madhuri, Brother – Kesava Rao, sisters – Eswaramma and Venkatamma, In-Laws and their family and relatives for their patience, abundant love and affection towards my education. Daneti Saradhi Babu 2008 i Dedicated To my Loving Parents & Wife ii TABLE OF CONTENTS ACKNOWLEDGEMENTS TABLE OF CONTENTS SUMMARY i iii viii NOMENCLATURE xi LIST OF TABLES xiv LIST OF FIGURES xv CHAPTER 1: INTRODUCTION 1.1 Background 1.2 Need for the research 1.3 Objectives and Scope 1.4 Organization of the thesis CHAPTER 2: LITERATURE REVIEW 11 2.1 Introduction 11 2.2 Cracking in concrete 11 2.3 Mechanism of shrinkage cracking 13 2.4 Mechanical properties of LWC 14 2.4.1 Foamed concrete 2.4.1.1 Air-void system 2.4.2 Lightweight aggregate concrete (LWAC) 14 16 18 2.5 Fracture parameters 20 2.6 Shrinkage of concrete 22 2.6.1 Autogenous shrinkage 23 2.6.2 Drying shrinkage 25 iii 2.6.3 Shrinkage of foamed concrete 28 2.6.4 Shrinkage of lightweight aggregate concrete 29 2.7 Creep of concrete 31 2.8 Shrinkage cracking 32 2.8.1 Methods to control shrinkage cracking and shrinkage effects 33 2.8.2 Methods to assess shrinkage cracking 34 2.9 Restrained ring test 37 2.10 Shrinkage cracking of LWC 37 2.11 Summary 39 CHAPTER 3: MECHANICAL PROPERTIES OF LIGHTWEIGHT CONCRETES 51 3.1 Introduction 51 3.2 Experimental investigation 53 3.2.1 Materials 53 3.2.2 Mix proportions 54 3.2.3 Test program 55 3.2.3.1 Air-void system 55 3.2.3.2 Rheology test 57 3.2.3.3 Fracture toughness 57 3.2.3.4 Compressive strength 60 3.2.3.5 Splitting and flexural tensile strength 60 3.2.3.6 Modulus of elasticity and stress-strain test 60 3.3 Results and discussion 3.3.1 Air-void system of foamed concrete 3.3.1.1 Experimental study: Effect of air-void system on mechanical properties 61 61 66 iv 3.3.1.2 Numerical study: Effect of air-void system on mechanical properties68 3.3.1.3 Relationship between air content, w/c ratio, density on strength and modulus 71 3.3.2 Fracture toughness 74 3.3.2.1 LWC without fibers 74 3.3.2.2 Fiber reinforced LWC 76 3.3.3 Mechanical properties of LWCs and their comparison with NWC 79 3.3.3.1 Compressive strength 79 3.3.3.2 Tensile strength 82 3.3.3.3 Fracture toughness 85 3.3.3.4 Modulus of elasticity of aggregates and concretes 87 3.3.3.5 Stress-strain behaviour 90 3.3.3.6 Poisson’s ratio 91 3.4 Summary 92 CHAPTER 4: DEFORMATIONAL PROPERTIES OF LIGHTWEIGHT CONCRETES 122 4.1 Introduction 122 4.2 Experimental investigation 124 4.2.1 Test program 124 4.2.1.1 Shrinkage test 124 4.2.1.2 Creep test 125 4.2.1.3 Microstructure test 125 4.3 Results and discussions 126 4.3.1 Autogenous shrinkage 126 4.3.2 Drying shrinkage 129 4.3.2.1 Effect of air content 129 4.3.2.2 Effect of aggregate density/type and aggregate volume 131 v 4.3.2.3 Effect of w/c ratio, curing, mineral admixtures, fibers and aggregate soaking 138 4.3.2.4 Relationship between shrinkage of foamed concrete vs LWAC and NWC 142 4.3.3 Creep 144 4.3.3.1 Effect of air content 145 4.3.3.2 Effect of aggregate density/type and aggregate volume 146 4.3.3.3 Effect of w/c ratio and mineral admixtures 151 4.3.4 Comparison of shrinkage and creep prediction models for LWCs 4.4 Summary 152 154 CHAPTER 5: SHRINKAGE CRACKING BEHAVIOUR OF LIGHTWEIGHT CONCRETES 181 5.1 Introduction 181 5.2 Experimental program 183 5.2.1 Specimen details and test program 183 5.2.2 Theoretical restrained shrinkage analysis 186 5.3 Results and discussion 5.3.1 Effect of filler (air or aggregate) volume and filler type/density 188 188 5.3.1.1 Stress development and age of cracking: Experimental study 188 5.3.1.2 Stress development and age of cracking: Theoretical study 196 5.3.2 Effect of fibers 204 5.3.3 Effect of mineral admixtures 207 5.3.4 Effect of curing and soaking condition of aggregate 209 5.3.5 Parameters influencing the potential for shrinkage cracking of LWCs 211 5.4 Summary 214 CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS 239 6.1 Review of the investigation 239 vi 6.2 Conclusions 242 6.3 Recommendations for further research 244 REFERENCES 245 ANNEX 256 ANNEX 258 ANNEX 259 PUBLICATIONS 267 vii SUMMARY Title: Mechanical and deformational properties, and shrinkage cracking behaviour of lightweight concretes. The study reported in this thesis addresses the role of constituent materials of different lightweight concrete (LWC) – foamed concrete without aggregate (FC), foamed concrete with aggregate (FCA) and lightweight aggregate concrete (LWAC) – on mechanical and deformational properties, and shrinkage cracking behaviour both theoretically and experimentally. The present investigation was divided in to three parts for a systematic approach to the study. The main constituent materials of LWC considered in the study include filler volume (air and aggregate), filler type or density, fibers, and mineral admixtures. The first part of the work focused on understanding the role of constituents on mechanical properties such as compressive strength, tensile strength, modulus of elasticity, fracture toughness and stress-strain behaviour. Particular emphasis has been given to study the effect of w/c ratio on air-void system of FC and their effect on mechanical properties through experimental and numerical analysis. The effects of filler volume, filler type and fiber on fracture toughness, strength, and modulus of elasticity of FC, FCA and LWAC were tested. The results indicate that the air-void system with a spacing factor of about 0.05 mm, average air-void size of lower than 0.15 mm and air content of 40%, were collectively found to be optimal for different w/c ratios at which foamed concrete with high strength to weight ratio can be achieved. The air-void system and w/c ratio control the mechanical properties of FC. Use of higher volume of lightweight aggregate (LWA) is not beneficial in improving the fracture toughness of LWAC, due to its porous nature. The performance of fibers in improving the toughness of FC is found to be as good as that in LWAC. 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Ziembika H., Effect of micropore structure on cellular concrete shrinkage, Cement and Concrete Research, July 1977, pp. 323-332. 255 Annex ANNEX RILEM equations for the estimation of fracture toughness: E= Sa0 g (α ) Ci b t (1) where the geometric function g2(α0) was calculated as : g (α ) = 0.76 − 2.28α + 3.87α 02 − 2.04α 03 + 0.66 (1 − α ) (2) where α0 = a + HO b + HO (3) and S, a0, HO, b and t are defined in Figs 3.4 and 3.5. According to the RILEM method of Jenq and Shah, the effective-elastic critical crack length ac could be defined in such a way that it caused an unloading compliance Cu within 95% of the peak load based on LEFM. Therefore, by using this, E could also be calculated from: E= Sac g (α c ) Cu b t (4) where the geometric function g2(αc) was similar to the one given in Equation 2, except that α0 was replaced by αc,, where αc = a c + HO b + HO (5) By equating Equations and 4, this resulted in: ac = a0 C u g (α ) C i g (α c ) (6) which was solved iteratively. Wh = W h S / L (7) where Wh0 was the self-weight of the beam. 256 Annex The geometric function g1(ac / b) was calculated as: g ( a c / b) = 1.99 − (a c / b)(1 − a c / b)[2.15 − 3.93a c / b + 2.70(a c / b) ] (8) π (1 + 2ac / b)(1 − ac / b) / The critical stress intensity factor, or fracture toughness, was then calculated using the following equation: K Ics = 3( Pc + 0.5Wh ) S πa c g1 (ac / b) (9) 2b t where Pc was the maximum load. Finally, the critical crack tip opening displacement was calculated using the following equation: ( Pc + 0.5Wh ) Sac g (ac / b)  a  × (1 − β ) + (1.081 − 1.149 c ) ( β − β 02 ) CTODc = Eb t b   1/ (10) where β0 = a0 ac (11) The geometric function g2(ac / b) was based on Equation 2, but α0 was replaced by ac / b. In this research, equations to 11 were keyed into Microsoft Excel spreadsheets. The iterative procedure was readily implemented using a Solver equation, with αc as the unknown. 257 Annex ANNEX Modulus of elasticity models for composite materials S.No Author (s) Chen et al. (2003) Balendran (1994) Hansen (1965) Modulus of elasticity model Remarks Ea = 6.3 Ec – 5.1 Em – 9.1 VaEc + 8.7 VaEm Ec = EaVa Em(1-Va) Ec = Em (1 − Va )E m + (1 − Va )Ea (1 + Va )Em + (1 − Va )Ea 1 − Va = + Ec Em  − Va   E + Ea  V  m a   Counto (1964) Voigt Model (1889) E c = E mVm + E aVa Reuss model (1929) V V = m + a Ec E m E Hirsch model (1962) Popovics model (1970) 1 1  =  + Ec  E cVoigt Ec Re uss  E c = (EcVoigt + Ec Re uss ) Ec, Em and Ea modulus of elasticity of concrete, mortar and aggregate, respectively. Vc, Va and Vv volume of concrete, aggregate and voids, respectively. 258 Annex ANNEX SHRINKAGE AND CREEP MODELS ACI 209R-92 (2002) Creep strain = σ Ecmto νt E cmto = 0.043γ / f c' (t )  t  f c' (t ) = f c'( 28)   α + βt  Creep coefficient, ν t = t 0.60 νu 10 + t 0.60 Shrinkage strain (ε sh )t = t is the age of concrete in days t (ε sh )u 35 + t In the absence of specific creep and shrinkage data for local aggregates and conditions, the average values suggested for νu and are: νu = 2.35 γc (εsh)u = 780 γsh x 10-6 in/in (m/m) γc and γsh are the product of applicable correction factors Correction factors: 1. Loading age: Creep, γla = 1.25(tla)-0.118 2. Ambient RH: Creep, γRH = 1.27-0.0067 RH Shrinkage, γRH = 1.40 - 0.010 RH 3.00 – 0.030 RH for RH > 40 for 40 ≤ RH ≤ 80 for 80 > RH ≤ 100 Average thickness: Creep, γh = 1.14 – 0.00092 h during 1st year after loading of member 1.10 – 0.00067 h for ultimate values Shrinkage, γh = 1.23 – 0.00015 h during 1st year after loading 259 Annex 1.17 – 0.00114 h for ultimate values Volume-surface ratio method Creep, γvs = 2/3[1-1.13 e(-0.0213 v/s)] Shrinkage γvs = 1.2 e(-0.00472 v/s) Concrete composition: Fine aggregate %, Creep, γψ = 0.88 + 0.0024 ψ Shrinkage, γψ = 0.30 + 0.014 ψ ψ ≤ 50% Shrinkage, γψ = 0.90 + 0.002 ψ ψ > 50% Creep, γs = 0.82 + 0.067s Slump Shrinkage γs = 0.89 + 0.041s Cement Shrinkage, γc = 0.75 + 0.00061c Creep, γ∝ = 0.46 + 0.09∝ but not less than 1.0 Air content (∝ - %) Shrinkage, γ∝ = 0.95 + 0.008∝ GL 2000 (2001) Modulus of elasticity E cmt = 3500 + 4300 f cmt MPa Ecmt = mean modulus of elasticity at age t fcmt = mean concrete strength at age t Strength development with time f cmt = f cm 28 t 3/ a + bt / for Type I cement concrete a = 2.8 and b = 0.77 Type II cement concrete a = 3.4 and b = 0.72 Type III cement concrete a = 1.0 and b = 0.92 fcm28 = mean concrete strength at 28 days fcm28 = 1.1 fck28 + 700 psi fck28 – Psi fcm28 = 1.1 fck28 + MPa fck28 – MPa fck28 = 28 day characteristic, or specified, concrete strength, 260 Annex Shrinkage ε sh = ε shu β (h) β (t ) β (h) = (1 − 1.18h ) 1/ ε shu  30   10 − = 1000 K  f  cm 28   t − tc β (t ) =   t − t c + 0.15(V / S ) h t tc K = = = = V/S fcm28 = =     0.5 humidity expressed as a decimal age of concrete, days age of drying commenced, end of moist curing, days Type I cement 0.7 Type II cement 1.15 Type III cement volume surface ratio, mm concrete mean compressive strength at 28 days, MPa Creep Specific creep = φ 28 Ecm28 – E at 28 days; φ28 – creep coefficient Ecm 28 φ28 =   (t − t )0.3   + Φ(t c )2 0.3   (t − t ) + 14   t o  If to = tc, Φ(tc )    0.5  t − to     t − to +  0.5  t − to + 2.5 − 1.086h   t − t o + 0.15(V / S ) (   to − tc = when to > tc, Φ (t c ) = 1 −     t o − t c + 0.15(V / S )2  Compliance J (t , t o ) = Ecmto )     0.5         0.5 0.5 + specific creep Ecmto = modulus of elasticity at time of loading fcmto = compressive strength when loading commenced, MPa to = age concrete loaded, days. 261     Annex CEB 90 model code (with Muller modifications) ε cs (t , t s ) = ε cso β s (t − t s ) Strain due to shrinkage/swelling Shrinkage ε cso = ε s ( f cm 28 )β RH     ε s ( f cm 28 ) = 160 + 10β sc  − f cm 28   −  10 f cmo   β sc = coefficient depending on type of cement for slow hardening cement for normal and rapid hardening cement for rapid hardening high strength cement β RH = -1.55 β sRH for 40% ≤ RH < 99% +0.25 for β sRH  RH  = 1−    RHo  ≥ 99%  (t − t s ) / t1  β s (t − t s ) =    β sH + (t − t s ) / t1  0.5 β sH = 350 (h/ho)2 t = age of concrete in days = age of concrete at the beginning of shrinkage, days ts fcm = mean compressive strength of concrete (MPa) RH = mean RH of ambient atmosphere (%) fcmo = 10 MPa = 100% RHo t-ts = duration of drying or swelling, days (Ac = c/s area of structural member in mm2; u = h = 2Ac/u perimeter of structural member mm) ho = 100 mm t1 = day Effect of elevated temperature T on shrinkage β sHT = β sH e [−0.06(T / T −20 )] o temperature dependent coefficient replacing β sH β RH ,T = β RH β sT    T / To − 20    40  103 − 100 RH / RH o   β sT = +  T - const. temp; To = 1oC; RHo = 100% 262 Annex Creep ε cσ (t , t o ) = ε ci (t o ) + ε cc (t , t o ) ε ci (to ) - Initial elastic strain at loading = ε cc (t, to ) - creep strain at time t ≥ to = σ c (t o ) Ec (t o ) σ c (t o ) Ec φ (t , t o ) φ (t , t o )  +  Ec   E c (t o )  ε cσ (t , t o ) = σ c (t o ) = σ c (t o )J (t , t o ) f  E c = Eco  cm 28   f cmo  J (t , to ) - creep function or creep compliance 1/ fcm28 = mean compressive strength of 150x300 mm cylinder at 28 days stored at 20oC±2. Eco = 21500 MPa fcmo = 10 MPa ( ) s 0.5   1− ( 28 / (t / t1 ) )   E c (t ) = E c e  s = coefficient depends on type of cement 0.2 Rapid hardening high strength cement 0.25 Normal or rapid hardening cement 0.38 slow hardening cement t = age of concrete in days t1 = day  T E c (T ) = Ec 1.06 − 0.003 To     EC(T) = modulus of elasticity at the temperature T EC = Modulus of elasticity at T = 20oC T = Temperature of concrete To = 1oC φ (t , t o ) = φRHβ ( f cm 28 )β (t o )β c (t − t o ) Creep coefficient 263 Annex 1− φRH = + β ( f cm 28 ) = β (t o ) = RH RH o  h 0.46  ho    1/ 5.3 ( f cm 28 / f cmo )0.5 0.1 + (t o / t1 ) 0.2  (t − t o ) / t1  β c (t − t o ) =    β H + (t − t o ) / t1    RH β H = 150 1 + 1.2   RH o    18 0.3  h  + 250 ≤ 1500  ho α   to = to , T  + 1 ≥ 0.5 days 1.2  + (t o , T / t1 , T )  to,T = age of concrete at loading in days t1,T = day ∝ = -1 for slow setting cement for normal or rapid hardening cement for rapid hardening high strength cement φRH , T = φT + [φRH − 1]φT 1.2 φT = e [0.015(T / T −20 )] o φRH , T = temperature dependent coefficient which replaces φRH T T = temperature while concrete is under load = 1oC Creep coefficient = Ratio of creep strain to initial elastic strain 264 Annex SAK model Shrinkage ε sh (t , t o ) = ε sh∞ = ε sh∞ (t − t o ) β + (t − t o ) α (1 − h )W + 150e β=  500  − '   f c 28  1 + ηt o 4W V / S 100 + 0.7t o [ η = 10 −4 15e (0.007 f ) + 0.25W ' c 28 ] ε sh (t, t o ) Drying shrinkage strain (µ) t, to current age and age at drying (days) when to > 98 days, to = 98. fc28’ compressive strength at 28 days (MPa) < 120 MPa h RH at atmosphere (0.4 < h < 0.9) W unit water content (130 < W < 230 kg/m3) V/S volume surface ratio (100 < V/S < 1000 mm) ∝ the factor to account the cement type (for Japanese data, ∝ = 11 to normal cement and ∝ = 15 to rapid hardening cement; for RILEM data, ∝ = 10 to normal OPC and ∝ = to slow hardening cement) Creep C r (t , t ' ) = A log e (t − t ' + 1) A= ( ) Cr t ,t ' ’ t f’ct’ 4W (1 − h ) + 350 12 + f ct' ' specific creep (µ/MPa); first application of load (days) compressive strength at age of t (MPa) < 120 MPa 265 Annex B3 model Shrinkage ε sh (t , t o ) = −ε sh∞ k h S (t )  t − to S (t ) =   τ sh kh τsh D ks 1-h3 kt(ksD)2 2V/S shape factor    1/ for h ≤ 0.98 effective c/s thickness 1.25 for an infinite square prism 1.0 can be assumed for simplified analysis ε sh∞ = ε s∞ E (7 + 600 ) E (t o + τ sh ) for simplified analysis one can assume ε sh∞ = ε s∞ . The typical values ε sh∞ according to the above equation range from 300 to 1100 x 10-6. [ ε s∞ = α 1α 26w 2.1 ( f c' ) −0.28 + 270 k t = 190.8t o−0.08 f c' α1 α2 1.0 0.85 1.1 1.0 ] (in 10-6) days/in2 for type I cement for type II cement for type III cement for specimens cured in water or at 100% RH Creep . Basic creep C o (t , t ') = ( n q t − m + q3 (t − t ') + (t − t ') ) 1− n + q4 t m = 0.5, n = 0.1 q1 = 0.6 x 106/E28 E28 = 57000(fc’)1/2 q2 = 451.1c0.5(fc’)-0.9 q3 = 0.29(w/c)4 q2 q4 = 0.14(a/c)-0.7 Drying creep [ C d (t , t ' , t o ) = q e −8 H (t ) − e −8 H ( t ') H(t) = – (1 – h) S(t); ] 1/ for t’ ≥ to Q5 = 7.57 x 105 fc’-1εsh∞-0.6 266 PUBLICATIONS 1. Wee TH, Saradhi Babu D, Tamilselvan T and Lim HS. “Air-void system of foamed concrete and their effect on mechanical properties”, ACI Materials Journal, vol. 103, No.1, Jan-Feb 2006, pp. 45-52. 2. Saradhi Babu D, Wee T.H and Tamilselvan T. “Mechanical properties of foamed concretes with and without aggregates”, Proceedings of the 3rd International Conference on Construction Materials: Perofrmance, Innovations and Structural Implications, Edited by Banthia, N. Uomoto, T. Bentur, A. and Shah, S.P., ConMat’05, Vancouver, 2005, p.101. (Won the Best Paper Award) 3. Saradhi Babu D, Wee T.H and Tamilselvan T. “Shrinkage cracking potential of lightweight aggregate concrete”, Proceedings of the 4th International Conference on Construction Materials: Perofrmance, Innovations and Structural Implications, Edited by Uomoto, T. Banthia, N. Bentur, A. and Shah, S.P., ConMat’09, Japan 2009. 4. Wee T.H, Saradhi Babu D and Tamilselvan T. “Effect of W/C ratio on air-void system of foamed concrete and their influence on mechanical properties”, Manuscript to Magazine of Concrete Research (under preparation). 5. Saradhi Babu D, Wee T.H and Tamilselvan T. “Shrinkage cracking potential of lightweight aggregate concrete” Manuscript to ACI Materials Journal (under preparation). 267 [...]... Fig 4.6 Effect of sand and LWA volume on autogenous shrinkage of FC 162 Fig.4.7 Effect of air content on drying shrinkage of FC and FC with sand 163 Fig 4.8 Effect of air content on pore size distribution of FC 163 Fig 4.9 Effect of aggregate type on drying shrinkage of FC 164 Fig 4.10 Effect of sand and LWA volume on drying shrinkage of FC 164 Fig 4.11 Shrinkage ratio (Sfca/Sfc) in terms of modulus ratio... at cracking 233 Fig 5.33 Effect of polypropylene fiber percent on stress and age of cracking of (30% air content) 234 Fig 5.34 Effect of (a) fiber percent and (b) fiber type on stress and age of cracking of LWAC (L9 LWA) 234 Fig 5.35 Effect of fiber percent and fiber type on age of cracking of different concretes (FC, LWAC and NWC) 235 Fig 5.36 Effect of fiber percent and fiber type on crack widths of. .. understand the shrinkage cracking behaviour of concrete, the need to understand the mechanical and deformational properties are important Therefore, this study was undertaken to comprehensively understand the mechanical and deformation properties, and shrinkage cracking behaviour of lightweight concrete with and without aggregate which are of paramount importance for the durability and serviceability of structures... toughness of LWC with and without agg and fibers Drying shrinkage and creep of LWC and measures to control Relationships between the mechanical properties and proposal of empirical equations Modulus of elasticity of aggregates and concretes and their relation with density Unrestrained drying shrinkage of concrete (experimental and theoretical study) Verification of shrinkage and creep models for LWC Shrinkage. .. the shrinkage cracking of FC than sand The use of higher volumes of aggregate, higher density aggregates (stronger aggregate) and low w/c ratio helps to mitigate the potential ix risk of shrinkage cracking in LWAC The tensile strain at cracking of LWAC (~213 µε) is twice that of NWC (~100 µε) and it is independent of the age of cracking The shrinkage cracking potential of foamed concrete with and without... 167 Fig 4.16 Shrinkage ratio (Sc/Sm) in terms of modulus ratio (Ec/Em) at 90-days of drying 167 Fig 4.17 Effect of w/c ratio on drying shrinkage of FC and LWAC 168 Fig 4.18 Effect of age of curing on drying shrinkage of FC and LWAC 169 Fig 4.19 Effect of mineral admixtures on drying shrinkage of FC and LWAC 170 Fig 4.20 Effect of fiber on drying shrinkage of FC and LWAC 171 Fig 4.21 Effect of aggregate... history of the development and applications of LWC, identifies the need for the research, and enumerates the main objective and scope of the work reported herein Chapter 2 provides a review of existing literature dealing with mechanical and deformational properties and shrinkage cracking of LWC A brief review of restrained shrinkage cracking and shrinkage mechanisms are presented Review of restrained shrinkage. .. concrete (σactual = Ec, Es, εsh, geometry and restraint) 4 Age of cracking = f(ft, σ, time dependent material properties development) Restrained Shrinkage cracking parameters Fig 1.2 Factors affecting shrinkage cracking of concrete 9 Mechanical and Deformational Properties, and Shrinkage Cracking Behaviour of Lightweight Concretes Introduction: Objectives and Scope of work Literature Review Parametric /... (d) Effect of w/c ratio 222 Fig 5.15 Effect of aggregate volume on (a) Age of cracking; (b) Stress in concrete @ cracking; and (c) Shrinkage rate @ cracking of LWAC with different aggregate type/density 224 Fig 5.16 Relationship between shrinkage rate @ cracking and age of cracking for LWAC 225 Fig 5.17 Relationship between shrinkage rate at cracking and age of cracking: Comparion of FC, FCA and LWAC... Influence of strength, shrinkage and creep on shrinkage cracking of concrete (Neville 1997) 226 Fig 5.19 Effect of LWA volume on restrained shrinkage cracking of FC with 30% air content (L6 LWA) 226 Fig 5.20 Effect of aggregate volume on restrained shrinkage cracking of LWAC (L9 LWA)227 Fig 5.21 Effect of aggregate density on restrained shrinkage cracking of concrete 228 Fig 5.22 Effect of w/c ratio . Title: Mechanical and deformational properties, and shrinkage cracking behaviour of lightweight concretes. The study reported in this thesis addresses the role of constituent materials of different. MECHANICAL AND DEFORMATIONAL PROPERTIES, AND SHRINKAGE CRACKING BEHAVIOUR OF LIGHTWEIGHT CONCRETES DANETI SARADHI BABU NATIONAL UNIVERSITY OF SINGAPORE. x risk of shrinkage cracking in LWAC. The tensile strain at cracking of LWAC (~213 µε) is twice that of NWC (~100 µε) and it is independent of the age of cracking. The shrinkage cracking