THE USE OF MULTIPLE COMBINED NON DESTRUCTIVE TESTING IN THE CONCRETE STRENGHT ASSESSENT: APPLICATIONS ON LABORATORY SPECIMENS

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1 THE USE OF MULTIPLE COMBINED NON DESTUCTIVE TESTING IN THE CONCETE STENGHT ASSESSENT: APPLICATIONS ON LABOATOY SPECIMENS affaele Puinotti Dipartimento di Meania e Materiali, Università Mediterranea di eggio Calabria, o. Feo di Vito eggio Calabria, Italy raffaele.puinotti@unir.it Abstrat - In this paper a series of non-destrutive tests has been performed with the purpose to investigate on the mehanial properties of the onrete employed in the ivil buildings. A series of speimens were prepared in order to orrelate the in situ onrete strengths obtained by multiple ombinated non-destrutive methods with the ubial and ylindrial strength obtained by destrutive methods. The multiple ombined methods (Soneb Methods + Windsor Probe Tests) were used to quality ontrol and strength estimation of the onrete. In partiular, a series of speimens by aggregates having various Mohs Hardness (inert of fluvial origin) and by aggregate with only a lass of Mohs Hardness (rushed aggregate) has been prepared. During the onrete asting a series of ubial speimens has been prepared. The omparison among non-destrutive tests, ubial strength and ores strength are arried out. Keywords: Non-destrutive investigations, onrete, Windsor Probe System, Soneb Methods, Combined Methods. 1 Introdution The non destrutive methods applied in the field of ivil engineering having a vast diffusion in this last years. The penetration resistane method (Windsor probe system), the surfae hardness method, the ultrasoni method and the ombined methods (SONEB method) are the prinipal non-destrutive methods used for quality ontrol and strength estimation of in situ onrete [1, 2, 3]. These methods, being influened in different and/or opposite mode from some fundamental parameters, allow to get outputs with least dispersions. In this paper the outputs of these methods are alibrated with the strength of ylindrial speimens (ores) extrat from investigated speimens whih the non-destrutive tests were applied. Windsor probe test, Shmidt rebound hammer, Ultrasoni Pulse Veloity method [, 11, 12, 14], Soneb method, Windsor method [8, 9, 13] and a three parameter ombined method, appointed as SonebWin Method, were utilised to investigate on the mehanial property of onrete. The last, derive from the ombination of the results obtained by the well-known Soneb method whit the results of Windsor probe test. The use of these methods is generally justifiable only if a reliable orrelation for a partiular type of onrete is developed prior to the evaluation of the subjet quality onrete. In the present paper some availability orrelation ures [1, 11] will be appropriately adapted to the onrete studied. 2 The Speimens A total of 6 onrete speimens 600x600x200-mm was designed and fabriated at the Laboratory of the Faulty of Engineering of Mediterranean University of eggio Calabria. In partiular, 4 speimens (Figure 1), in the following appointed as IF, were prepared by aggregates having various Mohs Hardness, i.e inert of fluvial origin. For this speimens values from 3 to 7 of aggregate hardness were measured and the estimated Mohs hardness equivalent was of Moreover, 2 speimens, following appointed as IS (Figure 2), prepared by aggregate with only a lass of Mohs Hardness, i.e. rushed limestone aggregate were onsidered. For this speimens a value of 4.5 of Mohs hardness equivalent were estimated.

2 Figure 1. Speimens IF prepared by aggregates of fluvial origin - Mohs hardness variable from3 to 7 and equivalent Mohs hardness equal to 3.15 All speimens were prepared to obtain a harateristi ube strength of 30 MPa. 3 The Soneb Method The ombination of Shmidt ebound Hammer with Ultrasoni Pulse Veloity results inrease the auray of the estimation of the in situ ompressive strength of onrete. In the draft reommendation (ILEM Draft eommendation) for in situ onrete strength determination by ombined non-destrutive methods [4], are ontained the riteria for benefiial ombinations: (i) eah method provides information about different properties that affet the strength of onrete; (ii) speial sample preparation should not be required; (iii) tests should be quikly arry out; (iv) test methods should provide strength estimations to a similar level of auray; (v) tests should not affet the strutural performane of the unit under test. Figure 2. Speimens IS prepare by rushed limestone aggregate Mohs hardness equal to 4.5 The following examples of double ombinations between simple non-destrutive methods are known [4]: a) longitudinal pulse veloity + rebound index (Soneb method);

3 b) longitudinal pulse veloity + indentation diameter; ) longitudinal pulse veloity + pull-out fore; d) longitudinal pulse veloity + attenuation of ultrasoni pulses; e) longitudinal pulse veloity + gamma-ray attenuation; f) longitudinal pulse veloity + damping of vibrations; g) longitudinal pulse veloity + transverse pulse veloity; h) longitudinal pulse veloity + maturity onept; i) rebound index + indentation diameter; j) rebound index + pull-out fore; k) pull-out fore + maturity onept. In partiular, the Soneb method, (based on ultrasoni pulse veloity and rebound hammer tehniques), is largely diffused with the objetive to determine the potential ompressive strength of in situ onrete when its quality is onsidered to be suspet, due the efforts of ILEM 43 CND [4]. The advantages in the use of Soneb tehnique is that the variation of some properties of onrete produes opposite effets on the result of eah omponent test. For example, an inrease in moisture ontent inreases the ultrasoni pulse veloity but dereases the value of the rebound hammer number. Then, the use of Soneb method redue the effets of (i) aggregate size, (i) ement type and ontent, (ii) water-to-ement ratio, (iii) moisture ontent. In the sientifi literature various expressions to determine in situ ompressive strength of onrete by means of Soneb method are available: 1 1,4 2,6 = 7,695 Im V (1) ,246 1,85 0, Im V = (2) 3 9 1,058 2,446 = 1,2 Im V (3) ' ,487 Son e b = Im V (4) In (1) (ompressive strength of equivalent ube) is expressed in dan/m2 and the veloity ultrasoni pulse in m/s [5 ]; in (2) is expressed in MPa and the ultrasoni veloity in Km/s [6]; in (3) is expressed in MPa and the ultrasoni veloity in m/s [7]. Last relation (4) was the orrelation urve applied in the ase study. In (4) is expressed in MPa and the ultrasoni veloity in m/s; this relation is related to a standard onrete with the property desribed in ILEM 43-CND [4]. Where different type of onrete is employed the following relation is appliable: Son e b ' = ( C C C C C C ) (5) Son e b d a f p m C C C C, C and C were, d, a, f p m are oeffiients of influene that onsent the extension of the (4) a the ase of a non standard onrete is utilized. In the ase of examined speimens the values of the oeffiients of influene are reported in table 1 [1]. Tabella 1: Coeffiients of influene Coeff. Infl. Speimens IF Speimens IS For the ement type C For ement ontent C d For aggregate type C a For the proportions of fines C f For the maximum aggregate size C p For admistures C m Moreover, for the speimens IF were possible to obtain the following orrelation urve:

4 = V I Corr Son e b 2.75 r (6) 4 The Soneb-Win Metod The ombination of values obtained using more simple non-destrutive methods inrease the auray of the estimation ompared with that from any single method. The following examples of triple ombinations between simple nondestrutive methods are known [4]: a) longitudinal pulse veloity + rebound index + pull-out fore; b) longitudinal pulse veloity + rebound index + attenuation of ultrasoni pulses; ) longitudinal pulse veloity + rebound index + transverse pulse veloity; d) longitudinal pulse veloity + slope at the first wave front + reverberation time. In this paper another triple ombination between simple non-destrutive methods was employed: a) longitudinal pulse veloity + rebound index + penetration fore (Soneb-Win); The orrelation urve in this ase was expressed by the following formula: C = a I V, L (7) b rm L s d e where: - L e is the length of the part of probe not penetrated in the onrete (figure 3); - V is the longitudinal pulse veloity; - I r is the rebound index; - a, b, and d are onstants definable by the appliation of last square priniple. Only for speimens IF were possible, also in this ase, to obtain a the orrelation urve; this has the following expression: = V I L Corr Son e b Win r e (8) 5 Appliations and results In this setion the more important results of non destrutive investigation ondued in situ on a series of onrete speimens are shortly disussed. For the speimens IF, ompressive strength of ores is ompared, with the assessment of onrete strength obtained by the appliation of Windsor method (Mohs hadness=3.15), Soneb method and Soneb-Win method in the figure 5. In partiular, the values of ompressive strength of ores are ompared with those obtained by Soneb and Soneb- Win ombined methods and with the Windsor method applied singularly. It is easy to see that the Soneb-Win method gives resistane values lose to atual ones. Moreover, the assessment of the strength by the penetrometri method (Windosor methot with equivalent Mohs hardness equal to 3.15) gives values of resistane in onordane with the atual value of strength of ores.

5 Holes of Cores Probe in the onrete Figure 3. Speimens IF after experimental tests Figure 4. Speimens IS during the experimental tests 45 ar Soneb,orr Soneb SPECIMENS IF Soneb-Win,orr Mohs=3.15 'Soneb [PMa] IF1 IF2 IF3 IF Figure 5. Speimens IF - Experimental Test esults Figure 6 show the omparison among the ores strength, Windsor strengh (Mohs hadness equal to 4.5), Soneb strenght and the strength assessment by appliation of Soneb-Win method. In this ase, where only two speimens were available (and where was not possible develop an adequate orrelation urve), the Windsor probe system is the more reliable method that gives resistane values lose to atual ones.

6 [MPa] ar Mohs=4.5 'Soneb SPECIMENS IS Soneb-Win,med Soneb 20 IS1 IS Figure 6. Speimens IS - Experimental Test esults 6 Conlusions A series of non-destrutive tests were arried out with the purpose to investigate on the mehanial properties of the onrete employed in the ivil buildings. In this purpose a series of speimens were prepared and afterwards subjet to non-destrutive tests (Windsor, Soneb and Soneb-Win ). With referene to Windsor Probe Systems, the study has evidened that, when a onrete by aggregate of fluvial origin is employed, the hardness of the aggregate assume a important role in the orret evaluation of strength. In this ase, the use of Windsor methods is generally justifiable only if a reliable orrelation for a partiular type of onrete is developed. The Windsor Probe Systems assessment of onrete strength is adequate in the ase of aggregate with only a lass of Mohs Hardness. The Soneb-Win method gives resistane values lose to atual ones. It is very suitable for the assessment of onrete strength when an appropriate orrelation urve is drawn up. Moreover, the advantages in the use of Soneb as well as of Soneb-Win tehniques is that the variation of some properties of onrete produes opposite effets on the result of eah omponent test. eferenes [1]. Puinotti (2006), Patologia e Diagnostia del Cemento armato (Indagini non Distruttive e Carotaggi nelle Opere da Consolidare) Dario Flaovio Editore Book, 2006; [2]. Puinotti,. A. De Lorenzo (2003), Nondestrutive in Situ Testing for the Seismi Damageability Assessment of Anient /C Strutures, Book of Proeedings, 3rd International Conferene on NDT, Chania, Crete, Greee, pp ; [3]. Puinotti, M. Versai,. A. De Lorenzo (2003), A Neuro-Fuzzy Approah to Correlate Probe Penetration Test esults and Compressive Strength of /C Strutures, Book of Proeedings, 3rd International Conferene on NDT, Chania, Crete, Greee, pp ; [4] ILEM Draft eommendation, 43-CND. (1993). Combined non-destrutive testing of onrete. Draft reommendation for in situ onrete strength determination by ombined non-destrutive methods. Materials and Strutures, 26, pp.43-49; [5] Giohetti., Laquaniti L., Controlli non distruttivi su impalati da ponte in alestruzzo armato, Nota Tenia 04, Università degli Studi di Anona, Faoltà di Ingegneria, Istituto di Sienza e Tenia delle Costruzioni, 1980; [6] Gasparirik J., Prove non distruttive in edilizia, Quaderno didattio A.I.P.n.D., Bresia, 1992; [7] Di Leo A., Pasale G., Prove non distruttive sulle ostruzioni in emento armato, Convegno Sistema Qualità e Prove non Distruttive per l affidabilità e la siurezza delle strutture ivili, Bologna, SAIE 94, 21 ottobre 1994; [8] Puinotti., L utilizzo del Metodo Windsor nella Valutazione della esistenza Meania del Conglomerato Cementizio, Convegno Internazionale Crolli e Affidabilità delle Strutture Civili, Università degli Studi di Messina Aprile 2006;

7 [9] Puinotti., D Elia A., De Lorenzo.A., Sonda Windsor: Sperimentazione su Campioni in Conglomerato Cementizio, atti del Convegno Nazionale Sperimentazione su Materiali e Strutture, pp , Venezia, 6-7 diembre, 2006; [] Puinotti., Indagini non Distruttive nella Valutazione del Degrado di Elementi Strutturali in Cemento Armato, L Industria Italiana del Cemento, n.8 giugno 2005; [11] Malhotra V. M., Carino N. J., CC Handbook on Nondestrutive Testing of Conrete, CC Press, 1991; [12] Braga F., Dole M., Masi A., Nigro D., Valutazione delle aratteristihe meanihe dei alestruzzi di bassa resistenza mediante prove non distruttive, L Industria Italiana del Cemento, 3, pp , 1992; [13] Malhotra V. M., and Painter K.P., Evaluation of the Windsor Probe Test for Estimating Compressive strength of Conrete, Mines Branh Investigation ep. I 71-50, Ottawa, Canada, 1971; [14] Boa P., Cianfrone S., (1983). Le prove non distruttive sulle ostruzioni: una metodologia ombinata. L Industria Italiana del Cemento, 6, pp ;