Techniques and laboratories of concrete testing
Tibério Situ Antunes Yan
Extended Abstract Department of Civil Engineering, Architecture and Georesources Instituto Superior Técnico, Universidade Técnica de Lisboa
Jury President: PhD Albano Luís Rebelo da Silva das Neves e Sousa Supervisors: PhD João Paulo Janeiro Gomes Ferreira PhD Inês dos Santos Flores Barbosa Colen Opponents: PhD Fernando António Baptista Branco PhD Manuel Francisco Costa Pereira
November 2013
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Abstract There are several organizations that produce normative documents, within the framework of construction materials (particularly concretes), namely: ISO (organization that produces worldwide standards in collaboration with other several member countries part of this organization), CEN (that produces standards at a European level in collaboration with European countries) and IPQ (Portuguese agency responsible for the development of the Portuguese standards). The characteristics of performance of concrete are evaluated through laboratories tests which test procedures are set out in standards and technical specifications. In this context this dissertation has prepared a synthesized document with a survey of all tests that can be performed on concretes in the fresh state, hardened state and durability tests, as well as their respective test standards in Portugal. The main aim of this study is to understand the functioning of the testing laboratories for concrete in construction, as well as the laboratory tests. Fieldwork study was carried out (which included making inquiries in the field and visiting laboratories facilities) in thirteen Portuguese laboratories belonging to the universities and polytechnics; to the cement manufacturers; to the concrete plants; to the public institutes; to the public/private institutions; to a military institution and to the private companies and construction companies. Based on this fieldwork study and the normative research conducted, it was possible to present the general characteristics of the testing laboratories for concrete in construction, interpret and evaluate laboratories trends at some aspects of the functioning such as: materials tested, deployment area and division of laboratory space, laboratory tests (standards and specifications adopted, accreditation and test frequency), type of maintenance and calibration of the compression test (periodicity), staff and users. Keywords: Standardization, concrete, laboratories, trends, testing, methodology
1. Introduction The comparison of different materials imposes the necessity of performing standard tests, namely technical and test procedures to evaluate certain properties of similar material. In producing a quality concrete knowledge and skills are needed. Thus, from the careful selection of the constituent materials and the compatibility between them, the production, placement, and work hardening, goes a long way of experimentation and tests leading to the assessment of conformity. Building material laboratories which depending on its nature performs these tests with different features, functions and constraints. This study appears in the context of improving the quality of operation of laboratories at various sites, including those of greatest interest such as tests carried out and respective standards / specifications followed, management of staff and users, and accreditation services and price variation testing laboratories. 3
In this connection there is also the need for a document to summarize all tests that can be performed in concrete and their respective methods to evaluate its performance characteristics. Therefore, it becomes necessary to perform an extensive study on legal rules along with technical documents, as well as achieving a better understanding of the material object of study and the type of tests that can be performed on concrete.
2. General characteristics of concrete Concrete has been object of much attention by Researchers on its specific properties, so that the increments and developments achieved allow increasingly higher demands on the level of compositional characteristics, manufacturing, transportation, placement and conservation, yielding important advances in terms of consistency, strength and durability. The evolution and outgrowth on quality have been achieved with improvements in the use of binders, careful selection of aggregates and the introduction of adjuvants chemical nature, which clearly improved some properties desired. So currently there are concrete with high strength, impermeability, durability, easily molding and commissioning work.
1 Regulatory Legacy of Concrete In the area of concrete, there is an extensive regulatory legacy around the quality control of concrete and its constituents. The areas of interest to standardization, the underlying type of tests and respective series of European standards / specifications LNEC and Portuguese, are presented in Table 1. In addition to the aforementioned legal rules, there Eurocodes - a set of European standards responsibility (CEN Technical Committee TC 250) that aims to unify criteria and normative calculation and design of structures. In this study, compared to Table 2.1, were only addressed the standards inherent in the specification, performance, production and conformity of concrete (EN 206-1), the characterization and performance of concrete in fresh and hardened state (NP EN 12350; NP EN 12390, EN 12504 NP), and the durability of concrete face of environmental actions (specifications LNEC). Table 1 - Areas of interest to standardization, type of tests and their respective sets of rules and LNEC specifications (LNEC, 2013; ANN, 2013) Areas of interest to the normalization Characterization and performance of the constituents of the concrete Specification, performance, production and conformity of concrete Fresh concrete composition
Type of test Testing aggregates Testing cement Testing additions Testing adjuvants Testing water -
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Series of European standards / specifications and Portuguese LNEC - (1) NP EN 206-1:2007 Amendment 1:2008 Amendment 2:2010 NP 1385:2010
Times caught fresh concrete Characterization and performance of concrete in fresh and hardened state Execution of concrete structures Review of the compressive strength of the concrete structures and pre manufactured products Characterization and performance of fibers in concrete Characteristics and performance of fibers inconcrete
Characteristics and performance of concrete face to environmental actions
NP 1387:2010 Testing fresh concrete Testing Hardened concrete Testing on concrete structures
NP EN 12350:(2009;2010) NP EN12390:(2009;2010;2011)(2) NP EN 12504:2007 (3)
-
NP EN 13670:2011 Amendment 1:2012
-
NP EN 13791:2008
Trials designed to concrete Testing on fiber methods concrete
Testing durability of concrete
NP EN 14487:2008 NP EN 14488:2008 (4) NP EN 14845: 2008 NP EN 14889: 2008 E 383:1993 E 387:1993 to E 413:1993 E 454:1999 E 461:2007 E 463:2004 E 464:2007 E 465:2007 E 475:2007 E 477:2007
(1)
The characterization and performance of the constituents of the concrete have not been studied in the present work.
(2)
NP EN 12390-4 (part 4) about characteristics of machines for testing the compressive strength was issued in 2003.
(3
NP EN 12504-2 (part 2) about determination of rebound number, published in 2003.
(4)
NP EN 14488-4 (part 4), about testing sprayed concrete bond strength of cores by direct tension, published in 2003.
2. Tests on Concrete Tests on concrete are essential to evaluate the consistency, the mechanical strength and durability of the concrete. These tests are related to concrete in fresh and hardened state and durability of concrete and its methodology are specified respectively, standards, specifications LNEC, test procedures and other official documents.
4.1. Tests on fresh concrete The tests on concrete in the fresh state (Table 2) aim to evaluate some important properties for the proper application of the concrete on site, such as consistency, workability, density and air content of fresh concrete (Brito et al., 2009) These tests enable to ensure proper fluidity without separation of the various constituent materials and to evaluate parameters which are premonitory on the quality of the same after hardening concrete (Evangelista, 2003). Table 2 - Testing fresh concrete and their test methods (ANN, 2013; André, 2012; Gomes and Pinto, 2009; ASTM C232).
Test Testing fresh concrete slampling Testing fresh concrete slump-test Testing fresh concrete vebe test Testing fresh concrete degree of compactability Testing fresh concrete flow table test 5
Test methods NP EN 12350-1:2009 NP EN 12350-2:2009 NP EN 12350-3:2009 NP EN 12350-4:2009 NP EN 12350-5:2009
Testing fresh concrete density Testing hardened concrete density of hardened concrete Testing hardened concrete depth of penetration of water under pressure Testing fresh concrete self-compacting concrete. V-funnel test Testing fresh concrete self-compacting concrete. L box test Testing fresh concrete self-compacting concrete. Sieve segregation test Testing fresh concrete self-compacting concrete. J-ring test Standard test method for bleeding of concrete Slip test *
NP EN 12350-6:2009 NP EN 12350-7:2009 NP EN 12350-8:2010 NP EN 12350-9:2010 NP EN 12350-10:2010 NP EN 12350-11:2010 NP EN 12350-12:2010 ASTM C232:2009 Internal precedure
*Test based on internal procedure of the laboratory
4.2 Tests on hardened concrete The tests to perform on the concrete in the hardened state aimed at assessing the behavior that these will have on service conditions, i.e., when they are to perform the functions for which they were designed (Evangelista, 2003). Taking into account the general properties required for concrete, tests on hardened concrete are divided into mechanical and physical tests. The mechanical and physical tests (Table 3), aim to determine the structural characteristics of the materials used (resistance to compression, tensile and flexural strength, modulus of elasticity, density, thermal expansion and creep and shrinkage) and analyze the structure behavior (Brito et al. 2009). In practice, most of these essays have the main purpose of quality control and verification of the specifications of the concrete. Table 3 - Testing hardened concrete and their test methods (ANN, 2013; Gomes and Pinto, 2009; ASTM C 1383, ASTM C803).
Tests
Test methods
Testing hardened concrete shape, dimensions and other requirements for specimens and moulds
NP EN 12390-3:2003
Testing hardened concrete flexural strength of test specimens
NP EN 12390-5:2003
Testing hardened concrete tensile splitting strength of test specimens
NP EN 12390-6:2011
Abrasion resistance
LNEC E 396:2003
Determination of modulus of elasticity of concrete in compression
LNEC E 397:2003
Testing hardened concrete density of hardened concrete
NP EN 12390-7:2003
Determination of retraction and expansion
LNEC E 398:2003
Determination of coefficient of creep in compression
LNEC E 399:2003
Testing hardened concrete depth of penetration of water under pressure
NP EN 12390-8:2009
Measuring the P-Wave Speed and the Thickness of Concrete Plates Using the Impact-Echo Method
ASTM C 1383:2010
Testing concrete in structures non-destructive testing. Determination of rebound number 6
NP EN 12504-2:2003*
Testing concrete determination of ultrasonic pulse velocity
NP EN 12504-4:2007*
Determination of pull-out force
NP EN 12504-3:2007*
Penetration resistance of hardened concrete
ASTM C 803:2010
* Non-destructive testing of concrete structures
4.3 Testing of durability Concrete is degraded by numerous factors such as reinforcement corrosion induced by carbonation and chlorides; action of freezing / thawing and chemical attack among others, and these may affect more or less the capacity and durability of structures (Antunes, 2010). Durability testing (Table 4) determines the characteristics of the materials and structure that may cause malfunctions in the long term (Brito et al, 2009).
5. Methodology and Case Study In order to get an overall view on testing laboratories modus operandi, it is necessary to conduct a work on-site based on a face survey to several laboratory building materials in order to collect information essential to the investigation. Table 4 - Testing the durability of concrete and their methods (Gomes and Pinto, 2009; ANN, 2013; ASTM C 1202; Ferreira and Jalali, 2001).
Test
Test methods
Accelerated carbonation
LNEC E 391:2003
Cholride difusion – migration test
LNEC E 463:2004
Water absorption by capillarity
LNEC E 393:2003
Water absorption by dipping (atmospheric pressure)
LNEC E 394:2003
Water absorption by dipping (under vacuum)
LNEC E 395:2003
Water permeability surface pressure - GWT method
LNEC E 475:2007
Air permeability test. Method of Torrent
SN 505 262/1:2003
Oxygen permeability test
LNEC E 392:2003
Gas permeability test
(1)
Gas diffusion test
(1)
Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration
ASTM C 1202:2012
Diffusion coefficient of chlorine
(2)
electrical resistivity
(2)
(1)
Internal precedure
(2)
Test procedure based on CTH Rapid Method by Luping.
5.1 Definition of the Universe and the Sample The target population of this study consists on 13 testing laboratories located in the district of Lisbon, Setubal and Oporto. The selection was based on laboratory carefully chosen depending on the type of 7
laboratory (public, private, and public / private), the number of tests on concrete and geographical location. During the field work was visited laboratories belonging to several entities, including consulting firms, manufacturers of cement, concrete producers, universities, military institutions within the state sector reporting to ministries, among others.
6. Analysis of survey results Whereas the study is quantitative, resorted to quantitative methodologies based on statistical tables and graphs in order to be able to analyze the different fields presented in the survey. An overall look shows that 77 % of the visited laboratories are small or medium-sized and 23 % are large with emphasis on those of the remaining volume of essays. Accordingly to the analysis of the survey results, one can see that the traditional concrete is the most tested on laboratories - 84% - following the self-compacting concrete and lightweight concrete with addition of expanded – respectively 70 % and 63 % of the testing laboratories. These concretes have been achieving larger interest in laboratories due to its special characteristics such as self-weight, placement and compaction of the work. For the tests of concrete, it can be seen that the tests of concrete in the fresh state are the most frequently performed in the laboratory, surpassing the 85 % of trials conducted in more than half of the visited laboratories. As to the tests in the hardened concrete, it is noted that the compressive-strength test is performed by all laboratories are certified by more than 60% and is most often referred to as performed by 92 % of the laboratories. This is the most common and frequent test. Durability testing are undertaken by less laboratories, being performed more frequently at university and research laboratories. In relation to validation tests (Picture 1) 71 % of essays in the hardened concrete and 67% of durability tests are performed with accreditation whereas in concrete tests in the fresh state is only 14% . One can conclude that the trials in fresh concrete tests are less believed. With regard to accredited laboratories carrying out tests (Figure 2), 62 % of laboratories perform tests on concrete in the hardened state with accreditation, compared to 23 % and 31% of accredited laboratories carrying out tests in the area and the durability of concrete in the fresh state, respectively. It can be concluded that most of the laboratories give preference to the tests with accreditation with hardened concrete.
8 Figure 1 – Accredited tests for eachtests classfor of each concrete (%) Figure 2 – Laboratories that perform accredited classtest of concrete test (%).
At the level of the regulatory legacy of the tests (Figure 3) we observe that in trials in the hardened concrete and fresh, more than 85% of tests are performed based on European standards. In durability tests, 58% of tests are performed based on specifications LNEC, compared to 42% of which are held by international standards and other test methods (internal procedures and national standards). It can be concluded that European standards have a higher implementation compared to international standards in testing concrete in fresh and hardened state. In durability tests, LNEC specifications, international standards and some testing procedures have had wider application. * Internal procedures and national standards
Figure 3 - Percentage of tests that follow international standards / or other European standards and / or specifications LNEC in each class test on concrete.
As to the training level of the staff in public and private laboratories (Figure 4) more than 80% of technicians have specific training being much higher than the percentage of the technicians with general education. The laboratory public / private displays the same percentage of technicians with both formations. Figure 4 - Percentage of technicians in training function. In terms of services, public laboratories, mainly university students, are geared for teaching and research while private laboratories primarily providing its services to companies related to the construction industry and domestic support company. It’s to underline that concrete plants primarily provide internal support service for companies of its own. In terms of accreditation, 62 % of the laboratories are accredited against 38 % which are not, respectively laboratories related to concrete plants and universities. In terms of marketing tests (Figure 5), it is concluded that 62% of the laboratories trade tests. There is only one university lab test that commercializes tests and no laboratory of concrete plants does. Regarding the change in prices of the tests (Figure 6) , it is observed that 88% of laboratories, the average test less expensive (per sample ) does not exceed € 30 and 63 % of laboratories, the average test more expensive (per sample ) is less than 500 € . It can be concluded that the vast majority of the tests are marketed within the price range between 30 and 500€. It should be noted that testing laboratories considered less costly popular is the compressive strength test specimens.
6. Conclusion and proposals for future developments 9
Figure - Percentage of laboratories to thetesting. fluctuation of trials. Figure 5 - 6Percentage of laboratories thatdue market
Through the statistical analysis on the different laboratories within the testing concrete it can be can concluded that most of the techniques and test procedures are based on standardized European standards and specifications LNEC, which have been replacing the old Portuguese Rules (NP). However there are certain tests which follow the American standards (ASTM) and the laboratory procedures The test results for the fresh and hardened concrete are the most common for most laboratories to effect quality control of concrete. However, the percentage of tests in the hardened concrete with accreditation is higher than the tests in fresh concrete, partly due to the fact that they are no longer commercialized. Durability testing in general is more expensive and with more restricted range (in terms of research or at the request of the designer) being, therefore, less performed. In terms of staff of public and private laboratories, the number of technicians with specific training is far higher to those with general training. One possible reason is the stronger control, accuracy and specificity of the tests and procedures that have been required by current standards. As for the marketing tests, more than a half of the accredited laboratories, trade tests. The test for compressive strength of the specimens is less expensive due to the high demand for this type of test, leading to more competitive prices accordingly to the law of supply and demand. This study can be further deepened in several areas related to testing laboratories. Therefore, we suggest several lines of inquiry that can complement this work : i. Development at study tests the constituents of the concrete; ii. Study of inter - laboratory tests responsible for RELACRE iii. Enlargement of the universe of the sample at the laboratory partnerships and construction companies in order to obtain a wider range of data iv. Flowcharting representing the major tests that can be performed on concrete v. Preparation of records of procedures to support the production of concrete specimens, testing and handling equipment required for testing
References André, J. (2012) - Da Amostragem ao Ensaio de Compressão do Betão. Betão Nº 29, Revista da Associação Portuguesa das Empresas de Betão Pronto. Lisboa: Associação Portuguesa das Empresas de Betão Pronto, pp. 26-28. ANN (2013) - Acervo Normativo Nacional sobre Betão e os seus Constituintes. Betão Nº 30, Revista da Associação Portuguesa das Empresas de Betão Pronto. Lisboa: Associação Portuguesa das Empresas de Betão Pronto. Antunes, E. (2010) – Efeitos estruturais das reações químicas expansivas no betão. Dissertação de Mestrado Integrado em Engenharia Civil: Instituto Superior Técnico, 181p, pp.1-3. ASTM C 1383 - Standard Test Method for Measuring the P-Wave Speed and the Thickness of Concrete Plates Using the Impact-Echo Method. ASTM: American Society for Testing and Materials, 2010. ASTM C 232 - Standard Test Methods for Bleeding of Concrete. ASTM: American Society for Testing and Materials, 2009. ASTM C 803 - Standard Test Method for Penetration Resistance of Hardened Concrete. ASTM: American Society for Testing and Materials, 2010.
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Brito, J. et al (2009) – Técnicas de Inspeção de Estruturas de Betão Armado. Slides da cadeira de Patologia e Reabilitação da Construção. Mestrado Integrado em Engenharia Civil: Instituto Superior Técnico, 29p. Evangelista, F. (2003) – Betões Executados com Agregados Finos Reciclados de Betão. Dissertação de Mestrado Integrado em Engenharia Civil: Instituto Superior Técnico, pp. 77-80. Ferreira, R. e Jalali, S. (2001) – Avaliação dos ensaios correntes para a medição da durabilidade do betão. Artigo de investigação do Departamento de Engenharia Civil, Campus de Azurém. Guimarães: Universidade do Minho, pp. 41-54. Gomes, A. e Pinto, A.P. (2009) – Módulos – Ensaios de Betão. Slides das Aulas Teóricas de Materiais de Construção II, Mestrado Integrado em Engenharia Civil: Instituto Superior Técnico, 18 p. LNEC (2013) –Especificações LE 17 - 3/2013. Especificações do LNEC. Lisboa: Laboratório Nacional de Engenharia Civil. Pimentel, J. (2007) – Betões Compactáveis – Resistência e durabilidade. Dissertação de Mestrado Integrado em Engenharia Civil. Lisboa: Instituto Superior Técnico, pp. 10-13.
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