Keywords: aggregates, European Standards, construction materials, TEE.

Transcript

1 Crushed limestone aggregates for concrete and masonry: Results from tests according to EN 12640, EN 13043, EN 13242, and EN standards. Dimitris Xirouchakis, Alexis Theodoropoulos Keywords: aggregates, European Standards, construction materials, TEE. ΠΕΡΙΛΗΨΗ: Τα θραυστά ασβεστολιθικά αδρανή αποτελούν την κύρια πηγή αδρανών για την βιοµηχανία παραγωγής σκυροδέµατος, κονιαµάτων, ασφαλτικών µιγµάτων και αδρανών οδοποιίας στην Ελλάδα. Ιστορικά, οι δοκιµές ελέγχου των αδρανών και οι εθνικές προδιαγραφές βασίστηκαν σε διεθνή πρότυπα, π.χ., ASTM International & AASHTO. Το πλαίσιο ελέγχου και πιστοποίησης της παραγωγής αδρανών στην Ελλάδα όπως και στην υπόλοιπη ΕΕ έχει αλλάξει µε την ενεργοποίηση των Ευρωπαϊκών Προτύπων. Στα πλαίσια ελέγχων και πιστοποιήσεων λατοµείων του Ελληνικού χώρου συνεχίζουµε την συλλογή και αξιολόγηση των γεωµετρικών, φυσικών, χηµικών και µηχανικών χαρακτηριστικών θραυστών ασβεστολιθικών αδρανών από διάφορα λατοµεία της ηπειρωτικής και νησιωτικής χώρας εκτός Ιονίων νήσων. Εδώ παρουσιάζουµε τα αποτελέσµατα των δοκιµών αρχικού τύπου για τον έλεγχο της παραγωγής αδρανών σκυροδέµατος και κονιαµάτων. Οι δοκιµές αφορούν υλικά µε τις κοινές εµπορικές ονοµασίες: 1) χαλίκι 2) ψηφίδα / γαρµπίλι και 3) άµµος. Εκτός µερικών (π.χ., αλκαλοπυριτική αντίδραση, χηµικοί προσδιορισµοί), οι δοκιµές εκτελέστηκαν σύµφωνα µε τα πρότυπα που αναφέρονται στα στα ΕΝ 12620:2002, EN 13043:2002/AC:2004, EN 13242:2002/AC:2004 και EN 13139:2002 και τα αποτελέσµατα συνοψίζονται παρακάτω. ABSTRACT: Crushed limestone aggregates are the main source of aggregates in the Greek Construction industry. Historically, testing followed the ASTM International and AASHTO standard test methods. In light of the changes across EU concerning the implementation of EN standard test methods as well as the legal and technical framework for construction products bearing the CE mark, we have been testing, collecting, and evaluating limestone aggregate testing data from quarries across Greece. Here we present an initial assessment of a small data set and the correlations observed. 1 Geologist, MSc., PhD, GeoTerra Ltd, Geomechanics & Quality Control Laboratory, 12 Anthrakorichon Street, Nea Ionia, dxirouch@gmail.com 2 Mining Metallurgical Engineer, MSc., A. Theodoropoulos P. Moskofoglou Partners. Q4U Consulting Engineers, 14 Patission Street 14, Athens, a.theodoropoulos@q4u.gr 1

2 INTRODUCTION We present the results from initial type testing of limestone aggregates according to EN standard methods which are referenced in EN 12640, EN 13043, EN 13242, and EN standards. Specifically, we have looked at the chemical, physical, and mechanical properties that are of interest to the construction materials industry. Our goal is to contribute towards a critically assessed data base of limestone aggregates properties as established with these methods in light of their widespread usage in Greece, particularly, and elsewhere in general. We used limestone aggregate samples from quarries located in the main land and the islands. The samples primarily represent deep and shallow sea Mesozoic limestones (Eldridge and Fairbridge 1997) with samples from central Greece and the islands exhibiting variable degrees of re-crystallization. Testing was mainly performed in two ISO accredited testing laboratories located in Athens. The results represent a self-consistent data set whereas data accuracy is secured through the interlaboratory testing programs of the respective laboratories. Chemistry DISCUSSION Chemically the samples cover the range from low quality (CaCO 3 is 85,0 93,5%) to highly pure limestones (CaCO 3 >98,5%) (Table 1). Preliminary powder XRD data indicate that they contain calcite (95,7 99,5%), dolomite (0,8 3,3%), and <1% iron oxides, iron sulfides, quartz and phyllosilicate minerals. Heavy metals (Table 2) were either not detected or detected at levels that are typical of marine carbonates globally (Turekian and Wedepohl, 1961). Alkali-Silica reactivity analyses show that reaction between alkalis and silica of limestone aggregates and cement in concrete this should not be a problem with the type of aggregates examined here (Table 3); all alkalinity and silica concentration analyses plot on the field of harmless aggregates (ASTM C 289, fig. 1). However, we do lack data in Greece to judge the reaction potential for alkalis and carbonate minerals in concrete. Furthermore, polyaromatic hydrocarbons were not detected and the radioactive decay measurements of isotopes such Ra 226, Ra 228, Th 228, Th 232, U 238 and K 40 are at innocuous levels (EU Council Directive 96/29/EURATOM 31/5/1996). Geometrical, physical, and mechanical properties Sand sieve analyses (Fig. 1) show that the all grains pass through the 8 mm sieve with D max between 4 and 8 mm, and exhibit a fairly wide range of values in between the 8 mm 2

3 and 63 µm sieves. Sand fines content is between 7 and 20%. The crushed limestone sands examined are devoid of organic substances such as humus and fulvic acid, moreover, their lightweight contaminants and water soluble components are negligible. The quality of fines (MB, SE), angularity (E cs ), durability (MS), and water absorption (WA 24 ) behavior is deemed more than satisfactory (Table 4). Mean apparent dry density values for sand as well as for fine and coarse gravel confirm the mineralogy data as they are much closer to that of pure calcite (CaCO 3 ) 2,71 g/cm 3 and much less to that of dolomite (CaMg(CO 3 ) 2 ) 2,85 g/cm 3 or any of the other carbonate minerals, i.e., siderite (FeCO 3 ) 3,87 g/cm 3, magnesite (MgCO 3 ) 3,0 g/cm 3, ankerite (CaFe(CO 3 ) 2 ) 3,2 g/cm 3. We take fine gravel to mean aggregates with D max equal to 12,5 with a range between 12,5 and 16, mm, and coarse gravel aggregates with D max equal to 31,5 (Fig. 1, 3, and 4). Other than that the physical and mechanical properties values of the two fractions are unsurprisingly close (Table 6 and 8) as these properties strongly depend on mineralogy and rock texture. For the interested reader, we note that ASTM and EN Los Angeles tests on the same material differ by two units with the ASTM LA value lower than the EN LA value. Correlations Meaningful correlations among physical and mechanical properties of sand arise in a few cases (Table 5). There is a positive correlation between MB and E cs values that may suggest that clay-size material or clays may inhibit flow of sand grains. The correlation between ρ α and E cs was anticipated since the E cs calculation is based on density. A close relationship between MB and SE did not materialize in these types of aggregates as they are generally devoid of clay-size or clay materials. However, if we include in the data set MB and SE values from all-in aggregates which are used in road pavement construction then the correlation becomes stronger as the data cover a greater range of values (Fig. 2). For fine and coarse gravel, significant (i.e. correlation coefficient > 0,5 ) and common in both aggregate types correlations are observed between the following pairs of tests: MS and V LA, MD E and LA, FI and SI (Table 7 and 9). The correlation between MS and V LA is surprising and needs further investigation as we have not seen it in the literature. Nonetheless, the strong relationships between these three pairs of tests suggest that it may be advantageous to use them as discriminant constraints of aggregate quality (Fig. 5, 6, and 7); aggregates falling in the lower right quadrangle should have a better overall behavior overtime. We do not find for limestone aggregates a statistically significant relationship between either water absorption or silica content and wet Micro-Deval test results as seen in Brennan et al. (2003) for igneous aggregates. In contrast, the data agree 3

4 with the Pétursson s conclusions (2000) regarding the strong correlation between FI and SI values in Icelandic, presumably, basaltic aggregates. REFERENCES ASTM C289, Standard Test Method for Potential Alkali-Silica Reactivity of Aggregates (Chemical Method), ASTM International, West Conshohocken, PA, (2007). Brennan, M.J., Crawley, K., Sheahan, J.N., and Jordan, J., Ranking the performance of aggregates using CEN test results, Road Materials and Pavement Design, Vol. 4, No4, , (2003). Moores, E.M., Fairbridge, R.W., Encyclopedia of European and Asian regional geology, Springer, (1997). European Aggregates Association Annual Report, (2007) EN 12620, Aggregates for concrete, (2008). EN 13043, Aggregates for bituminous mixtures and surface treatments for roads, airfields and other trafficked areas, (2002). EN 13139, Aggregates for mortar, (2002). EN 13242, Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction, (2008). Harrison, D.J., Industrial Minerals: Limestone, British Geological Survey Technical Report WG/92/29, (1993). Lorenz, W. and Gwosdz, W., Manual of the Geotechnical Assessment of Mineral Construction Material, Geologisches Jahrbuch Sonderhefte, Reihe H, Heft SH 15, Hannover, (2003). Pétursson Pétur, Testing of the aggregate bank with two CEN methods, MDE and FI, Public Roads Administration, Report E-38, Reykjavic, (2000). Turekian, K.K. and Wedepohl, K.H., Distribution of the Elements in some major units of the Earth's crust, Geological Society of America, Bulletin 72: , (1961). US Geological Survey Minerals Yearbook, (2007). 4

5 Table 1. Major and minor oxides Parameter Unit N µ S min max SO -2 4 (water-soluble) 2 nd Cl - 5 0,001 0,001 0,000 0,002 SO -2 3 (acid-soluble) 2 nd PbO 7 0,001 0,000 0,001 0,001 ZnO 11 0,001 0,002 0,000 0,010 P 2 O ,073 0,112 0,030 0,295 FeO 5 nd Fe 2 O ,074 0,056 0,01 0,28 Na 2 O 16 0,040 0,005 0,03 0,05 K 2 O 15 0,008 0,006 0,00 0,02 SiO ,220 0,792 0,22 6,03 Al 2 O ,080 0,064 0,02 0,19 MgO 16 0,657 0,633 0,15 2,66 CaO 16 54,0 1,4 50,9 55,4 CO ,9 0,9 40,5 43,6 H 2 O 16 0,12 0,03 0,07 0,19 Moisture 16 0,75 1,60 0,07 5,31 Sum 99,9 99,2 100,9 Table 1 (continued). Major and minor oxides Parameter Unit N µ S min max Loss on ignition % 16 43,2 1,2 41,4 46,9 CaCO 3 % CaO in CaCO 3 % Να 2 Ο eq % 16 96,1 2,3 90,8 99, ,7 1,4 95,4 100,1 16 0,05 0,01 0,03 0,06 Symbols: (n) number of measurements, (µ) average, (s) standard deviation, (min) minimum value, (max) maximum value, (nd) not detected. 5

6 Table 2. Heavy metals concentration Parameter Unit n µ s min max Co mg/kg 16 0,4 1,2 nd 3,8 Ni mg/kg 14 9,1 13,3 nd 33,5 Cr mg/kg 14 8,4 5,6 nd 22,0 Cd mg/kg 14 0,0 0,2 nd 0,6 Pb mg/kg 14 1,1 2,3 nd 5,8 Sb mg/kg 14 0,1 0,2 nd 0,8 As mg/kg 14 0,4 0,4 nd 1,1 Hg mg/kg 14 0,0 0,0 nd nd Table 3. Alkali-Silica reactivity data Parameter unit n µ s min max S c mmol/l 16 19,0 41,7 0,3 132,0 R c mmol/l ,4 31,2 16,0 1040,0 Silica concentration (S c ). Alkalinity (R c ). Figure 1. Range (solid lines) and mean (heavy solid line) of sand sieve analyses. 6

7 Table 4. Sand physical and mechanical characteristics Parameter Unit N µ s min max Methylene blue MB g/kg 18 0,5 0,3 0,2 1,2 Sand equivalent SE % Flow coefficient E cs Sec ,697 0,054 2,522 2,743 Apparent dry density ρ α Mg/m Water absorption (24 h) WA 24 % Mg 2 SO 4 test MS % Lightweight contaminators LPC % Water-soluble constituents WS % 18 0,9 0,1 0,5 1,1 17 3,4 2,1 0,2 7,4 16 0,210 0,524 0,000 1, ,084 0,154 0,000 0, ,603 0,101 1,372 1,754 Dry bulk density (loose) ρ b Mg/m Table 5. Correlation coefficient matrix for sand properties MB SE E cs ρ α WA 24 MS LPC WS ρ b MB 1,00 SE -0,23 1,00 E cs 0,86-0,10 1,00 ρ α -0,61 0,19-0,78 1,00 WA 24-0,07-0,27 0,15-0,21 1,00 MS 0,40-0,24 0,39-0,25 0,20 1,00 LPC 0,34 0,06 0,49-0,36-0,23 0,03 1,00 WS -0,13-0,23-0,16 0,12-0,42 0,33-0,11 1,00 ρ b -0,01 0,08 0,28-0,36 0,28 0,20-0,30 0,32 1,00 7

8 Figure 2. Sand Equivalent (SE) and Methylene Blue (MB) relationship among sand from crushed limestone aggregates for use in concrete and road base construction. The heavy solid line is a simple linear fit to the data with solid lines on either side marking the 95% confidence limits of the prediction ability of the equation for this type of aggregates only. Figure 3. Range (solid lines) and mean (heavy solid line) of fine gravel sieve analyses. 8

9 Table 6. Fine gravel physical and mechanical properties Parameter unit n µ s min max Apparent dry density Water absorption (24 h) WA 24 % Mg 2 SO 4 test MS % Resistance to fragmentation LA % Resistance to wear (wet) MD E % Shape Index SI % Flakiness Index FI % Resistance to thermal shock ,704 0,022 2,643 2,746 ρ α Mg/m V LA 18 0,5 0,1 0,3 0,8 17 2,9 2,0 0,4 7, ,3 4,4 21,0 42, ,5 6,9 8,5 32, ,5 7,8 5,1 29, ,6 5,8 7,7 24,2 16 2,3 1,4 1,0 4, ,393 0,056 1,328 1,505 Dry bulk density (loose) ρ b Mg/m Table 7. Correlation coefficient matrix for fine gravel properties ρ α WA 24 MS LA MD E SI FI V LA ρ b ρ α 1,00 WA 24 0,37 1,00 MS -0,14-0,13 1,00 LA -0,22-0,13 0,06 1,00 MD E 0,16-0,17-0,03 0,59 1,00 SI -0,01-0,20-0,43 0,18 0,19 1,00 FI 0,23 0,12-0,15 0,08-0,10 0,62 1,00 V LA 0,00 0,07 0,95-0,18-0,16-0,55-0,12 1,00 ρ b -0,42 0,64 0,64 0,23-0,26-0,53-0,11 0,52 1,00 9

10 Figure 4. Range (solid lines) and mean (heavy solid line) of coarse gravel sieve analyses. Table 8. Coarse gravel physical and mechanical properties Parameter unit n µ s min max Apparent dry density ,698 0,025 2,611 2,727 ρ α Mg/m Water absorption (24 h) WA 24 % Mg 2 SO 4 test MS % Resistance to fragmentation LA % Resistance to wear (wet) MD E % Shape Index SI % Flakiness Index FI % 18 0,4 0,1 0,3 0,6 17 2,8 2,2 0,1 7, ,6 5,3 17,0 42, ,9 7,3 9,9 32, ,4 5,7 6,0 22, ,1 4,8 4,8 23,6 Resistance to thermal shock V LA 15 1,9 1,4 0,2 4, ,378 0,050 1,281 1,466 Dry bulk density (loose) ρ b Mg/m 10

11 Table 9. Correlation coefficient matrix for coarse gravel properties ρ α WA 24 MS LA MD E SI FI V LA ρ b ρ α 1,00 WA 24-0,21 1,00 MS -0,31 0,04 1,00 LA 0,02 0,37 0,27 1,00 MD E 0,22 0,17 0,07 0,56 1,00 SI 0,54-0,44-0,24 0,15 0,36 1,00 FI -0,03-0,30 0,14 0,10 0,09 0,65 1,00 V LA -0,11-0,30 0,76-0,12-0,34-0,26 0,25 1,00 ρ b -0,33-0,20 0,47 0,13-0,16-0,32-0,15 0,53 1,00 Figure 5. Resistance to fragmentation vs. Resistance to wear values. Heavy solid lines represent the respective means. 11

12 Figure 6. Flakiness index vs. Shape index. Heavy solid lines represent the respective means. Figure 7. Magnesium sulfate vs. Thermal Shock Resistance values. Heavy solid lines represent the respective means. 12