The Effect of Recycled Aggregates on Creep Behavior of Structural Concrete: Gaza Strip a Case Study

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1 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (2): Scholarlink Research Institute Journals, 2011 (ISSN: ) jeteas.scholarlinkresearch.org Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (2): (ISSN: ) The Effect of Recycled s on Creep Behavior of Structural Concrete: Gaza Strip a Case Study 1 Y.S.Ghuraiz; 2 M. H. Swellam; 3 G. L. K. Garas; 2 A. M. Ragab 1 Ph.D student, Engineering Professions Dept, University College of Applied Sciences, 2 Faculty of Engineering, Cairo University 3 Civil Engineering Department, National Research Center. Egypt.Corresponding Author: G. L. K. Garas Abstract The huge amounts of demolition debris (DD) in Gaza Strip cause environmental, social and economical problems. The socio-economic development in Gaza Strip is also threatened by the depletion of natural aggregates. Such conditions necessitate the use of demolition debris waste (DDW) as aggregates in new concrete mixes. Concrete cylindrical specimens of 250 kg/cm 2 characteristic strength made of DD were tested to determine the creep behavior of that concrete. The main variables were the type and percent of replacement of demolition debris aggregates in its saturated surface dry conditions. The study concluded that concrete with natural sand and RA 1 (recycled coarse aggregate from crushed concrete fragments only) provided 32.8% higher creep strain than that of natural aggregate concrete while concrete with recycled fine aggregate and RA 1 provided 79% higher strain than that of natural aggregate concrete. In addition, concrete with recycled fine aggregates and RA 2 (recycled coarse aggregate from all crushed demolition fragments) provided 118% higher creep strain compared to natural aggregate concrete Keywords: recycled aggregates, natural aggregate, demolition waste, structural concrete, creep behavior I TRODUCTIO The conservation of natural resources has become a top priority in all production sectors that target maximizing production and profit (Martinez- Echevarria et al., 2008). The construction industry, faced with this challenge, promotes environmental management where proper methods to protect the environment are adopted (Vivian, 2006). Hence, considerable effort is being put into recycling demolition waste, turning it into re-usable products. (Sumeda, 2006). In developing countries more uses have been found for recycled construction and demolition waste. Investigating volumetric changes of concrete with recycled aggregates is an important issue to encourage sustainable and durable concrete with recycled aggregates (Leonardo, 2006 and Angulo et al., 2009). The creep of concrete is an important property to be investigated for recycled aggregate structural concrete. Some studies (Rao et al., 2007) and (Ajdukiewicz and Kliszczewicz, 2002) concluded that the test results for creep in normal laboratory conditions are not so clear and that the creep of recycled aggregate concrete had lower values than that of conventional concrete. This result contradicted (Poon and Chan, 2007) findings, which concluded that the creep of recycled aggregate concrete tested at one year was higher than that of the corresponding natural concrete. This study aims to investigate the effect of using recycled aggregate from DD on the creep behavior of structural concrete. Various concrete mixes with different types and proportions of recycled aggregate are tested simultaneously, in the same conditions. Natural aggregate concrete of almost the same characteristic strength is used as a base for comparison. CHARACTERISTICS OF USED MATERIALS The physical and chemical properties of concrete ingredients namely aggregate and cement are shown in tables (1-5). Testing of these materials was carried out according to the American Standard of Testing Materials (ASTM). Concrete mixes were designed to develop a characteristic compressive strength of 250 kg/cm 2. All tables and figures in this research present data undertaken from experimental work conducted at the Materials Testing Laboratory of Engineering Syndicate at Gaza Strip as well as at the Building Materials Laboratory, Faculty of Engineering - Cairo University. The coarse aggregate used in this research was natural aggregate (for comparison) as well as recycled aggregate, which was crushed concrete debris (RA 1 ) and crushed demolition debris RA 2 (a mix of concrete, bricks, tiles.etc). The natural coarse aggregate used in this study was crushed limestone. Three sizes are available in Gaza Strip and known as Folia (max. size 1"), (maximum size 5/8") and Semsemia (max. size 3/8"). The physical properties of these aggregates are shown in 308

2 table (1), where Saturated Surface Dry (SSD) as well as dry properties are depicted. Table (1): Physical properties of Natural Coarse Type Folia (25 mm) (19mm) Semsemia (9.5mm) Mix *Gs: Specific Gravity Also, the physical properties of recycled coarse aggregates are shown in table (2). Table (2): Physical Properties of Recycled Coarse Type RA 1 RA 2 Dry unit weight ɣ dry (kg /m 3 ) SSD unit weight (ɣ SSD) (kg/m 3 ) Dry Specific Gravity (Gs) *Gs (SSD) Absorption (%) % Unit Weight (kg /m 3 ) (Gs) Absorption (%) Finer than #200 sieve (%) Semsemia Semsemia 2.48 Table (3) summarizes the physical properties of the used natural sand and recycled fine aggregate while table (5) shows the sieve analysis results for the different used aggregates as well as the aggregate mix which was composed of 40%, 30% Semsemia and 30% fine aggregate. Table (3): Physical Properties of Natural Sand and Fine Recycled s Property Determined dry unit weight atural sand Crushing Value(%) Fine recycled aggregates 1666 (kg/m 3 ) kg/m 3 Moisture content 0.5% 1.75% Absorption 0.6% 7.9% Bulk (Gs) Fineness modulus 1.543% 2.01% % passing sieve 0.6 mm 98.5% 91.7% The grading curve for aggregate mix was developed through trials to get a well-graded mix of aggregates as shown in figure (1). Figure (1): Grading of Recycled in Concrete Mix Design Cement The used cement in this study was the Ordinary Portland Cement (Cem I, R,42.5), which was stored in dry place. The physical and mechanical properties of the used cement are presented in table (4) with their limits according to (ASTM C150, 2004). CO CRETE MIX DESIG The absolute volume method is used in this study to determine the concrete mix ingredient proportions according to ACI Many mixes with characteristic strength about 250 kg/cm 2 were designed and examined to give a slump that ranged between 70 mm and 80 mm. Table (4): Typical Properties of the Used Ordinary Portland Cement Property ormal Consistency Setting Time (min.) Initial Soundness(mm) Compressive Strength ( /mm 2 )- 3days Compressive Strength ( /mm 2 )- 7days Standard (ASTM C187 98) (ASTM C191 04) (Vicat test) (BS 4550 Part 3) Standard Limits 24-33% 27% >45 95 Final < (ASTM C109-02) < > > Test Results The used aggregate was in SSD condition. The proportions used in preparing the various mixes are shown in table (6). 309

3 Table (5): Grading for the Different Used s Sieve o. Sieve Opening Size (mm atural Aggregat e % Passing Type (1) (RA 1) Type (2) (RA 2) atural sand Recycled Fine Job Mix Semsem ia Semsemia 1 1/2" " /4" /2" /8" # # # # # # pan Table (6): The Quantities of Materials Required For Various Mixes Mix Type Type 1 Type 2 Type 3 Type 4 Materials Cement Natural agg.(3/4") Natural agg.(1/2") Natural Sand RA 1 (3/4") RA 1 (1/2") RA 2 (3/4") RA 2 (1/2") Fine recycled agg Water RA 1 : Recycled from crushed concrete. RA 2 : Recycled from all crushed demolition fragments. seven days. Three cylinders from each type were used to determine the compressive strength before starting the test and the fourth specimen of each type was used in the creep test. Apparatus The apparatus used in creep test is a compression creep frame consists of two parts, one for applying load and the other for measuring deformation. The first part is a frame with head and base between which the concrete cylinders are placed over each other. A loading jack is placed over the head and is used for applying load. The other part is a mechanical compress-meter with an accuracy of mm. Various parts of the apparatus used in creep test are shown in figures (2) and (3). MIXI G PROCEDURES All batches were mixed in a vertical axis revolvingdrum mixer of capacity about 0.1m 3. The mixing operation of concrete was accomplished for all samples according to (ASTM C192, 2004). EXPERIME TAL PROCEDURES The creep test was conducted according to (ASTM C , 2004). This test was used to compare creep potentials of the different four types of concrete in this study. Test specimens Four standard cylinders were cast for each type of mixes. The specimens were removed from the molds after 24 hours approximately and stored in water basin in the laboratory condition until the age of Figure (2): Compress-Meter Device For Strain Measuring 310

4 Figure (3): Creep of Concrete Apparatus Procedure At the age of 28 days, one specimen from each mix was placed in the frame and four compress meters were attached to the middle of cylinders (one for each cylinder) as shown in figure (3). The specimens were loaded at an intensity of not more than 40% of the compressive strength at the age of loading, so the applied load was 14 ton. Strain readings were taken immediately before and after loading, 2 to 6 hrs later, and then daily for one week. Weekly readings were recorded until the end of one month and monthly until the end of one year. The load was measured before taking each strain reading and it was adjusted in case the load varied more than 2% from the correct value. RESULTS A D A ALYSIS Creep test was conducted on four mixes to figure out the effect of different recycled aggregates on the creep behavior of the resulting concrete. The instantaneous strain results - at the instant of loading - of the four tested mixes are shown in table (7) which shows also the corresponding compressive strength and absorption percent for each type. Table (7): The Instantaneous Strains, Compressive Strength and Absorption of Loaded Specimens Equivalent Absorption cube (%) Mix Instantaneous compressive type strain strength (kg/cm 2 ) It should be noticed from the table that the instantaneous strains differ from one type to another. This is attributed to the difference in modulus of elasticity and compressive strength of the various mixes. The concrete mix of natural aggregates (mix 1) had the highest compressive strength and the least instantaneous strain, while mix 4 possessed the least strength and the highest strain. Figure (4) shows the recorded total strains for the four tested types for 360 days after the age of loading. One can observe that the total strain for the first mix after 360 days was , while the instantaneous strain was Hence, the creep strain for this mix was after one year (difference between the total strain at 360 day and the instantaneous strain). Similarly, the creep strain for mixes 2, 3 and 4 were , and respectively. The recorded strains show that at the end of the first month, the percentages of creep strain for mixes 1, 2, 3 and 4 were 25.8%, 40.6%, 40.3% and 51.7% of its yearly corresponding value respectively. In addition, at the end of six months all types recorded creep strain more than 90% of its yearly value. Figure (4): Total Strain of Loaded Specimens for 360 Days Mix 1 with natural aggregates provided the lowest creep strain due to its highest relative compressive strength and subsequently highest modulus of elasticity as well as its highest density, its lowest absorption that may infer least permeability, (Mindess et al., 2003). On the other hand, mix 4 provided the least strength and highest creep strain. The effect of the type of coarse aggregate on creep strain can be deduced from the comparison of the creep strain for mixes 1 and 2, where the creep strain of mix 2 exceeds that of mix 1 by about 32.8%. This substantial difference is attributed to the replacement of natural coarse aggregate with recycled coarse aggregate in mix 2. It is also noticed that the creep strain of mix 3 exceeds that of mix 1 by about 79%. This great variation is attributed to the replacement of 311

5 both natural coarse aggregate and natural sand with recycled coarse and recycled fine aggregate in mix 3. Comparing mix 3 to mix 2, the creep strain of mix 3 exceeds that of mix 2 by about 34.8%. This significant difference is attributed to the replacement of natural sand with recycled fine aggregate in mix 3. Also, the effect of the type of recycled aggregate (RA 1 or RA 2 ) can be deduced through the comparison between the creep strain of mix 3 and 4, where the creep strain of mix 4 exceeds that of mix 3 by about 21.8%. Such difference is attributed to the replacement of RA 1 (Recycled from crushed concrete) with RA 2 (Recycled from all crushed demolition fragments) in mix 4. The above observations are attributed to several factors. The first factor is the increase of concrete permeability upon the use of recycled aggregates (see absorption results on tables 1, 2, 3 and 7 ). Hence, outward viscous flow of capillary water, cement gel, water and anhydrate calcium silicate from the resulting concrete is easier and subsequently higher creep strain is observed. Secondly, the use of recycled aggregates has resulted in a lower compressive strength concrete (see table 7) and hence higher creep strains were observed. Thirdly, it should be noted that the applied load was the same for all concrete mixes (due to the availability of one apparatus) and hence, its percentage of the actual compressive strength was higher for concrete with relatively lower grade. This highest percentage has subsequently led to highest creep strains. Also, the creep strain of mix 4 with RA 2 is higher than that of RA 1 concrete while the compressive strength of RA 2 concrete is lower than that of the concrete with RA 1. This may be attributed to the difference in crushing values between RA 2 and RA 1 as well as the larger percentage passing # 200 sieve as indicated in table (2) (Neville, 1983). The above results agree with Poon and Chan (2007) results; where the creep of recycled aggregate concrete was higher than that of natural aggregate concrete. On the other hand, the results obtained in this study contradicted Rao et al., (2007) results as well as Ajdukiewicz and Kliszczewicz (2002). The contradiction may be attributed to the difference in properties of used materials specially the permeability, absorption, crushing value, percent of fine materials as well as the maximum aggregate size of large aggregates which highly affect the compressive strength and subsequently the creep strain as highlighted by (Neville, 1983). CO CLUSIO S 1. The creep strain of structural concrete increases with the use of these recycled aggregates from demolition debris. 2. The increase of creep strain ranged between 32.8% and 118% according to the type of recycled aggregate used in the concrete. 3. Replacing the recycled fine aggregate with natural sand is effective in decreasing the creep strain, where the specimens with natural sand recorded lower creep strain by about 34.8%. 4. The use of debris of concrete (RA 1 ) provided lower creep strain by about 21.8% than that of concrete with demolition debris (RA 2 ). 5. The concrete mix with recycled large aggregates and natural sand provided higher creep strain by about 32.8% when compared to natural aggregate concrete. 6. The concrete mix with RA 1 and recycled fine aggregates provided higher creep strain by about 79% when compared to natural aggregate concrete. 7. The concrete mix with RA 2 and recycled fine aggregates provided higher creep strain by about 118% when compared to natural aggregate concrete. REFERE CES Ajdukiewicz A., and Alina Kliszczewicz(2002). Influence of recycled aggregates on mechanical properties of HS/HPC. Cement & Concrete Composites Angulo S. C., Carrijo P. M., Figueiredo A. D., Chaves A. P. and John V. M. (2009). On the classification of mixed construction and demolition waste aggregate by porosity and its impact on the mechanical performance of concrete. Materials and Structures, DOI /s ASTM C 192/ C 192M-02, (2004). Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory. American Society for Testing and Materials. ASTM C , (2004). Standard Test Method for Creep of Concrete in Compression. American Society for Testing and Materials, Leonardo F. R. Miranda, Silvia M. S. Selmo (2006). CDW recycled aggregates renderings: Part I Analysis of the effect of materials finer than 75 µm on mortar properties. Construction and building materials, 20: Martinez-Echevarria M. J., Rubio M. C. and Menedez A. (2008). The reuse of waste from road resurfacing: cold in-place recycling of bituminous pavement, an environmentally friendly alternative to conventional pavement rehabilitation methods. WIT Transactions on ecology and the environment, Vol. 109, ISSN (on-line), doi: /WM

6 Mindess, S., Young, J.F., and Darwin, D. (2003). Concrete, second edition. Library of Congress Cataloging-in-Publication Data. ISBN Neville, A., M., (1983). Properties of Concrete. Third edition, PITMAN books limited, 128 Long Acre, London WC2E 9AN. ISBN Poon Chi-Sun and Dixon Chan (2007). The use of recycled aggregate in concrete in Hong Kong. Resources, Conservation and Recycling 50: Rao Akash, Kumar N. Jha and Sudhir Misra (2007). Use of aggregates from recycled construction and demolition waste in concrete. Resources, Conservation and Recycling, Volume 50, Issue 1, Sumeda Paranavithana and Abbas Mohajerani (2006). Effects of recycled concrete aggregates on properties of asphalt concrete. Resources, Conservation and Recycling, Volume 48, Issue 1, Pages Vivian W.Y. Tam and C.M. Tam (2006). Evaluations of existing waste recycling methods: A Hong Kong study. Building and Environment, Volume 41, Issue