A Study of The mechanical properties of cement mortar with nano- Al2O3 particles

Transcription

1 A Study of The mechanical properties of cement mortar with nano- Al2O3 particles Mahmoud Foroutan Naddafi Department of Engineering, Payame Noor University, Tehran, Iran Abstract: In this paper, the tensile strength and flexural strength with Replacement of concrete setting time of cement with nano-phase Al2O3 particles has been studied. Al2O3 nano particles that With an average diameter of 15nm with four different values of5.1% and.5%,5.5%, 5.1% by weight is used. Result showed that The use of nano-al2o3 particles to the replacement Maximum level of /2, due to improved tensile strength concrete It is. However, the ultimate strength of concrete at, /1 of Cement replacement is obtained. New concrete flexural With the increase of the Al2O3 nanoparticles increased. Setting time of fresh concrete by increasing the percentage of Al2O3 nanoparticles Declined. nfinally, results indicate that the replacement of cement Phase nano-al2o3 particles and improve the tensile strength and Concrete strength but have a hard time getting it reduced. Keywords: Nano-phase particles of Al2O3, Cement, Tensile Strength, The bending strength. Introduction: There are several reports on incorporation of nanoparticles in cement concrete. ( hui et al, 23) To explore the properties of cement mortar mixed with nanoparticles Super mechanical and smart) to measure temperature and pressure (potential Results [1]. Also useful applications of nano-sio2) silica of (Fuji Research Institute). Yet so far, Research has been done over the years, mainly with the aim of To achieve high mechanical performance with cement replacement materials At the micro level. Recently, the effect of adding SiO2 micro-particles of ash of Rice hulls concrete mix by Naji Givi et al. researchers Investigation showed that the size SiO2 particles at the micron level, increase the tensile strength. But There is lack of knowledge of the effect of particle size a super fine nano on concrete properties [2]. Lee and Yang study strength of 8 MPa on compressed samples [3] and Richard develop concrete responses- Made from 2-8 MPa to 4 KJ m [4]. Development of concrete which is made with high-strength May Using DSP system containing ultrafine particles homogeneously dense Arranged with super plasticizer and silica content [5]. Definition of Concrete with High Performance HPC high-strength and concrete with HSC from time to time are subject to change. by late 196, 35MPa and 42 MPa considered as HSC while in midyear MPa of concrete was considered as HSC. May to end of this year 15 MPa consider as HSC. HPC and HSC production challenge and to great many factors It depends. Also in the past 15 years, ultra-high performance concrete with High application be a prime proc duct of Industrial and construction such as tensile strength15-2 M Pa, tensile strength of 8-15 M Pa, with remained Cracking and fracture energy significant [ 7, 8]. In this work, the impact strength and tensile strength of nano-al2o3 Setting time of concrete mixtures were investigated with a binary. Except Aluminum with calcium hydroxide produced by the hydration of Calcium silicate reacts.pozzolanic reaction rate is proportional to the amount of surface area available for Reaction. Therefore, the possibility of adding high-purity nano-al2o3 with purity 99% and Large quantities of small grains to improve the specificity [5]. This study tries to prove HPC or HSC it is possible increase Costs. 2.Materials and Methods: 2-1 substances and mixtures : 2-1-1Cement : 43

2 Ordinary Portland cement OPC obtained from Holcim made of Malaysian Construction comply with the standard ASTM C15 was used. Physical and chemical properties of Cement are shown in Table 1. Table 1: Physical and chemical properties of Cement are shown materials SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO cement 21 / 89 5 / 3 3 / / 27 6 / 45 materials SO 3 Na 2 O K 2 O - - cement 3 / 67 / 18 / 98 3 / Nanoparticles of Al2O3: Al2O3 nano particles with average particle size of 15 nm using.properties of nano-al2o3 particles are shown in Table 2. Table (2): Al2O3 nano-particle properties purity )%( density surface to volume ratio Diameter (nm) m2/g) > < ±12 15 ± : Materials: Local natural sand with particles smaller than mm./5and Specific gravity of fineness modulus of 2/25 g/cm and specific weight of 2/58 available And is used as fine aggregate. Basalt stored in the laboratory with a maximum size 15 mm and Specific gravity 2/96 as coarse Was used mixing ratios: Two series of mixtures prepared in the laboratory experiments. C series mixtures were prepared as controls. Mix Control of natural aggregate, cement and water were made. Series N Prepared with different amounts of Al2O3 nano-sized particles The average particle size of15 nm. ready mix cement Replaced with weight of 5/ /1 5/1 2/. Ratio for all mixtures of fibers in/4 was considered [9]. Materials, mixtures containing a combination of crushed basalt and sand Well, the weight of the sand is 3 percent. Fiber content All mixes Mixing ratios are presented in Table 3. Table (3): ratio of Al2O3 nanoparticles blended concrete mix amount(kg/m3) NanoparticlesAl 2 O 3 Determination Sample Nano cement particleal 2 O 3 55 Co)control) 2 / /25 /5 5 /5 544 /5 1 / N2 8 / /25 N3 11 / 539 / 2 / N4 Water in Fiber[ Cements + nano-al2o3, Sand ]to / 4,Sand and seeds kg / m3 492kg and seeds 1148kg 2. 2 Preparation of test samples: Series N mixtures by mixing the sources of seed, granular And powdercement particles and nano Al2O3 (in a concrete drum Lab Mixer is ready. Powder mix series C was just cement. 431

3 They dry for two minutes, three minutes after the Add water. It was found falling from fresh concrete and immediate to verify The flexural strength was tested after mixing. Cylinder with a diameter of 15 mm and a height of 3 mm For the tensile strength and the cube of 2 mm 5 5 Mm edge for bending test in a two-layer density The vibrating table, where each layer is equal to 1 seconds Vibration is applied. Template with polyethylene sheets and moistened for 24 hours coverage Were given. The samples without the format and at water temperatures c 2 days before the test is given. Tensile strength testing in 7,28 and 9 days. Reported results of concrete samples of three experiments performed. 2.3 nanoparticles draft of Al2O3 mixed concrete: Tensile tests were performed according to standard ASTM C After heating The specified period has expired, cylindrical concrete tensile test Using a universal testing machine was used. Tests were performed on three samples of shredded average values Tensile strength, respectively. 2.4The strength of nanoparticles - Al2O3 mixed concrete: Flexural tests were performed according to ASTM C293 standard. Related Tensile, flexural tests on three samples done and the average flexural strength Values were obtained. 2.5 Setting time Nanoparticles of Al2O3 mixed concrete: Setting time according to the standard ASTM C191 Sample been Set. 3. Experimental results and discussion: splitting tensile strength: Tensile strength results of series C mixtures and N are shown in Table 4 Comparing the results of 7,28,9 Show that the splitting tensile strength of nano-particles of Al2O3 Increases to / 1and then replace and reduced after replacement of N2 Although results from N4 still higher than Plain cement concretec. has been shown that the use of Nano particles 2% / Al2O3 decrease the Tensile strength to a value close to the concrete Control. This may be because the amount of nano-al2o3 Particles pozzolan the mixture is higher than the amount required for Combine with the free lime during hydration process is Thus leading to excess silica leaching and cause defects In strength as it replaces part of the cementitious material [11]. Also, it may be due to defects generated in dispersion Nanoparticles is causing poor regions [12]. Table 4: Share of nano-al2o3 particles tensile strength of Mixcement mortar Transile strenth Sample Nanoparticle determination percental2o3 7days 28days 9days Co /5 2 /2 1 / 3 /1 2 /4 2 /5 2 / 1 /9 [cement + nano / water ratio of 4 Al2O3 fibers ] Higher tensile strength in N series concrete mixtures according to Rapid consumption of calcium, Ca (OH2) that Was formed during the hydration of Portland cement, specially In the early stage due to high reactivity of nano particles of Al2O3 [12]. As a result of the accelerated and larger volumes of cement hydration The reaction products formed. The nano- Al2O3 particles in Recovery particle density mixes, resulting in reduced The larger pore size in the cement paste. However, the tensile strength of the samples is higher and is like nanoparticles. 2.3flexural strength: - 432

4 The flexural strength of a series of mixtures of CO and N in Table 5Given. Similar tensile strength, flexural strength specimens increase with nano-al2o3 increases to /1 replacement of N2 and after it decrease it decreases, although the results /2 replacement of N4 (still higher than plain concrete. Again, the increase in strength is due to the use of Fast Ca Ca (OH2) that formed during cement hydration of Portland especially in the early stages related to the high reactivity Of the Al2O3 nanoparticles. 3.3 Set time: The results of the initial and final setting time, mortar Cement with Al2O3 nanoparticles are shown in Figure 1and 2. Figure 1and 2 shows that with increasing volume fraction of nanoparticles, Set the delay time show that Al2O3 nanoparticles with a Cement hydration reaction was faster than By its effective area, smaller particle size, and surface energy Defined above The smaller particle size allows a rapid increase in the level Led to a rapid increase in the number of surface atoms. The atoms Levels are very active and unstable, resulting in faster Faster response and hence a cautious approach to Setting time of the paste over the use of nano-al2o3 to Be adopted. Table 5: Setting time of the paste over the use of nano-al2o3 to Be adopted. Sample determination Co(control Al2O3 /5 1 / 2 / 7 days 2 /2 2 /4 28 days 2 /5 1 /9 9days 3 /1 Results: The results show that nano-al2o3 particles in concrete mixes stretching mode Higher flexural strength compared to concrete without nano-al2o3 particles This is indicative of better performance replace the cement particles Nano-Al2O3 particles in the range of 2% average size is 15 nm. However, the optimal placement of nanoparticles Al2O3 5% respectively. With However, the tensile strength of concrete using conventional amplifiers Such as needle nano particles my be improved. Sources: Li H, Xiao HG, Yuan J, Ou J. Microstructure of cement mortar with nano-particles. Composites Part B: Engineering 23; 35(March). [2] Naji Givi A, Abdul Rashid S, Aziz FNA, Salleh MAM. Contribution of Rice Husk Ash to the Properties of Mortar and Concrete: A Review. J Am Sci 21; 6(3): [3] Lu P, Young JF. Hot pressed DSP cement paste, Material Research Society Symposium Proceedings, 1992; 245. [4] Richard P, Cheyrezy M. Reactive powder concretes with high ductility and 2-8 MPa tensile strength, San Francisco: ACI Spring Convention, SP , [5] Jo BW, Kim CH, Tae G, Park JB. Characteristics of cement mortar with nano-sio2 particles. Const Build Mater 27; 21(6): [6] Ismail MS, Waliuddint AM. Effect of rice husk ash on high strength concrete. Const Build Mater1996; 1(1): [7] Sun MQ, Liu QP, Li ZQ, Hu YZ. A study of piezoelectric properties of carbon fiber reinforced concrete and plain cement during dynamic loading. Cem Concr Res2; 3: [8] Sorelli L, Constantinides G, Ulm FJ Toutlemonde F. The nano-mechanical signature of Ultra High Performance Concrete by statistical nano indentation techniques. Cem Concr Res 28; 38: [9] Zivica V. Effects of the very low water/cement ratio. Const Build Mater 29; 23(8): [1] Bui DD, Hu J, Stroeven P. Particle size effect on the strength of rice husk ash blended gap-graded Portland cement concrete. Cem Concr Compos 25; 27(3):

5 366. [11] AI-Khalaf MN, Yousift HA. Use of rice husk ash in concrete. Int J Cem Compos Lightweight Concr 1984; 6(4): [12] Kuo WT, Lin KL, Chang WC, Luo HL, Effects of Nano-Materials on Properties of Waterworks Sludge Ash Cement Paste. Journal of Indian Engineering Chemistry 2; 12(5):