EFFECT MANAGEMENT OF ELEVATED TEMPERATURE ON MECHANICAL AND MICROSTRUCTURE PROPERTIES OF REINFORCED CARBON FIBER LIGHTWEIGHT CONCRETE

Transcription

1 INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) International Journal of Civil Engineering and Technology (IJCIET), ISSN (Print), ISSN (Print) ISSN (Online) Volume 5, Issue 11, November (2014), pp IAEME: Journal Impact Factor (2014): (Calculated by GISI) IJCIET IAEME EFFECT MANAGEMENT OF ELEVATED TEMPERATURE ON MECHANICAL AND MICROSTRUCTURE PROPERTIES OF REINFORCED CARBON FIBER LIGHTWEIGHT CONCRETE Dr. Alya a Abbas AL-Attar 1, Dr. AmmarSaleem Khazaal 2, Dr. FirasKhairy Jaber 3 1 (Lecture, Technical College of Kirkuk, Iraq) 2 (Lecture, Dept.of Civil Engineering, TikritUniversity, Iraq) 3 (Lecture, College of Electrical and Electronic Engineering Techniques, Baghdad, Iraq) ABSTRACT This paper studies the effect management of high temperature on mechanical characteristics of carbon fiber reinforced light weight aggregate concrete. The effect of using high range water reducing agent HRWRA (High range water reducing admixture) with 8% SF (silica fume), as a partial replacement by weight of cement, on the behavior of LWAC (Light weight aggregate concrete) is also studied. Workability, fresh and hardened density, compressive strength, splitting tensile strength and modulus of rupture tests were performed, on specimens of both ages 7 and 28 days. The test results indicated that the inclusion of carbon fiber to the light weight concrete mix did not affect the compressive strength significantly, while the splitting tensile strength and the modulus of rupture were improved significantly. The addition of silica fume improves the compressive, splitting tensile, and modulus of rupture strengths of carbon fiber light weight concrete. The average improvement was about (26.5%, 71% and 73 %) respectively for carbon fiber LWAC containing silica fume. Microstructural properties were studied at ambient temperature and after heating. For each test, the specimens were heated at a rate of 1 C /min up to different temperatures (150, 450, 600, and 1000 C). In order to ensure a uniform temperature throughout the specimen, the temperature was held constant at the target temperature for one hour before cooling. In addition, the specimen mass was measured before and after heating in order to determine the loss of water during the test. The results allowed us to analyze the degradation of LWAC due to heating. Between 20 and 150 C, it was associated to an evaporation of free water as well as to an increase in porosity of the tested concretes. Between 150 and 600 C, in a similar way to the observed evolutions between 20 and 150 C, due to the departure of bound water, corresponding to a large mass loss. The improvement in microstructure could be attributed to a modification of the bonding properties of the cement paste hydrates (rehydration of the paste due to the migration of water in the pores). Beyond 165

2 600 C, the microstructure of the tested concretes deteriorated quickly. The specimens subjected to a heating up to 1000 C showed very weak physical properties (appearance of microcracking). Keywords: Light Weight Aggregate Concrete, Management Microstructure, Elevated Temperature. 1- INTRODUCTION The demand for structural lightweight concrete in many applications of modern construction is increasing, owing to the advantage that lower density results in a significant benefit in terms of load-bearing elements of smaller cross sections and a corresponding reduction in the size of the foundation. Structural lightweight concrete has its obvious advantages of high strength/weight ratio, good tensile strain capacity, and low coefficient of thermal expansion due to the voids present in the lightweight aggregates. lightweight concrete has successfully been used for many years for structural members and system in buildings weight, which permits saving in dead loads, and thus reducing the costs of both superstructure and foundation, it is more resistance to fire and provides better heat and sound insulation than concrete of normal density.the lightweight concrete have densities from 1000 to 2000 kg/m 3 and compressive strengths from 1 to 100 Mpa. They can be made light by adding lightweight aggregate such as plasticizers to cement, with fiber reinforcement to decrease their density while keeping their mechanical strength. In view of global sustainable development, it is imperative that supplementary cementing materials be used in place of cement currently used in the concrete industry. The most available supplementary cementing materials worldwide are silica fume (SF), a byproduct of silicon, and fly ash (FA), a byproduct of thermal power stations. As environment pollution become problem, the idea of using the west materials has gained popularity. In literature, the researchers have indicated that addition of SF highly dense the structure of concrete, which could result in an explosive swelling due to a build-up of pore pressure by steam. Since the evaporation of physically absorbed water starts at 80C, which induces thermal cracks, such concretes may show performance inferior to the pure concretes at elevated temperatures. 2- LITERATURE REVIEW Dhir et al.(1), studied the mix design and properties of all lightweight concrete made from Aglite aggregate. Eight mixes were prepared with cement content that varied from (250 to 600) kg/m 3. The water content for all mixes was 300 kg/m 3. Pulverized fuel ash (PFA) was used as a partial replacement by weight of cement. Water reducing admixture also was used in different dosages. They studied compressive strength, tensile strength, drying shrinkage and modulus of elasticity. The concrete containing (PFA) and water reducing admixture are capable to achieve 28 days compressive strength in the range of (25 to 50) MPa with densities between (1525 to 1703) kg/m 3. Al-Haddad (2), investigated the durability of porcelinite lightweight aggregate concrete containing high range water reducing agent and slag against sulfates and chlorides solution. Nine mixes were used with cement content that varied in the range (400 to 600) kg/m 3. The author studied the effect of using high range water reducing agent and high reducing agent with 10% slag as a partial replacement by weight of cement, on the durability of (LWAC). From this investigation he pointed out that it is possible to produce (SLWC) of 28 days compressive strength in the range (21.5 to 37.5) MPa with an air dry density between (1845 to 1965) kg/m 3. A1-Timimy(3), investigated the properties of glass fiber reinforced concrete using metakaolin material with (10, 30 and 50) % as a partial replacement by weight of cement. The micro structural characteristics obtained by the scanning electron microscopy are in agreement with results obtained 166

3 by the x-ray diffraction examination. These tests clearly indicated that the metakaolin concrete specimens have higher proportion of (C-S-H) and less amount of calcium hydroxide compared to concrete mixes without metakaolin. The test results showed that the mechanical properties of metakaolin composite are enhanced significantly as compared with reference and fiber reinforced concrete. Results also showed that the inclusion of the metakaolin into fiber reinforced specimens shows a significant reduction in the porosity and absorption as compared to reference and fiber reinforced concrete without metakaolin. Zeng and Chung(4), investigated the influences of chemical agents on the improvement of carbon fiber reinforced cement composite by using short pitch-based carbon fibers 0.5% by weight of cement, together with a water reducing agent and accelerating admixture. Results indicated that compressive, tensile and flexural strength of the carbon fiber reinforced cement mortar were found to increase by about (18 to 31) %, (113 to 164) % and (89 to 112) % respectively, compared to the corresponding plain cement values. 3- OBJECTIVE OF RESEARCH The research aims to study the significance of using LWAC in structural approach by improving the performance using mineral & chemical admixtures and fibers as well, and also to study the effect of exposure to fire, so that it states to which temperature the LWAC can sustain. 4- EXPERIMENTAL PROGRAM To produce structural light weight aggregate concrete, crushed porcelinite stone was used as a coarse light weight aggregate and natural sand as a fine aggregate. Chemical and mineral admixtures as well fibers were also used to enhance performance of light weight concrete. 4. 1) Materials ) Cement Ordinary Portland cement (Type I) was used in all mixes throughout this investigation. It was stored in air tight plastic containers to avoid exposure to atmospheric conditions. The percentage oxide composition indicated that the adopted cement conforms to the Iraqi specification No. 5/1984.). The Chemical composition and main compounds of cement used in this investigation show in table (1) and The chemical and physical properties of this cement are presented in Tables (2). Table (1): Chemical composition and main compounds of cement used in this investigation Oxides composition Content % Limit of Iraqi specification No. 5/1984 Line, CaO 62.5 % - Silica, SiO % - Alumina, Al 2 O % - Iron oxide, Fe 2 O % Magnesia, MgO 3.0 % 5 % Max. Sulfate, SO % 3 % Max. Loss on Ignition, (L.O.I) 1.0 % 4 % Max. Insoluble material 1.3 % 1.5 % Max. Lim Saturation Factor, (L.S.F) 0.9 ( ) Main Compounds (Bogues equation) C 3 S 48.7 % C 2 S 24.8 % C 3 A 6.6 % > 5 % C 4 AF 10 % 167

4 Table (2): Physical properties of cement used in this investigation* Physical Properties Test Results Limit of Iraqi specification No. 5/1984 Specific surface area (Blaine method), (m 2 /kg) m 2 /kg lower limit Setting time (vacate apparatus) Initial setting, hrs : min Final setting, hrs : min Compressive strength MPa For 3-day For 7-day 2:40 3:50 Not less than 45 min Not more than 10 hrs MPa lower limit MPa lower limit Expansion by Autoclave method 0.38 % 0.8 % upper limit 4.1.2) Fine aggregate Normal weight natural sand from AL-Tuz region was used as fine aggregate. The grading of the sand conformed to the requirement of Iraqi specification No. 45/1984, zone (3). Table (3) shown Grading of fine aggregate and The Physical and chemical tests on sand used throughout this work are shown in Table (4). Table (3): Grading of fine aggregate Sieve size Cumulative passing % Limit of Iraqi specification No. 45/ Table (4): Chemical and physical properties of the sand. Properties Specification Test Results Limits of specification Specific gravity ASTM C Absorption % ASTM C Dry loose unit weight, kg/m 3 ASTM C29/C29M/ Sulfate content (as SO 3 ), % (I.O.S.) No (max. value) Material finer than mm sieve, % (I.O.S.) No (max. value) 4.1.3) Coarse aggregate Local naturally occurring light weight aggregate of porcelinite stones was used as coarse aggregate. It was brought in large lumps from the State Company of Geological Survey. The lumps were firstly crushed into smaller sizes manually by means of a hammer in order to facilitate the insertion of lumps through the feeding openings of the crusher machine. The crushed aggregate is grouped to different sizes and then the required coarse aggregate was prepared to conform to ASTM C192M-02 (5) specification. Table (5) shows the grading of the used coarse light weight aggregate. Table (6) shows the results of tests of chemical and mineral analysis of porcelinite aggregate and the table (7) and Table ( 8) show the Chemical analysis of porcelinite aggregate and Mineral analysis of porcelinite aggregate respectively. 168

5 Table (5): Selected grading of coarse lightweight aggregate Sieve size (mm) Cumulative passing (%) Cumulative passing %ASTM C Table (6): Chemical and physical properties of porcelinite lightweight aggregate Properties Specification Test Results Specific gravity ASTM C Absorption % ASTM C Dry loose unit weight, kg/m 3 ASTM 29/C29M/97 775* Dry rodded unit weight, kg/m 3 ASTM 29/C29M/ Aggregate Crushing value % BS 812-part Sulfate content (as SO 3 ), % BS 3797-part Staining Materials:*** Stain intensity Stain index 169 ASTM Table (7): Chemical analysis of porcelinite aggregate Oxides % by Weight SiO CaO MgO 6.90 SO Al 2 O Fe 2 O TiO L.O.I 4.25 Total Table (8): Mineral analysis of porcelinite aggregate* Compounds % by Weight Opal-C Quartz 9.62 Dolomite 7.20 Gypsum 7.05 Halite 0.71 Apatite 0.74 Clay 9.77 No stain ) Super plasticizer (SP) A super plasticizer type (GLENIUM51) based on modified polycarboxylic either was used throughout this investigation. (It is free from chlorides and complies with ASTM C494M/04 types A and F. Table (9) indicates the technical description of the aqueous solution of super plasticizer used throughout this investigation.

6 Table (9): Technical description of high range water reducing admixture Main Action Concrete Superplasticizer Form Viscous Liquid Colour Light Brown Relative Density C g/cm 20 ph value 6.6 Viscosity C Transport No + classified as dangerous Labeling No hazard label required 4.1.5) Silica Fume Silica fume was used in this investigation Elkem micro silica produced by Efaco/Egypt. The chemical oxide composition of the silica fume is given in Table (10). The physical properties are given in Table (11). Table (10): Chemical analysis of silica fume Oxides Composition Oxide Content % SiO 2 94 Al 2 O Fe 2 O CaO Nil MgO 2.00 K2O Nil Na2O Nil Total Table (11): Physical and chemical properties of SF used Physical Properties Silica Fume (SF) Unit weight kg/m kg/m 3 Specific Gravity 2.32 The amount of Silica Fume remaining on a 45 µm sieve 4.8 % 4.1.6) Carbon fiber High performance high strength carbon fiber system for structural reinforcement was used in this investigation. It has a high impact resistance, very good tensile strength and elastic modules. Also it has a very good chemical resistance under variety of exposure condition. Table (12) shows the general properties of the used carbon fiber. Table (12): Physical properties of carbon fiber used in this investigation. Grade 300 HS Weight (g/m³) Design thickness (mm) 0.17 Tensile strength design (kgf/ cm²) Fiber length (mm) Carbon content (%) 98 wt Specific gravity 1.90 Elongation at break (%)

7 4.2) Concrete mixes Concrete mixes containing porcelinite aggregate as light weight aggregate should have an oven-dry density < 2000 kg/m³ and a compressive strength > 15 MPa to produce structural (LWAC). These mixes were designed in accordance with ACI commitlee In general, this experiments design was applied to investigate the effect of SF, carbon fiber and temperature on the compressive, tensile and flexural strength of porcelinite light weight concrete. The details of these mixes are given in Table (13), and Table (14) lists the variables and levels used in the experimental. Designation of mixture Cement content Kg/m 3 Table (13): Details of the mixes used throughout study Carbon Coarse Silica fume Kg/m 3 fiber % by lightweight volume aggregate kg/m 3 HRW Superplastizer % by weight of cement Table (14): Variables used in these experiments variables Temperature Silica fume Carbon fiber ) Preparation, casting and curing of specimens Steel moulds were used for casting all specimens. They were cleaned and oiled before casting. The fresh concrete was placed inside the molds with approximately equal layers of 50 mm and compacted by means of vibrating table. Care has taken to avoid segregation of mixes. After the top layer had been compacted, it has smoothed, then the mould covered with nylon sheets for 24 hours to reduce evaporation of water to avoid plastic shrinkage cracks. After 24 hours the specimens were de-molded and completely immersed in tap water until the time of testing. Demoulding was 24 h after casting and placed in a water tank at 25±2 C. After 28 days water curing, they heated in an electric furnace up to 150, 450, 600, and 1000 C. The heating rate was set at 1 C /min as used in previous research. Each temperature was maintained for 1 h to achieve the thermal steady state. The specimens were allowed to cool naturally to room temperature. Cubic specimens of dimension (100 x 100 x 100) mm, were prepared to determine the effect of temperature on compressive strength. Cylinder specimens of dimension (150 x 300) mm were prepared to determine the effect of temperature on tensile strength. Beam specimens of dimensions (100 x 100 x 500) mm were prepared to determine the effect of temperature on flexural strength. A slice from fracture surface specimen to be examined, is cut to a suitable thickness of (3-5) mm, and oriented in any required manner to make a polished section for examination by this technique. Most samples to be analyzed required vacuum drying and then a conductive coating with ultra-thin gold coating. Plate (3) reveals the type of Scanning Electronic Microscope (SEM) equipment used for the analysis of the specimens in this study. 171

8 Plate (3): Scanning Electronic Microscope apparatus (SEM) 4.4) Exposure to Elevated Temperature In order to study the effect of exposure to elevated temperatures on samples, exposure to temperature which were 150, 400, 600, and 1000 C, 12 samples of (Cubes, Cylinders, and Prisms) for each age, as indicated above were taken. The data after exposure to the temperature rates mentioned above were compared with their related samples not exposed to temperature. An electrical oven was used for heating samples in a range of 1C per minute up to reach the target temperature as shown in figure (1) in below. Plate (1) Specimens layout at furnace Fig. (1): Heating and cooling curves 5- EVALUATION OF MECHANICAL PROPERTIES 5.1 Compressive Strength The compressive strength test was determined according to B.S. 1881: part 116: This test was conducted on (150 x 150 x 150) mm cubes using an electrical testing machine with a capacity of 2000 kn at loading rate of 0.25kN per second. The average of three concrete cubes has adopted for each test, the test has conducted at ages of (7, 28, 60, 90, and 180) days for samples not exposed to high temperature and (7, 28, 60, 90, and 180) days for samples that were exposed to elevated temperature. 5.2 Flexural Toughness Flexural toughness test has carried out on ( ) mm simply supported prisms with a clear span of 450 mm under the third points loading according to ASTM C , This test has conducted at ages of (7, 28, 60, 90, and 180) days for samples not exposed to high temperature and (7, 28, 60, 90, and 180) days for samples were exposed to high temperature. The specimens were 172

9 tested using a Universal Machine. To facilitate deflection reading despite the fact that the test was performed upside down without harming the dial gauge. The load has applied by using hydraulic machine with capacity of 2000 kn. The mid span deflection reading has measured using a dial gauge sensitive to 0.01mm then the load deflection has drawn according to (ASTM C , 2004) as shown in Fig. (2). Fig. (2): Load-Deflection curve (ASTM C , 2004) 6- EVALUATION OF MICROSTRUCTURE PROPERTIES The (SEM) photographs results at an age of 60 days of curing revealed the typical cases of dense cement gel crystal of readily distributed shape in addition to uniform crystals from (C-H) layers as shown in Plate (4). Continuous with curing for age of 90 days the cement gel developed to dendritic fibers like shape was identified as shown in Plate (5). Plate (4): Micrograph of LWAC at age of 60 days Plate (5) Micrograph of LWAC at age of 90 days Plate (6): Micrograph of LWAC at 150 C Plate (7): Micrograph of LWAC at 450 C 173

10 Plate (8): Micrograph of LWAC at 600 C Plate (9): Micrograph of LWAC at 1000 C 6.1 Exposure to temperature rate of 150 C It is noted that at this temperature the re-cracks in the C-H layer began as shown in Plate (6), it can be seen more clearly where C-H layer turned to irregular shape with a clear segregation in layers of C-H and longitudinal grooves were present. This means start of deterioration in microstructure. 6.2 Exposure to temperature rate of 450 C: It is clearly that the microstructure seems good and developed to be semi homogenous so that C-H and C-S-H layers can be thoroughly distinguished, it can be concluded that a re-hydration was happened and leads to improvement in microstructure. It has noted also an entanglement in Needle like shape in dark areas (pores) and that means a re-combination is going forward to seal pores (or slots) in microstructure as has shown in plate (7). 6.3 Exposure to temperature rate of 600 C It seems that the microstructure gets instability and turned to be like reefs with distinguished separation in C-H layer and dark spots, X-Mas tree like shape, and cluster like shape. All the above like shapes are indications (or signs) to weakness in bond forces between particles of microstructure as shown in plate (8). 6.3 Exposure to temperature rate of 1000 C Significant deterioration in microstructure at this rate of temperature exposure and turned to be like mountains, valleys with more fragmentation in both C-H and C-S-H layers of distinguished heads and dark spots, also it is noted that both layers were arranged in vertical manner with part of them existing in horizontal planes which means a great destabilization in microstructure as shown in plate (9). 7- RESULTS AND DISCUSSION 7.1) Compressive Strength The compressive strength development at various curing ages for selected mixes Reference mix (R) and Hybrid mix (H) is presented in Table (15). Test results are illustrated that in general; R and H specimens exhibited continuous development in strength up to 90 days of curing. There is a considerable increase in compressive strength of (H) mix relative to its similar (R) mix without fibers. The percentages of increase are shown in Table (15). This behavior was due to a reduction in w/cm (water cementitious material ratio) as well as to the deflocculating or dispersion of cement agglomerates into individual particles; thereby a greater rate of cement hydration can be achieved in the well dispersion system according to Mehta, P. K., (1986).The development of compressive strength versus curing age for both R and H mixes are shown in Table (15) and Fig. (3). 174

11 Age, (Days) Table (15): Compressive Strength Results of R6 and H6 Mixes Compressive Compressive Strength Strength of (R) of (H) Mix,(MPa) Mix,(MPa) Increase in Compressive Strength% Mix6R Mix6H Compressive Strength, MPa Age, (Days). Fig. (3): Compressive strength versus curing age of (R) and (H) mixes 7.2) Elevated Temperature Effects The Specimens were subjected to four degree of temperature cycles up to 150, 450, 600, and 1000 C. The first part of each cycle consisted of heating at 1 C /min up to the target temperature. After that, the temperature was held constant for 1 h(hour) in order to ensure uniform temperature throughout the specimens, the last part of the cycles consisted of cooling down to ambient temperature as shown in Fig. (1), the rate of heating refers to the recommendations of the RILEM Technical Committee 129-MHT, The properties measured after heating and cooling were compared to initial properties. Table (16) shows the dispersions obtained for the compressive strength of both R and H mixes. Values of H mix are slightly higher than those of R mix due to homogeneity and reproducibility. During the test, spalling was observed for both mixes during the heating up to 600 C ; spalling occurred around 515 C and this observation agrees with M. Kanema, (2007). The two mixes (R) and (H) specimens possessed an initial compressive strength equal to 22 and 30 MPa, respectively. The variation of residual compressive strength versus temperature is well illustrated in Table (16) and Figs. (4) and (5). An important increase in compressive strength of about % between 150 and 450 C for (R) mix specimens at an age of 60 Days, and 6.22 % for H6 mix specimens for the same age were noted; while at an age of 90 days R6 mix specimens showed an increase of about 3.2% compared to 3.53% for (H) mix specimens. Several hypotheses were proposed in the literature to explain this increase; it attributes to re-hydration of the paste due to migration of water in the pores. Another study assumed that the Silanol groups lost a part of their bonds with water which induced the creation of shorter and stronger Siloxane elements (Si-O-Si) with probably larger surface energies that contributed to the increase in strength according to Khoury, (1992) and Xu et al., (2001). Beyond the 450 C, the mechanical properties of the tested (R) and (H) mixes specimens decreased rapidly. The specimens subjected to a heating up to 1000 C showed very weak mechanical properties associated with that of physical properties (Appearance of Cracking).It was noted that for (R) mix specimens, the compressive strength for temperature rate of 600 C shown in Table (16) decreased to 31.01% and 41.25% at an ages of 60 and 90 days respectively, compared to 175

12 their relatives in Table (15) not exposed to high temperature, and 41.32% and 48.39% for temperature rate of 1000 C at ages of 60 and 90 days respectively. It has noted that for (H) mix specimens, the compressive strength for temperature rates of 600 C shown in Table (16) decreased to 37.69% and 40.49% at ages of 60 and 90 days respectively compared to their relatives in Table (16), not exposed to high temperature, and 47.55% and 48.26% for temperature rate of 1000 C at ages of 60 and 90 days respectively due mainly to the alteration of the porous network (Departure of bond water and decomposition of hydrates and to microcracking) Fig. (4): Variation of residual compressive strength versus temperature exposure at age of 60days Fig. (5): Variation of residual compressive strength versus temperature exposure at age of 90 days Age, (Days) Table (16): Residual compressive strength results of R and H mixes versus exposure to elevated temperature rates Temperature, (C ) Compressive Strength of R6 Mix, MPa Compressive Strength of H6 Mix, MPa % of Difference R and R6 Mixes % of Difference H and H6 Mixes % of Weight Loss of R6 mix % of Weight Loss of H6 mix

13 7.3) Flexural Toughness 7.3.1) (R) Sample The fiber reinforced concrete not only shows its effect on the pre-cracking state, but also it is vital in the post-cracking state leading to an increase of ductility for fiber reinforced concrete after the first crack of concrete. Evidence showed that specimens containing no fibers could not sustain any load and failed suddenly when the first crack was developed and hence the toughness index for these specimens at all ages of curing is equal to 1. However, fiber reinforced concrete has the ability of energy absorption to the fibers after the first crack appears when it tends to hold the concrete prism together, without causing it to break into two parts. In general, the toughness index for the fiber reinforced concrete varied greatly depending on the fiber type and the distribution of the fibers. As the deformation of the concrete prism increased, the load capacity of the fibers was decreased. According to Figs. (7) and (8), it is noted that the flexural strength increased with age, and when the sample is subjected to increase in temperature exposure the behavior varies, so upon exposure to 450 C, there is a considerable increase in ultimate load and then there is a decrease upon temperature exposures of 600 and 1000 C. It is noted in Fig. (9), that the behavior is similar to that of the age of 60 days but with small rates of deflection and this is due to continuous hydration which results in robust microstructure that can sustain loads. Fig. (6): Load-Deflection curves of R6 mix versus curing age Fig. (7): Load-Deflection curves of R6 mix at age of 60 days versus temperature exposure 177

14 Fig. (8): Load-Deflection curves of R6 mix at age of 90 days versus temperature exposure 7.3.2(H) Sample Fig. (9), shows Load-Deflection Curves of H6 Sample at 5 different ages were planned to study the flexural strength of sample increased with increase in age. Fig. (10) shows load-deflection curves of H6 sample at the age of 60 days and exposed to temperature raise and as shown in the figure, the curves are interfered but the one exposed to 600 C has the lesser value of ultimate load and an improvement in sustaining flexural load was upon 450 C, at which a partial improvement in mechanical properties was noted. Load-Deflection curves of H6 sample at an age of 90 days are showing in Fig. (11), and by compare results with ones in Fig. (10), the difference is well illustrated under the same temperature conditions. Fig. (9): Load-Deflection curves of H6 mix versus curing age Fig. (10): Load-Deflection curves of H6 mix at age of 60 days versus temperature exposure 178

15 Fig. (11): Load-Deflection curves of H6 mix at age of 90 days versus temperature exposure 8- CONCLUSIONS On the basis of results of this investigation the following conclusions may be deducted:- 1. It is possible to produce a light weight aggregate carbon fiber concrete with a dry density ranged between (1820) to (1950)Kg/m3 the addition of (SF) does not affect the density significantly. 2. The required dosage of superplasticizer (SP) for carbon fiber LWAC increases with increasing the percentage volume fraction of fiber. The useful dosage range is (4 to8%) 3. The addition of carbon fiber to (SF) light weight concrete increases slightly the compressive strength. Also the compressive strength increases with increasing volume fraction of carbon fiber. 4. The effect of Silica fume, carbon fiber addition, and heat treatment temperature on flexural, tensile and compressive strength of porcelinite lightweight concrete was investigated experimentally. 5. The Analysis by SEM revealed the existence of C-H Crystals at early ages and the development of C-S-H Crystals gel with age. Also, the SEM showed the improvement of microstructure of FRSCC composites containing HRWRA and Mineral admixtures, and due to the effects of rate of hydration the gel products were increased and C-H crystals decreased with age of specimen. 6. The Micrograph of Microstructure revealed smooth dense contact at interface transition zone. The development of bond strength within the transition zone of fiber/matrix was done at earlier stage with superplactizer and mineral admixture, which eliminated the weakness points within the transition zone. 7. The SEM photograph shows that the distributions of PP fibers within FRSCC were randomly oriented. REFERENCES [1] Dhir, K., Mays, R.G.C and Chua, H.C., "Lightweight Structural Concrete with Aglite Aggregate: Mix Design and Properties", The International Journal of Cement Composition and Lightweight Concrete, Vol. 6, No. 4, November 1984; pp [2] AL-Haddad, M. Y., "Durability of Lightweight Porcelinite Concrete Containing Slag Exposed to Solution of Sulfates and Chlorides", M.Sc. Thesis, University of Technology, August

16 [3] AL-Timimy, B. A., "Improvement of the Durability of Glass Fiber Reinforced Concrete", M.Sc. Thesis, University of Technology, April 2001; pp [4] Zeng, Q. and Chung, D. D., "Carbon Fiber Reinforced Cement Composites Improved by Using Chemical Agents", Cement and Concrete Research, Vol. 19, 1989; pp [5] ASTM C192/C192M 02, "Standard Practice for Making and curing Concrete Test Specimens in the Laboratory", Annual Book of ASTM Standards, Vol , 2004; pp [6] Dr. V.Bhaskar Desai and A.Sathyam, Basic Properties of Artificial Lightweight Aggregate by using Industrial by Product (Fly Ash), International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 6, 2014, pp , ISSN Print: , ISSN Online: [7] Javaid Ahmad and Dr. Javed Ahmad Bhat, Flexural Strengthening of Timber Beams using Carbon Fiber Reinforced Polymer Plates, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 5, 2013, pp , ISSN Print: , ISSN Online: [8] Ghassan Subhi Jameel, Study The Effect of Addition of Wast Plastic on Compressive and Tensile Strengths of Structural Lightweight Concrete Containing Broken Bricks as Acoarse Aggregate, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 2, 2013, pp , ISSN Print: , ISSN Online: