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20320140504002

  1. 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 10 EFFECT OF ELEVATED TEMPERATURE ON SOME PROPERTIES OF TECHNICAL GYPSUM REINFORCED BY CELLULOSE FIBER Abbas S. Al-Ameeri1 1 (Civil, Engineering/ University of Babylon, Babylon City, Iraq) ABSTRACT In spite of the wide availability of gypsum called juss in Iraq, with a low cost, but it still used mainly as a finishing material in plastering. The present work aim is to study the effect of elevated temperate exposure on properties of cellulose fiber reinforced gypsum (FCG), namely (density, compressive strength, flexural strength and ultrasonic pulse velocity). Technical gypsum was exposed to elevated temperature (25, 200, 400 and 600°C) with two different exposure durations of (0.5 and 1 hours). Specimens were exposed to temperature and tested at age 28 days. The results indicate that Elevated temperatures and increasing of exposure duration had passively influenced on hardened properties of both plain and fiber reinforced gypsum. The hardened properties of two type of technical gypsum decreased with increased temperatures and increasing of exposure duration. Deterioration in strength increases with increases in periods of exposure to elevated temperatures for all mixes. The residual density of technical gypsum ranged between (93-88%) at 200 o C, (85-79%) at 400 o C and (82-80%) at 600 o C for all mixes. The residual compressive strength ranged between (52-98%) at 200 o C, (19-36%) at 400 o C and (13-26%) at 600 o C for mixes. The flexural strength was very sensitive to temperatures. Residual flexural strengths ranged between (41-84%) at 200 o C, and became zero at 400o C and 600 o C for all mixes. The residual ultrasonic pulse velocity was ranged between (68-83%) at 200 o C, (45-63%) at 400 o C and (43-50%) at 600 o C for mixes. Also the results indicate that cellulose fiber used in gypsum reduced the amount of deterioration of properties of fiber-reinforced gypsum (FCG) at 40 ᵒC and 200 ᵒC temperature, and the cellulosic fiber helped to improve the flexural strength of gypsum samples at 40 ᵒC and 200 ᵒC, and improvement the compressive strength gypsum samples at 200 ᵒC. Keywords: Elevated Temperature, Cellulose Fiber, Cellulose Fiber Reinforced Gypsum, Gypsum, Technical Gypsum. INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) ISSN 0976 – 6308 (Print) ISSN 0976 – 6316(Online) Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME: www.iaeme.com/ijciet.asp Journal Impact Factor (2014): 7.9290 (Calculated by GISI) www.jifactor.com IJCIET ©IAEME
  2. 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 11 1- INTRODUCTION Historians agree that the Iraqis are first to discover the bricks and plaster used in construction in Babylon and Nineveh. Building gypsum(Stucco) is a calcium sulphate united with a half molecule of water CaSO4.1/2 H2O) With strange substances in different percentage like (CaCo3 SiO2 , Al2O3). It is made from burning of gypsum deposits which is (CaSO4 . 2 H2O) a hydrous calcium sulphate). Pure gypsum is a white translucent crystalline mineral and is so soft that it can be scratched by a finger nail. When heated to 205°C, pure gypsum loses its luster and its specific gravity is increased from 2.3 to 2.95 due to the loss of water of crystallization [1]. In Iraq, there are two commercial varieties of crude gypsum, rock gypsum and gypsum or gypsite, Gypsum stone can be considered as sedimentary rocks, and can be classified metallically as a hydrous calcium sulphate (CaSO4. 2H2O) and some percentage of defect such as (2SiO2.Al2O3.2H2O), can be found in different forms locally called (Alabaster, Selenite, Gypsite, Massive gypsum rocks and Santinspar)[2]. The water of crystallization in the gypsum (CaSO4. 2H2O) is not held firmly by the mineral. Therefore, when it is heated to about (130-175)°C, it loses a part of water of crystallization and is known as half-hydrate gypsum or (hemihydrate calcined gypsum) according Eq. (1-1)[3] [1]. At still higher temperatures (About 200°C), gypsum loses all its water of crystallization and turns out into an hydrate soluble gypsum. When we increase the heat the gypsum turns out into (an hydrated un soluble gypsum) according Eq. (1-2). At high temperature of (1000 -1200) ºC the compound that results is called ( lime ), according Eq. (1-3). The lost water of crystallization can be regained under favorable damp or moist conditions according Eq. (1-4) and (1-5). CaSO4.2H2O CaSO4.1/2H2O 130- 175 ᵒ C + 3/2H2O (hemihydrate calcined gypsum) Eq. (1-1)....... CaSO4.1/2H2O CaSO4 205- 400 ᵒ C + 1/2H2O (an hydrated soluble gypsum) Eq (1-2)....... CaSO4 CaO 1000-1200 ᵒ C + SO3 (Lime ) Eq (1-3)....... Eq (1-4).......CaSO4.2H2OCaSO4.1/2H2O Hydration + 3/2H2O
  3. 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 12 When a half hydrated gypsum(Stucco) is mixed with water ,the reaction occurs universally as in the equations (1-4)(1-5). According to the crystallization theory proposed by Le-chatelier when water is added to gypsum, the latter dissolves forming a saturated solution of dehydrate gypsum. Since the solubility of semihydrate gypsum is about 3.5 times more than of dehydrated gypsum[1]. This will form acicular crystals which grow during their formation and inter look with each another and cohere. The size, shape and the velocity of crystals formation and its cohesion depends on type of raw material, method of preparation and the strange substances found in the raw materials [3]. Building Gypsum(Stucco) can be classified according to British Standard ( BS 1911)[4] into four types, Class A: include calcium sulphate united with a half molecule of water (CaSO4.1/2 H2O) with high purity which called (Plaster of Paris), Class B: similar to class A with some retarders used in different finishing, but Class C and Class D (keen, s cement) are an hydrated calcium sulphate (CaSO4) which characterized by slow setting time so accelerators may be used to improve setting time. The four types used in finishing purposes and precast units, gypsum boards, partitions and sound isolations in various buildings but not as binder material for building of unites. Sometime is used artificial or animal hair could be added to gypsum to reduce cracking. Gypsum products(Stucco) can be classified according to Iraqi standard (IQS 28- 1988) [5] into, Ordinary gypsum, Technical gypsum and Plaster of Paris, all types of gypsum are half-hydrate gypsum or (hemihydrate calcined gypsum), but they have different physical and chemical properties due to present on strange substances. The major application of gypsum is as a binder, finishing materials, precast units, gypsum boards, partitions and sound isolations in various buildings. According to the available literature, few investigations were carried out on gypsum material. Several recent and past studies were conducted on using some types of additives to improve and control the setting time, hydration, strength development, water resisting property and volume change characteristics of gypsum [6] [7] [8] [9] [10]. Another presented the effect of addition some chemical admixtures to gypsum was also studied to product suitable composition matrix for application on external brick walls exposed to weathering conditions [11] to improve the good performance in tensile strength of gypsum application were found by added the fiber to gypsum such as blocks or plates. The Various kinds of fiber are used to reinforce gypsum in structural applications, such as animal hair, artificial fiber and cellulose fiber from plant origin, all fiber must not affected by the corrosion phenomenon by building gypsum (stucco). In gypsum, the fibers have been applied to decrease width of cracks, to increase tensile and flexural strength, and to improve post-cracking behavior. fiber reinforcement influences the way cracks develop in gypsum and may impart improved crack growth resistance, increase surface roughness of individual cracks, and a greater likelihood for crack branching and multiple crack development, due to this[12]. AL-Baghdadi[13] found the best results of improvement the mechanical properties for stucco mortar reinforced by reed and coconuts skin fibers, with increasing of addition ratio together with fiber length up to (3%) and length of 40 mm for reeds and up to 4% with fiber length of 30mm for coconuts skin fibers, the amount of increasing in compressive strength ,tensile strength and modulus of rupture were (21,20,12)% respectively for reeds and (21,27,8)% respectively for coconuts fibers with respect to reference sample . AL-Naiemi [14] found the used cellulose fibers of palm trees increase the ductility, resilience and toughness, and the fiber also increased the ultimate tensile strength and decreased in compressive strength with reference samples. CaSO4.2H2OCaSO4 Hydration + 2H2O Eq (1-5).......
  4. 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 13 In the structural design of buildings, in addition to the normal gravity and lateral loads, it is, in many cases, necessary to design the buildings to safely resist exposure to fire [15]. It is also necessary to protect the building members such as beams, columns, slabs and walls by plastering materials (cement mortar and gypsum mortar) as finishing to decrease the structural deterioration for certain period of fire exposure. Such deterioration can be decreased if good finishing materials were used in the building. There are many ways of exposing buildings to fire. One of the most common types of exposure is by accidental fire. Normally such fires are of short duration but at high intensity with the temperature reached up to 1000 o C. Another type of heat exposure may be found in places exposed to sustained elevated temperatures ranging from 100-1000 o C. . Muhammed [16] found the compressive strength of the specimens at temperature up to 100 o C exhibited a slight increase as compared with reference values. And all gypsum specimens suffered a significant decreases in compressive strength when exposed to 500 o C and above. After a period of 0.50 hour, the exposure period was seen to have a slight effect on the residual strength of ordinary gypsum except at 900 o C. The results also show that no residual strength was observed at 500 and 900 o C for the plaster of Paris and ordinary gypsum specimens respectively. . In this study there is an attempt to investigate the influence of elevated temperature and exposure periods on the properties of technical gypsum reinforced by cellulose fiber. However, still limited amount of published literature is available about gypsum material. 2- EXPERIMENTAL PROGRAM 2-1 Material 2-1-1 Technical gypsum (Stucco) Technical gypsum (Stucco) was used in this study. (Stucco) was produced by Faloja Factory for Gypsum productions. The chemical analysis carried out according Iraqi Specification (I.Q.S.No.273 -91)[17], and physical properties were tested by using (I.Q.S. No.27 -88)[18] as shown in Table (2-1), physical and chemical properties were conformed to the Iraqi specifications (I.Q.S. No.28 -88)[5] requirements. Table (2-1): Physical and Chemical properties of Technical gypsum Physical properties properties Test results Limits of Iraqi specification No.28/1988 Fineness(remaining on sieve No.16 (1.18mm)) (%) 4 5 Initial setting time (Min.) 15 12 - 20 Compressive strength (N/mm2) 6 ≥ 6 Modulus of Rupture (N/mm2) 3 ≥ 2 Hardness Strength ( indention diameter of drop ball (dia.12.7 mm )) ( mm ) 3 ≤ 5 Chemical properties Oxide composition Test results (%) Limits of Iraqi specification No.28/1988 Sulphur trioxide (SO3) 52 40≥ Calcium oxide (CaO) 35 27≥ Soluble residual 0.2 0.25≤ Combined Water 6 9≤ Loss on Ignition (L.O.I) 4 9≤ Defects 2.8 ---
  5. 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 2-1-2 Water The potable water has been used for mixing with gypsum in this work. 2-1-3 Fibers In this work, type of cellulose fiber used. The characteristics of the cellulose were 25mm, (0.1-0.5) mm, 250 MPa and 0.9 2.2. Methodology The mix design method used in the present study was according to Iraqi Specification (IQS 27-88) [18]. The (water/ gypsum) used in the study was (0.64) by weight. Fibers were added in quantities ranging from 0 to 6 % by volume of the total mixture. Fibers were fed into mixed by hand to ensure that clumping and clustering effects were minimized. Fiber in Table (2). Table (2- Mix No. Mix Symbol 1 R 2 FC1 3 FC2 4 FC3 The mixes being cast into the moulds until it's fully filled. All specimens were demoulded after final setting, and kept out at laboratory weather until the test The specimens are exposed to different temperatures in an electrical furnace, the specimens were tested at the ages of (28 days). with two different exposure duration of 0.5 and 1 hour. After h cool inside the electrical furnace for 2 hours after end of the heating and stored in a laboratory environment about 24 hours , the test were carried out for specimens. Plate (2-1): Cellulose fibers used in the study International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 14 The potable water has been used for mixing with gypsum in this work. In this work, type of cellulose fiber from plant origin having geometry of cylindrical was cellulose fiber; length, diameter, tensile strength, specific gravity 250 MPa and 0.9 kg/cm3 respectively, as shown in Plate (2 The mix design method used in the present study was according to Iraqi Specification (IQS [18]. The (water/ gypsum) used in the study was (0.64) by weight. Fibers were added in quantities ranging from 0 to 6 % by volume of the total mixture. Fibers were fed into mixed by hand to ensure that clumping and clustering effects were minimized. Fiber content in mixtures are detailed -2): Fiber content in SCFRC mixtures Mix Symbol Fiber Content (Vol.%) R Reference mix without fiber FC1 2 % cellulose fiber FC2 4 % cellulose fiber FC3 6% cellulose fiber The mixes being cast into the moulds until it's fully filled. All specimens were demoulded after final setting, and kept out at laboratory weather until the test as shown in Plate (2 The specimens are exposed to different temperatures in an electrical furnace, the specimens were tested at the ages of (28 days). Four temperature levels of 40, 200, 400 and 600 with two different exposure duration of 0.5 and 1 hour. After heating, the specimens were allowed to cool inside the electrical furnace for 2 hours after end of the heating and stored in a laboratory environment about 24 hours , the test were carried out for specimens. Cellulose fibers used in the study Plate (2-2): Sample were stored at laboratory International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), having geometry of cylindrical was tensile strength, specific gravity kg/cm3 respectively, as shown in Plate (2-1). The mix design method used in the present study was according to Iraqi Specification (IQS [18]. The (water/ gypsum) used in the study was (0.64) by weight. Fibers were added in quantities ranging from 0 to 6 % by volume of the total mixture. Fibers were fed into mixed by hand content in mixtures are detailed The mixes being cast into the moulds until it's fully filled. All specimens were demoulded as shown in Plate (2-2). The specimens are exposed to different temperatures in an electrical furnace, the specimens 200, 400 and 600 o C were chosen eating, the specimens were allowed to cool inside the electrical furnace for 2 hours after end of the heating and stored in a laboratory Sample were stored at laboratory
  6. 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 15 2.3 Testing program The mechanical properties studied were compressive strength, flexural strength and ultrasonic pulse velocity. Furthermore, Density test was used. The compressive strength test was performed in accordance with IQS No.27-1988 using 50 mm cube specimens. The density test was carried out on 50 mm cube specimens. The test procedure given in IQS No.27-1988 was used to determine the flexural strength using 40 × 40 × 160 mm prisms. The ultrasonic pulse velocity was performed according to IQS No.300-1993[19] by using 40 × 40 × 160 mm prisms. 3. RESULTS AND DISCUSSIONS 3.1. The fresh Properties of Gypsum All mixes of technical gypsum (TG) and Cellulose Fiber Reinforced gypsum (FCG). The workability were decreased with increasing of Cellulose Fiber content. These test was carried out by slump flow by using hollow pipe with dimension (dia 3.5 cm and height 5cm), this test was tested according IQS (27-1988). The setting time of gypsum were decreased with increasing of Cellulose Fiber content. 3.2. The effect of Cellulose fiber on hardened properties of technical gypsum exposure to elevated temperatures 3.2.1 Density of Technical gypsum samples Results are reported in Table(3-1). It was observed that bulk density decreases with increasing temperatures. Figs.(3-1) through (3-4) show the relation between bulk density and elevated temperature for all specimens at age (28) days. While Table (3-1) and Figs.(3-2) show the percentage residual bulk density values which are found for the mixes of Technical gypsum (R, FC1, FC2 and FC3), exposed to elevated temperature (200, 400, and 600° C) at ages (28days). Table (3-1): The Density and Percentage Residual Density of Technical gypsum at elevated Temperature Temp. ºC Duration Hour Density of Technical gypsum Residual Density of gypsum Volume fiber fraction (Vf )% Volume fiber fraction (Vf)% R= 0% FC1=2% FC2=4% FC3=6% R=0% FC1=2% FC2=4% FC3=6% 40 - 1243 1226 1199 1220 100 100 100 100 200 0.5 1155 1125 1111 1094 93 92 93 92 1 1094 1077 1067 1050 88 88 89 88 400 0.5 1050 1037 1016 999 84 85 85 84 1 1026 1016 993 945 83 83 83 79 600 0.5 1016 1003 989 976 82 82 82 82 1 1020 979 986 965 82 80 82 81
  7. 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. Fig.(3-3) Effect of temperature on Density of technical gypsum with different percentage of cellulose fiber content at period of exposure (0.5hr) Also the results show the density of technical gypsum were decreased with increasing of cellulose content at samples for different temperature and (3-2) and Fig(3-5). The exposure of technical gypsum to high temperature leads to evaporation of moisture unbound by hydrated compounds (free moisture) leaving voids in gypsum mass at below temperature 130 ᵒC, after this the gypsum loses all its water of crystallization and hydrate soluble gypsum or an hydrate un soluble And the reason of decreasing of density due to increased the cellulose fibers content is the took the portion of volume of gypsum, pure technical gypsum (without fiber) (gypsum + fiber). C C- C- C- C- Density(kg/m3) Temp.- time (ᵒC-hr) fiber fiber Fig.(3-1) Density of Technical Gypsum with different percentage of cellulose fiber and different temperature & period of exposure Density(kg/m3) Temperature (ᵒC) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 16 3) Effect of temperature on Density of technical gypsum with different percentage of cellulose fiber content at period of exposure Fig.(3-4) Effect of temperature on Density of technical gypsum with different percentage of cellulose fiber content at period of exposure (1hr Also the results show the density of technical gypsum were decreased with increasing of different temperature and period of exposure, as shown at Table The exposure of technical gypsum to high temperature leads to evaporation of moisture unbound by hydrated compounds (free moisture) leaving voids in gypsum mass at below gypsum loses all its water of crystallization and gypsum or an hydrate un soluble gypsum [1] [3][16]. the reason of decreasing of density due to increased the cellulose fibers content is the took the portion of volume of gypsum, and the density of cellulose fiber was lower than density of pure technical gypsum (without fiber), in this case leads to reduction of total density of samples C- C- C- C- ResidualofDensity(%) Temp.- time (ᵒC fiber fiber C- C- hr) fiber fiber 1) Density of Technical Gypsum with different percentage of cellulose fiber and different temperature & period of exposure Fig.(3-2) The percentage of residual Density (with respect to specimen at 40°C for mix R, FC1, FC2and FC3)at 28 days fiber fiber fiber fiber Density(kg/m3) Temperature (ᵒ International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), 4) Effect of temperature on Density of technical gypsum with different percentage of ent at period of exposure (1hr) Also the results show the density of technical gypsum were decreased with increasing of as shown at Table The exposure of technical gypsum to high temperature leads to evaporation of moisture unbound by hydrated compounds (free moisture) leaving voids in gypsum mass at below turns out into an the reason of decreasing of density due to increased the cellulose fibers content is the fiber was lower than density of this case leads to reduction of total density of samples C- C- C-hr) fiber fiber fiber fiber 2) The percentage of residual Density (with respect to specimen at 40°C for mix R, FC1, FC3)at 28 days ᵒC) fiber fiber fiber fiber
  8. 8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. Fig.(3 Density of technical gypsum of temperature and period of exposure at28 days Table (3-1): The residual percentage of 3-2-2 Compressive strength of Technical gypsum samples The compressive strength is one of the most important properties of hardened gypsum. Results reported in Table (3-3). It observed that compressive strength decreasing with increasing temperatures. Fig.(3-6) shows the relation between compressive strengths and elevated temperature for all specimens. While Table (3 strength values for the mixes of technical 600 ° C) at ages (28 days). It was found that: Temp. ºC Duration Hour 40 - 200 0.5 1 400 0.5 1 600 0.5 1 Density(kg/m3) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 17 Fig.(3-5) Effect of cellulose fiber content on Density of technical gypsum of different temperature and period of exposure at28 days The residual percentage of Density of ( FC1,FC2 and FC3) with respect R 2 Compressive strength of Technical gypsum samples The compressive strength is one of the most important properties of hardened gypsum. It observed that compressive strength decreasing with increasing the relation between compressive strengths and elevated temperature for all specimens. While Table (3-3) and Figs.(3-7), show the percentage residual compressive technical gypsum, exposed to elevated temperature (200, 400, 600 ° C) at ages (28 days). It was found that: Duration Hour Residual percentage of Density of technical gypsum Volume fiber fraction (Vf)% FC1=2% FC2=4% FC3=6% - 99 96 96 0.5 97 96 95 1 98 98 96 0.5 99 97 95 1 99 97 92 0.5 99 97 96 1 96 97 95 cellulose fiber content (% C C- C- C- C- C- C- International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), Density of ( FC1,FC2 and FC3) with respect R The compressive strength is one of the most important properties of hardened gypsum. It observed that compressive strength decreasing with increasing the relation between compressive strengths and elevated temperature 7), show the percentage residual compressive gypsum, exposed to elevated temperature (200, 400, and
  9. 9. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. Table (3-3): The compressive strength and Percentage Residual compressive strength of Technical gypsum at elevated Temperature Temp. ºC Duration Hour compressive strength Volume fiber fraction ( R= 0 % FC1=2% 40 - 9.6 9 200 0.5 5.9 7 1 5 6.6 400 0.5 3.2 3.2 1 2.6 2 600 0.5 1.6 1.6 1 1.2 1.4 - For periods of exposure (0.5 and 1 hours) and at 200° C temperature, the percentage residual compressive strength for technical (98-91%) for mixes (R, FC1, FC2 and FC3) respectively. - At 400 °C temperature and for periods of exposure (0.5 and 1 hours), the residual compressive strength ranged between (33-27 and FC3) respectively. - Raising the temperature to 600 °C caused some specimens have been destroyed residual compressive strength (22-23%) and (23-20%) for mixes - For above the all specimens at ages 28 days compressive strength decreased with increasing periods of exposure (0.5 and 1 hour) as shown in Table ( C C- C- C- C- fcu(MPa) Temp.- time (ᵒC- fiber fiber Fig.(3-6) Compressive strength (fcu) of Technical Gypsum with different percentage of cellulose fiber and different temperature & period of exposure International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 18 Fig.(3-7) The percentage of residual Compressive strength (fcu) (with respect to specimen at 40°C for mix R, FC1, FC2and FC3) The compressive strength and Percentage Residual compressive strength of Technical gypsum at elevated Temperature compressive strength of gypsum Residual compressive strength Volume fiber fraction (Vf )% Volume fiber fraction ( FC2=4% FC3=6% R=0% FC1=2% FC2=4% 7.4 8.8 100 100 100 6.4 8.6 61 78 86 5 8 52 73 68 2.4 2 33 36 32 2.7 1.6 27 23 25 1.6 1.8 17 18 22 1.7 2 13 16 23 For periods of exposure (0.5 and 1 hours) and at 200° C temperature, the percentage residual technical gypsum ranged between (61-52%), (78-73%),(86 FC2 and FC3) respectively. At 400 °C temperature and for periods of exposure (0.5 and 1 hours), the residual compressive 27%), (36-23%), (32-25%) and (23-19%) for mixes Raising the temperature to 600 °C caused some specimens have been destroyed residual compressive strength of technical gypsum ranged between (17-13 for mixes (R, FC1, FC2 and FC3) respectively. all specimens at ages 28 days compressive strength decreased with increasing hour) as shown in Table (3-3) and Fig (3-8)& (3 C- C- -hr) fiber fiber C- C- C- C- Residualfcu(%) Temp.- time (ᵒC strength (fcu) of Technical Gypsum with different percentage of cellulose fiber and different temperature & period of exposure International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), 7) The percentage of residual Compressive strength (fcu) (with respect to specimen at 40°C for mix R, FC1, FC2and FC3)at 28 days The compressive strength and Percentage Residual compressive strength of Technical compressive strength Volume fiber fraction (Vf)% FC2=4% FC3=6% 100 100 86 98 68 91 32 23 25 19 22 20 23 23 For periods of exposure (0.5 and 1 hours) and at 200° C temperature, the percentage residual 73%),(86-68%) and At 400 °C temperature and for periods of exposure (0.5 and 1 hours), the residual compressive %) for mixes (R, FC1, FC2 Raising the temperature to 600 °C caused some specimens have been destroyed. The percentage 13%), (18-16%), all specimens at ages 28 days compressive strength decreased with increasing (3-9). C- C- C-hr) fiber fiber
  10. 10. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. Fig.(3- compressive strength of gypsum of different temperature and period of exposure at 28 days It can be noticed that the compressive strength suffers a noticeable deterioration when exposed specimens to elevated temperatures, it due to a lot of physical and chemical changes in gypsum. Heating to a temperature of 200 °C does have compressive strength of concretes, a small loss of strength was observed with comparison with another temperature. It was associated to an evaporation of free water as well as to an increasing in porosity of the tested gypsum. This porosity increases due to expansion of the pore diameters, due to convert the gypsum from phase (CaSO4.2H increase in permeability. When temperatures reach above 200ºC, gypsum loses all crystallization and turns out into an hydrate soluble gypsum. When we increase the heat gypsum turns out into (an hydrated un soluble gypsum ) according Eq. (1 begin to dehydrate generating more water vapor and also the compressive strength of technical gypsum in range of 300ºC and 600ºC [16] that the color of specimens changed to gray, and color change increased when temperature and the period of exposure increased. The induction of color change meaning loss in mechanical properties. Also the results indicate to the relation between steel fiber content and compressive strength at elevated temperature are summarized in Table (3 exposure period. It was observed the compressive strength of fiber reinforced gypsum increases with steel fiber content compared with plain gypsum at ages 28days and at temperature (40,200 ᵒC) It has been found that cellulose f after exposure to elevated temperatures. cellulose fibers had been used to reduce the damage and cracking due to high temperature for (FC1, might be attributed to their bond to the matrix which can be enhanced by mechanical anchorage or surface roughness[20].But at and 400 leads to burn the cellulose fiber and lost this benefit. fcu(MPa) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 19 -10) Effect of cellulose fiber content on compressive strength of gypsum of different temperature and period of exposure at 28 days It can be noticed that the compressive strength suffers a noticeable deterioration when exposed specimens to elevated temperatures, it due to a lot of physical and chemical changes in gypsum. Heating to a temperature of 200 °C does have little significant effects on the compressive strength of concretes, a small loss of strength was observed with comparison with It was associated to an evaporation of free water as well as to an increasing in porosity of gypsum. This porosity increases due to expansion of the pore diameters, due to convert .2H2O) to phase (CaSO4.1/2H2O)[1], and therefore leads to an increase in permeability. When temperatures reach above 200ºC, gypsum loses all crystallization and turns out into an hydrate soluble gypsum. When we increase the heat gypsum turns out into (an hydrated un soluble gypsum ) according Eq. (1-2)[3] gypsum begin to dehydrate generating more water vapor and also bringing about significant reduction in the compressive strength of technical gypsum in range of 300ºC and 600ºC [16] that the color of specimens changed to gray, and color change increased when temperature and eased. The induction of color change meaning loss in mechanical Also the results indicate to the relation between steel fiber content and compressive strength at elevated temperature are summarized in Table (3-4) & plotted in Figs.(3 exposure period. It was observed the compressive strength of fiber reinforced gypsum increases with steel fiber content compared with plain gypsum at ages 28days and at temperature It has been found that cellulose fibers improve the residual compressive strength of FCG after exposure to elevated temperatures. cellulose fibers had been used to reduce the damage and cracking due to high temperature for (FC1, FC2 and FC3) mixes at temperature (200 ibuted to their bond to the matrix which can be enhanced by mechanical anchorage But at and 400 ᵒC and 600 ᵒC, the damage at gypsum was increased leads to burn the cellulose fiber and lost this benefit. cellulose fiber content (%) C C- C- C- C- C- International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), It can be noticed that the compressive strength suffers a noticeable deterioration when exposed specimens to elevated temperatures, it due to a lot of physical and chemical changes in little significant effects on the compressive strength of concretes, a small loss of strength was observed with comparison with It was associated to an evaporation of free water as well as to an increasing in porosity of gypsum. This porosity increases due to expansion of the pore diameters, due to convert and therefore leads to an increase in permeability. When temperatures reach above 200ºC, gypsum loses all its water of crystallization and turns out into an hydrate soluble gypsum. When we increase the heat the 2)[3] gypsum will bringing about significant reduction in the compressive strength of technical gypsum in range of 300ºC and 600ºC [16] . It is observed that the color of specimens changed to gray, and color change increased when temperature and eased. The induction of color change meaning loss in mechanical Also the results indicate to the relation between steel fiber content and compressive 4) & plotted in Figs.(3-10), for two exposure period. It was observed the compressive strength of fiber reinforced gypsum increases with steel fiber content compared with plain gypsum at ages 28days and at temperature ibers improve the residual compressive strength of FCG after exposure to elevated temperatures. cellulose fibers had been used to reduce the damage and and FC3) mixes at temperature (200 ᵒC) This ibuted to their bond to the matrix which can be enhanced by mechanical anchorage C, the damage at gypsum was increased
  11. 11. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 20 Table (3-4): The residual percentage of compressive strength of (FC1, FC2 and FC3) with respect R 3-2-3 Flexural Strength of Technical gypsum It can be seen that flexural strength decreased with increasing temperatures for all specimens, as shown in Table (3-5) and Figs.(3-11). The percentage residual flexural strength is summarized in Table (3-5) and Figs.(3-12), for mixes of SCC (R, FC1, FC2 and FC3), exposed to high elevated temperature (200, 400 and 600° C) at ages 28 days. It was found that: - The percentage residual flexural strengths ranged between (70-41%), (84-56%),(60-47%) and (60-51%) for mixes (R, FC1,FC2 and FC3) respectively, at 200° C temperature and for periods exposure (0.5 and 1 hours). - At 400°C and 600°C temperature for periods exposure (0.5 and 1 hours) the residual flexural strengths became zero, because all technical gypsum sample were cracked and destroyed by heating. - Flexural strengths decreased with increasing periods of exposure (0.5 and 1 hours), as shown in Fig(3-13)(3-14) at all temperatures and at ages 28 days. Table (3-5): The flexural strength and Percentage Residual flexural strength of Technical gypsum at elevated Temperature Temp. ºC Duration Hour compressive strength of gypsum Residual compressive strength Volume fiber fraction (Vf )% Volume fiber fraction (Vf)% R= 0 % FC1=2% FC2=4% FC3=6% R=0% FC1=2% FC2=4% FC3=6% 40 - 2 2.5 3 3.5 100 100 100 100 200 0.5 1.4 2.1 1.4 2.1 70 84 47 60 1 0.82 1.4 1.8 1.8 41 56 60 51 400 0.5 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 600 0.5 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 Temp. ºC Duration Hour The Residual percentage of compressive strength Volume fiber fraction (Vf)% FC1=2% FC2=4% FC3=6% 40 - 94 77 92 200 0.5 119 108 146 1 132 100 160 400 0.5 100 75 63 1 77 104 62 600 0.5 100 100 113 1 117 142 167
  12. 12. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. It can be seen that flexural strengths decrease with high temperature as a result of the shrinkage of technical gypsum cause decomposition cracks inside specimens which reduces the flexural strengths It was observed the flexural strength cellulose fiber content compared with Fig.(3-15) Cellulose fiber reinforced gypsum have better for mixes that exposed to 40 ᵒC and 200 crack resistance of the composite and to the ability of fibers to resist forces after the gypsum matrix has failed. Also, the percentage of increase in flexural strength was found to be increased with the increase in fiber content. This behavior is mainly attributed to the role of cellulose fibers in releasing fracture energy around crack tips which is required to one side to another side [21] as shown It has been found that cellulose fibers improve the residual exposure to elevated temperatures. cracking due to high temperature for (FC1 might be attributed to their bond to the matrix which can b or surface roughness [20]. But at and 400 leads to burn the cellulose fiber and lost this benefit as shown C C- C- C- C- fr(MPa) Temp.- time (ᵒC-hr) fiber fiber Fig.(3-11) flexural strength (fr) of technical gypsum with different percentage of cellulose fiber and different temperature & period of exposure International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 21 can be seen that flexural strengths decrease with high temperature as a result of the cause decomposition its compounds leading to the occurrence of cracks inside specimens which reduces the flexural strengths [3] [16]. flexural strength of fiber reinforced gypsum increased with increasing compared with plain gypsum at ages 28days, as shown in Cellulose fiber reinforced gypsum have better to flexural strength than gypsum without fibers C and 200 ᵒC temperature . This is mainly due to the increasing in crack resistance of the composite and to the ability of fibers to resist forces after the gypsum matrix led. Also, the percentage of increase in flexural strength was found to be increased with the increase in fiber content. This behavior is mainly attributed to the role of cellulose fibers in releasing fracture energy around crack tips which is required to extent crack growing by transferring it from as shown Plate (3-1). It has been found that cellulose fibers improve the residual flexural strength exposure to elevated temperatures. Cellulose fibers had been used to reduce the damage and cracking due to high temperature for (FC1, FC2 and FC3) mixes at temperature (200 might be attributed to their bond to the matrix which can be enhanced by mechanical anchorage . But at and 400 ᵒC and 600 ᵒC, the damage at gypsum was increased leads to burn the cellulose fiber and lost this benefit as shown Plate (3-2). C- C- hr) fiber fiber C- C- C- C- Residualfr(%) Temp.- time (ᵒC Fig.(3-12) The percentage of residual flexural strength (fr) (with respect to specimen at 40°C for mixes R, FC1, FC2and FC3)at 28 days 11) flexural strength (fr) of technical gypsum with different percentage of cellulose fiber and different temperature & period of exposure International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), can be seen that flexural strengths decrease with high temperature as a result of the compounds leading to the occurrence of of fiber reinforced gypsum increased with increasing as shown in Table (3-6) and to flexural strength than gypsum without fibers This is mainly due to the increasing in crack resistance of the composite and to the ability of fibers to resist forces after the gypsum matrix led. Also, the percentage of increase in flexural strength was found to be increased with the increase in fiber content. This behavior is mainly attributed to the role of cellulose fibers in releasing extent crack growing by transferring it from strength of FCG after been used to reduce the damage and and FC3) mixes at temperature (200 ᵒC) .This e enhanced by mechanical anchorage C, the damage at gypsum was increased C- C- ᵒC-hr) fiber fiber fiber 12) The percentage of residual flexural strength (fr) (with respect to specimen at 40°C for mixes R, FC1, FC2and FC3)at 28 days
  13. 13. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. Fig.(3-13) Effect of temperature on flexural strength (fr) of gypsum with different percentage of cellulose fiber content at period of exposure (0.5hr) Fig.(3 flexural strength (fr) of gypsum of different temperature and period of exposure at 28 days Table (3-6): The residual percentage Temp. ºC Duration Hour 40 - 200 0.5 1 400 0.5 1 600 0.5 1 fr(MPa) Temperature (ᵒC) fr(MPa) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 22 fr(MPa) Temperature (ᵒC) 13) Effect of temperature on flexural strength (fr) of gypsum with different percentage of cellulose of exposure (0.5hr) Fig.(3-14) Effect of temperature on flexural strength (fr) of gypsum with different percentage of cellulose fiber content at period of exposure (1hr) Fig.(3-15) Effect of cellulose fiber content on flexural strength (fr) of gypsum of different temperature and period of exposure at 28 days The residual percentage of flexural strength of (FC1, FC2 and FC3) Duration Hour Residual percentage of flexural strength Volume fiber fraction (Vf)% FC1=2% FC2=4% FC3=6% 125 150 175 150 100 150 171 220 220 0 0 0 0 0 0 0 0 0 0 0 0 fiber fiber fiber fiber cellulose fiber content (%) C C- C- C- C- C- C- International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ᵒC) fiber fiber fiber fiber on flexural strength (fr) of gypsum with different percentage of cellulose nt at period of exposure (1hr). FC2 and FC3) with respect R flexural strength
  14. 14. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 23 Plate (3-1) Cellulose fibers used to decrease cracks Plate (3-2) Burn of cellulose fiber due to heating above 400ᵒC temperature 3-2-4 Ultrasonic Pulse Velocity Results (U.P.V) The results of ultrasonic pulse velocity test are listed in Table (3-7). The Figs.(3-16), shows the relationship between pulse velocity and elevated temperature (200, 400 and 600°C), for all specimens at two period of exposure . It was observed that pulse velocity decreases with increasing temperatures. While Table (3-7) and Figs.(3-17), shown the percentage residual pulse velocity values for the mixes of technical gypsum (R, FC1,FC2, and FC3), exposed to elevated temperature (200, 400 and 600°C) at ages 28 days). It was found that: - For periods exposure (0.5 and 1 hour) and at 200°C temperature the percentage residual pulse velocity for SCC ranged between (83-79%), (83-75%),(83-73%) and (81-68%) for mixes (R, FC1, FC2 and FC3) respectively. - The percentage residual pulse velocity for technical gypsum samples ranged between (56-50%), (60-45%), (63-50%) and (61-46%) for mixes (R, FC1,FC2 and FC3) respectively, at 400°C and for periods exposure (0.5 and 1 hour). - More reduction pulse velocity took place when the temperature increased to 600 °C. The percentage residual pulse velocity for technical gypsum samples were (50-46%), (48-47%), (48-44) and (43-43%) for mixes (R, FC1,FC2and FC3) respectively for periods of exposure (0.5 and 1 hour). - When specimens exposure to temperatures (200, 400 and 600°C) the pulse velocity showed significant losses with increasing in periods of exposure (0.5 and 1 hours), at ages 28 days), as shown Fig (3-18)(3-19). It can be seen that the pulse velocity decreases with the temperature increases. Since the exposure of concrete to high temperature leads to the evaporation of moisture unbound by the hydrated compounds (free moisture) leaving voids behind in the concrete mass [22]. In addition, the heating process leads to fine cracks resulting from volume changes. Also, the chemical and physical effects of the heating process at higher temperature (dehydration of gypsum at about 200°C) [3], the volume changes which play the main role in the cracking and deterioration of samples at high temperatures. These voids retard the ultrasonic pulse leading to increase in the travel time and consequently a decrease in the velocity[22].
  15. 15. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. Fig.(3-18) Effect of temperature on Ultrasonic Pulse Velocity(UPV) of gypsum with different percentage of cellulose fiber content at period of exposure (0.5hr) Table (3-7): The UPV and Percentage Residual Temp. ºC Duration Hour compressive strength of gypsum Volume fiber fraction ( R= 0 % FC1=2% 40 - 2.1 2.2 200 0.5 1.74 1.82 1 1.66 1.66 400 0.5 1.18 1.33 1 1.05 1 600 0.5 1.05 1.03 1 0.97 1.05 Fig.(3-16) Ultrasonic Pulse Velocity (UPV) of gypsum with different percentage of cellulose fiber and different temperature & period of exposure C C- C- C- C- UPV(km/sec) Temp.- time (ᵒC-hr) fiber fiber UPV(km/sec) Temperature (ᵒC) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 24 18) Effect of temperature on Ultrasonic Pulse Velocity(UPV) of gypsum with different percentage of at period of exposure (0.5hr) Fig.(3-19) Effect of temperature on Ultrasonic Pulse Velocity(UPV) of gypsum with different percentage of cellulose fiber content at period of exposure ( and Percentage Residual UPV of Technical gypsum at elevated Temperature compressive strength of gypsum Residual compressive strength Volume fiber fraction (Vf )% Volume fiber fraction ( FC1=2% FC2=4% FC3=6% R=0% FC1=2% FC2=4% 2.2 2.35 100 100 100 1.82 1.9 83 83 83 1.6 1.6 79 75 73 1.38 1.43 56 60 63 1.11 1.08 50 45 50 0.97 1 50 47 44 1.05 1 46 48 48 Fig.(3-17) The percentage of residual Ultrasonic Pulse Velocity (UPV) (with respect to sp 40°C for mix R, FC1, FC2and FC3)at 28 days 16) Ultrasonic Pulse Velocity (UPV) of gypsum with different percentage of cellulose fiber and different temperature & period of exposure C- C- hr) fiber fiber f = fiber fiber fiber UPV(km/sec) Temperature (ᵒC) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), 19) Effect of temperature on Ultrasonic Pulse Velocity(UPV) of gypsum with different percentage of cellulose fiber content at period of exposure (1hr) of Technical gypsum at elevated Temperature Residual compressive strength fraction (Vf)% FC2=4% FC3=6% 100 100 83 81 73 68 63 61 50 46 44 43 48 43 17) The percentage of residual Ultrasonic Pulse Velocity (UPV) (with respect to specimen at 40°C for mix R, FC1, FC2and FC3)at 28 days C- C- time (ᵒC-hr) fiber fiber fiber fiber ᵒC) f = fiber fiber fiber
  16. 16. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. Fig.(3-20) Effect of cellulose fiber content on Ultrasonic Pulse Velocity (UPV) of gypsum of different temperature and period of exposure at 28 days The results indicated, the samples that affected the ultrasonic pulse velocity at 40 Figs.(3-20). After this temperature (above 200 not clear, sometime the UPV increases and another decreased 4. CONCLUSIONS According to the experimental results presented in the preceding above, temperatures do affect the plain gypsum sample and fiber reinforced gypsum samples in a hardened state. On the basis of the observations made in the present work, the following conclusions were fou 1. Overall, the workability and setting time decrease with the increase in cellulose fiber content of the technical gypsum mixtures with respect to plain mixtures. 2. The residual density of technical gypsum 400 o C and (82-80%) at 600 o residual percentage of density of (FC1, between (96-99%) at 40 o C, (95 28 days. 3. The residual compressive strength ranged between (52 and (13-26%) at 600 o C for mixes (R, FC1, percentage of compressive strength (R)ranged between (77-94%) at 167%) at 600 o C at age 28 days. 4. The flexural strength was very sensitive to temperatures. Residual flexural strengths between (41-84%) at 200 o C, and became zero at 400 and FC3) at age (28 days), and the residual percentage of flexural strength of (FC1, FC3) with respect to plain gypsum (R) 200 o C and became zero at 400 5. The residual ultrasonic pulse velocity was ranged between (68 400 o C and (43-50%) at 600 o residual percentage of ultrasonic pulse velocity of (FC1, UPV(km/sec) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 25 20) Effect of cellulose fiber content on Ultrasonic Pulse Velocity (UPV) of gypsum of different temperature and period of exposure at 28 days , the samples that incorporating cellulose fibers in concrete positively affected the ultrasonic pulse velocity at 40ᵒC and 200ᵒC temperatures, as shown in Table (3 fter this temperature (above 200 ᵒC), the role of cellulose fiber at gypsum sample was , sometime the UPV increases and another decreased. the experimental results presented in the preceding above, temperatures do affect the plain gypsum sample and fiber reinforced gypsum samples in a hardened state. On the basis of the observations made in the present work, the following conclusions were fou Overall, the workability and setting time decrease with the increase in cellulose fiber content gypsum mixtures with respect to plain mixtures. density of technical gypsum ranged between (93-88%) at 200 o C for mixes (R, FC1, FC2 and FC3) at age (28 days), and the residual percentage of density of (FC1, FC2 and FC3) with respect to plain gypsum (R)ranged (95-98%) 200 o C, (92-99%) at 400 o C and (95- 99) at 600 The residual compressive strength ranged between (52-98%) at 200 o C, (19 C for mixes (R, FC1, FC2 and FC3) at age (28 days), and the residual percentage of compressive strength of (FC1, FC2 and FC3) with respect to plain gypsum 94%) at 40 o C, (100-132%) 200 o C, (62-104%) at 400 C at age 28 days. The flexural strength was very sensitive to temperatures. Residual flexural strengths C, and became zero at 400o C and 600 o C for mixes (R, FC1, and FC3) at age (28 days), and the residual percentage of flexural strength of (FC1, FC3) with respect to plain gypsum (R) ranged between (125-175%) at 40 and became zero at 400o C and 600 o C at age 28 days. The residual ultrasonic pulse velocity was ranged between (68-83%) at 200 o C for mixes (R, FC1, FC2 and FC3) at age (28 residual percentage of ultrasonic pulse velocity of (FC1, FC2 and FC3) with respect to plain cellulose fiber content (%) C C- C- C- C- C- C- International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), incorporating cellulose fibers in concrete positively C temperatures, as shown in Table (3-8) and , the role of cellulose fiber at gypsum sample was the experimental results presented in the preceding above, temperatures do affect the plain gypsum sample and fiber reinforced gypsum samples in a hardened state. On the basis of the observations made in the present work, the following conclusions were found: Overall, the workability and setting time decrease with the increase in cellulose fiber content 88%) at 200 o C, (85-79%) at FC2 and FC3) at age (28 days), and the FC2 and FC3) with respect to plain gypsum (R)ranged 99) at 600 o C at age C, (19-36%) at 400 o C FC2 and FC3) at age (28 days), and the residual FC2 and FC3) with respect to plain gypsum 104%) at 400 o C and (100- The flexural strength was very sensitive to temperatures. Residual flexural strengths ranged C for mixes (R, FC1, FC2 and FC3) at age (28 days), and the residual percentage of flexural strength of (FC1, FC2 and 0 o C, (100-120%) 83%) at 200 o C, (45-63%) at FC2 and FC3) at age (28 days), and the FC2 and FC3) with respect to plain
  17. 17. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 26 gypsum (R)ranged between (105-112%) at40 o C ,(96-109%) 200 o C , (95-121%) at 400 o C and (92-108%) at 600 o C at age 28 days . 6. Deterioration in strength increases with increases in periods of exposure to elevated temperatures for all mixes. 7. Cracking and Spalling occur when specimens are exposed to high temperatures at 400 o C and for long period of exposure. . 8. The optimum fiber content was (2% by Vol.) improves hardened properties against the high temperatures. 9. The cellulosic fiber helped to improve the flexural strength of gypsum samples at 40 ᵒC and 200 ᵒC and improvement the compressive strength gypsum samples at 200 ᵒC. REFERENCE [1] Duggal S.K., "Building Materials", Third Revised Edition, New Age International Publishers, New Delhi, 2008, pp.(458-466). [2] Raof Z.M., "Fibrous Plaster Boards", Iraqi Industrial Union, Consulting Corp for construction Industries, August 1996. [3] AL-Ameeri A.S., "Building Materials", Lectures of Building Materials, First Stage, Civil Engineering ,Babylon university, 2007. [4] British Standard Institution, BS 1191 Part1 -1973, "Specification of Gypsum Building Plasters. [5] Central Organization for Standardization & Quality Control, Iraqi Standard, IQS 28-1988, "Building Gypsum". [6] Faiyadh, F.I., Mahmood, D.B.A. and Khalaf, F.M., "Proposals in Improvement the Pure Iraqi-Gypsum properties", Journal of Building Research, Vol.6, No.2, 1987. [7] Al-Taee M.H., "Improvement of properties of gypsum private sector produced from Secondary Gypsum at Center and South of Iraq", Journal of Building Research, Vol.7, No.1, 1988. [8] Al-Aubaidi L.S., "Improvement of properties of gypsum by Using Additive Materials", M.Sc. Thesis, Building and Construction Department, University of Technology, 2007. [9] Al-Qaisi W.A., "Some of the effect of chemical additives on the Setting time for Iraqi technical Gypsum ", Journal of Engineering and Development, Vol.23, No.1, 2004. [10] Fraih K.J, Al-Qaisi W.A. Abdul Khaliq L.S., "The Effect of Some Natural Admixtures on the Setting Time of Iraqi Plaster of Paris", Journal of Engineering and Development, Vol.24, No.9, 2005. [11] Al-Sudani, M. A., "The Use of Gypsum Materials as a substitutes in Building and Finishing Work", M.Sc. Thesis, Building and Construction Department, University of Technology, 2001. . [12] Al-Ramadhani K.A., "Gypsum products, ceramic and marble materials Light", Building Symposium, Baghdad, 1994. [13] AL-Baghdadi A.A., " Improvement of Mechanical properties for Juss Mortar Using vegetable and their plants Fibers", Technology Journal, Vol.23, No.1,2010. [14] AL-Naiemi Y.H., "Gypsum Boards Reinforced with Cellulose Fibers", M.Sc. Thesis, Civil Department, University of Baghdad. [15] Iraqi Ministry of Construction and Housing, Iraqi Building Code 405 -, "Protect buildings from fire", 2014. [16] Muhammed S. M., "Residual Compressive Strength of Iraqi-Gypsum Subjected to Elevated Temperature Exposure ", Journal of Babylon University, Vol.18, No.5, 2010.
  18. 18. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME 27 [17] Central Organization for Standardization & Quality Control, Iraqi Standard, IQS 273-1991, "Chemical Test of Gypsum for Building Purposes". [18] Central Organization for Standardization & Quality Control, Iraqi Standard, IQS 273-1991, "Physical Test of Gypsum for Building Purposes". [19] Central Organization for Standardization & Quality Control, Iraqi Standard, IQS 300-1993, "Determine Ultrasonic Pulse Velocity in Concrete". [20] Sawamy R.N., "New Reinforced Concrete", Surrey University Press, 1985. [21] Teng Y.S. and Shah S.P., "Crack Propagation in Fiber Reinforced Concrete", Journal of Structural Engineering, Vol. 112, No. 1, (1986), pp.(19-34). [22] Hassan, S. A., "Effect of High Elevated Temperature on the Compressive Strength and Ultrasonic Pulse Velocity of High Strength Concrete", Journal of Engineering and Development, Vol. 11, No. 1, 2007 pp. 58-69. [23] Abbas S. Al-Ameeri, K.A.Al- Hussain and M.S Essa, “Constructing a Mathematical Models to Predict Compressive Strength of Concrete from Non-Destructive Testing”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 4, 2013, pp. 1 - 20, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. [24] Alaa Abdul Kareem Ahmad, “The Effect of Gypsum Compensative on Mortar Compressive Strength”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 3, 2013, pp. 168 - 175, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316. [25] Abbas S. Al-Ameeri and Rawaa H. Issa, “Effect of Sulfate on the Properties of Self Compacting Concrete Reinforced by Steel Fiber”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 2, 2013, pp. 270 - 287, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.

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