Papers by Keyword: Flexural Strength

Abstract: This paper presents the flexural and splitting tensile strength of high strength concrete (HSC) with diatomite micro particles (DMP) as a mineral additive. In order to have micro particles, the diatomite from Aceh Besar District was ground and sieved with sieve size of 250 mm. The particles were then calcined at the temperature of 600 °C for 5 hours. Four mixtures were designed with different DMP to binder ratio (DMP/b). The ratio was 0%, 5%, 10% and 15%, and the water to binder ratio was 0.3. Four beam specimens with a size of 10 cm × 10 cm × 40 cm and four cylinder-specimens with 10 cm diameter and 20 cm high were prepared for each mixture. Flexural and splitting tensile tests were conducted based on ASTM C78 and ASTM C496/496M. The maximum flexural strength was reached at DMP/b of 5% while the maximum splitting tensile strength was reached at DMP/b of 0%.

Abstract: Polymethylmethacrylate (PMMA) resin is the main polymeric material used in removable orthodontic appliances. However, it can promote the adhesion of microbes due to its surface porosity and from long-term use. While vanillin incorporated PMMA resin has been reported to have antimicrobial effects against Candida albicans, the influence of vanillin incorporation on the physical properties of self-curing orthodontic PMMA resin has not been studied. Objective: To determine the flexural strength and flexural modulus of self-curing orthodontic PMMA resin incorporated with vanillin in different concentrations. Materials and methods: Three groups of self-curing orthodontic PMMA with incorporated vanillin concentrations of 0.1%, 0.5% as well as PMMA without vanillin as a control were prepared with ten specimens per group. Flexural strength and flexural modulus were tested by a 3-point bending machine according to ISO 20795-2:2013 specifications. One-way ANOVA and Tukey’s multiple comparison tests at a p<0.05 significance level were used to analyse the data. Results: The 0.1% vanillin incorporated group met ISO standard requirements (flexural strength = 60.48 MPa, flexural modulus = 1756.60 MPa), while the 0.5% vanillin incorporated group failed to pass this standard (flexural strength = 46.94 MPa, flexural modulus = 1423.49 MPa). The means of both flexural strength and flexural modulus showed significant differences among the three groups. Increasing the concentration of vanillin would decrease the flexural strength and flexural modulus of PMMA resin. Conclusion: The incorporation of vanillin into self-curing orthodontic PMMA resin can affect its physical properties, namely flexural strength and flexural modulus. At a concentration of 0.1% vanillin incorporation, PMMA resin displayed physical properties within the ISO standards.

Abstract: Glass fiber reinforced cement (GRC) is a new type of composite material formed by using alkali-resistant glass fiber as a reinforcing material and cement paste or cement mortar as a matrix. GRC is widely used in construction engineering. However, the durability of GRC is still a major problem in engineering applications, especially GRC materials have been in the hot and humid building engineering environment for a long time. The alkaline environment of the cement matrix will cause serious erosion of the glass fiber, and Will significantly reduce the mechanical properties such as flexural strength and toughness of GRC. In this paper, ordinary Portland cement is mixed with active mineral admixtures such as fly ash and silica fume to reduce the alkaline environment of GRC matrix, and to delay the erosion rate of glass fiber and increase the flexural strength and compressive strength of GRC; At the same time, the effects of different hot and humid building engineering environments on the mechanical properties of GRC were studied.

Abstract: There are more than 1000 species of cellulose plants available in fiber form. A number of them are by-products from the major food crops contain lignocellulosic sources and being investigated as composite reinforcement materials. Sugarcane bagasse and rice husk are potential reinforcement materials and they were used to reinforce polylactic acid (PLA) matrix to make green composites. In this research work, sugarcane bagasse was given two different kinds of treatment; some were alkali treated using 8 wt.% NaOH at room temperature for an hour and some other were steam treated at 0.75 MPa for 30 minutes. The fiber content of the composites changed with weight percentage ratios of sugarcane bagasse/rice husk/PLA was 25/0/75, 25/5/70 and 25/10/65. Flexural strength was tested in accordance with ASTM D790-17 and structural evaluation was evaluated using scanning electron microscope (SEM) on the fracture section of the flexural test samples. Composites produced using steam treated sugarcane bagasse and rice husk have lower area density (1277-1385 g/m²) compared to the ones formed using NaOH treated bagasse and rice husk (1162-1500 g/m²). Both values of area density are below the density of neat PP and wood flour reinforced PP/PE composites used as reference materials. The flexural test shows the NaOH treatment on the bagasse fibers improve the flexural strength of the composites but the rice husk content introduced to the structure reduces the strength of the composites. SEM evaluation shows fiber fracture and few pull-out.

Abstract: A type of porous resin was proposed to replace the existing plaster mould for Ceramic Slip Rotary Moulding (CSRM) system. The proposed resin is often used in high pressure casting of ceramic sanitary ware and table ware. The effect of resin mould in terms of mechanical strength (flexural properties), porosity percentage and percentage of water absorption as well as moulding process were recorded and compared with previous studies of plaster mould. Five (5) samples of porous resin were prepared according to ASTM 790 for flexural test and ASTM D570 for water absorption test. To determine the porosity percentage, mercury porosimeter test was conducted. The result shows that higher the water plaster ratio resultant in higher porosity percentage and water absorption. The result showed that, the proposed porous resin has great potential in replacing plaster mould as mould material for CSRM system. The mould has a uniform open pore to enable the filtration process to take place within the mould and the slip and has a great mechanical strength. However, porous resin is still a semi-permanent mould with definite service life.

Abstract: In this research, the results of different weight percentage of glass fiber (30, 40 & 50), cement (0, 3 & 6) and polyester resin (70, 60 & 50), on the properties of glass fiber-cement-polyester composites are investigated. The specimens are prepared by hand lay-up technique. All the specimens are tested for tensile and flexural strength as per ASTM standards. Results showed that escalation in glass fiber wt.% improved the tensile strength (by 9% at 40 wt.% and 17% at 50 wt.%) and flexural strength (by 10% at 40 wt.% and 16.5% at 50 wt.%). Whereas an increase in cement weight percentage decreases tensile strength and increases flexural strength. The failure of the sample is due to glass fiber pull out and rupture of the matrix, under tensile load.

Abstract: This research is a comparative study, the use of carbon fiber and steel fiber for Self-Compacting Concrete (SCC). In previous studies, it was proven that the addition of steel fibers can increase the compressive and tensile strength of SCC. While carbon fiber is one of the most widely used materials for structural reinforcement in recent years. Therefore it is necessary to do a comparative study of the use of carbon fiber if applied to SCC. The percentage increase in carbon fiber and steel is 0.5%, 1%, and 1.5%. Then do the testing of: slump test, compressive strength, tensile strength and flexural strength. The results showed the optimal percentage of steel fiber addition of 1.5%, can increase the compressive strength of SCC by 11%. However carbon fiber and steel do not increase the tensile strength of SCC, and tend to reduce flexural strength. Other results show that carbon fiber is not suitable for use in SCC.

Abstract: Utilization of secondary aluminium dross (SAD) as a constituent material in production of concrete is one of the recycling and value-added alternatives of reusing the waste due to the environmental friendliness, economy and improved performances associated with the material. This present study investigates the feasibility of incorporating SAD as a replacement binder in normal strength concrete (NSC). X-ray fluorescence (XRF) analysis revealed that the investigated SAD is rich in alumina content while exhibiting expansive property when tested via Le Chatelier apparatus. The studied fresh concrete samples blended with SAD recorded low workability and densities as the replacement levels increase. Compressive, split tensile and flexural strength tests conducted on the hardened concrete indicated a reduce strength as the percentage contents of the SAD increases when compared with the reference mixture. Moreover, the water absorption results also revealed higher water absorption capacity of the hardened concrete samples with increasing percentage contents of the SAD in the concrete samples. It is, therefore, suggested that blend of Portland cement (PC) with SAD content within 10% will be beneficial in the production of normal strength concrete for the structural purpose by the construction industry, while also limiting the impact of the aluminium waste on the environment.

Abstract: The paper presents results of tests conducted on self-compacting mixes with the addition of engineered steel fibres. There were used four types of fibres. The fibres were added at 5 levels of the volume ratio. Firstly, fresh mixes were tested (slump flow, class of viscosity and rheological characteristics). Secondly, properties of hardened concretes were tested (compressive strength and flexural strength). Hardened concretes were also tested using non-destructive method, namely X-ray computed tomography. The tests confirmed the possibility of using steel fibres for reinforcing self-compacting concrete. The workability of mixes was maintaining and the assumed technological parameters for hardened concretes were kept. It was found that longer fibres are more likely to be oriented parallel to the direction of the mix flow. Thus, they can operate efficiently under flexural loading of the cast beam.

Abstract: The paper presents the impact of doses of an air-entraining additive on the mechanical properties of a composite based on aluminous cement. The presented data have been selected from the authors’ most recent research, which supports an economic development of a lightweight composite with the ability to withstand elevated temperatures of up to 1000 °C. The interest in the behaviour of concrete at high temperatures mainly results from the many cases of fires taking place in buildings, high-rises, tunnels, and drilling platform structures. Operation at high temperatures is also of fundamental importance to many major sectors of industry, including material production and processing, chemical engineering, power generation and more. Concrete has a great intrinsic behaviour when exposed to fire, especially when compared to other building materials. However, its fire resistance should not be taken for granted and proper structural fire protection is certainly necessary, e.g. in the form of high-temperature barriers. For the purposes of this experiment, the specimens were composed of cement paste and an air-entraining additive dosage between 2 – 10 % by weight of the cement dose. The properties of investigated specimens, dried at a temperature of 105 °C, were compared with each other. Values of compressive strength, flexural strength, and bulk density are measured in this work. The purpose was to evaluate the effects of the air-entraining agent on the workability of a fresh mixture, its bulk density, and mechanical properties after drying. In the case of a mixture with added short basalt fibres, the effects after high thermal loading were also evaluated. The proposed composites with air-entraining additive over 8 % shown the values of bulk density below 1800 kg/m³, along with the satisfactory strength results.