Flexural Behavior of 3D printed Concrete Beam with Fiber Reinforcement

3D printing with concrete is a promising new method for rapid, low cost construction. The flexural strengths for reinforced/unreinforced and 3D printed/cast concrete Warren trusses were tabulated and the failure mechanisms were reported. The types of reinforcement used were rebar(basalt and steel), and mesh (basalt and aramid). The effect of loading geometry and loading speed was measured for basalt mesh and aramid mesh composite, respectively. Due to the expected variation in flexure between samples, it cannot be said whether small differences for various tests are significant. Variation stems from a microscopically uneven surface and random inhomogeneities in the bulk of the tested material which act as a microcrack catalyst and propagator. Since the tested beams are short specimens the numerical findings of other studies will vary based on the intended design. This paper is intended to assess the performance of various reinforcements in a qualitative sense by comparing basalt reinforcement with other reinforcements. It was found that cast beams tolerated deflection better but had a similar flexure strength compared as the printed beams. The steel and basalt rebar reinforced beams had the highest flexure strengths where the traditional steel rebar reinforcement outperformed the basalt in flexure by 36% and the basalt outperformed the steel in deflection by 40%. The basalt mesh outperformed the cast and printed unreinforced bars by a small margin but had only 25% of steel rebars’ deflection at maximum flexure strength. The aramid mesh tolerated the biggest deflection out of any sample at 2.26 cm.

Bending Strength of Magnesium Oxide Board

Magnesium Oxide (MgO) board has been widely used in prefabricated lightweight steelframe wall systems and as the floor board covering component. It is a non-insulating sheathingboard product which consists of sustainable materials with the characteristics of fire resistance,weather-ability, strength, resistance to mold and mildew. Although MgO board has recentlyworldwide used in façade construction but the research data related to the laboratory work such asthe bending strength is still limited. The previous studies on the bending strength of MgO board arebased on various standards such as ASTM, JC688 and British Standard subjected to the productscharacteristics and patterns. Therefore, the bending strength values obtained were inconsistent andnot convincing. Thus, this paper aims to examine the bending strength of MgO board with threedifference thicknesses (6mm, 9 mm and 12 mm) based on BS EN 310:1993 subjected to threepoints bending test. The failure modes during three points bending test was observed and theexperimental results obtained were compared with the theoretical values and others relevantstandards. A total of thirty six specimens with twelve specimens for each thickness in two groupdirections namely longitudinal (length) and transverse (width) direction were tested. The specimenswere prepared based on BS EN 326-1:1994 and BS EN 325:2012. The maximum flexure load of thespecimens was recorded and arithmetic mean bending strength for each thickness was presented.The experimental results showed the tested MgO board was not achieved minimum bendingstrength for load bearing used. It is recommended to be used in non-load bearing façade claddingconstruction.

Ductility and Durability Enhancement of Concrete EPS by New Reinforcement Arrangements and PP FRC Utilization

A majority of precast concrete electric pole structures (EPSs) consist of prestressed concrete (PSC) and reinforced concrete (RC) hybrid members with high slenderness ratios. Currently, large prestressing (PS) forces are being applied to EPSs to carry heavier weights of electric transformer machineries and to reduce deflection by increasing structural stiffness. Moreover, when EPSs are exposed to an outdoor environment year-round, their durability decreases. Therefore, this study’s objectives are to transform the failure behavior of EPSs from brittle to ductile by varying the number of PS tendons and steel rebars, and to improve the EPSs’ ductility and durability by using short polypropylene (PP) fiber-reinforced concrete to control crack formation and propagation. Six different types of EPS specimens were manufactured and tested to evaluate their maximum flexure capacity and to verify their ductility behavior. The results showed that the modified EPSs displayed ductile failure behavior while either maintaining their original flexural strength capacity or improving it compared with the current EPSs sold on the market.

Research on Mechanical Property of Single Panel Fire-Resistant Glass with Cs+ Ion and Rb+ Ion Exchange

The effect of Cs+ ion and Rb+ ion in the molten salt of different proportion on the single panel fire-resistant glass is discussed in this paper. The single panel fire-resistant glass was prepared by the method of ion-exchange, with proper amount of additives and adding KNO3 and CsNO3 , KNO3 and RbNO3 as the main part of molten salt. The proportion of the molten salt was changed separately, a contrast test was performed to measure the flexure strength. The results indicated that the flexure strength of the single panel fire-resistant glass increased firstly and then stabilized as the ratios of w(CsNO3)/w(KNO3) and w(CsNO3)/w(RbNO3) increased respectively. With the ratio of w(CsNO3)/w(KNO3) =1.5%, the mechanical property of the single panel fire-resistant glass was proper and the maximum flexure strength was 274 MPa. In the case of RbNO3, the flexure strength of single panel fire-resistant was 244 MPa with the ratio of w(CsNO3)/w(KNO3) = 0.3%. According to the research, it is found that the method of ion-exchange of Cs+ and Rb+ into plain glass to prepare single panel fire-resistant glass is feasible, the sample melted under the condition of 1 hour and 780 without any trace of thermal explosion.

The Effect of Glass Chemistry on the Microstructub and Properties of Self Reinforced Silicon Nitride

ABSTRACTThe advantage of self-reinforced silicon nitride is the in-situ control of the microstructure. This control is provided in large degree by the chemistry of glassy phase which can be adjusted to tailor the morphology of silicon nitride grains as well as the matrix - reinforcement interface. The presence of high aspect ratio silicon nitride grains is necessary but not sufficient condition to produce materials with optimum properties. For maximum flexure strength and fracture toughness an optimized glass matrix is required.