No abstract

This work analysed the free vibration and stability of thick isotropic and orthotropic plates with SSSS and SSFS support conditions by applying the alternative II theory based on polynomial shape function. The total potential energy which was obtained by combining the strain energy and external work was reduced to three governing equations using Ritz method. Polynomial shape function which varies with Poisson’s ratio was substituted into the governing equation to obtain the fundamental natural frequency, linear frequency and critical buckling load. The values of frequencies of the first mode and critical loads obtained were compared with those obtained using first order shear deformation theory. For span depth ratio of 10, the fundamental linear frequency for orthotropic SSFS plate corresponding to modulus of elasticity ratios (E1/E2) of 10, 25 and 40 are 0.00156, 0.00219 and 0.00255Hz. The corresponding values using first order shear deformation theory are 0.00152, 0.00212 and 0.00245Hz. Keywords: Fundamental natural frequency, SSSS plate, SSFS plate, Ritz method, Orthotropic thick plate, Isotropic thick plate, Stability, Free vibration

Abstract:The strength characteristics of binary blended cement composites made with Ordinary Portland Cement (OPC) and Plantain Leaf Ash (PLA) were investigated in this work. 105 concrete cubes and 105 sandcrete cubes of 150mm x 150mm x 150mm were produced at percentage OPC replacement with PLA of 5%, 10%, 15%, 20%, and 25% and crushed to obtain their compressive strengths at 3, 7, 14, 21, 28, 50, and 90 days of curing. The 3-21 day compressive strength values of OPC-PLA binary blended cement concrete were found to be much lower than the control values; the 28-50 day strengths were comparable to the control values; while the 90 day strengths were higher than the control values especially at 5-10% replacements of OPC with PLA, ranging from 24.40N/mm 2 for 10% replacement of OPC to 25.80N/mm 2 for 5% replacement of OPC compared with the control value of 23.60N/mm 2 . This same trend was observed for OPC-PLA binary blended cement sandcrete. The variation in density was not significant. Mathematical models were developed for predicting compressive strengths of OPC-PLA binary blended cement composites using polynomial regression analysis.The model values of compressive strengths obtained from the various model equations were found to be either exactly the same as those of the equivalent laboratory values or very close to them, with differences ranging from 0 to 0.6N/mm 2 . Thus, OPC-PLA binary blended cement composites could be good for civil engineering works and the developed model equations can be used to estimate their strengths for various curing ages and percentage OPC replacement with PLA.

This work investigated the compressive strength of ternary blended cement sandcrete containing cassava waste ash (CWA) and oil palm bunch ash (OPBA). 105 sandcrete cubes of 150mm x 150mm x 150mm were produced with OPC-CWA binary blended cement, 105 with OPC-OPBA binary blended cement, and 105 with OPC-CWA-OPBA ternary blended cement, each at percentage OPC replacement with pozzolan of 5%, 10%, 15%, 20%, and 25%. Three cubes for each percentage replacement of OPC with pozzolan and the control were tested for saturated surface dry bulk density and crushed to obtain their compressive strengths at 3, 7, 14, 21, 28, 50, and 90 days of curing. The 90-day strengths obtained from ternary blending of OPC with equal proportions of CWA and OPBA were 11.70N/mm 2 for 5% replacement, 11.10N/mm 2 for 10% replacement, 10.80N/mm 2 for 15% replacement, 10.00N/mm 2 for 20% replacement, and 9.60N/mm 2 for 25% replacement, while that of the control was 10.80N/mm 2 . This shows that very high sandcrete strength values could be obtained with OPC-CWA-OPBA ternary blended cement with high quality control at longer days of hydration. Thus, OPC-CWA-OPBA ternary blended cement sandcrete could be used for various civil engineering and building works where early strength is not a major requirement.