Journal of Civil Engineering and Materials Application
Volume:4 Issue: 2, Spring 2020

The main problem with saturated fine-grained soils is the slowness of consolidation procedure and the occurrence of large soil settlements. Generally, to expedite consolidation procedure, preloading method would be used along with prefabricated vertical drains. Soil improvement process under this condition would be subjected to design method and vertical drains’ modeling. In the current paper and to understand the consolidation behavior of clayey soils improved with vertical drains, a parametric study has been performed by PLAXIS 2D finite element software. The results are indicative of an increase in average consolidation degree from 74 to 84% after a period of 6 months through the reduction of vertical drains’ distances from 4.5 to 1.5m. Moreover, it became clear that an increase would be made in the rate of settlement, consolidation, and dissipation of excess pore water pressure through increase made in length and diameter of vertical drains and increase of their discharge capacity. Also, it became specified that increase of diameter is less effective on the expedition of consolidation procedure compared to that of distance reduction among drains.

Due to the high volume of agricultural waste, the use of some of them in the manufacture of concrete reduces the production residues and the problems caused by their lack of recycling. Bagasse is a pulp produced after sugar cane extraction. The sugar cane factories produce about 1.2 million tons of excess bagasse annually due to the lack of conversion industries. In today's modern world, due to advances made in various scientific fields, the concrete industry has also evolved. The production of concrete containing pozzolan bagasse is also the result of the same improvements; concrete. In this study, for the production of synthetic pozzolan sugarcane bagasse, according to studies bagasse was burned for 30 minutes at a controlled temperature of 4 ° C. Then, by replacing 1, 2, 3, 2, and 2% of bagasse ash instead of cement in concrete, compressive strength, electrical strength, chloride penetration were evaluated by RCMT, water pressure, and sulfate resistance. The results showed an increase in compressive strength of the specimens up to 5% of cement replacement at different ages and a higher percentage of compressive strength loss was observed in the control specimen, but the electrical resistance at different ages increased by up to two-fold in the control specimen and also decreased. Before this, attention was drawn to the amount of water and chloride ion penetration. Sulfate resistance also increased by up to 5% replacement, but the highest sulfate resistance was observed in the sample by 5% replacement.

One of the well-known and highly used extensions of vehicle routing problem (VRP) is Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD), in which delivery and pickup for each customer is carried out simultaneously. In this study, it is attempted to present an optimal method for solving VRPSPD using genetic algorithm. In this method, genetic algorithm is improved by modifying genetic parameters and presenting efficient and proper operators. Three Randomized, Nearest neighbor and Cheapest Insertion algorithms are utilized to create the initial population. Given the different structure used in each of these methods, the initial solutions are varied and include all feasible regions. In addition, by making modifications in these methods, the initial population was tried to be created through higher quality solutions to help genetic algorithm reach a better future generation. Also, 4 algorithms were invented for mutation operators, which prevented convergence in local optimums and helped finding better solutions by comparing the results. The proposed algorithm is executed on 40 different standard examples. After comparing the results by this algorithm and the best solutions by other algorithms, improvement is observed in 3 of the examples.

In recent years, geopolymers, as a new class of green cement binders, have been considered as an environmental-friendly alternative to Ordinary Portland Cement (OPC) which can potentially reduce negative environmental impacts of OPC effectively. In this experimental research, effects of different alkaline activator solutions and variations of associated parameters, including KOH concentration and Na2SiO3/KOH weight ratio, on the compressive strength of fly ash-based geopolymer concrete were investigated. The obtained results showed that using NaOH provided greater 3- and 7- day compressive strengths as well as faster hardening. Conversely, using KOH resulted in higher 28-day compressive strength. Additionally, simultaneous inclusion of 50% NaOH and 50% KOH resulted in decline of the compressive strength. Furthermore, the obtained results indicated that increasing the KOH concentration up to 14 M resulted in the highest compressive strength, while weight ratio of 1.5 for Na2SiO3/KOH was the optimum value to achieve highest 7-and 28-day compressive strengths.

The crave for a sustainable green environment and yearning for lightweight structures in society today have prompted engineers to seek more alternative materials to reduce the negative sides of concrete structures. Often time, composite materials or fibers are incorporated into the concrete matrix to give better performance. In this regard, the fiber enhances the concrete aggregates against stresses. This study assessed the performance of Luffa aegyptiaca (sponge gourd), a natural fiber as a polymer reinforcement in concrete for better operation. Different layering arrangements were adopted (lamina, mesh, longitudinal, and disperse) to get the best fit. The compressive strength test, as well as the flexural strength test, among other tests carried out, indicated that laying the fiber longitudinally in the concrete matrix can give better performance in strength. The average compressive and flexural strength of 25.8 MPa and 10.2 MPa respectively are recorded for the longitudinal arrangement, which stands as the highest strength. The fiber can work well in improving concrete spalling. An extended study on the mechanical properties of the Luffa aegyptiaca to ascertain its performance is therefore recommended.