Performance evaluation of cashew nutshell ash as a binder in concrete production

The agro-industrial sector annually produces large volumes of waste by-products which as a result of the ignorance of their values as well as their ineffective management, pose environmental, societal and economic threats. Thus, this study explored the ash from cashew nutshell waste and replaced it with Portland limestone cement (PLC) at 5%,10%,15% and 20% using a mix design ratio of grade 25 MPa concrete (M 25). The cashew nutshell was sun-dried for 14 days and then burnt in a gas furnace at a temperature of 750 �C for 5 h to obtain cashew nutshell ash (CNSA). The chemical and physical properties of the CNSA were examined while the workability of the fresh concrete was investigated. Moreover, the mechanical and durability properties of the hardened concrete were carried out while the microstructures of the concrete samples were analyzed. The experimental findings revealed that CNSA met the requirements for use as a pozzolanic material. The slump and the compacting factor increased with increasing CNSA content. Moreover, both compressive, splitting tensile and flexural strengths of the hardened concrete increased as the content of CNSA increased but optimum at 15% replacement level. Furthermore, the CNSA concrete resisted more sulfate attack than the Portland cement concrete (control). The micromorphological analysis exhibited a reticular structure and adequate filling ability with the incorporation of CNSA content in the mix. Hence, it is recommended that CNSA can be incorporated as a construction material in the concrete production at the optimum replacement with PLC at 15% for structural application and 20% for non-load bearing application. This study is advantageous because fresh concrete would remain workable for longer periods, thus, resulting in the reduction of construction joints. Moreover, the utilization of CNSA concrete is also beneficial in an environment with high sulfate content. Finally, the developed model equations from this study can be used in the development of mix design of blended concrete as well as a better refinement of existing procedure of concrete mix design provided the chemical composition of the materials is established

Effect of Ammonium on the Hydraulic Conductivity of Kaolin and Bentonite as Clay Liners

: Landfill liners are underlying materials with low permeability whose main function is to mitigate the infiltration of toxic contents into ground water lying beneath. Landfill liners are primarily made of bentonite clay. Bentonite has a very low hydraulic conductivity, that might not be readily accessible, unlike kaolin which is found to have a lower hydraulic conductivity compared to that of bentonite and can be extensively obtained from numerous different sources. Explored, for the purposes of the present research paper, were various ratios of bentonite and kaolin and their hydraulic conductivity, in particular ratios of 90:10 kaolin to bentonite, 80:20 kaolin to bentonite, 70:30 kaolin to bentonite, 60:40 kaolin to bentonite and 50:50 kaolin to bentonite in an effort to achieve an acceptable barrier suitable as a liner / where tap water and ammonium solution were used as permeants. It was concluded that the ratios not lower than 20% bentonite (80:20, 70:30, 60:40 and 50:50) all had their hydraulic conductivity value reduced compared to the 100% kaolin

Predicting the splitting tensile strength of concrete incorporating anacardium occidentale nut shell ash using reactivity index concepts and mix design …

The prevalence of global warming and climate change are associated with carbon dioxide (CO2) emitting from fossil fuel combustion and Portland cement (PC) production. However, in a bid to minimize over-reliance on PC, this study recycled a supplementary cementitious material (SCM), anacardium occidentale nutshell ash (AONSA), for the production of green concrete. AONSA was used as a replacement for Portland limestone cement (PLC) at 0, 5, 10, 15, and 20 % using the mix design proportions (MDPs) of grades 25 (M 25), 30 (M 30), and 40 (M 40) concrete. The chemical compositions of both AONSA and PLC were analyzed. Moreover, the chemical moduli of each and mixed binder were determined and evaluated, hence quantifying the reactivity indexes (RIs). Consequently, RIs and MDPs were applied to predict the splitting tensile strength. Compared with the experimental results, the predictive splitting tensile strength relative to the RIs and the MDPs yielded a high precision with 95 % R2 at 28 days curing. Therefore, the model equations proposed by this study can be applied to the concrete mix design procedure for the splitting tensile strength of green concrete incorporating SCMs provided the chemical compositions of each and mixed material are established

Optimising the Workability and Strength of Concrete Modified with Anacardium Occidentale Nutshell Ash

Strength failure persists both in structural and mechanical analysis. One of its prominent characteristics is the adequate provision for parameters that minimise or maximise strength objectives while satisfying boundary conditions. The previous optimisation of concrete strength usually neglects mix design mechanisms induced by optimisation. Recent efforts to accurately optimise the concrete compressive strength have factored in some of these mechanisms. However, optimising concrete strength modified with high silica and alumina precursors, and crucial mix design factors are rare. Consequently, this paper optimised the concrete workability and strength, incorporating binding, water/binder ratio, binder/aggregate ratio, and curing mechanisms using the Box–Behnken design approach (BBDA). A waste material, anacardium occidentale (cashew) nutshell ash, was valorised and used at 5, 10, and 15 wt.% of cement. The composites were made, cured and tested at 14–90 d. The results revealed a high precision between the experimental slump and the optimisation slump at 97% R2. In addition, a 5% increase in compressive strength was obtained compared with the target compressive strength. Besides, the correlation between the model equation obtained from this study and predictions of previous studies via BBDA yielded a strong relationship