High-strength gypsum binder with improved water-resistance coefficient derived from industrial wastes.

The article presents the possibility of increasing the water resistance of gypsum binders (GBs) obtained based on synthetic gypsum by introducing additives derived from industrial wastes. Regularities were obtained for the influence of the type and amount of additives on the water/gypsum ratio (W/G), strength indicators and water resistance of high-strength GB. The introduction of a single-component additive to improve water resistance does not have a significant effect. Complex additives based on Portland cement, granulated blast-furnace slag, electric steel-smelting slag, expanded clay dust and granite screenings of various fractions have been developed that make the maximum contribution to improving the water resistance of a high-strength GB based on synthetic calcium sulphate dihydrate, which made it possible to increase the water-resistance coefficient from 0.39 to 0.82.

Modeling and optimization of green-Al 6061 prepared from environmentally source materials.

Recent studies are evaluating the use of particulates fabricated from agro-based residues as reinforcement for enhancing the properties of aluminium alloys. This report focuses on the optimization approach and modeling of responses for future prediction, which are absent from the majority of studies involving particle reinforcement of an aluminum matrix. Herein, palm kernel shell ash (PKA) and rice husk ash (RHA) were incorporated with 4 wt% of WSD and used as fillers in the Aluminium-6061 matrix at variable proportions. The response surface approach was utilized in the experiment design, modeling, and outcome optimization. The independent variables are the proportions of PKA and RHA and stir casting temperature. Yield, ultimate tensile, impact strength, elastic modulus, and fracture toughness are examined as response parameters. The results demonstrated that the microstructural property played a significant role in the responses. Incorporating PKA and RHA into the Al-6061 matrix improved the response parameters. Temperatures in the range of 700 and 800 °C enhanced the property parameters, even though temperatures within 800 and 900 °C caused a decline in response. The dependence of the responses on the pattern between property variables was revealed by surface and contour plots. The development of models for predicting responses. Optimal conditions were reached at 4.03% PKA, 5.12% RHA, and 787 °C, with an error <5% when compared to the forecast responses, thus validating the model.

Approaches for filtrate utilization from synthetic gypsum production.

Waste recycling and industrial wastewater treatment have always been of interest. A green approach was developed for the filtrate of synthetic gypsum production from water treatment coagulation sediments and spent sulfuric acid. Due to the high concentration of iron sulfate, concentrated filtrate showed good coagulation results, which were 5% lower than pure iron sulfate. In addition, a high concentration of iron facilitates its use as a precursor for synthesizing magnetic sorbents and photocatalysts. Such materials were synthesized by the solution combustion synthesis method. Oil sorption capacity reached 1.8 g/g, comparable to some synthetic materials and higher than sorption materials based on natural materials. Photodegradation of acid telon blue dye after 90 min of irradiation time was 82.7% with catalyst derived from filtrate compared to the just dye solution with 17.6% efficiency. The reaction rate constant for the photocatalyst sample was up to 11.4-fold higher compared with only UV treatment. The neutralized filtrate containing sulfur, calcium, magnesium, and sodium has been tested as a complex fertilizer. The results of bioindication for oil radish showed up to a 15% increase in the shoot length. A number of techno-economic indicators show that such an approach is advantageous from a technological, environmental, and economic point of view.

Reuse of walnut shell waste in the development of fired ceramic bricks.

The development of agricultural waste-doped fired bricks is an important step toward achieving lightweight eco-efficient bricks with improved thermal insulation property. Recent research in masonry has been tailored towards the production of energy-efficient building by incorporating waste materials as additives. This effectuates a safe waste disposal, cost effectiveness, and also serve as a giant stride towards environmental sustainability. This study examines the viability of using walnut shell as additive in fired clay at various firing temperatures. Pulverized walnut shell was added to clay at a proportion of 0-10 wt.% by weight of clay. The samples were fired at temperatures of 950 °C and 1100 °C. The samples were probed for mechanical properties and durability. Morphology of the brick samples were examined under scanning electron microscope. The result of the research showed increased water absorption and specific heat capacity while mechanical and bulk density were observed to reduce. Linear shrinkage and thermal conductivity reduced with increase in walnut content of which linear shrinkage and thermal conductivity values experienced at 1100 °C was higher than at 950 °C. Resistance of bricks to salt crystallization increased with firing temperature. All samples met various standard requirement for masonry except sample prepared with 10 wt.% walnut shell whose compressive and flexural strengths fell below the required standard. The study established the use of walnut shell for development of sustainable energy-efficient bricks.

Paperbricks produced from wastes: modeling and optimization of compressive strength by response surface approach.

The high cost of building materials occasioned by the increased cost of constituent materials has contributed immensely to the problem of housing deficit faced in Africa and major developing countries of the world. Waste paper can be recycled into bricks but there are limited studies to that effect. Waste glass is used as partial cement replacement to reduce the cost of cement and is also used as a pozzolan. This study focused on the development of paperbricks from the wastes of paper and glass. Response surface method (RSM) was involved in the design of the experiment involving 4 factors: glass powder replacement of cement (A), curing duration (B), compaction pressure (C), and water/cement ratio (D). Box-Behnken method was engaged for the 4-factor, 3-level design. The result of ANOVA showed that experimental inputs had a significant effect on compressive strength response. Factors A, B, and C had a synergetic effect on the response while factor D had an antagonistic effect on the response. Combined interaction between the factors that the response depended on the interactive patterns of the factors. A statistical fit model was developed to predict the compressive strength of the composite. RSM optimization revealed a combination of 36.68%, 57.82 days, 8.50 MPa, and 0.364 for factors A, B, C, and D, respectively, predicting a strength value of 7.358 MPa. Validation experiment carried out using the optimal conditions yielded 7.54 MPa; a deviation of + 0.0247. Since the deviation is less than ± 0.05, the model was statistically validated and fit.

Modeling, multi-response optimization, and performance reliability of green metal composites produced from municipal wastes.

For the purpose of reducing and reusing municipal wastes, used aluminum products, waste glass, and rice husk were selected and reprocessed into green-metal composite. The process entailed recycling of waste glass and rice husk into glass powder (GP) and rice husk ash (RHA), respectively. These were employed as additives in recycled aluminum melt. Composite samples development entailed group mixes A, B, C, and D. Group mix A was prepared by the blend of 3 wt.% RHA at constant proportion with 2, 4, 6, 8, and 10 wt.% GP. Regarding group mixes B, C, D, the same proportion of GP was blended with 6, 9, 12% RHA at constant dosage respectively. Mechanical properties; tensile, impact, flexural and compressive strengths, and fracture toughness were investigated. The significance of the additives on the composites was appraised via performance reliability index (PRI) as a measure of effective property based on variable experimental inputs. From the results, the commix of 3% RHA and 4, 6, 8% GP; 6% RHA and 2, 4, 6% GP; 9% RHA and 2, 4% GP exhibited enhancement of effective property. The compressive strength of the composites was showcased to be the most improved mechanical property. Maximum improvement was obtained at the collage of 4% GP and 6% RHA, yielding a PRI of 1.35. Results of the ANOVA revealed that the experimental inputs had significant contribution on each property response. Mathematical models were developed for each property response, and multi-response optimization predicted an optimum mix of 3.93 wt.% GP and 6.14% RHA. The difference between the property value of the predicted and confirmation experiment is < ± 0.05, validating the models.

Mechanical performance and Taguchi optimization of kenaf fiber/cement-paperboard composite for interior application.

Demand for particleboards keeps increasing and as such more trees are fell for its production, engendering deforestation. For the purpose of reducing falling of trees, this study, focused on recycling of waste paper in the development of paperboard as alternative to particleboards used for furniture and interior household applications. Kenaf fiber (KF) was blended at varying proportions of 0, 1, 2, 3, 4, and 5 wt.% with 20 wt.% constant cement and 20 wt.% constant coconut shell powder while the remaining was paper pulp. Board specimen developed were cured for 14, 28, and 90 days and mechanical properties were examined. Results obtained showed that fiber dosage improved bond strength and screw holding strengths as compared with the control mix. Similarly, modulus of rupture was enhanced with KF loading as compared with control mix while 1 to 3 wt.% KF spawned enhancement of modulus of elasticity. However, 4 and 5 wt.% KF led to a reduction in the modulus. Infusion of the fiber enhanced tensile strength from 1 to 3 wt.% content. 14-day and 28-day curing periods were observed to improve properties while the 90-day curing period is detrimental to all properties. Optimization via signal-to-noise ratio revealed an optimum mix of 2 wt.% obtained for fiber and an optimum curing duration of 28 days.

Recycling of synthetic waste wig fiber in the production of cement-adobe for building envelope: physio-hydric properties.

Waste wigs are often disposed off in their volume on landfills, thus constituting a nuisance to the environment. Recycling these wigs in masonry bricks is a way via which they can be recycled and reused. On such premise, waste wig fiber (WWF) was recycled by incorporating into the cement-sand-clay composite mix for masonry bricks production. The challenges masonry bricks face include shrinkage and water susceptibility; hence, the contributory effect of WWF on physio-hydric properties was assessed in this study. Sample preparation entailed blending of cement, sand, clay soil, and waste wig fiber. The control mix was prepared by commixing clay with 10% cement (by clay volume) and 20% sand (by clay volume). Other mix proportions were reinforced with 1, 2, 3, 4, and 5% WWF by clay volume. Prepared composite brick samples were cured for 28 and 56 days and tested for physio-hydric properties. Results revealed WWF contributed significantly in improving hydro-resisting properties by minimizing porosity, water and moisture absorption, capillary suction, and water permeability. Furthermore, WWF contributed to dimensional stability by reducing shrinkages and weight loss. Hydration time impacts significantly in reducing apparent porosity, water permeability coefficient, moisture and water absorption, and capillary suction coefficient and increasing apparent density, weight loss, linear, and volumetric shrinkage. The general outcome depicts that WWF showed promising performance in bricks developed in enhancing water and moisture susceptibility resistance and promoting mass and dimensional stability, hence can be employed in reinforcing cement adobe bricks at an optimum mix of 5% vol fraction.