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.

This research presents the influence of cement fineness on the structural characteristics of normal concrete. The cement was divided into different fineness zones (150 µm – 7 5µm, 75 µm – 45 µm and 45 µm – 0 µm). Thirty (30 Nos.) cement mortar cubes, 54 Nos. of 150 x 150 x 150 mm concrete cubes and 36 Nos. of 150 x 300 mm cylinder specimens were cast, cured by immersion and tested at 3, 7, 14, 21, 28 and 45 days. A concrete mix ratio of 1:2:4 (Cement: Fine aggregate: Coarse aggregate) with water/cement ratio of 0.5 was used. The results reveal that an increase in the fineness of cement particle led to an increase in workability. The setting times (initial and final setting time) reduces progressively as the cement fineness is increased from 175mins (initial setting time) for sizes 150 µm – 75 µm to an initial setting time of 140mins for sizes 45µm - 0µm. The final setting time also reduces from 300 mins to 240 mins as the cement fineness is increased. The tensile and compressive strengths recorded an increase due to the increase in cement within the concrete matrix. It was concluded that the finer the cement particle the greater the concrete strength.

The study investigated the effects of rest period on the short-term mechanical property of geopolymer concrete (GPC) that could possibly be easy to embrace in the field to achieve an optimum strength performance. The study utilized both corncob ash (CCA) and ground granulated blast furnace slag (GGBFS) as sustainable construction binders with a view to building sustainable infrastructure. Also, sodium silicate gel (Na₂SiO₃) and sodium hydroxide (NaOH) solution was used as an alkaline activator, and prepared in 14 molar concentration of NaOH pellets using a mix ratio of grade 30 MPa and grade 40 MPa concretes. GGBFS was substituted in 0, 20, 40, 60, 80, and 100% by volume of CCA. The rest periods (RP) for the fresh concrete were selected as 1, 2, 3, 4 and 5 days before being demoulded. Thereafter, the concrete samples were removed from the moulds and cured under ambient conditions for 7, 28, 56 and 90 days. The compressive strength of the hardened concrete samples was then determined. The study findings reveal an optimum strength performance at 4 days rest period for all classes of concrete produced when compared with 1, 2, 3 and 5 days. Thus, this result can be practically employed and incorporated in the design of geopolymer concrete and at the construction site.

This study examined the rheology of slag-based geopolymer concrete (GPC) incorporated with corncob ash (CCA). In an attempt to sustain an effective way of recycling our waste products and remedying land, water and air pollution, the study harnessed both ground granulated blast furnace slag (GGBFS) and corncob ash (CCA) as sustainable binders. In addition, sodium hydroxide (NaOH) solution and sodium silicate gel (Na₂SiO₃) were used as alkaline liquid. Method of volume by batching was adopted where GGBFS was replaced by CCA in 0, 20, 40, 60, 80, and 100%. The paste normal consistency was used to prepare the specimens for both initial and final setting times of the fresh concrete. However, slump and compacting factor values on the freshly made concrete were determined on both grade 30 MPa and grade 40 MPa concretes using the activation of 12, 14 and 16 molar concentrations of NaOH pellets. The experimental results show that the initial and final setting times increased with increasing CCA content; while the slump, compacting factor tests also increased with increasing CCA content. On the other hand, the workability of GPC reduced with increasing grade of concrete and molarity of NaOH solution. The study finding is beneficial in that fresh concrete remains workable for longer periods, thus resulting in lesser joints. It is also advantageous especially in hot weather conditions.