Performance Evaluation of Rice Husk Ash as Partial Replacement of Cement in Concrete in a Marine Environment at Escravos River, Niger Delta Area, Nigeria

Cement has proven to cause environmental problems during its production and to be a relatively high-cost material in concrete production. Environmentally friendly, alternative binders like Rice Husk Ash (RHA) have recently been brought to bear. Therefore, the objective of this paper is to evaluate the performance of RHA (under controlled temperature and burning time) as a partial (10% and 20%) replacement of cement in concrete in a marine environment at Escravos River, Niger Delta Area, Nigeria. Concrete samples prepared with the 10% and 20% RHA in the laboratory were exposed to brackish water samples from the Escravos River, at 3 days, 7 days, 28 days and 90 days and the results compared with that of PLC concrete cast. Data obtained show that the workability of fresh concrete reduced with increase in RHA and further reduced, mixing with salt water. RHA contributed positively to the setting time of the concrete as it increased the initial setting time and reduced final setting time. 10%RHA concrete performed best under all conditions, with about 10% increase in strength. Further increase led to a slight decline in strength. As the amount of RHA increased, the ability of the concrete to resist chloride penetration, increased, with lesser average penetration depth. 10%RHA concrete showed the strongest rebar-concrete bond. 10% RHA is optimum for partial replacement of cement in concrete in marine environment, as it enhances the performance of the concrete

Compressive Strength and Resistance to Sodium Sulphate Attack of Concrete Incorporated with Fine Aggregate Recycled Ceramic Tiles

In this experimental study, compressive strength and resistance to sodium sulphate attack of concrete incorporating recycled ceramic tiles (RCT) as fine aggregate were investigated. RCT was used as partial replacement for river sand at four levels (0%, 33%, 66%, 100%). Samples for sulphate resistance tests were immersed in 5% Na2SO4 solution for 180 days after they had been cured under water for 28 days, and were monitored for change in physical appearance, mass change and loss of compressive strength. From experimental results, RCT was found to be capable of producing light weight concrete compared to river sand. The results showed increase in compressive strength as the level of RCT content increased. On resistance to sulphate attack, sodium sulphate seems not to attack C-S-H bond which is produced in excess in RCT concrete, rather it attacks calcium hydroxide and calcium aluminate which are produced in equal amounts for both RCT and control samples. Hence, RCT might not play much direct role in concrete’s resistance to strength loss due to sulphate attack. However, the residual compressive strength of the RCT samples after the attack was seen to be much higher than that of the control samples because of their initial higher strength before the attack. This shows that RCT can improve the properties of concrete when incorporated as fine aggregates

Effect of Curing Age on the Prospect of Used Plastics to Enhance Engineering Properties of Road Pavements within a Development and Property Agency Estate in Benin City, Edo State, Nigeria

This study investigated the effect of curing age on the possibility of using plastic powder to enhance the engineering properties of subgrade for road pavements. The soil samples utilized for the study were collected from four distinct locations within the Edo Development and Property Agency estate in Benin City, Edo State, Nigeria using appropriate standard methods. They were stored in airtight polythene bags and taken to the University of Benin Geotechnical Laboratory for testing. Polyethylene terephthalate (PET) plastics sourced from recycled soft drink and bottled water containers were pulverized and added to the soil in various proportions of 2%, 4%, 6%, 8% and 10% by weight of the soil. The resulting mix was subjected to various tests such as Atterberg limits, compaction and California Bearing Ratio (CBR). The results showed that the addition of the PET plastic powder led to substantial transformation in the soil’s properties. There was a reduction in the liquid limit, plastic limit and plasticity index, as the proportion of the plastic powder increased. The maximum dry density (MDD) and the optimum moisture content (OMC) was also seen to increase and decrease correspondingly as the proportion of the plastic powder was increased in the soil. The results also showed that as proportion of the plastic powder in the soil was increased, the CBR of the soil also increased. This increase in the soil strength was also observed as the curing age of the CBR samples increased from 0 to 14 days. This shows that a combination of extended curing periods and a larger proportion of plastic powder can significantly improve the load-bearing capacity and saturation resistance of the soil. This study underscores the considerable potential of plastic powder stabilization in elevating the engineering properties of subgrade materials, thereby conferring notable benefits to the domain of road pavement construction