The effective use of residual laterite soils is usually hindered because of their mineralogy and high fines content. This paper studied the potential improvement in the geotechnical and mineralogical properties of Fly ash-treated residual laterite collected from Southwest Nigeria. Some physical and geotechnical properties, such as plasticity, compaction, unconfined compressive strength (UCS), and California Bearing ratio (CBR) of untreated and treated laterites were determined using ASTM standard methods. Stabilization was achieved by mixing the laterite with varying proportions (0%, 3%, 6%, 9%, 12%, and 15% by mass of dry laterite) of Fly ash. Mineralogical analysis of untreated and treated laterite was done using the X-ray diffractometer (XRD). The results showed a slight initial increase at low proportions of Fly ash (at 3%) in the plasticity properties and a subsequent decrease (of up to 65%) afterward. The UCS and CBR of the treated laterite increased over 100% (maximum UCS 110% and maximum CBR 183%) at 6% Fly ash content. XRD analysis showed the formation of new minerals, predominantly portlandite, within the stabilized soils. This study confirmed that using Fly ash for the stabilization of residual laterite soils is potentially viable for road construction.

This paper reports the results of the investigation done on bricks made using bottom ash and Fly ash. Bricks were made with various proportions of bottom ash, Fly ash and cement. Tests for workability, density, strength, water absorption and ultrasonic pulse velocity (UPV) were conducted. Results show that the compressive strength ranged from 5.5 MPa to 11.68 MPa, maximum water absorption was 15.7% and the UPV ranging from 2260.2 m/s to 2916.1 m/s. The strength of bricks increases with the increase in Fly ash; water absorption, and UPV with the increase in Fly ash. It is concluded that bricks of good quality can be made using bottom ash and Fly ash whereby contributing to sustainable development.

The demand for aggregates for civil engineering construction is high in the market. The broad adoption of Fly ash for producing Fly ash aggregate is the best sustainable solution to fulfill aggregate demand and utilization of unused Fly ash. Crushing is an essential step for producing angular-shaped aggregate. In this paper, an experimental study using a laboratory-scaled impact crusher was carried out to investigate the effect of crushing process parameters (feed block size, crusher speed and outlet sieve size) on the quality (particle size distribution, flakiness-elongation index and mechanical properties) of angular-shaped Fly ash aggregates produced after crushing high-strength Fly ash blocks. Particle size distribution and flakiness-elongation index were found to be changed with crushing parameters. Higher crushing speed resulted in small-size Fly ash aggregates. Better particle size distribution of crushed Fly ash aggregate was produced using a 60 mm outlet sieve compared to a 30 mm one. Well-graded Fly ash aggregates with good particle shape (less flaky and less elongated) for the subbase layer of the road were obtained after crushing Fly ash blocks of one-third feed size in a laboratory-scaled impact crusher at a crushing speed of 527 rpm and an outlet sieve of 60 mm. Mechanical properties (impact, crushing and abrasion values) of the Fly ash aggregate were not much affected by crushing process parameters. The findings of this study will help in optimizing the crushing operation of the industrial impact crusher to produce high-quality angular-shaped Fly ash aggregate on a large scale.