Physicomechanical Characterization of Basement Rocks for Construction Aggregate: A Case Study of Kajuru Area, Kaduna, Nigeria

Abstract

This study evaluates the physical, mechanical and in-situ properties of the rock aggregates in Kajuru, Kaduna State, Nigeria as sources of aggregate for construction purpose. The uniaxial compressive strength was determined by using Universal Testing Machine to crush cored samples and Schmidt rebound number by Schmidt hammer apparatus. While the engineering destructive tests were carried out on aggregates using various apparatus. Na2SO4 solution was used for soundness test and glass jar for determination of specific gravity. The results indicate that specific gravity ranges from 2.48 to 2.88, the moisture content of samples are within 2%. The UCS ranges from 95.76Mpa to 169.70Mpa while the Schmidt rebound number ranges from 29.4 to 35.3. Comparing the Los Angeles abrasion, impact and crushing value obtained from the laboratory destructive test with the B.S standards, most of the rock can be used for construction works. The results also indicate that there is direct proportional relationship between compressive strength with Schmidt rebound number and specific gravity. Inverse relationship exists between moisture content with specific gravity and compressive strength. The physical and geotechnical properties were found to be dependent on the chemical and petrographic characteristics of the rock. This paper exhibit the geotechnical and physical properties of rock as the second part of the research on Characterization of Basement Rocks in Kajuru area, Kaduna, Nigeria for Construction Aggregate. Kaduna is located on a basement rock that is widely used as construction materials for highways, bridges, dams, rail tracks and buildings. The excessive excavation of river sand is becoming a serious environmental problem (Jayawardena and Dissanayake, 2008) that leads to failure of river banks, lowering of river beds, damages to bridge foundations and other structures situated closer to the rivers. Similar trend is obtainable in northern Nigeria. Therefore rocks are also quarried for manufacture of quarry dust and are used as sand replacement for construction purposes and moulding of bricks. They are also used as granite and marble for production of magnificent walls, floor tiles and grandeur kitchen tops etc. In the various ways rock aggregates are used, they are exposed to a variety of stresses, and the response of the structure in which it is used will largely depend on the properties of the aggregate. It needs to resist heavy loads, high impacts and severe abrasion, and it needs to be durable in the prevailing environmental condition (Egesi and Tse, 2012). This study was initiated from the observation that there are variations in properties and strength of rock and aggregate obtained from one geological location to the other. Therefore it is imperative to systematically characterize aggregates obtained from this area and evaluate factors that control the compressive strength of rock in order to develop practical quality-control specifications and ease optimum aggregate selection. The present study aims to highlight the basic engineering properties of aggregates source rock and integrate factors controlling them from this area. II. Materials and Methods Gamin76 (GPS) was used to survey the drill holes locations and their coordinates were recorded in the field work book. Cored rocks were obtained from 12 different drills holes spread across the research area at depth ranges from 12m to 15m. Samples collected at 5m depth intervals were placed in polythene bag which were accurately labelled for uniaxial compressive strength test. Large boulders were obtained from rock outcrops in situ and these outcrops were crushed into smaller sizes by local crusher to determine the physical properties. Specific gravity and water absorption rate were measured using weight balance, oven and glass jar. Destructive test of impact and crushing value was carried out using their apparatus. Los Angeles abrasion test was done with abrasion testing machine while Na2SO4 solution was used for soundness test. Bulk samples taken from the specimens were also cut into blocks for Schmidt hammer test.