Response of Oyster Shell Ash Blended Cement Concrete in Sulphuric Acid Environment

An experimental investigation was carried out to study the potentials of oyster shell ash (OSA) to be used as supplementary cementitious material (SCM) exposed to sulphuric acid environment. Experiments were carried out by supplementing 5 – 20 % of OSA by weight of cement in concrete. The mix ratio used was 1:2:4 (binder, sand and granite) with water cement ratio maintained at 0.5. A total of 320 cube specimens (150mm x 150mm x 150mm) were cast and tested for compressive strength at 7, 14, 21 and 28 days of curing in potable tap water and (5, 7.5 and 10 %) sulphuric acid solutions. It has been deduced that the compressive strength of concrete specimen progressively increased with longer curing periods and decreased with OSA content for specimen immersed in water whereas for specimen immersed in sulphuric acid solutions the compressive strength decreased with longer curing period, OSA content as well as sulphuric acid content. Generally, results of the statistical analysis showed that sulphuric acid concentrations, OSA contents and curing periods have significant effect on the compressive strength of concrete. The use of OSA as SCM did not mitigate the adverse effects of sulphuric acid on the compressive strength of cement blended with OSA. Keywords: Compressive strength, Oyster shell ash, Statistical analysis, Sulphuric acid environment, supplementary cementitious material DOI: 10.7176/CER/11-4-07 Publication date:May 31st 201

Desiccation-Induced Volumetric Shrinkage Characteristics of Highly Expansive Tropical Black Clay Treated with Groundnut Shell Ash for Barrier Consideration

Contamination of underground water as a result of excessive crack on clay liner material is a prevalent phenomenon in an engineered landfill. Volumetric shrinkage strain (VSS) is one of the veritable properties considered for selection of materials suitable for liners and cover in waste containment systems. Material devoid of excessive shrinkage and cracking during climate change could possibly make a better barrier material that will eventually limit or control infiltration of leachate in an engineered landfill. Hence, to obtain a clay liner and covers system that are safe and robust, stabilization of such soil (expansive clay soils) becomes imperative. In order to stabilize or reduce excessive cracking and shrinkage of this soil, earlier researchers have employed cement, chemicals, and fibers. However, in recent times, the ill effects of these stabilizers on the environment have been realized, and hence their replacement with sustainable materials that are mostly agro and or industry by-products is becoming necessary. Tropical dark grey clay treated with up to 8 % Groundnut shell ash (GSA), was carried out. Specimen were compacted using British standard light (BSL) and British standard heavy (BSH) compactive efforts; at water contents between 2% dry and 4% wet of optimum. The compacted specimens were extruded and subjected to drying under laboratory conditions to evaluate its desiccation induced shrinkage and hence its suitability as a cover material in waste containment facilities. Results of this study show that changes in mass and volumetric shrinkage strain were large within the first five days of drying. Volumetric shrinkage strain increased with higher moulding water contents (MWC) and water contents relative to optimum (WRO). The effect of GSA treatment on VSS was not consistent from -2 to +2 % of optimum moisture content. For specimen prepared at +4 % of optimum moisture content, VSS decreased up to a threshold of  28% at 6 % GSA and 30% at 4% GSA for BSH and BSL compactive effort, respectively. Generally, lower compactive effort (BSL) with higher moulding water content and lower dry density produced higher VSS. A regression function was developed from the data to estimate VSS given the compaction water content relative to optimum (WRO), groundnut shell ash content (GSA), plasticity index (PI), percentage fine content (PF) and compactive effort (CE). Compaction water content relative to optimum significantly correlated with VSS, thus should be strictly regulated during field compaction to realize a durable hydraulic barrier. Keywords: Atterberg limit, compaction, desiccation, expansive soil, groundnut shell ash, statistical analysis DOI: 10.7176/CER/11-8-06 Publication date:September 30th 201

Measurement of the proton structure function F2 at low Q2 in QED compton scattering at HERA.

The proton structure function F2(x,Q2) is measured in inelastic QED Compton scattering using data collected with the H1 detector at HERA. QED Compton events are used to access the kinematic range of very low virtualities of the exchanged photon, Q2, down to 0.5 GeV2, and Bjorken x up to 0.06, a region which has not been covered previously by inclusive measurements at HERA. The results are in agreement with the measurements from fixed target lepton–nucleon scattering experiments