Regression Models for the Prediction of Strength Properties of Waste Tyre Ash (WTA) - Mortar

Sustainable development is an emerging political and social issue of global significance, Environmental scientists are generally of the view that Portland cement is not particularly environmentally friendly. Thus, the challenges of producing and using concrete, is aggravated by the high need and consumption of cement which is causing the using concrete, is aggravated by the high need and consumption of cement which is causing the environmental threats as outlined by the environmentalists. The background of this study emanates from this development and forms the basis for conducting the research. Waste Tyre Ash (WTA) is the ash residue that is obtained after slices of waste or scrap tyres are burnt at a temperature of 5000C for a period of 5 hrs.  Therefore, the aim of this study is to determine the effect of using WTA as a partial replacement of cement in WTA-Mortar and to develop models for the prediction of strength properties. Cement was partially replaced with WTA at 0%, 5%, 10%, 15%, 20%, 25% and 30% by weight. The findings showed that WTA decelerates setting time of cement and strength development in mortar. Compressive strength and flexural strength of mortar increases with increase in WTA up to 20% and 15% replacement of cement respectively. Strength predictive models for WTA-Mortar have good correlations with experimental data with average of R2 of 0.91, RMSE of 0.57 and COE of 0.66.  Statistical models drawn from the results of this research will also provide a means to predict WTA mortar strengths and behavior

Study of Microstructure of Waste Tyre Ash (WTA) Concrete Using the Scanning Electron Microscopy (SEM) and X – ray Diffraction (XRD) Techniques

This paper reports the findings of an investigation into the microstructure of WTA – Concrete. The WTA was obtained by open burning of waste tyre slices to a temperature of about 5000C for about five (5) hours at the local open burning sites in Kano. And after allowing to cool, it was sieved through 75 µm BS Sieve and characterized. The ash was subjected to chemical composition analysis using the X-Ray fluorescence (XRF) analytical method using the X –Ray spectrometer machine. The investigation was carried out on a concrete of 29 N/mm2 compressive strength, Water – cement ratio (w/c) of 0.65 and slump range of 10 – 50mm. The microstructure assessment was conducted on the concrete at WTA replacement levels of 0, 5, 10, 15, 20, 25, and 30% of cement weight, respectively to determine the influence of WTA on the microstructure of WTA – Concrete using SEM and XRD techniques. Both SEM analysis and XRD results of WTA – concrete indicated the occurrence of pozzolanic reaction between WTA and cement and that the WTA has more porous micro-structure than OPC concrete especially at hi

Causes of variation order in building and civil engineering projectsin Nigeria

Variation does not only affect labour productivity but also leads to the dispute, time and cost overrun. Consequently, it affects projects performance. It is, therefore, imperative for construction professionals to eliminate unnecessary additional cost from a project so as to optimize the client’s benefit against input resources. This paper identifies and examines the most significant causes that contribute to the variation orders. Also, Nigerian construction industry is used as a case study. Variation orders causing factors were assessed. Questionnaires were administered to clients, consultants and contractors to elicit information regarding variation causing factors. These factors were analyzed using frequency aggregation, mean score method and subsequently ranked according to their severity. The result revealed three most significant causes of variation which are: ‘Change of plan’’ with the highest frequency of 58% then followed by ‘‘Conflicting contract documents (50%). The next most frequent causing factors were the “substitution of materials” and “change in design” each with frequency of 43%. The least causing factor of variation was the “error and omission in design” with the frequency of 10%. Also differing site condition, new government regulation, weather condition were identified as other cause of variation with the frequency of 27%, 29% and 10% respectively. It has also shown that most critical source of variation order is the client due to change of plan then followed by consultant due to conflicting contract document