An Investigation into the Thermal Performance of Rubber-Concrete

The Thermal properties of concrete incorporating pulverized automobile tires as partial replacement for mineral coarse aggregate (granite) was investigated in other to assess its suitability as a construction material and also a solution to the environmental problems constituted by non-biodegradable waste tires. Replacement was made at: 5%, 10%, 15%, 20% and 25% by volume. Thermal properties were measured base on the transient line heat source (TLS) method using a KD 2 Pro thermal analyzer. Thermal properties most especially the thermal conductivity of concrete (1.816W/mk) have been greatly reduced to 1.283W/mk indicating 29.4% reduction after 25% partial replacement of mineral aggregate with the rubber particles which makes it a better insulator while the specific heat capacity of concrete (3.040 MJ/m3.k) have been reduced to 2.137MJ/m3k indicating 29.7% reduction with same 25% rubber particles which may adversely reduce thermal mass effect. Other thermal properties such as thermal resistivity increased by 29.4%, thermal diffusivity decreases by 65.1% while thermal effusivity decreases by 37.6% with 25% rubber particles content in concrete. The result indicates that the potential use of such composite material for building applications is viable. DOI: 10.5901/ajis.2014.v3n5p2

Effects of Load Ratio Variation on the Safety of Timber Concrete Composite Floor

This paper presents the structural reliability appraisal of timber concrete composite floor designed in line with Eurocode 5 (2004) and Eurocode 2, (2004). Limit state expressions for timber concrete composite floor subdued to tension, bending, tension and bending, shear and compression were generated and their entailed reliability degrees were assessed. The basic variables associated with the design are considered to be random variables with their properties espoused from the previous studies. Reliability analysis was performed using reliability mothed i.e. first order reliability method (FORM) owing to assess the safety levels of the composite floor structural elements by considering six different modes of failure. The analysis comprised of different selected species of softwood, hard wood and glue laminated timber whose strength class were obtained from BS EN 338, 2008 and concrete of strength class C30 from Eurocode 2. The results obtained disclosed that safety indices decrease as the load ratio steps up that led to cut down of the strength. It was detected that timber with strength classes D70, D50 and C50 are safe against all different failure modes looked at except C50 and D50 against shear failure at load ratio of 1, 1.5 and 2. It was conclude timber of strength classes D70, D50 and C50 would reliable for the construction of composite floor i.e. timber-concrete floor

Prediction of the Compressive Strength of Concrete Admixed with Metakaolin Using Gene Expression Programming

One of the problems of optimization of concrete is to formulate a mathematical equation that shows the relationship between the various constituents of concrete and its properties. In this work, modelling of the compressive strength of concrete admixed with metakaolin was carried out using the Gene Expression Programming (GEP) algorithm. The dataset from laboratory experimentation was used for the analysis. The mixture proportions were made of three different water/binder ratios (0.4, 0.5, and 0.6), and the grades of concrete produced were grade M15 and M20. The compressive strength of the concrete was determined after 28 days of curing. The parameters used in the GEP algorithm are the input variables which include cement content, water, metakaolin content, and fine and coarse aggregate, while the response was designated as the compressive strength. The model was trained and tested using the parameters. The R-square value from the GEP algorithm was compared with the use of conventional stepwise regression analysis. With a coefficient of determination (R-square value) of 0.95, the GEP algorithm has shown to be a good alternative for modelling concrete compressive strength