Empirical investigation to explore potential gains from the amalgamation of Phase Changing Materials (PCMs) and wood shavings

The reduction of gained heat, heat peak shifting and the mitigation of air temperature fluctuations are some desirable properties that are sought after in any thermal insulation system. It cannot be overstated that these factors, in addition to others, govern the performance of such systems thus their effect on indoor ambient conditions. The effect of such systems extends also to Heating, Ventilation and Air-conditioning (HVAC) systems that are set up to operate optimally in certain conditions. Where literature shows that PCMs and natural materials such as wood-shavings can provide efficient passive insulation for buildings, it is evident that such approaches utilise methods that are of a degree of intricacy which requires specialist knowledge and complex techniques, such as micro-encapsulation for instance. With technical and economic aspects in mind, an amalgam of PCM and wood-shavings has been created for the purpose of being utilised as a feasible thermal insulation. The amalgamation was performed in the simplest of methods, through submerging the wood shavings in PCM. An experimental procedure was devised to test the thermal performance of the amalgam and compare this to the performance of the same un-amalgamated materials. Comparative analysis revealed that no significant thermal gains would be expected from such amalgamation. However, significant reduction in the total weight of the insulation system would be achieved that, in this case, shown to be up to 20.94%. Thus, further reducing possible strains on structural elements due to the application of insulation on buildings. This can be especially beneficial in vernacular architectural approaches where considerably large amounts and thicknesses of insulations are used. In addition, cost reduction could be attained as wood shavings are significantly cheaper compared to the cost of PCMs

Behavior of FRP-confined normal- and high-strength concrete under cyclic axial compression

An important application of fiber-reinforced polymer (FRP) composites is as a confining material for concrete, both in the seismic retrofit of existing reinforced concrete columns and in the construction of concrete-filled FRP tubes as earthquake-resistant columns in new construction. The reliable design of these structural members against earthquake-induced forces necessitates a clear understanding of the stress-strain behavior of FRP-confined concrete under load cycles. This paper presents the results of an experimental study on the behavior of FRP-confined normal- and high-strength concrete under axial compression. A total of 24 aramid and carbon FRP-confined concrete cylinders with different concrete strengths and FRP jacket thicknesses were tested under monotonic and cyclic loading. Examination of the test results has led to a number of significant conclusions in regards to both the trend and ultimate condition of the axial stress-strain behavior of FRP-confined concrete. These results are presented, and a discussion is provided on the influence of the main test parameters in the observed behaviors. The results are also compared with two existing cyclic axial stress-strain models for FRP-confined concrete. © 2012 American Society of Civil Engineers.Togay Ozbakkaloglu and Emre Aki

The sulphate resistance of cements containing red brick dust and ground basaltic pumice with sub-microscopic evidence of intra-pore gypsum and ettringite as strengtheners

This paper presents a laboratory study on the deterioration of blended cement combinations of plain Portland cement (PPC) with red brick dust (RBD) and ground basaltic pumice (GBP). One type of clinker, same Blaine values and two different proportions of additive by mass of clinker, were employed. In addition to these blends, Portland cements without additives were prepared as control specimens. The compressive strength and the sulphate resistance of cements have been experimentally studied in this paper. A series of laboratory tests were undertaken on all specimens. A large quantity of sheet-like C-S-H was found in the mortars incorporating RBD and GBP. The results indicated that the increase in the additive content caused a significant increase in the sulphate resistance of the mortars. Hence, the studied RBD and GBP can be recommended for use as admixtures in cement production. The development of the particular microstructure including the secondary minerals in the plain and blended cements were studied via SEM analysis. SEM images revealed the presence of ettringite and Portlandite minerals, where the former was most probably responsible for the increase (together with the gypsum roses) as well as a decrease of strength based on its formation at different sites and crystal form. Portlandite was responsible for an increase in the specimen strength. © 2011 Elsevier Ltd. All rights reserved