Papers by Keyword: High Strength Concrete

Abstract: The influence of silica fume (SF) inclusion on the compressive strength development of high strength concrete (HSC) containing high volume of palm oil fuel ash (POFA) has been investigated. A HSC containing 100% ordinary Portland cement (OPC) and another HSC mix with 50% POFA as part of the binder were prepared. Due to the reduction in early strength of the HSC with the inclusion of high volume of POFA in the binary blended binder HSC, attempt was made to partially replace the OPC with SF at 5, 10, 15 and 20%, thus creating a ternary blended binder HSC. The results show that the compressive strength development of the HSC containing high volume of POFA was significantly improved with the inclusion of SF. The ternary blended binder HSC with 15% SF exhibited the highest increase in early age strength, even though it did not surpass the OPC-HSC, and it provided the highest strength at 7 and 28 days in comparison to other HSC mixes. Thus, ternary blended binder containing more than 60% supplementary cementitious material (POFA and SF) could be utilized to produce HSC.

Abstract: More high-rise structures are currently being constructed and correspondingly, the compressive strength of concrete has been increased. However, compared to conventional strength concrete the high strength concrete (HSC) exhibits coarse inner pore structure which blocks escape routes of vapour generated in the event of fire. This results in spalling and subsequently, are responsible for fire vulnerability of the structure. In addition, spalling phenomena is also affected by the section dimensions of HSC which is also another crucial factor from socio-economic considerations. Thus, this study was carried out to evaluate the fire resistance performance of hybrid fiber (i.e. steel-polypropylene-fibre)-reinforced HSC columns with different cross-section dimensions. The result of the fire resistance performance testing using 100MPa concrete showed that delay to failure was observed by approximately 76 per cent.

Abstract: The article describes the influence of fine natural pozzolana as supplementary cementitious material on the properties of high strength concrete. Natural pozzolana (NP) is a porous material which results in higher porosities and thus lower compressive strength when used in high replacement levels. But if only a small part of cement (up to 10% of weight) is substituted by NP it has positive consequences. The open porosity is on the contrary lowered, resulting in better strength in compression. Thermal characteristics are as usually enhanced with the growth in the content of pores which is in disagreement of mechanical properties and durability of concrete.

Abstract: Basic physical properties, pore structure, hygric properties and frost resistance concrete containing supplementary cementing materials. The amount of SCMs was kept constant to replace 10% of cement. Experimental results show that bulk density and matrix density of studied material vary only slightly except the mixture with fine natural pozzolana which achieved lower values in comparison with the reference material. This is in agreement with open porosity and transport of liquid water - its highest values manifest the worst performance of fine natural pozzolana among the studied materials. Frost resistance was found to be satisfactory for all mixtures except material with fine natural pozzolana and with fly ash.

Abstract: Crushed brick (CB) used in high strength concrete as partial replacement of cement is the subject of this paper. It is a waste material and so its exploitation is needed to be found. Concrete industry can be proper area as CB is a fine material and is pozzolanic active. Basic physical properties and mechanical properties were investigated. Open porosity and bulk density achieved the best values when 30% of cement was replaced by CB. Matrix density decreased with rising addition ratio. The values of compressive strength was the highest for 30% replacement level and with 60% addition ratio were not lower than for the reference mixture. The conclusion is, that according to studied parameters 30% of cement substituted by CB is the most profitable addition ratio.

Abstract: In order to research on the mechanical properties of high strength desert sand concrete, the compressive experiment of high strength desert sand concrete with different desert sand replacement ratio was carried out. The influence of desert sand replacement ratio on the compressive strength and specific energy absorption of high strength desert sand concrete was analyzed. Experimental results shows that the optimum desert sand replacement ratio is from 0 to 40%, which provides advice and guidance to the utility of high strength desert sand concrete in practice.