Self-compacting concrete containing different powders at elevated temperatures – Mechanical properties and changes in the phase composition of the paste (original) (raw)
Related papers
Cement and Concrete Research, 2007
Self-compacting concrete, as a new smart building material with various advanced properties, has been used for a wide range of structures and infrastructures. However little investigation have been reported on the properties of Self-compacting when it is exposed to elevated temperatures. Previous experiments on fire test have shown the differences between high performance concrete and traditional concrete at elevated temperature. This difference is largely depending on the microstructural properties of concrete matrix, i.e. the cement paste, especially on the porosity, pore size distribution and the connectivity of pores in cement pastes.
The current research studied the effect of elevated fire temperature and cooling regime on the fire resistance of self-compacting concrete (SCC) and normal concrete (NC). Both concretes were exposed to elevated degrees of fire temperature of 200, 400, 600 and 800 °C. In addition, the temperature was maintained at 800 °C while the exposure durations have been increased to 15, 30, 60 and 120 minutes. After that the samples were cooled to room temperature using three different cooling regimes namely; air cooling, CO2 powder cooling and water cooling. Reductions in both compressive and tensile strength results along with the extent of spalling were examined. The effect of fire and cooling regime on both porosity and absorption capacity of SCC and NC were also investigated. The results indicated that residual compressive and tensile strengths of SCC are generally higher than those of NC. In other words, elevated fire temperature is more damaging to the NC compared with SCC. Same has been confirmed by the obtained results of spalling which were found to be higher for NC compared with those of SCC. The results also indicated that adopting CO2 powder as a cooling regime provided the least extent of damage to both NC and SCC concretes while water cooling regime provided the greatest damage. It is worth mentioning that the incorporation of polypropylene fibre improved the fire resistance of concrete regardless of the concrete type and cooling regime. Increasing the dosage of self-compacting admixture did not significantly affect the mechanical properties and fire resistance of SCC.
EFFECT OF AGGREGATE TYPE ON THE FIRE RESISTANC OF NORMAL AND SELF-COMPACTING CONCRETES
In this research, the influence of coarse aggregate type and incorporation of polypropylene fibres on the mechanical properties of normal concrete (NC) and self compacting concrete (SCC) were investigated. Three types of local aggregates namely natural gravel, basalt and dolomite were used. Fire resistance of the produced concrete in terms of residual strengths and spalling was studied. Different elevated degrees of temperature of 200, 400, 600 and 800 °C were considered. The latter degree of temperature (800 °C) was maintained constant while the effect of exposure durations of 15, 30, 60 and 120 minutes were investigated. Compressive strength, indirect tensile strength, porosity, near surface absorption and spalling were measured before and after exposure to elevated degrees of temperature. The results indicated that, aggregate type has a minor effect on the concrete resistance to fire. However dolomite aggregates provided the highest resistance to fire while natural aggregate gave the least resistance. The incorporation of polypropylene fibres improved the indirect tensile strength results as well as the concrete resistance to spalling. It was also recorded that the degradation of the mechanical and permeation properties of SCC increases with increasing the degree of elevated temperature. It is worth mentioning that the performance of SCC exposed to high elevated degrees of temperature is better than that of the NC. Key words: Self-compacting concrete, Fire, Coarse aggregate, Polypropylene fibres.
Materials and Structures, 2009
In this paper, the studies concern the influence that different fillers have on the properties of SCC of different strength classes when exposed to high temperatures. A total of six different SCC and two conventional concrete mixtures were produced. The specimens produced are placed at the age of 180 days in an electrical furnace which is capable of reaching 300°C at half an hour and 600°C at 70 min. The maximum temperature is maintained for an hour. Then the specimens are let to cool down in the furnace. The hardened properties measured after fire exposures are the compressive strength, splitting tensile strength, water capillary absorption and the ultrasonic pulse velocity. Explosive spalling occurred in most cases when specimens of higher strength class are exposed to high temperatures. The spalling tendency is increased for specimens of higher strength class C30/37 irrespective of the mixture type (SCC or NC) and the type of filler used.
Self-compacting concrete at fire temperatures
betoni.com
This report describes experimental studies of the mechanical performance of Self-Compacting Concrete, SCC, under compressive loading at fire temperatures. The SCC contains different amounts of polypropylene fibre, different types of cement and air content, preconditioned either in the air or in water. The result of the studies was compared with the corresponding properties of normal concrete, with the same w/c and air content. Half a year's or one year's age applied at the time of testing. The strength development of the concrete was followed in parallel. Seven SCCs with w/c = 0.40, 0.55 or 0.70 and one normal concrete, NC, with w/c = 0.40 were studied for compressive strength in a fire temperature oven. The temperatures were 200 °C, 400 °C and 800 °C. Both testing at elevated temperature and after cooling took place. Elastic modulus, ultimate strain at maximum strength, dynamic modulus and relative humidity, RH, were studied in parallel. Supplementary tests of were performed, after cooling from 600 °C, of strength, elastic modulus, ultimate strain at maximum strength. Supplementary tests were also performed on capillary suction, porosity and resistance to water penetration at water suction. The results of the laboratory tests were compared with results of full-scale tests on twelve SCCs with w/c = 0.40, 0.55 or 0.70 and 4 NCs with w/c = 0.40, 0.55 or 0.70 on fire spalling carried out in a high-temperature oven. The same concrete was studied in the laboratory and in full-scale tests. The concrete was air-cured at an ambient RH = 60%, or water-cured from demoulding until testing. The effects of increased amount of polypropylene fibres, age, different types of cement and air content, capillary suction, porosity, moisture content, hydration losses, preconditioning either in the air or in water, were studied.
Powder Materials and Their Effect on the Behaviour of Self-Compacting Concrete in Malaysia
IOP Conference Series: Materials Science and Engineering, 2018
This paper discusses the effect of powders on the properties of self-compacting concrete. Fillers like kaolin, limestone, metakaolin and fly ash pozzolans are used by weight to prepare 17 different mixtures of mortar. In addition, four concrete mixes were made to study the effect of filler on shrinkage concrete mixes. From the series of experiments conducted, it has been found that 20% replacement of sand with limestone produces an enhanced strength and stability of the mix with low water absorption compared to the same water to powder ratio in the early stages. The combination of kaolin, primarily enhance the stability of mixture and fly ash enhance the rheology characteristics and hence the compressive strength. The replacement of 10% meta-kaolin provides a very high strength improvement compared to reference mix minimizing water absorption. The use of powders gave good workability and strength and thus would reduce of the use chemical admixtures and cement and consequently reduce the cost. The concrete mixes with fly ash and limestone powders gave better hardened properties with low cost compared to the reference mix.
Effect of elevated temperature on physico-mechanical properties of blended cement concrete
Construction and Building Materials, 2011
This study aims to investigate the effect of thermally treated temperatures up to 800 °C on the physical properties, microstructure and phase composition of pozzoloanic cement pastes. Pozzolanic cement was prepared from three different pozzolans, namely silica fume (SF), ground granulated blast-furnace slag (WCS) and ground clay bricks (GCB). The samples were subjected to heat treatment at the rate of 10 o C/min, and then kept for 3 hours from 200 up to 800 o C, then cooled to the room temperature in the furnace switched off. It was concluded that the cement paste M.10 (70 % OPC + 10 % WCS + 10 % GCB + 10 % SF) is the optimum mix which gives a higher compressive strength up to 600 °C. It was also found that M.10 has more hydration products than other mixes. The microstructure shows a massive dense closed texture, with the lower number of voids and pore size, with the formation of inner fibers and crystalline needle like CSH hydrated which is responsible for the increase in compressive strength up to 500 °C. 158 thereby causing progressive breakdown of cement gel structure, reduced durability, increased tendency of drying shrinkage, structural cracking and associated aggregate colour changes [1].
2008
This study aims to investigate the effect of thermally treated temperatures up to 800 °C on the physical properties, microstructure and phase composition of pozzoloanic cement pastes. Pozzolanic cement was prepared from three different pozzolans, namely silica fume (SF), ground granulated blast-furnace slag (WCS) and ground clay bricks (GCB). The samples were subjected to heat treatment at the rate of 10 o C/min, and then kept for 3 hours from 200 up to 800 o C, then cooled to the room temperature in the furnace switched off. It was concluded that the cement paste M.10 (70 % OPC + 10 % WCS + 10 % GCB + 10 % SF) is the optimum mix which gives a higher compressive strength up to 600 °C. It was also found that M.10 has more hydration products than other mixes. The microstructure shows a massive dense closed texture, with the lower number of voids and pore size, with the formation of inner fibers and crystalline needle like CSH hydrated which is responsible for the increase in compressive strength up to 500 °C. 158 thereby causing progressive breakdown of cement gel structure, reduced durability, increased tendency of drying shrinkage, structural cracking and associated aggregate colour changes [1].
The industrial structures in the past couple of decades have been subjected to abnormal elevated temperatures due to various reasons like change in technology, change in raw materials causing serious damages to the structures and hence huge economical and production losses. Similarly, the fire accidents in the other structures including residential complexes induce extreme stresses in the structural members seldom causes irreparable damages. These situations necessitate the use of appropriate fire resistant materials development of designs for construction industry. The recent development in the new construction materials for fire resistance includes the use of concretes mixed with admixtures like Fly Ash (FA), Micro Silica (MS), Ground Granulated Blast Furnace Slag (GGBS), Metakaolin (MK), Rice Ash Husk etc. However, the use of ternary blended concrete is yet to be studied in detail for possible applications in the industry. The present investigation aims at study of mechanical property of concrete viz., compressive strength of ternary blended concrete prepared with the constituents of Ordinary Portland Cement (OPC), Micro Silica (MS) and Metakaolin (MK) and to arrive at the optimum proportions of various constituents of Ternary blended concrete suitable even at elevated temperatures to which the concrete is likely to be subjected.
In this study, an experimental investigation was performed to evaluate the influence of elevated temperatures on the mechanical properties of self-consolidating micro-concrete containing the mineral additives. The ordinary Portland cement (OPC) was used as binder, and limestone powder was used as mineral additive materials. The OPC were partially replaced by 0, 10, 20 and 30% of mineral admixture. The blended concrete paste was prepared using the water-binder ratio of 0.5 wt% of blended cement and natural sand. The hardened specimens were thermally treated at 20, 200, 400, 600, 800 and 1000 o C for 2 hours. The compressive strength, tensile strength and loss of density of self-consolidating micro-concretes were compared with those of the pure ordinary Portland concrete. The results showed that the addition of limestone powder to OPC improves the performance of the produced blended micro-concrete when exposed to elevated temperatures.