The porous aggregate pre-soaking in relation to the freeze–thaw resistance of lightweight aggregate concrete (original) (raw)
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Freeze-thaw resistance of concrete with porous aggregate
Procedia Engineering, 2010
This paper deals with the influence of periodic freezing on lightweight concrete characteristics. Sets of lightweight concrete prismatic specimens are cyclically frozen in range from +20°C to-20°C and non-destructively tested after every 25 cycles. Freeze-thaw resistance is determined from measurement of the frost-attacked and non-frost-attacked (referential) specimens. The referential specimens are air/water-cured. Non-destructive methods, especially ultrasonic impulse method and resonance method are used for determination of specimen's degradation. Experiments are finished with destructive test in order to determine the static modulus of elasticity.
Freeze-thaw resistance of normal and high strength recycled aggregate concrete
2018
The reuse of Construction and Demolition Waste (CDW) employed as aggregates for new concrete production, leading to the so-called Recycled Aggregate Concrete (RAC), is an excellent solution from the environmental point of view. In fact, the influence on the use of Recycled Concrete Aggregate (RCA) on the resulting RAC's properties has been widely investigated in the recent years, but evaluation of concrete's performance should not be limited only to its behavior under "ordinary" conditions and the characterization of RAC in terms of durability become of extreme importance for structural application. For instance, in cold regions, the concrete's performance over time is closely related to its reaction to freeze-thaw cycles. As a matter of fact, when concrete is exposed to this type of attack, the porous structure tends to absorb water and, then, this water may turns into ice due to temperature variations. This process causes changes in the internal pore structure, reduction in mechanical the properties and appearance of cracks. In this context, this study investigates the mechanical and physical performance of different RAC mixtures after the exposure to fast freeze-thaw cycles. Specifically, normal and high strength mixtures (i.e., 35 and 60 MPa) with 100% RCAs were subjected to 150 cycles in which temperature variation from 4°C to-18°C was applied. The experimental results showed that degradation induced by freeze-thaw cycles was more pronounced in the normal strength concrete samples.
Structural Concrete, 2018
This article presents the results of a study dealing with the concrete resistance to repeated cycles of freezing and thawing of nonair entrained, fine lightweight aggregate (LWA) and air‐entrained concrete when tested in accordance with ASTM C 666, procedures A and B. The water‐to‐binder ratios (w/b) of the mixtures ranged from 0.25 to 0.35, and the percentage of cement replacement by silica fume were 7% on a weight basis and constant throughout study. Binder dosage was 500 kg/m3 and constant. LWA was pumice aggregate (PA) and expanded perlite aggregate (EPA). PA and EPA were replaced by 10, 20, and 30% of total volume of 1 m3 as a fine aggregate (0–2 mm fine aggregate fraction). Also one group was produced with air entraining agent by 0.1% ratio of binder dosage. The 200 freeze–thaw cycles were carried out according to ASTM C666/C666M‐15, procedure A and B. The compressive strength, ultrasonic pulse velocity, relative dynamic modulus of elasticity and dry unit weight of mixtures we...
Mechanical and durability properties of concrete subjected to early-age freeze-thaw cycles
Materials and structures, 2021
Early-age frost damage to concrete used in winter construction or in cold environments negatively affects the development of the hydration process and the performance of the concrete, thereby reducing the service life of the building structure. Experimental research was carried out to investigate the compressive strength, resistance to chloride penetration and resistance to freeze-thaw of concrete specimens subjected to earlyage freeze-thaw cycles (E-FTCs). The effects that different pre-curing times of concrete and mineral admixtures have on the properties of early-age frostaffected concrete were also analyzed. Results show that the earlier the freeze-thaw cycles (FTCs), the poorer the later-age performance. Later-age water-curing cannot
Freeze-thaw durability of recycled concrete from construction and demolition wastes
2017
Road engineering is one of the most accepted applications for concrete including recycled aggregates from construction and demolition wastes as a partial replacement of the natural coarse aggregates. Amongst the durability concerns of such application, the deterioration due to freeze-thaw cycles is one of the most important causes decreasing the life span of concrete in countries with a continental climate. Moreover, the use of de-icing salts, which is a common practice to prevent ice formation on roadways and walkways, increases the superficial degradation of concrete due to frost-salt scaling. Thus, this paper aims to assess the resistance to frost salt with de-icing salts of two recycled concrete mixtures containing a 50% replacement of the conventional gravel by recycled aggregates both of mixed and ceramic nature, i.e. containing ceramic percentages of 34% and 100%, in comparison to a conventional concrete made with siliceous gravel. Therefore, the surface scaling was evaluated...
Freeze-Thaw Resistance of Concrete: Insight from Microstructural Properties
2018
Composite cements offer low carbon alternatives to conventional CEM I. These also generally tend to perform better than CEM I in aggressive chemical environments. However, the freeze-thaw resistance, evident through surface scaling and internal damage is usually impaired. Postulated theories on freeze-thaw induced damage do not fully explain the origin of this weakness in composite cement concretes. This contribution systematically presents the phase assemblage changes associated with the freeze-thaw of concrete specimen made from composite cements with and without limestone. The freeze-thaw test was performed on concrete according to CIF method based on CEN/TR 15177 and the corresponding cement pastes characterized by X-ray powder diffraction (XRD) and thermogravimetric analysis (TGA). In all investigated composite cements, portlandite was already depleted after the 7d capillary suction. The implications of this and other modified assemblages during the conditioning and the freeze-...
Computers and Concrete, 2006
Thermal conductivity coefficients of concretes made up of mixtures of pumice aggregate (PA) and normal aggregate were measured. To determine the effect of PA ratio, different cement dosage, and slumps on the thermal conductivity of concrete, 25%, 50%, 75%, and 100% pumice ratios were used in place of normal aggregate by volume, 200-, 250-, 350-, 400-, and 500-kg/m 3 cement dosages, and 3 F 1-, 5 F 1-, and 7 F 1-cm slumps were used in this study. The analysis of the test results leads to the conclusion that PA decreased the density and thermal conductivity of concretes up to 40% and 46%, respectively. Increasing the cement dosage in the mixtures caused both density and thermal conductivity of the concrete to increase. The effect of slump on the density and thermal conductivity fluctuated.
Effect of Freezing-Thawing Cycles on the Physical and Mechanical Characteristics of Concrete
2010
Concrete is the most used construction material in practically all of civil engineering fields due to its economical and technical advantages. However, its microstructure is porous and may be completely or partially water saturated. In severely cold climates, this water freezes and degradations develop gradually with the freezing-thawing cycle’s number, in forms of internal cracking, chipping and scaling. Frost behaviour is based on the coupling between the 9% volumetric increase during water transformation into ice, the cryo-suction phenomena, the non frozen water transport within the porous network and the thermo-mechanical behaviour of each component of the frozen media. It is thus obvious that the frost resistance depends on the microstructure (pore size distribution and permeability) and the mechanical characteristics of the material. In this paper, physical and mechanical characteristics evolution during freezing-thawing cycles was followed. The results show that the reduction...
Evaluation of freeze-thaw damage on concrete material and prestressed concrete specimens
Construction and Building Materials , 2016
The pore structure of the hardened concrete and the microscopic changes of a few selected pores throughout the freeze-thaw test were investigated by a method combining RapidAir and digital metalloscope. Traditional tests were also performed to evaluate the macroscopic change caused by freeze-thaw cycles (FTCs). The investigation shows that the concrete material, of which the spacing factor is 0.405 mm and the air content is 2.38%, can still withstand more than 300 FTCs. Severe microscopic damages occurred after approximately 200 FTCs and the freeze-thaw damage were gradually aggravated afterwards. Prestress forces have a remarkable impact on the failure pattern under FTCs. It was further found that the compressive strength as an indicator is more reliable than the relative dynamic modulus of elasticity in evaluating the freeze-thaw damage on concrete material. In addition, the test and analysis show that the measured prestress losses of bonded specimen are larger than that of unbounded specimen under the attack of FTCs due to the duct grouting effect. The ultimate freeze-thaw prestress loss is about 5% of rcon of for both the bonded and unbonded specimens because the grouting cement paste will eventually be completely destroyed.
Studia Geotechnica et Mechanica, 2021
This paper presents experimental research on expanded clay aggregate concrete. The aim of the investigations was to determine if the pre-wetting of expanded clay aggregate has an effect on the freeze-thaw durability of the expanded clay aggregate concrete. Five concrete series based on the same concrete mix design were made and tested. The degree of pre-wetting of the aggregate was varied: dry aggregate was used in the first series, aggregate with a moisture content of 10% was used in series IA and IB and aggregate with a moisture content of 25% was used in series IIA and IIB. Also the approach to the production process was varied: in series A the water contained in the aggregate was taken into account in the global water-cement ratio (consequently a reduced amount of water was added to the mix), whereas in series B the nominal amount of water was added to the mix (as in the case of dry aggregate). The freeze-thaw resistance criterion was based on the assessment of the decrease of c...