Effect of Shrinkage Reducing Admixture on Drying Shrinkage of Concrete with Different w/c Ratios (original) (raw)
Related papers
2019
High drying shrinkage of concrete has the potential to impact adversely on the durability, aesthetics and serviceability of concrete structures. Methods to reduce drying shrinkage of concrete have traditionally been to use special cements (e.g. SL Cement), water reducing admixtures and more recently, shrinkage reducing admixtures (SRA’s). This paper assesses the shrinkage reduction potential of two common shrinkage reducing agents and compares it with a new, low shrinkage concrete (trademarked as ENVISIA TM ). A 32 MPa ENVISIA TM concrete was compared against a typical 32MPa concrete with addition of each agent at the dosage of up to 7 litres per cubic meter. It was noted that addition of shrinkage reducing agent had lower water demand, longer setting time, more or less bleed water (depending on the admixture type), and slightly lower 1-day compressive strength but higher later compressive strength. The free drying shrinkage can be reduced up to 30-37% when 7L per cubic meter dosage...
A review on the influence of shrinkage reducing admixtures on concrete
Sustainability, Agri, Food and Environmental Research, 2021
Shrinkage cracking is a common source of distress in concrete structures. In addition to being unsightly, these cracks serve to accelerate other forms of damage in concrete, thereby shortening the service life of structures. One solution to reduce the potential for shrinkage cracking is to incorporate a shrinkage reducing admixture (SRA) in concrete mixtures. SRAs belong to a special type of organic chemicals (i.e., surfactants) that when mixed in water, reduce the surface tension of the liquid, and thereby reduce the magnitude of capillary stresses and shrinkage strains that occur when concrete is losing moisture. Various studies show that SRAs have proven to reduce drying, autogenous, and plastic shrinkage, which has been summarized in this literature. Keywords—Shrinkage Reducing Admixtures, Surfactants, Drying shrinkage, Plastic shrinkage, Autogenous shrinkage.
Five year drying of high performance concretes: Effect of temperature and cement-type on shrinkage
Cement and Concrete Research, 2017
This experimental study imposes limited relative humidity (RH) gradients to small mature concrete samples, at a constant temperature T = 20, 50 or 80°C. Mass loss and shrinkage are recorded until stabilization at each RH and T, for up to 1991 days. Firstly, our mass loss data are consistent with those presented in former research (on different samples of the same batch). After presenting and analyzing shrinkage kinetics, experimental data are fitted with usual models for shrinkage prediction, at each temperature of 20, 50 and 80°C. An adequate match is obtained by combining capillarity (i.e. Vlahinic's model coupling poro-elastic constants and water saturation level) and desorption (Bangham's equation). Subsequently, relative mass variation (RMV) is plotted against shrinkage ε sh dry data. Three distinct phases are obtained at 20 or 50°C and down to 30%RH; up to four distinct phases are observed at T = 80°C and down to 12%RH. The latter are confirmed by experiments on (60°C; 7%RH) dried concrete. The four phases in the (RMV ε , sh dry) diagram are interpreted against shrinkage data on mature cement paste dried at 60°C; 7%RH and against the literature.
Molecules, 2020
This work investigates the effect of calcium stearate (Ca(C18H35O2)2) on concrete shrinkage behaviors by using experimental testing. The test specimens are cubes with each dimension given as 100 × 100 × 285 mm for shrinkage tests and cylinders with 150 mm diameter and 300 mm height for compressive strength tests. The calcium stearate with fractions of 0, 0.1, 0.2, and 0.3% from the weight of cement are used in the tests. The results showed that the shrinkage occurred in amounts of 0.079, 0.062, 0.065, and 0.060 mm for the specimens containing calcium stearate of 0, 0.1, 0.2, and 0.3%, respectively. Moreover, we also perform shrinkage modelling to explore a possibility to incorporate the calcium stearate fraction into the standard concrete shrinkage model. There are three well-known shrinkage models used here, i.e., the Sakata, the Japan Standard and the Bazant-Baweja models, where only the latter one is capable to capture our experimental results very well for different fractions of...
Effect of materials and curing period on shrinkage of concrete
The ASTM C157 free shrinkage test is used to evaluate the effects of mix proportioning parameters and curing on concrete shrinkage with the goal of providing recommendations that will reduce concrete shrinkage in bridge decks. Specimens are dried up to 365 days at 23 ± 2 o C (73 ± 3 o F) and 50 ± 4 percent relative humidity. Parameters include aggregate content; cement fineness; water-cement ratio; curing period; partial cement replacement by slag, Class C fly ash, or silica fume; superplasticizer dosage; the use of a shrinkage reducing admixture; and aggregate type. The results indicate that increasing the aggregate content (decreasing the paste content) of a concrete mix decreases shrinkage and that water-cement ratio has little effect in and of itself. For a given aggregate content and water-cement ratio, concretes made with Type I/II cement shrink more than concretes made with Type II coarse-ground cement. Concrete containing a 30 percent cement replacement (by volume) of either Class C fly ash or granulated ground blast-furnace slag exhibit higher shrinkage than concrete with only Type I/II cement when cured for three days. Limestone coarse aggregate produces concrete with higher shrinkage than concrete made with quartzite coarse aggregate. Increased curing periods lead to a decrease in shrinkage for concretes made with either Type I/II or Type II coarse-ground cement. No consistent effect of dosage rate on shrinkage was observed for concretes made with the superplasticizers tested. The use of a shrinkage reducing admixture at a dosage rate of 2 percent by weight of cement reduced the shrinkage of concrete nearly iv 32 percent after 365 days. The shrinkage reducing admixture, however, produced concrete that at times exhibited an unstable air content.
IRJET, 2022
Through its lifespan, concrete undergoes several physical and chemical changes, which normally led to shrinkage of concrete, especially at an early age, when the initial hydration processes take place. The shrinkage of concrete at an early stage of hardening may lead to the initial formation of cracks that vary in shape and size and depends on the concrete constituents and surrounding conditions, including temperature and/or the moisture state that may lead to volumetric deformation Many studies have shown that the total prevention of concrete from undergoing shrinkage is impractical. However, different practices have been used to control various types of shrinkage in concrete and limit its magnitude. This paper provides the shrinkage behavior of cement concrete incorporated with different mineral admixtures and fibers.
IRJET, 2022
Volumetric shrinkage occurs frequently in cement-based materials, which may cause tensile strains and cracking. The volume changes brought on by water evaporation are known as shrinkage. Volume variations in concrete can happen early in the material's life or later on. Plastic shrinkage occurs at the plastic stage of concrete. The change in volume after the setting has occurred is known as drying shrinkage. Autogenous shrinkage is the shrinking that occurs in a conservative system, or one in which moisture cannot migrate into or out of the paste. This study tries to examine the impact of various SCMs such as fly ash, GGBFS, silica fume, etc. and fibers such as steel fiber, polypropylene fiber, glass fiber, etc. in the shrinkage characteristics of concrete.
Cement and Concrete Research, 2009
The water-absorption behavior of cement pastes ͑w / c = 0.30͒ containing varying concentrations ͑i.e., 0, 0.2, and 5%͒ of a shrinkage-reducing admixture ͑SRA͒ was measured. Moisture ingress was monitored using X-ray absorption. A decrease in both the depth of water penetration and the rate of water absorption was observed with increasing specimen maturity and admixture concentration. This agrees with theoretical considerations that suggest water sorption is a function of the surface tension and the viscosity of the fluid ingressing into the pores. The Boltzmann-Matano method was successfully employed to determine the moisture content dependent moisture diffusivity of the material, which exhibited a dependence on both the pore structure ͑specimen maturity͒ and the SRA concentration.
Effect of drying conditions on autogenous shrinkage in ultra-high performance concrete at early-age
Materials and Structures, 2011
This experimental study investigated the effects of drying conditions on the autogenous shrinkage of ultra-high performance concrete (UHPC) at early-ages. UHPC specimens were exposed to different temperatures, namely, 10, 20 and 40°C under a relative humidity (RH) ranging from 40 to 80%. The effects of using a shrinkage-reducing admixture (SRA) and a superabsorbent polymer (SAP) as shrinkage mitigation methods were also investigated. The results show that autogenous and drying shrinkage are dependent phenomena. Assuming the validity of the conventional superposition principle between drying and autogenous shrinkage led to overestimating the actual autogenous shrinkage under drying conditions; the level of overestimation increased with decreasing RH. Both SRA and SAP were very effective in reducing autogenous shrinkage under sealed conditions. However, SRA was efficient in reducing drying shrinkage under drying conditions, while SAP was found to increase drying shrinkage. Generally, results indicate that adequate curing is essential for reducing shrinkage in UHPC even when different shrinkage mitigation methods are applied.