Influence of aggregate materials characteristics on the drying shrinkage properties of mortar and concrete (original) (raw)
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Effect of Coarse Aggregate Characteristics on Drying Shrinkage of Concrete
An experimental program was carried out to determine the influence of concentration and nominal size of coarse aggregate on the development of lateral and pore water pressures of self-consolidating concrete (SCC). Nine mixtures prepared with sand-total aggregate ratios (S/A) varying between 1.0 and 0.30 were evaluated. The mixture made with an S/A value of 0.50 was repeated three times with different coarse aggregate gradations of 10-5, 14-5, and 20-5 mm. An experimental column measuring 2800 mm in height and 200 mm in diameter was used to determine lateral pressure and pore water pressure during the plastic stage of cement hydration. Rheological characteristics were assessed to determine the relationship between internal friction and lateral pressure development.
Effect of limestone and granite coarse aggregate on drying shrinkage of a concrete
MATEC Web of Conferences, 2016
In this paper the effect of limestone and granite aggregate on drying shrinkage of a concrete is investigated. Mixes containing limestone and granite with different D max and cement paste volume were tested. A two level, full factorial experiment with three independent factors was conducted which allowed not only to determine the influence of every single factor itself but also potential interactions between them. Measurements of shrinkage were performed up to 98 days after demolding on the beams (10x10x50 cm), in accordance with the procedure from polish standard PN-84/B-06714/23 (Amsler's method). The multivariate analysis of variances (MANOVA) was used for the statistical analysis of the results. The obtained results confirm that the cement paste volume has a decisive influence on a drying shrinkage of a concrete. However statistical analysis showed that with the assumed variability, either the D max or type of coarse aggregate has no significant influence on drying shrinkage, still those parameters may potentially be crucial in some cases. A statistically significant interaction between D max and type of aggregate has been found. Furthermore the results of drying shrinkage measurements were compared with estimation results from Bażant-Baweja B3 Model and Eurocode 2. The comparison shows that B3 Model provided more accurate results than Eurocode 2.
Volume Change of Limestone and its Effects on Drying Shrinkage of Concrete
Advanced Materials Research, 2010
Recently, the cracks of concrete by drying shrinkage become one of the problems in the construction industry in Japan. The drying shrinkage decreases when the concrete is produced with limestone aggregate. However, it is not clear why the drying shrinkage is decreased. The purpose of this study is to clarify the relation between the drying shrinkage of concrete and the limestone aggregate. In this study, the experiments about the strength, elasticity and drying shrinkage of concrete and the physical properties and shrinkage of coarse aggregates were conducted. It is thought that the volume change of aggregates affects directly the drying shrinkage in concrete.
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.
2018
The main difference of the Recycled Concrete Aggregate (RCA), compared to the natural ones, is their greater porosity and, consequently, higher water absorption. Many researches have been carried out to investigate the influence of the use of RCA on the mechanical properties of concrete, but studies on the effects of RCA on the main concrete deformations is still very limited. The drying shrinkage is an important property, because it produces internal tensions and mass loss and, consequently, reduction in the concrete volume. This process can cause multiple cracking, damaging the durability of the material.<br> In this context, this study presents the results of an experimental campaign to evaluate the influence of RCAs on the drying shrinkage and the mechanical properties of different Recycled Aggregate Concrete (RAC) mixtures. RCAs from laboratory-produced waste were used in two size fractions (i.e., 4.8 mm to 9.5 mm and 9.5 mm to 19 mm). Normal and high strength concrete (3...
Materials and Design, 2010
Drying shrinkage is generally classified as an important hardened concrete property. It expresses the strain occurring in hardened concrete due to the loss of water. During the drying process, free and absorbed water is lost from the concrete. When the drying shrinkage is restrained, cracks can occur, depending on the internal stresses in the concrete. The ingress of deleterious materials through these cracks can cause decrease in the compressive strength and the durability of concrete. In this study, being as a fine aggregate in mortars, crushed tile (CT) effect on drying shrinkage and drying shrinkage cracking is investigated. Thus, compressive and flexural strength, modulus of elasticity, and free and restrained drying shrinkage tests are conducted on mortar specimens produced with and without crushed tile fine aggregate. The ring test has been used in order to investigate the cracks induced by restrained drying shrinkage. In this way, free drying shrinkage strain, along with the number and development of drying shrinkage cracks, of the crushed tile fine aggregate mortar composites are quantified and observed.
Shrinkage in Concrete Made from Recycled Aggregate
2017
Drying shrinkage is one of the type of shrinkage occurs at the very beginning due to the loss of moisture added to the concrete mix after the cement ingredients react with water. A comprehensive study has been conducted on thirty samples of different concrete mixes. The study focusses on the effect of relative humidity and recycled aggregate. Different ratio of recycled coarse aggregated (RCA) were used (0, 25, 50, 75, 100%) and compare with natural aggregates. The dimensions of the specimen used in this study were 7.5, 7.5, 28.5 cm .The results of drying shrinkage for samples cured under dry environment were 8 times than samples cured under full humidity. Also, the results indicated that specimens with recycled aggregate produce more drying shrinkage than Natural aggregate.
Drying Shrinkage and Thermal Expansion of Synthetic Lightweight Aggregate Concrete
2014
In this research, the drying shrinkage and thermal expansion of lightweight aggregate concrete (LC) was studied experimentally. The lightweight aggregate used was synthesized from silt wastes in a water treatment plant and industrial byproduct ashes. The recycling of these wastes not only offers an excellent constituent for lightweight aggregate concrete but also reduces an environmental impact. The LC mixes in this study were made with a constant water to binder ratio (w/b) of 0.55 but with a variable amount of coarse aggregates at 45-60% of the bulk density and a variable amount of water in the range of 220-250 kg/m. For a comparison, normal aggregate concrete (NC) having identical mix proportions to the LCs were also tested. The results of the drying shrinkage test within 14 days demonstrated that the shrinkage of the LCs was higher than that of the NC. In addition, from the thermal expansion test results at temperature ranging from 35 to 100 degree Celsius demonstrated that the ...
Effect of Aggregate Size on the Restrained Shrinkage of the Concrete and Mortar
Medcrave Online Journal of Civil Engineering, 2018
Mostly, there are investigations about the shrinkage of the concrete. In that research, only the effect of the coarse aggregate on shrinkage is investigated; the fine aggregate is taken into account with the coarse aggregate. When the aggregate grain size increases or decreases, which results will be obtained and how this situation affecting the shrinkage should be determined. In this study, firstly, a widely literature research related to the effect of the aggregate grain size on the shrinkage were carried out. Then, with the help of the experimental studies, it is possible to determine the effect of the aggregate grain size on the shrinkage of the concrete and mortar whether if the aggregate grain size decreases or increases. These experimental researches are on the restrained and drying (free) shrinkage, moreover the compressive and tensile strength tests were carried out. When the effect of the aggregate grain size on the shrinkage, the shrinkage of the mortars with the 4 mm maximum grain size is low if the amount of the aggregate is high. Compared to the mortars (especially maximum grain size is 9mm) the shrinkage value is lower. When the concrete with the 16 mm maximum grain is produced according to the same ratios of the mortar, the shrinkage of the concrete is less than the shrinkage of the mortar. According to these results, the shrinkage decreases while the maximum grain size is bigger than 9 mm. Coarse aggregate restrains the development of the crack and supply as a micro-crack. The aggregate restrain the shrinkage if the strength of the concrete is high. The compressive and tensile strengths of the mortar and concrete are high at 28 days and decrease at 42 days because the micro-cracks reduce the strengths a little.
Structural Engineering, Mechanics and Computation, 2001
This paper presents the results of the study on the influence of superplasticizer and varying aggregate size on the drying shrinkage and compressive strength of laterised concrete. Four different samples of laterised concrete were made from prescribed mix ratio of 1:1:2 which include; two control specimens made with different coarse aggregate sizes (12.5mm and 19mm) and another two specimens that have the same composition as the control samples with addition of superplasticizer (Conplast 430). The compressive strength and drying shrinkage were determined at the curing periods (7, 14, 21 and 28 days). The results showed that specimens made with 12.5mm diameter coarse aggregate and superplasticizer developed a maximum compressive strength (44N/mm 2) at 28 th day. This maximum compressive strength was 29.6%, 31.8% and 4.6% greater than the compressive strength developed by the control specimens and specimens made with 19mm diameter coarse aggregate and superplasticizer. Specimens made with 19mm diameter coarse aggregate and superplasticizer developed the minimum shrinkage strain (1.48⨯0-3) at 90 th day. This value was 17%, 13.5% and 8.1% less than shrinkage strain of the control specimens and specimen made with 12.5mm coarse aggregate size and superplasticizer. The addition of superplasticizer increased the compressive strength and reduced the shrinkage strain of all specimens; while increase in coarse aggregate size reduced both compressive strength and drying shrinkage.