Experimental Evaluation of Shrinkage, Creep and Prestress Losses in Lightweight Aggregate Concrete with Sintered Fly Ash

Abstract

The paper presents the experimental results of shrinkage, creep, and prestress loss in concrete with lightweight aggregate obtained by sintering of fly ash. Two concrete mixtures with different proportions of components were tested. Concrete with a density of 1810 and 1820 kg/m3, and a 28-day strength of 56.9 and 58.4 MPa was obtained. Shrinkage and creep were tested on 150 × 250 × 1000 mm3 beams. Creep was tested under prestressing load for 539 days and concrete shrinkage for 900 days. The measurement results were compared with the calculations carried out according to the Eurocode 2 as well as with the results of other research. A very low creep coefficient and lower shrinkage in relation to the calculation results and the results of other research were found. It was also revealed that there is a clear correlation between shrinkage and creep, and the amount of water in the concrete. The value of the creep coefficient during the load holding period was 0.610 and 0.537, which is 56.0 and 49.3% of the value determined from the standard. The prestressing losses in the analyzed period amounted to an average of 13.0%. Based on the obtained test results, it was found that the tested lightweight aggregate concrete is well suited for prestressed concrete structures. Shrinkage was not greater than that calculated for normal weight concrete of a similar strength class, which will not result in increased loss of prestress. Low creep guarantees low deflection increments over time.

Experimental and Numerical Research of Post-Tensioned Concrete Beams

“…Kim et al [6] conducted tests on full-size specimens of PSC bridge girders to obtain friction characteristics of post-tensioning tendons. Szydłowski and Łabuzek [7] analysed shrinkage, creep and prestressing losses in post-tensioned concrete beams as a result of using a lightweight aggregate obtained by sintering fly ash. Some of the work was aimed at confirming that the new theoretical approaches lead to a good agreement between the results of analytical and experimental studies.…”

Assessment of Properties of Structural Lightweight Concrete with Sintered Fly Ash Aggregate in Terms of Its Suitability for Use in Prestressed Members

“…On the other hand, since lightweight concretes have the ability to internal curing owing to water accommodated in LWA, the development of their shrinkage may be slower in time and less dependent on conditions of external curing such as temperature and humidity conditions. It was proved in numerous studies [19][20][21][22][23] that the shrinkage of high-strength concretes with lightweight aggregate was characterized by a slower increase even up to 1 year of curing, but later, it began to develop faster and finally reached the value by about 20% than the shrinkage of normalweight concrete of the same strength. Generally, the experimental studies proved that in the case of lightweight concrete, like for normal-weight concrete, the following rule is applied: the higher the compressive strength, the lower the creep.…”

“…Mayer and Khan [28] showed that the use of high-strength lightweight concrete allowed the design of load-bearing structures with a larger span. It was proved in [2,6,[22][23][24][25] that achievement of LWAC of higher strength class, necessary for prestressed structural members, is not a problem. Nevertheless, in the available literature, there are not so many examples of research carried out on prestressed structural members due to the large size of such elements as well as complicated, long-term, and more expensive performance.…”

Evaluation of the Superiority of Lightweight-Aggregate-Concrete Prestressed Box Girders in Terms of Durability and Prestress Loss

“…In contrast, when LWC is stressed, the situation is more complicated, as it depends on the elastic modulus of the LWAs and whether its strength is higher or lower than that of the mortar [33]. Therefore, the complex relationship between the two materials makes the mechanical behavior and collapse mechanism of LWCs applied to reinforced-concrete and prestressed-concrete members quite different from those of NCs [34,35]. In general, the elastic modulus of LWCs may be 15-60% lower than that of NCs of the same strength class, depending on the density of the concrete and the aggregate used [36,37].…”

“…Furthermore, the final creep deformation of the tested LWCs was more than two times lower than that of the corresponding NCs. The study by Szydłowski and Łabuzek [34] showed that compared with NCs, LWCs with higher strength, especially high-strength LWCs, can exhibit similar-and sometimes even lower-creep strains [58][59][60]. Kayali [60] showed that different types of LWAs produce distinct drying shrinkage behaviors.…”