Effect of carbonation curing on sulfate resistance of cement-coal gangue paste

Steam curing at atmospheric pressure is a method used to raise concrete strength at early ages. The steam curing method is based on the application of hot water vapor at a temperature between 40 °C and 100 °C for a limited period. The highest temperatures and the longest curing period are determined based on the characteristics of the target concrete, the cost, and the production cycle. This study presents the effect of steam curing regime application on concrete properties. Steam curing has a negative effect on the microstructure of concrete, and this effect increases with higher temperatures. The curing period and the precuring period in addition to the cooling period influence the properties and the strength of concrete. This study summarizes the previous literature related to the effect of steam curing regime application on the properties of concrete. Previous studies confirm that concrete exposed to steam curing regime at low temperatures ranging between 45 °C and 80 °C and a longer period within a 24-hour cycle achieve better concrete properties. In addition, raising the steam curing temperatures above 80 °C has a negative effect on concrete microstructure and other concrete properties in general. This study also concludes that adding pozzolanic or complementary cement materials contributes to reducing the damage resulting from the application of steam curing regime on concrete at later ages. Such verification is required to clarify the behavior of concrete under the influence of steam curing systems, understand their effect on the properties of concrete, and look for ways to reduce the damage from degrees of application of steam curing regime. 

Review on effect of steam curing on behavior of concrete

Effects of pre-soaked zeolite and CaO-based expansive agent on mechanical properties and autogenous deformation of early-age concrete

Evolution of temperature stress and tensile properties of concrete during steam-curing process

Crack extension resistance of steam-cured concrete under different curing temperature conditions

Volume deformation of steam-cured concrete with fly ash during and after steam curing

Traditional cement-based repair materials are brittle and prone to cracking. The failure of more than half of repaired concrete structure is due to the re-cracking of the repair material itself or delamination and peeling from the concrete matrix. Thus, a second repair is required in a short period, increasing the maintenance cost. To reduce cracking, Strain Hardening Cement-based Composite (SHCC), with strain hardening and multiple cracking property, is prepared to study the influence of interface roughness and repair layer thickness on the shrinkage, cracking and delamination modes of SHCC-repaired concrete beams. The results show that under the shrinkage stress, multiple fine cracks instead of local fractures occur in the SHCC repair layer, and the interfacial delamination is effectively controlled. Interfacial bonding property is the main factor that affects the shrinkage and deformation coordination of SHCC-repaired beams. When the interface roughness is different, the crack width of the SHCC repair layer is similar. However, it has a greater influence on the interfacial delamination length and maximum delamination height of the repaired beam. With the increase of interface roughness, the delamination length and height of the repaired beam are greatly reduced. Therefore, before using SHCC to repair the existing structures or components, the bonding surface should be roughened to improve the bond strength between SHCC and the old concrete. With the increase of the repair layer thickness, the cracking and delamination of the repair layer tend to be alleviated. Although the crack width of the repair layer can be effectively controlled after cracking, the overlarge shrinkage (985.35 × 10−6, about twice the shrinkage value of ordinary concrete) of the SHCC prepared in this research results in the cracking of the repair layer and the delamination of the repair interface under the restraint of concrete; thus, SHCC fails to repair the concrete efficiently. In terms of shrinkage deformation control, materials with high toughness and low shrinkage are required to repair the existing concrete structures. The implication of this research may provide a theoretical basis for the preparation and application of SHCC with high toughness and low shrinkage.

https://www.mdpi.com/1996-1944/13/7/1757/pdf

Research on Bonding and Shrinkage Properties of SHCC-Repaired Concrete Beams.

In order to better predict the development of shrinkage deformation of steam-cured concrete mixed with slag, a deformation-temperature-humidity integrated model test, a hydration heat test, and an elastic modulus test were performed. The effects of the steam-curing process and the content of slag on shrinkage deformation, hydration degree and elastic modulus of concrete were studied. The results indicate that during the steam-curing process, the concrete has an “expansion-shrinkage” pattern. After the steam curing, the deformation of concrete is dominated by drying shrinkage. After the addition of slag, the shrinkage deformation of steam-cured concrete is increased. The autogenous shrinkage increases by 0.5–12%, and the total shrinkage increases by 1.5–8% at 60 days. At the same time, slag reduces the hydration degree of steam-cured concrete and modulus of elasticity. A prediction model for the hydration degree of steam-cured concrete is established, which can be used to calculate the degree of hydration at any curing age. Based on the capillary tension generated by the capillary pores in concrete, an integrated model of autogenous shrinkage and total shrinkage is established with the relative humidity directly related to the water loss in the concrete as the driving parameter. Whether the shrinkage deformation is caused by hydration reaction or the external environment, this model can better predict the shrinkage deformation of steam-cured concrete.

https://www.mdpi.com/1996-1944/14/7/1647/pdf

Hua Fu

Papers

Volume deformation of steam-cured concrete with fly ash during and after steam curing

Research on Bonding and Shrinkage Properties of SHCC-Repaired Concrete Beams.

Volume Deformation of Steam-Cured Concrete with Slag during and after Steam Curing.