Papers by Keyword: Steam Curing

Abstract: This study examines the mechanical performance, cost-effectiveness, and environmental impact of steam-cured cementless mortar incorporating stainless steel slag (STS slag) with ground granulated blast furnace slag (GGBFS) and natural gypsum. As the STS replacement ratio increased, flowability decreased by about 15%, while air content remained within acceptable limits. The STS10 mixture retained over 90% of the control’s compressive strength. Life cycle cost (LCC) analysis showed overall cost reductions of 3.6, 7.1%, and cost–benefit (CBA) evaluation yielded positive net present values and internal rates of return exceeding standard discount rates, confirming economic feasibility. Life Cycle Assessment (LCA) indicated continuous decreases in life-cycle CO₂ emissions with higher STS contents, with additional reductions of 4.4% and 8.8% in the construction phase for STS10 and STS20, respectively. Overall, incorporating 10% STS slag under steam curing offers an optimal balance of mechanical performance, economic efficiency, and environmental sustainability.

Abstract: Experimental investigations on the early age, strength gain properties of fly ash blended cement concretes containing low and high volume fly ash replacement were studied. Concrete mixes were prepared with two different fly ash contents and varying concrete ingredients with water to binder ratio (w/b), fine to coarse aggregate ratio (F/c) and accelerator dosage. Five different curing techniques, namely controlled humidity curing; hot air oven curing, steam curing, hot water curing and normal water curing were adopted for curing the fly ash based concretes. Test results showed evidence the influence of accelerating admixtures and accelerated curing for obtaining the high early strength properties in fly ash mixed concrete. Most notably a maximum 1 day compressive strength of 40.20 MPa and 34.60 MPa with low (25%) and high (50%) volume fly ash concretes were obtained respectively in this study. Experimental results clearly indicated that the improvements on the strength gain properties with the careful selection of mix ingredients; accelerator addition and accelerated curing in fly ash based concrete mixes. Also, significant improvements on the flexural strength, elastic modulus, dynamic modulus and the ultrasonic pulse velocity test were noticed.

Abstract: The effect of early strength improvement of concrete with C-S-H type accelerator was studied for precast concrete efficient production under the steam curing condition. From the mortar test result, the effect of this improvement was confirmed to tend lager as the W/C is lower. This accelerator could short the curing time for 0.5-2.0 hours under the same temperature condition, and could reduce the curing temperature under the same curing time. Then the compressive strength was considered to be predicted by some formula, and it showed higher estimation accuracy of the Arrhenius’s Law than that of the Maturity Method.

Abstract: Pre-cast concrete products are sometimes manufactured in two cycles daily. It is ensured that they have the required strength at an early stage of demolding by increasing the steam curing temperature to reduce cost or increase productivity. However, the reduction in durability because of cracking due to thermal stress is a topic of concern. On the other hand, it has been known that fine blast-furnace-slag powder and expansive agents show high temperature dependence. Although they are used even in precast concrete products, the effect of steam curing on these materials is not known. Thus, in this study, the expression of compressive strength and expansion that are critical in improving the quality and productivity of precast concrete products was investigated, using high early-strength cement and two types of expansive agents, namely, ettringite-based and lime-based agents. Consequently, the strength expression was accelerated by the addition of expansive agent to ordinary cement and high early-strength cement. The extent of restrained expansion is greater for the lime-based expansive agent than for the ettringite-based expansive agent, and when an expansive agent is added to high early-strength cement, the extent of restrained expansion falls to a level lower than that in the case of ordinary cement.

Abstract: nanosilica porous thermal insulating composites belong to super thermal insulations, which are prepared by dry molding technology. They have many advantages in comparison with aerogel such as easy preparation and good mechanical property. However, springback phenomenon is found in the process of molding. The springback is easy to lead to cracking of the samples, which directly affects applications of the composites. In order to solve this problem, steam curing method is introduced and the effects of steam curing medium and steam curing time on springback ratio are investigated. The results show that the springback ratio of composites is only 6.45% when water is selected as steam curing medium and the optimum steam curing time is 30 min.

Abstract: For researching principle and production line state of steam curing of composite wallboard, the art have been conducted through actual investigation and field test. Based on the influence of steam curing on the strength of high performance concrete, durability and volume stability, put forward suggestions of steam curing system; Several problems have been raised for steam curing in the actual production, then some correlative improve measurements are given. Provide the reference for the production and development of the residential part in our country.

Abstract: A basic study is performed on the application of highly ductile SHCC(Strain Hardening Cementitious Composites) to precast method. A special focus was placed on applying class C fly ash with a high CaO content to secure early-age strength of the steam cured SHCC. The flexural strength of the SHCC panels dependent on fly ash type and varied curing methods were evaluated. The results showed that class C fly ash could enhance the flexural strength of 1 day-old steam cured SHCC panels. Additionally, 1 day-old steam cured specimens produced with class C fly ash exhibited up to 58% of the flexural strength of 28 day-old wet cured specimens produced with class F fly ash.

Abstract: The experimental study was performed on the relationship between the mechanical and durability properties of high-strength concrete with metakaolin (MK) and slag. The compressive strength, chloride penetrability and pore structure of the OPC and the concrete with MK and slag were measured. It is found that MK can significantly increase the compressive strength, decrease the chloride ions migration coefficient and improve the pore structure of the steam cured high-strength concrete. The chloride resistance is improved obviously by 5% MK and further increase of the MK dosage performs a little change of the chloride migration coefficient. Better improvement effect on the mechanical and durability properties is obtained with the incorporation of 10% MK and 10% slag. Linear relationship is found between the coarse pore porosity and the compressive strength, while the chloride migration coefficient correlates well with the capillary pore volume.

Abstract: This paper carried out experiments to investigate the change of water absorption gradient of standard curing concretes and steam-cured concretes cured at 60°C. The effect of steam curing on concretes water absorption was evaluated, and the corresponding mechanism was also discussed. Results indicate that the change of water absorption gradient of standard curing concretes is non-significant with the change of the specimen height; Steam curing has exacerbated the inhomogeneity between the top surface and interior surface of concretes. It is observed that noticeable gradient difference in aborption characteristics between top, the second (1cm below top surface) and the third (3cm below top surface) surfaces of samples. Top surface absorption capacity has been the highest, and the second surfaces are in rather good accordance with the third surface. Thus the effect depth of steam curing is near to the concrete open surface. The addition of silica fume to a concrete decrease the water sorptivity of steam curing and standard curing concretes, but for the improvement of the uniformity of concrete, the effect is not markedly obvious.

Abstract: The kinetics of cement hydration can be accelerated by steam curing and this kind of curing can be responsible for increasing concrete porosity, since a greater portion of non hydrated cement particles can be present. The increased porosity results can result in increased permeability. The aim of this work was to investigate the influence of curing on concrete quality by air permeability and compressive strength test. It was measured by means of a non steady state air permeameter. Concretes were produced with Portland cements containing 0%, 27% and 53% of ground granulated blastfurnace slag. The amount of slag in cement influenced concrete performance and steam curing increased air permeability of concrete.