Effects of Curing Temperature and Chemical Admixture Type on Fresh Properties and Compressive Strength of Ultra High-performance Concrete

Abstract

 Three types of chemical admixtures and curing regimes were used with ultra-highperformance concrete (UHPC).  150 MPa compressive strength is secured after 72 hours using Hyperplast PC-202 and curing at 90ºC.  UHPC mixtures require high admixture dosages, resulting in prolonged setting time.The types of post-setting curing and high range water reducing (HRWR) admixture used in Ultra-High-Performance Concrete (UHPC) mixtures play significant roles in determining their rheological and mechanical properties. This study compares the performance of three types of HRWR admixtures commercially available when added to UHPC mixtures under three different curing regimes. Mixtures made with the different superplasticizers were evaluated for their flow, 45mins flow retention, and setting time as fresh mix properties. Compressive strength was also tested for each mixture after 3, 7, and 28 days of curing at the investigated various curing regimes. Sika Viscocrete 180GS produced the highest mixture flow and flow retention levels with a 241 mm flow and 93.7% flow retention. Sika Viscocrete 168-1 produced the best results of setting time with 3 hours as compared to 12 hours with Sika Viscocrete 180GS. Using Hyperplast PC-202, the required 150 MPa compressive strength was secured as early as 3 days of curing with a 48hrs-90ºC curing regime. Using the same HRWR admixture, compressive strength values slightly lower than 150 MPa were reached after 7-28 days when the 72hrs-60ºC regime was adopted. The last curing regime was recommended for producing architectural UHPC units to minimize the delayed formation of ettringite.

Manufacturing of Sustainable Ultra-High-Performance Concrete Using Response Surface Methods

“…The strength result was 151.2 MPa using heat curing at 90 °C. This finding agrees with references [17,21,33], which found that the compressive strength of UHPC was significantly affected by the temperature of curing water due to the rate of hydration increasing with increasing temperature. Moreover, the thermal water cure has a greater impact on t early ages, and the formation of hydrated structures is improved by a thermal curing regime.…”

“…The curing process is essential for UHPC to develop its desired mechanical and durability qualities. Due to the low water contents, it is essential to increase the hydration reactions using the restricted amount of internal water and to take major precautions to prevent any water loss due to evaporation [17]. Prem et al, [18] concluded that 48 hours post-moulding-out is the optimal time for heat curing of UHPC.…”

“…The two curing regimes had similar compressive strengths at 91 days. However, particular material specifications and admixtures may cost more than heat curing for the cost-intensive UHPC [17]. This study aims to design and manufacture UHPC by avoiding using QP (replacing it with local limestone powder).…”

Evaluation of the Performance of Steel Slag and Waste Glass as a Cement Replacement

“…Flow table test conforming to ASTM C1437 determined the effects of SS and WG on mortars' workability [27,28]. Ovendried graded standard sand as per ASTM C778 was used [29].…”