Effects of Curing Temperature on Expansion of Concrete Due to ASR.

In the laboratory study of alkali-silica reaction (ASR), models attempt to predict the service life of concrete due to ASR by correlating the performance of concrete at high and low temperatures. However, the consequences of elevating temperature are not so encouraging. In this paper, the influence of temperature on the expansion of 2-graded concrete and 3-graded concrete caused by ASR was investigated by curing the concrete under different temperatures ranging from 40 °C to 80 °C.

Kinetics of Alkali-Silica Reaction: Application to Sandstone.

Despite extensive research, the relationship between the progression of the alkali-silica reaction (ASR) and the expansion of concrete due to ASR, particularly for the heterogeneous aggregate with slow reactivity, is not thoroughly understood. In this paper, the dissolution kinetics of reactive silica present in sandstone when exposed to NaOH solutions, alongside the expansion characteristics of rock prisms under ASR conditions, were studied. The experimental results indicate that ASR behaves as a first-order reaction, accompanied by an exponential decrease in the concentration of OH over time, and the dissolution rate of silica is predominantly governed by diffusion dynamics.

Influence of Ultrafine Fly Ash and Slag Powder on Microstructure and Properties of Magnesium Potassium Phosphate Cement Paste.

This study investigated the influences of ultrafine fly ash (UFA) and ultrafine slag powder (USL) on the compressive strengths, autogenous shrinkage, phase assemblage, and microstructure of magnesium potassium phosphate cement (MKPC). The findings indicate that the aluminosilicate fractions present in both ultrafine fly ash and ultrafine slag participate in the acid-base reaction of the MKPC system, resulting in a preferential formation of irregularly crystalline struvite-K incorporating Al and Si elements or amorphous aluminosilicate phosphate products. UFA addition mitigates early age autogenous shrinkage in MKPC-based materials, whereas USL exacerbates this shrinkage.

Effects of MgO Expansive Agent and Steel Fiber on Crack Resistance of a Bridge Deck.

To prevent cracks caused by shrinkage of the deck of the Xiaoqing River Bridge, MgO concrete (MC) and steel fiber reinforced MgO concrete (SMC) were used. The deformation and strength of the deck were measured in the field, the resistance to chloride penetration of the concrete was measured in the laboratory, and the pore structure of the concrete was analyzed by a mercury intrusion porosimeter (MIP). The results showed that the expansion caused by the hydration of MgO could suppress the shrinkage of the bridge deck, and the deformation of the deck changed from -88.

Effects of Steel Slag Powder and Expansive Agent on the Properties of Ultra-High Performance Concrete (UHPC): Based on a Case Study.

In view of the performance requirements of mass ultra-high performance concrete (UHPC) for the Pang Gong bridge steel cable tower in China, the UHPC incorporating of steel slag powder and hybrid expansive agents is optimized and prepared. The effects of steel slag powder and hybrid expansive agents on the hydration characteristics and persistent shrinkage of UHPC are investigated. The results indicate that 15 wt.

Temporal effect of MgO reactivity on the stabilization of lead contaminated soil.

Elevated soil lead (Pb) concentrations are a global concern owing to the toxic effects of this heavy metal. Solidification/stabilization (S/S) of soils using reagents like Portland cement (PC) is a common approach for the remediation of Pb contaminated sites. However, it has been reported that under long-term field conditions, the performance of PC treatments can diminish significantly.