Analysis of the Influence and Mechanism of Diatomaceous Earth Internal Curing on the Autogenous Shrinkage and Early Crack Resistance of Cement-Based Materials with Low Water–Binder Ratio

Abstract

Diatomaceous earth (DE), a kind of natural and environmentally friendly concrete admixture with good pozzolanic and water absorption properties, is a potential high-quality internal curing material. DE internal curing agent was prepared by calcining excavated diatomaceous earth and applied in cement-based materials with a low water–binder ratio of 0.35 to study its effects on the autogenous shrinkage and early crack resistance of the materials. The results showed that DE was a kind of microfine powder with a unique and orderly microporous structure, and its main component was SiO2, which had good water-holding and -releasing properties. Pre-absorbed DE could effectively improve the internal relative humidity of cement-based materials with a low water–binder ratio. Under the standard of not reducing the 28 d compressive strength of mortar, compared to the benchmark group without DE, when 1% of cement is replaced by DE of equal mass, DE could effectively reduce the 7 d autogenous shrinkage of mortar by about 36.7% and delay the initial cracking time of mortar under the restraint condition of the ring by 10.7%. Therefore, it is an internal curing material with excellent performance.