The recovery behavior for strength and impermeability of cementitious composites embedded with organic microcapsules was investigated in this study. Mortar specimens were formed by mixing the organic microcapsules and a catalyst with cement and sand. The mechanical behaviors of flexural and compression strength were tested. The results showed that strength could increase by up to nine percent with the addition of a small amount of microcapsules and then decrease with an increasing amount of microcapsules. An orthogonal test for investigating the strength recovery rate was designed and implemented for bending and compression using the factors of water/cement ratio, amount of microcapsules, and preloading rate. It is shown that the amount of microcapsules plays a key role in the strength recovery rate. Chloride ion permeability tests were also carried out to investigate the recovery rate and healing effect. The initial damage was obtained by subjecting the specimens to compression. Both the recovery rate and the healing effect were nearly proportional to the amount of microcapsules. The obtained cementitious composites can be seen as self-healing owing to their recovery behavior for both strength and permeability.

Self-healing cementitious composites have been developed by using microcapsules. In this study, the effect of the healing agent on the crosslinking and curing reaction kinetics was analyzed. The effect of the diluent n-butyl glycidyl ether (BGE) on the reaction was investigated for five fractions, namely 10.0%, 12.5%, 15.0%, 17.5%, and 20.0% mass fractions to epoxy resin. The Kissinger and Crane equations were used to obtain the activation energy and reaction order with different mass fractions of diluent, as well as the kinetic parameters of the curing reaction. The optimal fraction of BGE was determined as 17.5%. Likewise, the effect of the curing agent MC120D on the reaction kinetics was investigated for 10%, 20%, 30%, 40%, and 50% mass fractions to the diluted epoxy resin. The optimal fraction was determined as 20%. The mechanism of the curing reaction with the healing agent was investigated. The infrared spectra of the cured products of 20% MC120D with BGE/E51 (0.0%, 12.5%, 15.0%, 20.0%, 100%) were analyzed. It is shown that not only the epoxy resin E-51 was cured, but also that the BGE was involved in the cross-linking reaction of the epoxy resin E-51 with MC120D.

Anti-washout admixture used for anti-washout underwater concrete is composed of flocculant (e.g., paste stabilizer), superplasticizer, setting retarder, strengthening agent, etc. Good compatibility among those constitutes is necessary to release the vast material potential of anti-washout admixture. In the study, effects of polycarboxylate superplasticizer on fresh cement paste mixed paste stabilizer of various ionic type were experimentally investigated. Based on the experimental results, the optimizations on the ionic type and molecular weight of paste stabilizer, regarding the compatibility with polycarboxylate superplasticizer, were hence obtained. Additionally, suitable content ranges of polycarboxylate superplasticizer, molecular weight and content of paste stabilizer have been determined through systematic tests, such as saturation point test, fluidity test, and anti-washout test.

Slurry stabiliser is one of important composition for anti-washout admixture; this study focuses on the effect of slurry stabiliser on paste by fluidity, shear stress and viscosity test. To obtain stable rheology data, the test investigated the effect of setting retarder on rheology, test results show that rheology of paste is kept stable by mixing 4‰ of setting retarder by the weight of cement, slurry stabiliser can improve shear stress and viscosity, and the effect is more obvious with larger molecular weight.

Early strength agents are beneficial to improving early strength of concrete, thereby shorting curing time as well as production efficiency of concrete products, and consequently saving production costs. This study investigated the influence of triethanolamine, potassium carbonate, Calcium formate and Potassium aluminum sulfate on properties of specified density concrete, based on orthogonal experiment, composite early strength agent is determined.

Anti-permeability is one of critical properties of concrete, as a porous material, ceramsite in specified density concrete leads to many performance changes compare with ordinary concrete, such as mechanical properties, volume stability, durability, et al. combined with micro-test technology, this study investigated the effect of replacement rate and pre-wetting degree of ceramsite, water to binder (W/B) ratio, the content of fly ash, and the composite of aggregate on specified density concrete, and concluded appropriate range of above narrated factors.