Caijun Shi

This study investigated the T2 spectrum of hydrogen nuclear magnetic resonance (1H NMR) signals in cement paste with water-to-cement ratios (w/c) of 0.2, 0.35, and 0.5 under three different saturation methods (natural soak, vacuum saturation, and vacuum saturation with high pressure). The saturation degree and pore structure of the cement paste und...

This study investigates the heterogeneity of steel fiber reinforced concrete (SFRC) and its rough fracture surface characteristics at different directions (anisotropy) and regions (nonuniformity). The sensitivities of different roughness parameters to fracture morphology are thus analyzed. Four roughness parameters such as root mean square deviatio...

The use of supplementary cementitious materials (SCMs) is an effective way to reduce CO2 emissions within the cement industry. In this paper, the Cement-Metakaolin (MK)-Sugarcane Bagasse ash (SCBA) ternary composite was designed based on the simplex centroid design method. The influence of MK and SCBA on mechanical properties of ternary composite w...

Fine coral aggregate has a porous structure and high water absorption, which can be used as an internal curing medium. In this study, the pore characteristics and water absorption-desorption of fine coral aggregate were investigated, as well as the difference in internal curing of fine coral aggregate between freshwater and seawater mixed cement mo...

This study investigates the nonlinear behavior of flow passing through 28 crack topographies in concrete at various pressure gradients using water permeability test. Artificial cracks were generated and quantified by point-cloud matching technique. Results indicate Darcy’s law becomes biased for calculating an apparent transmissivity of cracked con...

Accelerated carbonation curing has several advantages compared with traditional moisture curing in terms of decreasing the duration time of early curing and improving the mechanical properties, dimensional stability and durability of concrete. This study investigated the effect of accelerated carbonation curing and further water curing on corrosion...

In this work, the flexural behavior of glass fiber textile reinforced seawater sea-sand concrete (GTR-SWSSC) exposed to the simulated marine environment was studied. Four-point bending tests were carried out on GTR-SWSSC after different drying-wetting cycles and seawater immersion time, and the flexural performance of GTR-SWSSC was evaluated. At th...

The influence of pumping on the rheological properties of self-consolidating concrete (SCC) is widely recognized, but there is still limited understanding of its behavior within the pipeline. In this study, we propose a novel approach using equilibrium distances to investigate the evolution of rheological properties along the pipeline. Full-scale h...

Understanding the flexural behaviour of reinforced alkali-activated slag-based concrete beams after exposure to a fire is imperative to ensure their safety use and develop adequate retrofitting measures. However, up to this point in time, no relevant investigations on this specific subject have been reported. This paper presents an experimental stu...

As no study on fire behavior of RC columns using alkali-activated concrete has been reported so far, this paper presents an experimental program comparatively investigating the thermal response and structural behavior of reinforced columns using alkali-activated slag-based concrete (AAC) and Portland cement-based concrete (PCC) during and after sub...

Natural aggregate (NA) can be replaced by recycled concrete aggregate (RCA) in the construction industry, which can solve the problem of construction waste disposal and reduce the gap between demand and supply. Various methods that were used to pretreat the RCA from the published research can be divided into the removal of adhered mortar, polymer i...

Effects of using a cement mixture containing bagasse ash (SCBA) and slag (BFS) on the corrosion properties of steel in sea-sand mortar were investigated. The electrochemical impedance spectra, open circuit potential, and corrosion current density of steel were measured, along with the chloride ions content, pH value, and hydration products. Results...

当地下水含较高浓度的碳酸和氯离子时，碳酸水溶液对地下混凝土结构的腐蚀会导致氯离子在混凝土中的迁移更快。本工作研究了碳酸水溶液环境里氯离子在砂浆中的迁移特性，用 X 射线衍射分析(XRD)、热重分析(TG-DTG)和扫描电子显微镜(SEM-EDS)分析了碳酸水溶液-氯离子侵蚀下净浆侵蚀产物以及微观形貌的变化。结果表明：碳酸水溶液侵蚀前期，氢氧化钙和 C-S-H 凝胶脱钙碳化生成碳酸钙填充了砂浆的孔隙结构，抑制了氯离子在砂浆中的迁移；侵蚀后期，由于碳酸钙的溶解以及低钙硅比的 C-S-H 凝胶转变为无定型硅胶共同导致了砂浆孔隙率增大，氯离子在砂浆中的迁移加快；碳酸水溶液侵蚀导致了水泥基材料中 Friedel’s 盐的分解以及 C-S-H 凝胶吸附氯离子能力的下降；降低水灰比能增加砂浆抗 碳酸水溶液...

CO 2 curing can improve the properties of cement-based materials and absorb the CO 2 , which is an effective method for precast concrete. However, the application of CO 2 curing is limited for the on-site concrete because the CO 2 is hard to diffuse into inner fresh concrete. A new enhanced carbonation curing method has been proposed by using monoe...

Bond strength deterioration between reinforcing bars and surrounding concrete is critical to structural performance loss during a fire. However, available studies on the bond behavior between alkali-activated concrete and reinforcing bars at elevated temperatures are insufficient. This study conducted pull-out tests on alkali-activated slag-based c...

Effect of carbonation curing on the early resistance to carbonic acid water corrosion of cement-based materials was investigated. The compressive strength, and corrosion depth of carbonation cured specimens were tested after immersion in carbonic acid water for varying periods. Microstructure and corrosion mechanisms were analyzed using X-ray diffr...

As a part of ongoing research to apply alkali-activated slag-based concrete in building structures, the shear transfer behavior of alkali-activated slag-based concrete was experimentally examined through the push-off tests of 32 initially uncracked reinforced planes. The test parameters were concrete type, concrete strength, shear reinforcement rat...

The pumping pressure loss of fresh concrete has traditionally been modeled as a linear function of the pumping distance. However, previous studies have suggested that this relationship is nonlinear in nature. This research has identified that the nonlinearity is due to changes in the rheological properties of fresh concrete during pumping. In this...

A series of new low calcium CO2 sequestration cementitious materials (LCC) with different Ca/Si ratios were prepared by sintering waste concrete fine powder (WCP) and calcium carbide slag (CCS) at different ratios. Their carbonation reaction activity, carbonation hardening properties, phase assemblages, and microstructure were systematically cha...

Superabsorbent polymer (SAP) as internal curing agent can effectively mitigate the autogenous shrinkage and promote cement hydration of ultra-high performance concrete (UHPC). However, it has a risk of impairing the mechanical performance of UHPC given the macro pores left. This study developed ultra-fine SAP powder aiming at securing the lower shr...

The high alkalinity of concrete restricts the application of basalt fiber-reinforced polymer (BFRP) bars as reinforcement in seawater and sea sand concrete (SWSSC), but lowering the alkalinity enhances the durability of BFRP bars. This work focuses on the degradation of BFRP bars embedded in SWSSC in the laboratory and real marine environments. The...

This study evaluates the influences of coral coarse aggregate (CCA) and cement contents on the durability performance of basalt fiber-reinforced polymer (BFRP) bars embedded in seawater sea sand coral aggregate concrete (SSCC). The evaluation is conducted by characterizing the changes in interlaminar shear strength after accelerated exposure in a s...

Accelerated carbonation can promote the application of steel slag in construction materials. This method can not only resolve the fatal volume expansion of steel slag, but also sequestrate CO 2. The carbonation thermodynamics, carbonation degree, carbonation methods and influencing factors of steel slag were reviewed. The theoretical CO 2 uptake of...