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Geopolymer mortar can be used as an environmentally friendly sustainable construction material for the repair and strengthening of already-existing structures with the utilization of various recycled materials, such as fly ash, slag powder, etc. With mature application of fibers and nanoparticles in construction materials, nano-SiO2 (NS) and polyvinyl alcohol (PVA) fibers have been utilized to enhance the properties of geopolymer mortar, which has a major impact on the rheological properties of geopolymer mortar. The rheological property tests of geopolymer mortar were carried out in this study, and three indices including dynamic yield stress, static yield stress, and plastic viscosity were studied as rheological parameters. The results of the study were used to establish the relationships between PVA fiber content as well as NS content and rheological parameters. The results showed that a tendency of first decreasing and then increasing was observed in the rheological parameters with the addition of NS content from 0 to 2.5%. Compared with the geopolymer mortar without NS addition, the dynamic yield stress, static yield stress, and the plastic viscosity increased by 22.6, 12.4, and 22.9%, respectively, when NS content was 2.5%. The results showed that the rheological parameters of geopolymer mortar increased linearly with the increment in PVA fiber content which was less than 1.2%. In comparison to the geopolymer mortar without PVA fibers, the dynamic yield stress, static yield stress, and plastic viscosity increased by 65, 56, and 161%, respectively, as the PVA fiber content was 1.2%.

【Objective】 Acrylate polymer blended with poly (vinyl chloride) resin (ABR) is a composite material to make pipes. This paper investigates the pipe network manufactured by it for irrigation and drainage. 【Method】 The study was based on field experiments and CFD simulations. Based on performance of the network under different configurations, we optimized the system and applied it to dry-land chili pepper grown in Shandong plains in Northern China. 【Result】 ①Compared with single-ring and tree-like pipe network configurations, the double-ring and equidistant pipe network configuration in the ABR system reduced the coefficient of variation of water discharge for each irrigation-drainage pile by 1.327 to 0.766, thereby enhancing water supply balance. ②The suitable area for a single set of pipe network systems was 1.5 hm2, and the distance between the irrigation-drainage piles was 50 m. Under these conditions, water flow velocity at the outlet of each pile varied from 0.60 to 0.24 m/s, and each irrigation event can be completed in 12 h. ③The drainage capacity of each pile was 28.8 m3/h, sufficient to alleviate waterlogging during heavy rainfalls. 【Conclusion】 The proposed irrigation-drainage system significantly improved irrigation and flooding-control for the chili pepper grown in the dryland in the study area. It has a wide implication and application for crop productions in other regions.

In this study, polyvinyl alcohol (PVA) fibers and nanoparticles were incorporated to enhance the durability of geopolymer mortar (GM) with metakaolin (MK) and fly ash (FA). The dosage of nano-SiO2 (NS) was 0–2.5% and that of PVA fiber was 0–1.2%. The durability of GM includes resistance to chloride ion penetration, freeze–thaw cycles, and sulfate erosion. Compared with the single BP neural network (BPNN) model, a particle swarm optimized BPNN (PSO-BPNN) model was utilized to predict the resistance to chloride ion penetration, freeze–thaw cycles, and sulfate erosion of GMs with different dosages of nanoparticles and PVA fibers. In the model, the dosage of NS, PVA fiber, FA, and MK were used as input layers, and the durability parameters of electric flux, mass loss, and compressive strength loss of GMs were used as output layers. The result exhibits that the root mean square errors (RMSEs) of BPNN for resistance to chloride ion penetration, freeze–thaw cycles, and sulfate erosion of GM mixed with nanoparticles and PVA fibers are 145.39, 6.43, and 2.19, whereas RMSEs obtained from PSO-BPNN are 76.33, 2.87, and 1.03, respectively. The NN optimized by particle swarm algorithm has better prediction accuracy. The PSO-BPNN can be utilized for estimating durability of GM reinforced by NS and PVA fiber, which can provide a guide for the proportion design of GM with PVA fiber and NS as well as for the engineering practice in the future.

A study was conducted through quantitative calculations on the correlation between the micron-scale pores and the strength of nano-SiO2 (NS) sol reinforced cement mortar. The strength, pore structure, and microstructure of NS sol modified mortar were investigated, and the mortars were made equivalent to a two-phase material comprised of pores and mortar matrix; the model was applied to conduct a quantitative analysis of the correlation between pores and the strength. According to the research results, the modification made to the mortar using the NS sol led to significantly increased early strength and the level of porosity was also increased. Furthermore, the addition of NS caused a change to the C–S–H gel morphology of cement hydration products. As revealed by the results of quantitative analysis, the addition of 1.5 and 3% NS improved the mortar matrix strength by 29.3 and 56.6%, respectively. Moreover, the ratio between the mortar strength (f c) and matrix strength index (K) exhibited a nonlinear correlation with the porosity negatively. It was thus inferred that the increase in mortar porosity inhibited the improvement of mortar strength under the influence of NS sol.

The method of set pair analysis was used to evaluate the comprehensive performance of geopolymer mortar (GM) based on metakaolin and fly ash modified by nano-SiO2 (NS) and polyvinyl alcohol (PVA) fiber, and the design of mix proportion for GM was optimized. According to the experimental results, the addition of the NS and PVA fiber can improve the comprehensive properties of GM. The properties of GM are better when the NS content is 1.5% and PVA fiber content is 0.6%. The comprehensive performance of GM included workability, mechanical properties, fracture properties, and durability, and the typical performance parameters were selected as slump flow, compressive strength, bending strength, fracture energy, loss ratio of compressive strength after cycles of freezing-thawing, and electric flux values. The results show that the weights of each indicator derived from the method of set pair analysis have reduced subjective arbitrariness, improved the evaluation accuracy, and made the conclusions obtained from the set pair analysis method more scientific and reasonable. The method of set pair analysis combines the mechanical properties, durability, and workability of GM blending in PVA fiber and NS to achieve a comprehensive qualitative and quantitative evaluation, which can provide a new method for assessing the comprehensive performance of the GM composites blending in PVA fiber and NS in the future.

In this study, the influence of nano-CaCO3 (NC) and nano-SiO2 (NS) on engineering properties of cementitious composites reinforced with polyvinyl alcohol (PVA) fibers was investigated including slump and fracture properties as well as compressive, flexural, tensile, and strengths. The influence mechanism of NS content on properties of cementitious composites was revealed. The combined effects of NS and NC were evaluated on the composites made with 0.9% volumetric PVA fiber addition. The experimental results showed that the addition of nanoparticles decreased the workability of fresh cementitious composites reinforced with PVA fibers. Higher NS content deceased more workability and NC reduced more workability than NS for the composites. There was an initial increase and later decrease in compressive and flexural strengths as NS content alters from 0% to 2.5%, while the continuous increase was found in tensile strength. 1.5% NS maximally increased compressive strength and flexural strength, while 2.5% NS is optimal for tensile strength. The composite containing NC exhibited lower strengths than the composite containing the same content of NS. The fracture energy, initiation, and unstable fracture toughness slightly increased with the NS content varying from 0% to 1.5%, while they reduced when NS content was higher than 1.5%. The effects of NS and NC on fracture energy and toughness were inapparent. The failure mode of PVA fibers in the tensile strength test was changed from pull-out to fracture with the addition of NS based on microstructure characterization.

Emerging nanomaterials provide an invaluable opportunity for the development of cementitious materials. Many scholars have explored the influence of graphene (GP) and graphene oxide (GO) on the performance of the cementitious materials. This article reviews the previous research on the effect of GP and GO on the properties of cementitious materials. Detailed review of the mechanical properties and durability of cementitious materials containing GP or GO nanofilms is presented, and the mechanism is discussed. The mechanical properties of GO-cementitious materials are significantly enhanced. The optimal improvement of GO-modified compressive, flexural, and tensile strengths is 77.3%, 78.3%, and 78.6%, respectively. The durability of GO- and GP-modified cementitious material is compared with the control group. The incorporation of GP or GO significantly improves the sulfate attack resistance, and the transport properties can be decreased, while the frost resistance of GO- and GP-modified cementitious materials needs further research. This literature review shows that the microstructure of GO- and GP-modified cementitious material is improved in three aspects: accelerating the cement hydration, refining the pore structure, and hindering the crack propagation.

A non-linear 3D finite element model was established to simulate the three edge-bearing test of TRC reinforced concrete pipe. The pipe load-displacement curve, cracking load, and ultimate load simulation values are in good agreement with the test values. Subsequently, a parametric study was conducted. The effects of reinforcement layer bonding mode, mesh size of concrete element, mesh distribution rate and concrete compressive strength on the performance of reinforced concrete pipeline strengthened by TRC were considered. It provides a basis for the design of TRC reinforced concrete pipes.