•A super absorbent polymer was used to modify sulphoaluminate cementitious materials.•Water absorption rate increased with the increase of polymer addition.•Water/fertilizer retention performance was greatly enhanced by 0.5 wt.% polymer.Porous concrete as plant bedding has been appropriately named planting concrete. Planting concrete is mainly used to prevent soil erosion and desertification, for instance, along a motorway and to protect water and soil loss, for instance, on a river bank. Plans can grow in planting concrete and their roots can progress through it to the soil underneath. Compared to ordinary concrete, planting concrete could protect slopes and beautify the natural and built environment. This paper presented an investigation of water absorption and water/fertilizer retention performance of super absorbent polymer (SAP) modified sulphoaluminate cementitious materials for plants growing. SAP was used to partially replace sulphoaluminate cement (SAC) for the preparation of a material with advanced water absorption capacities and water/fertilizer retention properties which are necessary for plants growing in planting concrete. Mercury intrusion porosimetry (MIP) was adopted to characterize the effects of SAP on the pore structure of hardened SAC-based pastes for plant growing. Hydration heat-evolution was employed for characterising the hydration process of SAC-based materials. Experimental results revealed that SAC-based materials delivered their best performance at the 0.5 wt.% SAP content. At this cement replacement level, the water absorption rate of hardened SAC paste increased by 38.3% while its water retention capacity increased by 23.4% at the age of 180 h. Additionally, other property advancements were measured including reduction of the fertilizer pervasion rate which was found increasing by up to 11.2 wt.% at 35 days and the compressive strength of up to 55.2 MPa at 28 days.

•AlN/Al2O3 composites are obtained via vacuum hot-pressing.•The phase formation of AlON by reaction of AlN and Al2O3 is achieved.•The finally obtained phases are Al2O3, AlN and AlON phases after oxidation.•The amount and distribution AlON phase control the oxidation behavior.Samples with various ratios of AlN/Al2O3 were fabricated via vacuum hot-pressing at 1700 °C under an applied pressure of 30 MPa for 90 min using Y2O3 as a sintering aid. The densification process, microstructural development, and formation of AlON phase from Al2O3 and AlN were investigated. Al2O3 additive can improve the physical and mechanical properties, and purification of the grain boundaries. AlON are almost formed completely when the content of Al2O3 is 80 vol%. The effects of composition, microstructure, and exposure time at 1400 °C on the oxidation behavior of AlN samples with different amounts of Al2O3 were investigated. The sample with 80 vol% alumina has the best oxidation resistance.

Laminated ZrC–SiC composites were fabricated by a tape-casting process and vacuum hot-pressing. The microstructures, fracture behaviour, and crack propagation paths of the resulting composites were studied. The laminated ZrC–SiC composite had a bending strength of 167 MPa and exhibited non-brittle failure behaviour due to the propagation and deflection of cracks. The observed crack propagation path in the ZrC–SiC laminated composites indicated that crack deflection and crack termination were observed during the fracture process. The crack tip decreased as the crack traversed through each layer.

A reduced transport property of the superficial part of concrete structures is beneficial for enhancing their durability, due to the blocking of the migration of aggressive agents. In this study, influences of colloidal nano-SiO2 (CNS) with a mean particle size of 20 nm and its precursor, tetraethoxysilane (TEOS), on the transport properties of hardened cement pastes with water-to-cement ratios of 0.26, 0.38, 0.60 and 1.0 by mass were investigated by measuring the water absorption ratio and water vapor transmission coefficient, after the samples were first soaked in treatment agents for 1 h. Results showed that CNS and TEOS are capable of reducing the transport properties of hardened cement pastes by altering the pore structures. CNS reduces the threshold value and volume of the pores larger than about 0.1 μm, while TEOS reduces the threshold value and volume of the pores smaller than 0.1 μm, and TEOS also reduces the ratio of the ‘ink-bottle’ pore volume to the throat pore volume to a greater extent. A linear relationship between the volume of capillary pores smaller than 0.1/0.01 μm and the transport property was found, which can be ascribed to the reduction of transport properties of hardened cement pastes after surface-treatment with CNS or TEOS.

A series of receiving type piezoelectric composites were designed and fabricated by cutting and filling technique. The piezoelectric composites were also optimized from such aspects as matrix phase, functional phase and composite connectivity. The researches show that these piezoelectric composites have larger piezoelectric voltage factor, thickness electromechanical coupling coefficient and lower acoustic impedance than the pure piezoelectric ceramic. The early cement hydration reaction process monitoring result indicates that the ultrasonic wave receiving ability of the piezoelectric composite is obviously better than that of the pure piezoelectric ceramic. Therefore, these kinds of piezoelectric composites have potential application prospect in cement hydration reaction process monitoring.Highlights► Kinds of piezoelectric composites were designed for cement hydration monitoring. ► The piezoelectric composites have good electric and acoustic properties. ► The composite has better receiving ability of ultrasonic wave than PZT-5 ceramic. ► Piezoelectric composites can effectively monitor the early cement hydration process.

A 1-3 piezoelectric ceramic–cement composite has been fabricated using sulphoaluminate cement and lead niobium-magnesium zirconate titanate ceramics (P(MN)ZT) as matrix and functional component, respectively. The influences of piezoelectric ceramic volume fraction, aspect ratios of piezoelectric ceramic rods and temperature on the piezoelectric and dielectric properties of the composites were studied. This composite was shown to exhibit an improved electromechanical coupling coefficient with the mechanical quality factor reduced. Furthermore, the acoustic impedance of the composites could also be adjusted to match concrete structures. It has been demonstrated that by adjusting the piezoelectric ceramic volume fraction and shape parameters, the developed composite can be eventually used as sensing element in structural health monitoring.

PZT piezoelectric ceramic was used as sensing element to fabricate piezoelectric sensor. The fabricated PZT piezoelectric sensor was embedded into and affixed to the structure to detect the structural damage, respectively. The structural crack damage was investigated using the impedance spectra of the sensor. The results show that the electric impedance of the PZT piezoelectric sensor with both different arrangements can reflect the variations of the structural crack damage in the testing frequency ranges. In the frequency range of 20–70 kHz, both the impedance value and the resonance frequency of the embedded PZT piezoelectric sensor can show the incipient crack damage and the increase of crack depth clearly. The impedance spectra of the affixed and embedded PZT piezoelectric sensors show the similar variation regularity with increasing the structural crack damage degree. Furthermore, the impedance spectra variation of the PZT piezoelectric sensor with different arrangements in the thickness resonance frequency range is more obvious than that in the planar resonance frequency range. A scalar damage metric is presented based on the impedance spectra of the PZT piezoelectric sensor around the resonance frequency, and the cracks in different positions of the structure were also analyzed using the damage metric. The variation of structural crack damage can be observed effectively and obviously using this damage metric.

Composites with 2–2 connectivity were fabricated from plates of “PMN” ceramic embedded in a sulphoaluminate cement matrix by a cut-filling process. The influences of the water–cement ratio in the matrix on the properties of the composite were analyzed. The results show that when the water–cement ratio is less than 0.4, the piezoelectric stain factor d33 and piezoelectric voltage factor g33 increase smoothly. When the water–cement ratio is larger than 0.4, d33 and g33 increase obviously with increasing the water–cement ratio. This is attributed to a more effective contact between the active and matrix phases. d33 = 322 pc N− 1 and g33 = 20.9 mV mN− 1 at a water–cement ratio of 0.45. The planar electromechanical coupling coefficient Kp of the composite is nearly independent of the water–cement ratio. With increasing the water–cement ratio, the thickness electromechanical coupling coefficient Kt of the composite increases, while the mechanical quality factor Qm exhibits the trend of decrease.