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Highlights • Ammonia gas can be converted into bio-magnesium ammonium phosphate in cementation process. • Loose desert sand particles can be cemented by the bio-magnesium ammonium phosphate cement. • Micro-structure of the bio-sandstones has been studied. Abstract Loose desert sand grains can be cemented through the microbially-induced magnesium ammonium phosphate sediment into sandstone. Ammonia and ammonium were produced by Sporosarcina-Pasteurii hydrolyzing urea and effectively became environmentally friendly magnesium ammonium phosphate in the presence of HPO 4 2− ions (hydrogen phosphate). This a new kind of the bio-cement based on Sporosarcina-Pasteurii , and the bio-phosphate mineral has cementation. The chemical components of the bio-sandstone were mainly MgNH 4 PO 4 (H 2 O) 6 (struvite) and quartz, as discovered through X-ray diffraction (XRD) analysis. The internal micro-structure of the desert sand was observed by scanning electron microscopy (SEM), and its morphology was of irregular spheres with a size in the range of 100–300 µm. SEM images of the bio-sandstones showed the morphology of the cementation products as irregular flakes. The average hardness of two bio-sandstones cemented by spraying 1 and 3 times with cementation solution was 4.4 and 12.3, respectively. The evolution law of the micro-structure for the bio-sandstone cemented by spraying 3 times with cementation solution was revealed by the X-ray computed tomography (XRCT) technique. Maximum defect volume and average porosity of the bio-sandstone was 134 mm3 and 18.39%, respectively. Interface binding forces between the bio-cement and smooth sheet glass (SiO 2) were determined with WS-2005 coating adhesion scratch tester, which was 3.69 ± 1.02 N. [ABSTRACT FROM AUTHOR]

Using bio-composite cement, loose sand particles can be aggregated into bio-sandstone with good mechanical strength. The average compressive strength, hydraulic conductivity, and porosity of bio-sandstone made with 6 injections of bio-composite cement were 1.33 MPa, 2.03 × 10 −2  cm/s, and 25.15%, respectively. The ingredients of the bio-sandstone, as determined through X-ray diffraction (XRD) analysis, were mainly quartz sand, MgNH 4 PO 4 (H 2 O) 6 , and Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O. Scanning electron microscopy (SEM) images of the bio-sandstone showed that the cementation products have an irregular flake morphology. The maximum defect volume of the bio-sandstone creating using 2, 4, and 6 injections of bio-composite cement was 1401 mm 3 , 930 mm 3 , and 738 mm 3 , respectively. The internal microstructure of quartz sand, as observed by SEM, was found to be irregular spheres of 100–300 µm. The wind erosion rate of bio-sandstone created by spraying bio-composite cement on quartz sand 1 or 3 times was 0 g/m 2 /h, after 1 h of wind erosion. [ABSTRACT FROM AUTHOR]

Loose sand particles could be cemented by the microbial induced phosphate and carbonate precipitation into a bio-sandstone with a certain mechanical strength when the Sporosarcina pasteurii contained K 2 HPO 4 ·3H 2 O and the mixture solution of urea and MgCl 2 in the 1:1 of volume ratio were injected by a peristaltic pump into quartz sand mold. The result shows that loose quartz sand particles are well cemented into a bio-sandstone, and the compressive strength of bio-sandstones is greater than 1.0 MPa. Ammonia/ammonium was produced during the hydrolysis of the urea and could be effectively become into environment-friendly struvite in the cementation process. In addition, the ingredients of the bio-sandstones were mainly quartz sand, struvite and hydromagnesite through XRD analysis. The internal microstructure of bio-sandstone was observed by SEM and the bio-phosphate and carbonate composite cement between sand particles indicated the shape was mainly irregular particles. The solidified layer of the surface of dust and sand particles was formed after spray bio-phosphate and carbonate composite cement, and wind erosion rate of dust and sand is 0 g/m 2 /h and 0 g/m 2 /h, respectively. [ABSTRACT FROM AUTHOR]

Loose sand particles can be cemented by the microbial inducing the slurry of barium hydrogen phosphate precipitation into a bio-sandstone with certain mechanical strength, which is a new technique to bound loose sand particles with biological phosphates. This paper confirms the feasibility of biological phosphates binding loose sand particles and presents results from laboratory researches on the influence of standing time and content of the slurry on the mechanical properties of sandstone biological phosphates bound. The results show that standing time and content of the slurry have a strong influence on the mechanical properties of bio-sandstone. The best standing time, which is 24 h, of the slurry mixing with quartz sand and obtained higher compressive strength of sand column (bio-sandstone) than three other standing times. The maximum compressive strength of bio-sandstone is 2.1 MPa when the content of the slurry reaches 50% with 24 h standing time. In addition, the ingredients of the slurry and bio-sandstone are mainly hydrogen phosphate barium through XRD analysis. The corresponding variation of porous characteristics of sand column is observed by scanning electron microscope (SEM) and indicated that the cementitious materials between quartz sand are mainly irregular sphere clusters in shape. The technique can be used in other fields: including dust-fixing, foundation reinforcement, slope and so on. [ABSTRACT FROM AUTHOR]