Effect of water-to-cement ratio on sulfo-aluminate type cementitious grouting materials

The supplementary cementious materials (SCMs) or mineral admixtures like fly ash, silica fume, metakaolin and ground granulated blast furnace slag (GGBS) are used in cement composite by partial replacement of cement about 20%. The effect of SCMs in Ordinary Portland cement (OPC) with regard to water requirement for consistency, setting time and cement mortar cubes with and without addition of super-plasticizer (SP) has been studied. It has been observed from the experimental studies that the cement consistency for OPC is 27.5% and addition of different mineral admixtures demands more water than cement consistency. Particularly, the mix with metakaolin demands 39% water for consistency. It is observed that with the addition of SP, the water required for consistency found reduced to 25% in all the mixes. The use of mineral admixtures influence fast setting time and with the addition of SP, the setting time is much faster. For preparation of mortar cubes demand 1 % more water as compared to IS-1489. XRD test has been conducted on cement and other cementitious materials, such as fly ash, silica fume, metakaolin, GGBS, to know the nature of particles present in that, which have more influence in imparting strength property. River sand and standard sand has been used in the present study. The compressive strength has been determined for these mixes at 3, 7, 28, 56 and 90days and the compressive strength determined at 90 days indicates that all the mixes with mineral admixtures give more or less same strength except the mix with fly ash in both conditions i.e. with river and standard sand, which gives 10.20 % less by using River sand and 16.5% less by using standard sand. With the addition of SP, the compressive strength of cubes prepared using river and standard sand is more compared to the strength of cubes prepared without SP. The compressive strength of the mortar cubes using standard sand gave better results on compared to cubes using river sand. The compressive strength of cubes for silica fume using River sand gave higher strength of about 56.38Mpa and by using standard sand cement with silica fume gave higher strength of about 57.52MPa. With the addition of SP, the compressive strength of the mortar cubes using river and standard sand, silica fume gave higher strength of about 60.25 and 61.11MPa respectively.

Overburden bed separation grouting is a green mining method to control surface subsidence and protect surface buildings (structures). The performance of cementitious grouting material is the key factor affecting grouting filling. Although offering good fluidity and low cost, the fly ash (FA) slurry demands a significant water supply, undergoes high dehydration rates, and lacks cementing property. These factors result in low grouting efficiency and negatively impact the safety of operations in complex-structure areas. This work developed a CBF + D series all-solid-waste cementitious grouting filling material with blast furnace slag (BFS), FA, carbide slag (CS), desulfurization gypsum (DG), and calcium chloride (CaCl2) as components. Based on the orthogonal test, the basic performance test of the grouting material was carried out using macroscopic and microscopic test methods. The influences of the water–cement ratio, the mass ratio of BFS to FA, the proportion of CS, and the proportion of DG on the slurry density, fluidity, water extraction rate, and uniaxial compressive strength (UCS) of the stone body were assessed. The material’s hydration mechanism was analyzed by combining X-ray diffraction (XRD) and scanning electron microscopy (SEM) microscopic experiments. The optimal parameters for this test were as follows: a water–cement ratio of 0.7, a mass ratio of BFS to FA of 3:1, a proportion of CS of 40%, and a proportion of DG of 4%. Under the optimal conditions, the density of the slurry was 1.41 g·cm−3, with a fluidity of 15.7 cm, a water extraction rate of 0.107, and a UCS of the stone body of 6.25 MPa. The water extraction rate of the slurry is 67% lower than that of the FA slurry and the slurry has good cementation performance, while still maintaining its fluidity. This significantly enhanced the safety and applicability of the grouting filling process. In addition, CBF + D series all-solid-waste cementitious materials have solved the large accumulation of industrial wastes such as FA, BFS, and CS, which maximized the resource utilization rate of these wastes and brought significant economic benefits.

The engineering practice shows that the application of grouting technology to treat underground engineering has strong applicability and is one of the most commonly used technical means at present. Based on the underground engineering, this paper introduces the research achievements of grouting materials in recent years, including cement-based grouting materials, mixed grouting materials, anti-scouring grouting materials, and ultra-fine cement grouting materials. Current demand of grouting materials in underground engineering, there exists large dosage of cement, high content, high cost, serious environmental pollution problems, such as looking for alternatives or mixed with other raw materials for preparation of cementation material become the development trend, compared with the cement grouting material, chemical grouting material with higher performance, but in smaller projects within the scope of application. How to reduce the production cost of chemical grouting materials, simplify the production process, overcome the existing toxicity, reduce environmental pollution and improve the durability of solidified body has become the bottleneck of its popularization and application. Some achievements have been made in the modification of cement or chemical materials by nanometer components, but there is still a long way to go before the large-scale application of grouting engineering.

Effect of calcium sulfate variety and content on hydration mechanism of grout sealants for coal-bed methane drainage boreholes

Cement-based ductile rapid repair material modified with self-emulsifying waterborne epoxy

Ground falls are one of the significant hazards in underground mining which lead to severe fatalities and injuries. Effective roof support is critical to prevent ground falls and ground fall accidents. Several roof support techniques have been used in mining industry, including rock bolts, cribs, posts, long wall shields, cans, and pumpable roof supports. Among them, pumpable roof supports have advantages over other roof support systems and have been increasingly used in underground mines. The major constituent of a pumpable roof support system is the cementitious material such as calcium-sulfo-aluminate (CSA) cement and Portland cement currently used in practice. However, these conventional cementitious materials cannot achieve the normally conflicting responses such as high stiffness and large residual strength required for an effective roof support system. The present study investigates the feasibility of utilizing Class F fly ash and natural biopolymer to develop a hybrid geopolymer-biopolymer cementitious material having high load stiffness, high peak strength, and large residual strength. A series of laboratory tests, including setting time, viscosity, and unconfined compression tests, have been carried out. The results indicate that the new hybrid material is a promising pumpable cementitious material which can possess the normally conflicting properties of high load stiffness, high peak strength, and large residual strength.

Utilization of red mud in high-performance grouting material for semi-flexible pavement

Plasma-functionalized graphene fiber reinforced sulphoaluminate cement-based grouting materials

Carbon nanotubes (CNTs) have high strength and stable chemical properties, offering the potential to enhance the mechanical performance of cementitious grouting materials and finding wide applications in the field. This paper reviews the recent research on the application of CNTs in cementitious grouting materials. It introduces the basic structure of CNTs and commonly used dispersion methods in cementitious grouting materials, analyzing and summarizing hydration and microstructure, mechanical properties, and early shrinkage performance of carbon nanotubes-cementitious grouting materials, highlighting current research challenges. Additionally, the future research on CNTs in cementitious grouting materials is also envisioned.

Calcium sulfoaluminate (CSA) is a comparatively new cementitious material that is mainly established in China where it is produced in a large scale. CSA cement is not covered by European standards. However, it provides different beneficial properties such as rapid hardening and high early strength development. Furthermore, the usage of CSA cement can save energy during production process in comparison to established cementitious materials. Therefore it is also more environmental friendly. Insufficient knowledge of this material behaviour restricts the possibilities and makes further research necessary. The research project applied a laboratory test program to elaborate the characterization of the materials. The obtained knowledge from these tests was then applied to further tests to determine application relevant key properties of CSA based pastes and mortars.The properties of pure CSA cement had been compared with the properties of CSA blends. The additions were PC, HAC, FA and GGBS with quantities of 10, 20 and 30%. The water to cement ratio was varying between 0.4, 0.5 and 0.6. General tests like fineness, XRD and XRF were used to define the present non-standardized material. Investigation of fresh pastes included measurement of setting time and calorimetry. Hardened mortar specimens of different ages were examined for compressive strength. The results showed that CSA itself hardens very rapidly and gives an early strength development. Possible ways of utilization of CSA based mortars and concretes were also emphasized in the paper.

Grouting materials can be used for reinforcement and water plugging of underground engineering in sandy strata. This study examines the mechanism of alkali-activated cementitious materials by selecting steel slag and ground slag to replace cement in double-liquid grouting materials. Various retarders were used to adjust the gel time, making it controllable for grouting materials. The results show that when the sodium silicate volume is in the range of 20–40%, the W/B is in the range of 0.7–1.0, and the steel-slag-to-ground-slag ratio (SS:SL) is 3:7, the macroscopic properties of the grouting material reach the optimal value, the microstructure is denser, and the hydration products are calcium hydroxide, calcium–silicate–hydrate (C-S-H) gel, and ettringite. When the cement content is 40%, the W/B is 0.8, the sodium silicate volume dosage is 30%, and the SS:SL ratio is 3:7, the 3 d compressive strength of the slurry reaches 14.57 MPa and the 28 d compressive strength reaches 21.14 MPa. To analyse the solidification effect of double-liquid grouting materials with mixed SS and SL on sandy soil, experiments were conducted to study the impacts of the soil moisture content, soil particle size distribution, and slurry quantity on the strength of consolidation. This study conducts an in-depth investigation into optimising the proportioning of industrial solid wastes and the multi-component synergistic mechanisms. This study provides a new method for the effective utilisation of industrial waste and a reference for the practical application of industrial waste as supplementary cementitious materials in the future.

On the one hand, calcium sulfoaluminate (CSA) eco-cements release about 40% less carbon dioxide (CO2) than Portland cement during fabrication; on the other hand, phase change materials dispersed in a cementitious matrix can help to optimise the indoor temperature of buildings, reducing carbon dioxide emissions related to heating/air conditioning. However, this is only economically viable if it is used as a thin layer (a coating). In addition, the combination of both materials supposes a double environmental benefit. Consequently, the main objective of this work is the preparation of a suitable homogeneous and well-adhered bilayer sample, composed of CSA and CSA-MPCM. To achieve this, in the first step, the effect of pH, temperature and stirring was studied for microencapsulated phase change material (MPCM) aqueous suspensions (47.3 wt%); second, the MPCM (45 wt% with respect to dry cement) was dispersed in a CSA paste; then, in a third step, a homogeneous well-adhered coating of CSA-MPCM, with undamaged MPCM, was obtained on a CSA matrix. This was achieved through rheological measurements and checked by microscopy. Finally, the corresponding CSA and CSA-MPCM mortars were characterised through their mechanical properties (compression) (70 and 13 MPa at 7 days, respectively) and thermal conductivity (2.06 and 1.19 W/mK, respectively).

Mechanical properties of solid waste-based composite cementitious system enhanced by CO2 modification

Grout-concrete interface bond performance: Effect of interface moisture on the tensile bond strength and grout microstructure

This study proposes a method to manufacture cementitious materials with municipal solid waste incineration fly ash (MF) and water sludge (WS) sintered at temperatures ranging from 1000°C to 1300°C. The utilized wastes contain a variety of cement components, such as Ca, Al, Cl, Si and SO3. The mixing ratio of MF to WS was determined according to the stoichiometry molar ratio of Ca/Al of calcium chloroaluminate, Ca12Al14O32Cl2. When the mixture was sintered at sintering temperature between 1000oC and 1100oC, calcium chloroaluminate (Ca12Al14Cl2O32) and melilite (Ca4Al2MgSi3O14) were formed as cementitious materials, and calcium sulfoaluminate (Ca4Al6SO14) was formed accompanying the consumption of calcium chloroaluminate starting at a sintering temperature of 1200oC. In the hydration reaction, calcium chloroaluminate, melilite and calcium sulfoaluminate synthesized through the sintering process formed Ca4Al2Cl2O6·10(H2O), Ca5Al2(OH)4Si3O12 and ettringite (Ca6Al2(SO4)3(OH)12·26H2O), respectively, as hydrates. The leaching concentrations of heavy metals (As, Cd, Cr, Cu, Pb and Zn) from the sintered products were well below Korea's regulatory levels for such elements.