Cement-based Foam Research Articles

Influence of Foam Content and Concentration on the Physical and Mechanical Properties of Foam Concrete

Foam concrete has been used in various real-life applications for decades. Simple manufacturing methods, lightweight, high flowability, easy transportability, and low cost make it a useful construction material. This study aims to develop foam concrete mixtures for various civil and geotechnical engineering applications, such as in-fill, wall backfill and soil replacement work. A blended binder mix containing cement, fly ash and silica fume was produced for this study. Its compressive strength performance was compared against conventional general purpose (GP) cement-based foam concrete. Polypropylene (PP) fibre was used for both mixtures and the effect of various percentages of foam content on the compressive strength was thoroughly investigated. Additionally, two types of foaming agents were used to examine their impact on density, strength and setting time. One foaming agent was conventional, whereas the second foaming agent type can be used to manufacture permeable foam concrete. Results indicate that an increase in foam content significantly decreases the strength; however, this reduction is higher in GP mixes than in blended mixes. Nevertheless, the GP mixes attained two times higher compressive strength than the blended mix’s compressive strengths at any foam content. It was also found that the foaming agent associated with creating permeable foam concrete lost its strength (reduced by more than half), even though the density is comparable. The compressive stress–deformation behaviour showed that densification occurs in foam concrete due to its low density, and fibres contributed significantly to crack bridging. These two effects resulted in a long plateau in the compressive stress–strain behaviour of the fibre-reinforced foam concrete.

Preparation and fire extinguishing characteristics of inorganic solidified foam with large amount of slag

ABSTRACT Aiming at the problems of conventional cement-based foam plugging and filling materials, such as large amount of cement, low utilization rate of solid waste, unclear bonding, and plugging mechanism, it was proposed that a kind of plugging and preventing fire material named inorganic solidified foam was prepared from industrial slag, cement, and water-based foam as the main raw materials. Based on the fluidity, expansion ratio and mechanical strength of solidified foam, it was determined that S105 slag powder with high content of 60%~65% and the optimal content of the chemical activator 6%. The dry density of solidified foam was about 410~450 kg/m3, and the compressive strength reached 0.5~0.55 MPa. The formation process, the bonding-reinforcement mechanism, and the fire prevention characteristic fire of solidified foam were explored. The results showed that solidified foam could significantly improve the pozzolanic activity of solid waste under the effect of physical and chemical synergy, promoted the hydration reaction of the material, increased the structural compactness of the hydration product of the material, further improving the strength. Fire-fighting experiments and field application exhibited that solidified foam could rapidly diffuse and accumulate to high places through crack channels, quickly extinguish and cool down, and coat loose high-temperature coal piles, showing excellent effect of preventing coal spontaneous combustion. Moreover, the field test results showed that the solidified foam could quickly plug the air leakage, and reduce the CO concentration in the air leakage are. Specifically, the CO concentration of high falling area decreased from 315 ppm to 22 ppm in 3 days, eventually stabilizing below 10 ppm, thereby timely inhibiting the development of spontaneous combustion fire.

Explainable ensemble learning predictive model for thermal conductivity of cement-based foam

Cement-based foam has emerged as a strong contender in sustainable construction owing to its superior thermal and sound insulation properties, fire resistance, and cost-effectiveness. To effectively use cement-based foam as a thermal insulation material, it is important to accurately predict its thermal conductivity. The current study aims at coining an accurate methodology for predicting the thermal conductivity of cement-based foam using state-of-the-art machine learning techniques. A comprehensive experimental dataset of 504 data points was developed and used for training ensemble learning models including XGBoost, CatBoost, LightGBM and Random Forest. The independent variables of this dataset affecting the thermal conductivity are the cast density, percentage of pozzolan, porosity, percentage of moisture, and duration of hydration in days. Using the Isolation Forest algorithm proved effective in detecting and eliminating outliers in the dataset. All the ensemble learning techniques explored in this study achieved superior predictive accuracy with a coefficient of determination greater than 0.98 on the test dataset. The influence of the input features on the thermal conductivity was visualized using the SHapley Additive exPlanations (SHAP) approach and individual conditional expectation (ICE) plots. The cast density had the greatest effect on thermal conductivity. The explainable machine learning models demonstrated superior accuracy, efficiency, and reliability in estimating the thermal insulation of cement-based foam, opening the door for wider acceptance of this material in sustainable energy efficient construction.

Influence of initial casting temperature on the properties and microstructure of ultra-light cement-based foam composites for energy-saving buildings

Influence of initial casting temperature on the properties and microstructure of ultra-light cement-based foam composites for energy-saving buildings

Properties and microstructures of 3D printable sulphoaluminate cement concrete containing industrial by-products and nano clay

Owing to its sound/thermal insulation and the elimination of the conventional moulds, 3D printable foam concrete (FC) has gained increasingly attention among researchers. In this study, the producibility of calcium sulphoaluminate cement-based foam concrete (CSA-FC) through concrete extrusion was confirmed, which also contains nano-clay (NC) and industrial by-products. The fresh and hardened properties, microstructures as well as extrudability of prepared samples were investigated. The initial results highlight the benefits of using appropriate amount of NC and desulfurized gypsum (FGD gypsum) for the hydration acceleration and extrudability improvement of samples. Meanwhile, the use of NC could alleviate the performance degradation owing to the use of industrial wastes in samples due to its nucleation and pozzolanic effects. Further, through the extrusion technology, a suitable mix design of CSA-FC with satisfactory performance, low carbon footprint and cost was proposed, which eliminates the conventional moulds during its production.

Effects of mineral admixture on properties of cement-based foam material developed for preventing coal spontaneous combustion

This study investigated the cement-based foam material (CBFM) used in mine fire-extinguishing materials by using a self-made compound foaming agent, water, cement, mineral admixture included fly ash (FA), blast furnace slag (BFS) and silica fume (SF), etc. The effects of mineral admixture type, dosage, foam content and water-binder ratio on the properties of CBFM were analyzed using the orthogonal tests, further determining the optimal ratio of CBFM. Moreover, the influence of mineral admixture type on the performance of the CBFM was analyzed by comparing the scanning electronic microscope and X-ray diffraction test. As a result, when the BFS content was 20%, the foam content was 2 times that of the cementitious slurry, and the water-binder ratio is 0.5, the overall performance of CBFM could be optimized. The surface morphology and mineral component investigation exhibited that CBFM with BFS as a mineral admixture had the more uniform closed-cell structure than FA and SF. Moreover, the novel material had the inhibitory effect on the transformation of calcium aluminate hydrate and hydrated calcium sulfoaluminate, which in turn could maintain the strength of the composite. The experimental results showed that the fire extinguishing and cooling effect of CBFM was better than that of traditional fly ash foam, and it could quickly cool down the temperature burning coal pile within 30 min. In addition, the solidification products of CBFM would form a wrapping layer on the surface of the loose coal pile, inhibiting the contact between coal and air, further preventing coal spontaneous combustion effectively.

Synergic effect of compositions and processing method on the performance of high strength alkali activated slag foam

Using inorganic porous materials for the insulation of a building improves energy efficiency. Alkali activated slag (AAS) foam concrete with a lower carbon footprint presents to be an alternative to cement-based foam concrete. In this study, the influence of various preparation parameters of AAS foam concrete on setting time, workability, compressive strength, bulk density, drying shrinkage and pore structure were investigated. A modified model was proposed to fit the relationship between compressive strength and geometrical information. Existing six structural models were used for the analytical description of the relationship between thermal conductivity and total porosity. Results show that increasing the mixing time can effectively extend the setting time and improve the workability of AAS foam slurry. The optimized mix proportion of AAS foam concrete exhibited a compressive strength of 24.1 MPa, thermal conductivity of 0.2322 W/(m·K) and adjustable setting time and workability for on-site casting. According to the comparison of the fitting results with other models, the proposed modified model for the relationship between compressive strength and geometrical information provided a better correlation with the experimental data. Analysis of the six structural models for the thermal conductivity showed that AAS foam concrete in this study favored the gaseous phase for heat transfer similar to the characteristic of dry sand.

A Detailed Review on Foam Concrete Composites: Ingredients, Properties, and Microstructure

With the development of new cement-based raw materials, foaming agents and fillers used for special applications of foam concrete, the use of foam concretes has become widespread. Foam concrete is a type of concrete that stands out with its lightness, waste potential, controlled low strength, thermal insulation, acoustics performance, and durability. The knowledge base is still developing for this particular building material. This article describes in detail the fresh, hardened, and physical properties of foam concrete. The properties of materials such as cement, aggregate, foam, and fiber used in foam concrete production are explained and their effects on microstructure are discussed. In addition, physical properties, such as fresh state properties, fresh state and consistency, stability, workability, drying shrinkage, air void system, and water absorption, as well as strength and durability properties are emphasized. The main findings of the presented study are to show the current level of the cement-based foam concretes and their shortcomings, which needs more investigations. The effect of fibers on the characteristics of foam concrete and acoustic characteristic of foam concretes are seen as the main topics to be focused on in the studies.

Effect of Fly Ash on Bonding and Shrinking Behaviors of High-Belite Sulphoaluminate Cement–Based Foam Concrete

A sandwiched foam concrete (FC) layer with good bond and thermal properties is crucial to the overall performance of a prefabricated insulation panel. In this study, the effects of grade and the dosage of fly ash (FA) on the dry density, specific strength, thermal conductivity, bonding strength, shrinkage, and moisture loss rate of high-belite sulphoaluminate cement (HBSC)–based foam concrete (HBFC) were investigated. The shrinkage differences between HBFC and portland cement-based foam concrete (PCFC) were also compared. The results show that the bonding strengths of HBFC doped with Grade-I and Grade-II FA are higher than that doped with Grade-III FA. When the Grade-III FA dosage is less than 5%, or the Grade-I and Grade-II FA dosage are less than 15%, the bonding strengths of HBFC meet the requirements of the prefabricated insulation wall panel. The shrinkages and moisture loss rates of HBFC in all groups increase fast within 24 h of curing. The 672 h shrinkages of the HBFC doped with all grades of FA increase with the FA dosage, which are still much lower than those of PCFC. The shrinkages of HBFC doped with Grade-I and Grade-II FA are lower than that with Grade-III FA, and the rule is the same as the moisture loss rates of the HBFC. HBSC doped with a 15% dosage of Grade-II FA is the most suitable binder for a preparing cost-effective HBFC panel with the dry density, specific strength, thermal conductivity, bonding strength, and 672 h shrinkage of being 302.9 kg/m3, 1,276.6 N·m/kg, 0.0791 W/m·k,0.128 MPa, and 2.930 mm/m, respectively, and the corresponding cost for preparing 1 m3 of HBFC is about $41.30.

Characterization of 3D microstructure, thermal conductivity, and heat flow of cement-based foam using imaging technique

Characterization of 3D microstructure, thermal conductivity, and heat flow of cement-based foam using imaging technique

Experimental investigation on cement-based foam developed to prevent spontaneous combustion of coal by plugging air leakage

Cement-based foam material (CBFM) was prepared by mixing the cementitious system and foam system for preventing coal spontaneous combustion. Different types of surfactants and organic polymer (OP) material were selected to prepare a foam system with high stability and water-retention characteristics. The orthogonal experiment was designed to analyze the fluidity, expansion ratio and mechanical strength of CBFM under different ratios including fly ash content, foam system content and water-binder ratio. The result showed that the high stability foam system could be obtained by mixing the anionic surfactant and the zwitterionic surfactant in the mass ratio of 6:4 with 4‰ OP. Based on the orthogonal experiment, the optimized ratio of CBFM was obtained including 25% for the fly ash, 2 times the volume of the gelling slurry for the foam, and 0.5 for the water-binder ratio. Microscopic test indicated that CBFM was composed of a porous uniform structure with closed cells, which would affect the airtightness and anti-impact force of material, implying that CBFM shows the potential to be utilized as airtight plugging material for preventing coal spontaneous combustion.

Hydrated Products Influencing the Thermal Conductivity of Cement-Based Foam with Pozzolan

Hydrated Products Influencing the Thermal Conductivity of Cement-Based Foam with Pozzolan

Factors Influencing the Pore Structure Parameters of Lightweight Cement-Based Foams

Abstract This study quantifies the pore wall spacing and shape factor of lightweight cement-based foam pore structure and investigates its correlation with density, pozzolan, compressive strength, and thermal conductivity. The lightweight cement-based foam mixtures were prepared for the densities of 800–400 kg/m3 and by replacing cement with fly ash, silica fume, and metakaolin up to 20 % by mass. The nondestructive technique of X-ray microtomography was used for quantifying the pore structure parameters. In addition, the transient plane heat source technique was used to evaluate the thermal conductivity of these mixtures. The results show that the optimal pore wall spacing increases from 0.28 to 0.55 mm as the density rises from 400 to 800 kg/m3. It was observed that the median pore wall spacing (SP50) values increases as the cast density get higher. While the reduction in thermal conductivity was noticed for lower SP50 values. Furthermore, incorporating pozzolanic admixtures at higher cement replacement ratios affects the pore wall spacing. Moreover, spherically shaped pores were found in all mixtures.

Preparation and characterization of a fly ash and cement-based foam composite

Industrial waste fly ash and ordinary Portland cement (PO42.5) were used as the main raw materials, Ca(OH)2 as the alkali activator, modified rosin soap as the foaming agent, and glass fiber as the reinforcing agent. A physical foaming technology was chosen to fabricate a fly ash and cement-based foam composite. The effects of water-to-binder (W/B) ratio and glass fiber addition on the performance of the foam composite were studied. The structure formation and reinforcement mechanism of the foam composite were discussed, and the optimal formulation was determined, which provides a new technical approach to utilize fly ash and improve the strength and reliability of foam cement products. The results show that different water-to-binder ratios directly affect the stability of the pores during the foaming process, and the glass fiber has a protective effect on the foam. When the W/B ratio is 0.5, meanwhile the addition of glass fiber is 1.5%, the fly ash and cement-based foam composite can achieve better physical performance: the dry density is 368 kg/m3, the water absorption rate is 39.12%, and the 28-day compressive strength is increased by 86.31% (reaching 3.47 MPa) compared to that of the sample without a glass fiber.

Microstructural parameters of fiber reinforced cement-based foam and their influence on compressive and thermal properties

This study presents the results of microstructural parameters of fiber reinforced cement-based foam and examines their influence on thermal conductivity and compressive strength, for a range of density and pozzolanic admixtures. X-ray tomography, which is a non-destructive technique, was employed for measuring the pore size distribution, pore spacing, and shape factor. The thermal conductivity was evaluated by using the Transient Plane Source. Three series of cement-based foam mixtures were prepared by adding polypropylene (PP) micro-fibers at a volume fraction of 0.2% and cast to 800, 600 and 400 kg/m3. In two separate series of mixtures, 20% of cement was replaced by fly ash and silica fume, respectively. The results showed that a mean pore diameter of 30 μm was the optimal pore size across all mixtures, including pozzolans blended binders. The optimum pore spacing recorded was 1110 μm for 800 kg/m3, and 270 μm for 600 kg/m3 and 400 kg/m3 , respectively. It was found that the inclusion of fibers increases the number of pores, as does the presence of silica fume. Most of the pores were found to be spherical. Furthermore, the median pore diameter (D50) and spacing (SP50) values were found relating linearly to compressive strength and thermal conductivity.

Application of cement-based foams for narrow-trench backfilling

In modern urban traffic scene, it has become a necessity to cut the trenches for carrying service lines, especially cables for various uses, as narrow as possible in order to keep the disturbance to the traffic to the minimum. The rising cost of construction also demands that the time for, and cost of, such service line laying be kept to the minimum. These demands are well met by resorting to narrow trench cutting alongside the roads in use. However, the backfilling of such very narrow trenches requires that the backfilling material must satisfy certain engineering properties as opposed to the traditional earthfills. Cement-based foams are considered to be a good backfill material. This study characterises their mechanical performance, thermal shrinkage, and bonding with the bituminous substrate. Nine different mixtures ranging in density from 600 to were considered here. The hardened cement-based foam mixtures were tested first to ascertain their strength, modulus of elasticity and Poisson's ratio. This was followed by evaluating their drying shrinkage and coefficient of thermal expansion. Lastly, these mixtures were assessed for their bond performance with the asphalt concrete. The test outcomes were used to rank the mixtures on the basis of an analytic hierarchy process. The results show that the lightest mixtures yield the best performance and substantial benefit accrues from blending in fly ash into the binder. Aside from showing immense promise as a backfill material for narrow trenches, the results now constitute a valuable database to be used by future researchers for simulating and designing the back fills of narrow trenches as a composite structure.

Evaluation of thermal conductivity of cement-based foam reinforced with polypropylene fibers

This study quantifies the results of the thermal conductivity for cement-based foam reinforced with polypropylene fibers and correlates the influence with pozzolans, porosity, moisture content, and pore parameters. Here, the mixtures were prepared for the densities range of 400–800 kg/m3 in which cement was replaced in the ratios of 10% and 20% (by weight) with fly ash, silica fume, and metakaolin. Along with pozzolan, polypropylene micro-fibers were added at the volume fraction of 0.2%. The thermal conductivity was measured variously at the hydration age of 60–210 days by using the transient plane source technique. While the porosity and the pore parameters were evaluated by using X-ray microtomography, a non-destructive technique. The results revealed that polypropylene fibers contributed to reducing the conductivity and among the three pozzolans, fly ash was the most efficient. However, the porosity increases with the inclusion of fibers but drops significantly with the addition of pozzolans, especially for lower densities mixtures. Also, it was found that D50 relates linearly with conductivity. However, based on experiment results, a modified thermal conductivity predictive model for cement-based foam reinforced with fiber was developed.

Fresh Properties of Fiber Reinforced Cement-Based Foam with Pozzolans

This paper investigates the fresh properties of cement-based foam reinforced with fibers and examines the influence on density, pozzolan, spreadability, and flowability. Here, marsh and flow cone testing were employed for measuring the flowability and spreadability. This testing was conducted on seven series of cement-based foam mixtures prepared by adding polypropylene (PP) microfibers at the volume fraction of 0.2% in 800, 600, and 400 kg/m3 cast densities. In six series, the 10% and 20% of cement were replaced by fly ash, silica fume, and metakaolin, respectively. The results showed that the slurry flow time increases in the presence of polypropylene fibers and pozzolans, with metakaolin blended mixtures, recorded the longest time. Similarly, an increase in the foam volume was noticed in all mixtures except for the metakaolin series with higher substitution. Also, it was observed that the spread diameter reduces in fiber reinforced cement-based foam mixtures, but for fly ash series increase was noticed. Based on these results, models were developed for predicting the foam volume and spreadability for mixtures with pozzolan and polypropylene fibers.

Preparation and Physical Properties of High-Belite Sulphoaluminate Cement-Based Foam Concrete Using an Orthogonal Test.

Prefabricated building development increasingly requires foam concrete (FC) insulation panels with low dry density (ρd), low thermal conductivity coefficient (kc), and a certain compressive strength (fcu). Here, the foam properties of a composite foaming agent with different dilution ratios were studied first, high-belite sulphoaluminate cement (HBSC)-based FCs (HBFCs) with 16 groups of orthogonal mix proportions were subsequently fabricated by a pre-foaming method, and physical properties (ρd, fcu, and kc) of the cured HBFC were characterized in tandem with microstructures. The optimum mix ratios for ρd, fcu, and kc properties were obtained by the range analysis and variance analysis, and the final optimization verification and economic cost of HBFC was also carried out. Orthogonal results show that foam produced by the foaming agent at a dilution ratio of 1:30 can meet the requirements of foam properties for HBFC, with the 1 h bleeding volume, 1 h settling distance, foamability, and foam density being 65.1 ± 3.5 mL, 8.0 ± 0.4 mm, 27.9 ± 0.9 times, and 45.0 ± 1.4 kg/m3, respectively. The increase of fly ash (FA) and foam dosage can effectively reduce the kc of the cured HBFC, but also leads to the decrease of fcu due to the increase in mean pore size and the connected pore amount, and the decline of pore uniformity and pore wall strength. When the dosage of FA, water, foam, and the naphthalene-based superplasticizer of the binder is 20 wt%, 0.50, 16.5 wt%, and 0.6 wt%, the cured HBFC with ρd of 293.5 ± 4.9 kg/m3, fcu of 0.58 ± 0.02 MPa and kc of 0.09234 ± 0.00142 W/m·k is achieved. In addition, the cost of HBFC is only 39.5 $/m3, which is 5.2 $ lower than that of ordinary Portland cement (OPC)-based FC. If the surface of the optimized HBFC is further treated with water repellent, it will completely meet the requirements for a prefabricated ultra-light insulation panel.

Study on mix proportion design of cement foam concrete

In this paper, the influence of four main factors on the compressive strength of cement-based foam concrete is studied by orthogonal test with L_9 (3 ^ 4) orthogonal table. They are the amount of foam agent, the amount of water reducing agent, the amount of foam stabilizer and the water cement ratio. The results show that the main factors affecting the 7-day compressive strength of cement-based foam concrete are: water cement ratio > foam agent content > water reducer content > foam stabilizer content. The best test mix is: water cement ratio 0.41, foam agent 0.66%, water reducer 0.20%, foam stabilizer 0.021%. Its 7-day compressive strength is 2.65 MPa, dry density is 444 kg/m^3, water absorption rate is 23%, in line with JG/T 266-2011 “foam concrete” and JGJ/T 341-2014 “foam concrete application technical specification” stipulated in the performance requirements.