Fire Behavior of Raw Earth Bricks: Influence of Water Content and Cement Stabilization

This study focus on the effects of both water content and cement stabilization on the fire behavior of earth bricks. To observe the effect of cement stabilization, two materials are formulated: raw earth with only soil and water, and stabilized bricks with soil, water and cement (3.5% by mass of soil). Since the material’s mechanical strength can strongly influence its fire behavior, the raw bricks were compacted at 50 MPa to reach a compressive strength similar to the one of stabilized bricks. Four different water contents were tested; dry state obtained with oven drying and three others achieved through equalization at 50%, 75% and 100% of relative humidities. Bricks are then subjected to an ISO 834-1 standard fire. Results show that water content has caused a thermal instability behavior on the raw earth bricks after equalization at 50% and 75% relative humidities. Thermally stable bricks displayed a noticeable diffusion of cracks on their heated face. Furthermore, cement stabilization helps to prevent from thermal instabilities.

Stabilization of Johor Peat Soil using Sugarcane Bagasse Ash (SCBA)

Peat soil have been categorized as a problematic organic soil, because they have a high settlement rate when placed any structure on it. Therefore, the peat soil must first be stabilized using cement before it can be used. However, massive use of cement can lead to environmental pollution. Therefore, this study intends to use sugar cane bagasse ash as a substitute for cement in peat soil stabilization. The mix ratio of 5% to 20% was used to find the optimal mix ratio. Various tests were carried out on samples such as basic properties tests, Unconfined Compressive Strength (UCS) and Scanning Electron Microscope (SEM). After all the tests, the 5% replacement SCBA mix ratio gave the highest unconfined compressive strength if compared to the other mixtures ratio. Therefore, it is selected as the optimum mix ratio. The soil strength achieved by the SCBA 5% replacement ratio was found to be higher than cement stabilization alone due to the presence of secondary pozzolan reactions. The microstructure result from the SEM test had shown that the 5% replacement SCBA mix ratio filled in the hollow left by the peat soil. Hence, able to improve its soil structure and thus increasing its strength.

Optimizing stabilization of laterite as walling unit

Purpose Over dependence on river/sea sand as building material has impacted the environment negatively. However, laterite, which is an environment-friendly indigenous building material in sub-Saharan Africa, has been less exploited as a suitable alternative. This paper aims to ascertain the optimum cement–laterite mix proportion at which laterite can be stabilized for production of walling units. Design/methodology/approach Using an experimental method, laterite was collected from three borrow pit sites. Sieve analysis was performed to determine the particle size distribution. Also, the degree of workability of the cement–laterite mix was ascertained using slump test. Compressive strengths were determined at cement stabilization percentages of 3%, 7% and 10% on 12 cubes of100 mm cast and cured for 14 and 28 days, respectively. Findings The results showed that the lateritic soil investigated, achieves its optimum strength in 28 days of curing, at a stabilization level of 10%. An average compressive strength of 2.41 N/mm2, which is 20.5% greater than the target strength, was achieved. Practical implications To meet the desired compressive strength of alternative walling units while achieving environmental sustainability and efficiency in production, cement stabilization of lateritic soils should become a recommended practice by built environment professionals in sub-Saharan Africa. Originality/value This paper is one of the first research works that attempts to determine the optimum level at which the abundant sub-Saharan laterite can be chemically stabilized for the production of non-load bearing walling units. This research promotes an environment-friendly alternative building material to sea sand, river sand and off-shore sand.

The use of fibers in cement stabilized base course of pavement

Nowadays, various materials are being analyzed as a possible component of pavement structure with the goal of using sustainable building materials and protecting the environment. Waste and recycled materials are added to pavement layers in order to improve it. Also, the possibility of using natural, renewable materials by incorporating them into existing standard materials is been examined. Cement-stabilized base course increases load-carrying capacity of the pavement but is prone to cracking which causes reflection cracks in an asphalt surface. Reinforcement of cement-stabilized base course can be achieved by the addition of fibers. Fibers added to the cement stabilization tend to prevent or delay the crack initiation and propagation by redistributing the resulting stresses. Considering the research conducted to-date and the need to use sustainable materials in combination with cement stabilization, some attempts are being made to achieve improvements of this pavement layer. Natural fibers are locally available, economical, renewable and degradable, and can be used as reinforcement. In the Mediterranean area, a possible source of cellulose fibers is found in the wild plant named Spanish Broom (Spartium junceum L). This paper offers an overview of research studies about fiber reinforcement of cement-stabilized base course. It also presents current research on Spanish Broom fibers in cement composites, as well as possible ways of obtaining and treating fibers. Based on the results of this research, a method for obtaining the fibers can be selected which might improve the mechanical properties of cement-stabilized course.

Engineering Properties of Sandy soil Improvement with Bacillus Simplex

Purpose: Stabilization of weak soil can be achieved through different methods, some of which include: jet column, cement stabilization and fly ash stabilization. Unfortunately, the use of the aforementioned methods of soil improvement affects the environment negatively thereby leading to environmental degradation. With the aforesaid impediment in mind, the need for devising methods of weak soil improvement becomes pertinent. Methods: Bacillus sp. - a non-pathogenic organism found abundantly in soil - was investigated in this study as a potential agent of soil improvement. The usability of Bacillus sp. in soil improvement was investigated with direct shear tests and permeability tests under optimum conditions in this study.Result: Time-dependent study on the effect of the ureolytic bacteria Bacillus simplex induced calcium carbonate precipitation shows reduction in permeability and increase in the strength of the soil under study. On exhaustion of the available nutrients in the soil however, the strength of the soil is not negatively impacted.Conclusion: Microbially induced calcium precipitation by Bacillus sp. is effective in soil improvement as such it may serve as substitute for conventional soil stabilisation techniques. The ability of the bacteria to precipitate calcium carbonate in the soil leads to reduction in the permeability and increase in the shear strength of the soil.

Applications of Cement in Pavement Engineering

Recycled materials primarily Reclaimed Asphalt Pavement (RAP), and Recycled Concrete Aggregate (RCA) are produced from pavement rehabilitation and construction-demolition activities. Generally, these materials are utilized for landfills, parking lots, shoulders, and other places that are not environmentally friendly. The top layers of the pavement and concrete structures are constructed using superior qualities of aggregates that satisfy the specification. During their service life, the aggregates present in these structures undergo deterioration due to environmental and traffic factors. After reaching the end of their service life, the deteriorated structures are dismantled and considered as waste. Nevertheless, these recycled materials will have some retain value which can be used in different layers of the pavements in different percentages. The reuse of these materials in place of conventional aggregates preserves the environment and become a sustainable construction practice. Further, the direct utilization of these materials in the pavements may not satisfy the mechanical characteristics. To fulfill these gaps, cement stabilization of recycled materials is the best option. With this background, the proposed book chapter will highlight the usage of cement in pavement application, and a few types of research works carried in cement treated pavement layers will be discussed in a detailed and scientific manner.

Characteristics of almond leaf-ash cement stabilized lateritic soil

The use of Almond leaf-ash for stabilization purposes has not been given consideration. This paper was thus aimed at evaluating the characteristics of almond leaf-ash for the essence of stabilizing lateritic soil. Sourced lateritic soil was divided into 3 components (unmodified soil sample, cement stabilized soil sample and almond leaf-ash cement stabilized soil sample). Almond leaves were calcined at 250°C and subjected to granulation process. Preliminary tests such as; sieve analysis, Atterberg’s limit and specific gravity tests were done on the unmodified soil sample for the purpose of classification. CBR tests were performed on the cement stabilized soil sample and on the almond leaf-ash cement stabilized lateritic soil sample. A model was developed using the Scheffe’s simplex theory with the cement component fixed at 10% of the dry lateritic soil. Results revealed that the soil was observed to be a Silty Clay soil (A-4) with Plasticity index of 9.24%, therefore requiring stabilization. CBR results for the developed trial mixes were greater than the 15.20% obtained for 10% cement stabilization showing that Almond leaf-ash significantly improved the CBR of the cement stabilized lateritic soil. The CBR model developed for the Almond leaf-ash cement soil also proved adequate from the verification test conducted using χ2 statistics. Keywords: Almond Leaf Ash, stabilization, California Bearing Ratio, Scheffe’s theory, lateritic soil.