Gotowa bibliografia na temat „Cement Stabilised Soil Compacts”

Road layers should be properly compacted to obtain an adequate bearing capacity and durability. Both the unbound and hydraulically bound mixtures used in the layers require compaction. After compaction and hardening, soil mixed with a binder acquires mechanical features that unbound soil lacks, including tensile strength (Rit) and unconfined compressive strength (Rc). The effect of the compaction ratio (DPr) of the low-strength cement-stabilised soils on these features has rarely been investigated. This study investigates the influence of the compaction ratio on the mechanical properties of hardened, stabilised mixtures of medium-grained sand with 5%, 6.5%, and 8% Portland cement. Cement–soil stabilisation tests showed that compressive strength depends exponentially on the compaction ratio, whereas tensile strength and the stiffness modulus depend linearly on the compaction ratio. For tensile strength and the dynamic stiffness modulus, the effect is not statistically significant, and the usual practice of ignoring compaction dependence is justified. For compressive strength, however, the effect is significant, especially when DPr = 98–100%. When the values of Rc and Rit strengths at various DPr were normalised by those at 100%, it was found that mixtures with higher strengths are the least resistant to changes in the compaction ratio. Knowing the percentage by which the value of a given parameter changes with compaction can be extremely valuable in engineering practice.

Earthen materials are the world’s oldest and cheapest construction materials. Compacted soil stabilised blocks are unfired admixed soil blocks made up of soil plus stabilisers such as binders, fibres, or a combination of both. The manufacturing and usage of cement and cement blocks raises a number of environmental and economic challenges. As a result, researchers are attempting to develop an alternative to cement blocks, and various tests on unfired admixed soil blocks have been performed. This investigation undertakes use of agricultural waste (i.e., paddy straw fiber and sugarcane bagasse ash) and industrial waste (i.e., marble dust) in manufacturing unfired admixed soil blocks. The applicability of unfired soil blocks admixed with marble dust, paddy straw fiber, and bagasse ash were studied. The marble dust level ranged from 25% to 35%, the bagasse ash content ranged from 7.5% to 12.5%, and the content of paddy straw fibre ranged from 0.8% to 1.2% by soil dry weight. Various tests were conducted on 81 mix designs of the prepared unfired admixed soil blocks to determine the mechanical properties of the blocks, followed by modeling and optimization. The characterization of the materials using XRD and XRF and of the specimens using SEM and EDS were performed for the mineral constituents and microstructural analysis. The findings demonstrate that the suggested method is a superior alternative to burned bricks for improving the mechanical properties of unfired admixed soil blocks.

Evaluating the structure of soil prior to building construction is valuable in a large variety of geotechnical and civil engineering applications. To built an effective framework for assessing the strength of the stabilised soil, the presented workflow includes a complex approach of simplex lattice design and X-ray diffraction for the analysis of soil structure. Different from the traditional in situ measurements, we propose a statistical framework for effective decision-making on binder combination to stabilise soil collected in three localities of Southern Sweden—Bromölla Municipality (Skåne County), Petersborg (Östergötland County) and Örebro (Örebro County). A practical solution is presented that includes the evaluation of strength properties of various types of soil using ordinary Portland cement (OPC), slaked lime and steel slag as pure agents and blended binders. The specimens were collected in Southern Sweden and included sandy silty tills and clay till (clay content 6–18%). The preprocessing included the mineralogical analysis of mineral composition and soil structure by X-ray diffraction (XRD) and a sieve. The soil samples were fabricated, compacted, rammed, stabilised by six binder blends and assessed for uniaxial compressive strength (UCS). The moisture condition value (MCV) and water content tests were done for compacted soil and showed variation in the MCV values for different binders. The study determined the effects from binder blends on the UCS gain in three types of soil, measured on days 7, 28 and 90. Positive effects were noted from the steel slag/lime blends on the UCS gain in sandy silty tills. A steel slag/slaked lime mixed binder performed better compared to the pure binders. The effectiveness of the simplex lattice design was demonstrated in a series of ternary diagrams showing soil strength evaluated by adding the stabilising agents in different proportions.

Abstract The classic test for soil or aggregate bearing capacity in road construction is the CBR test. The results of the CBR were determined for gravelly sand and sand with the addition of 1.5% cement, as well as for their mixtures with 18 mm long polypropylene fibres in the amounts of 0.1%, 0.2% and 0.3%. The effect of compaction and time of curing of samples stabilised with hydraulic binder were also determined. The natural soil without cement and fibre additions had relatively high CBR values. The additions of 0.1% and 0.2% polypropylene fibres to the dry mass of the soil resulted in an approximately 2-fold increase in the CBR value for the samples compacted using the standard method. Increasing the amount of fibres to 0.3% caused a reduction in the CBR value to that obtained without fibre addition. For samples compacted using the modified Proctor method, the observations are different. Only the sample with 0.2% fibre addition achieved a slightly higher CBR value. Moreover, the addition of 1.5% cement and the length of treatment increased the CBR values.

This paper presents a study on the stabilisation performance of Sarawak soils using GeoCrete® Technology. GeoCrete is used for stabilisation treatments where the soils are treated with ordinary Portland cement (OPC) as a binder and GeoCrete® powder (GCP) as an alkaline additive to improve their strength and elasticity. The use of GCP in soil stabilisation was proven to improve the compressive strength of soils by more than twice the initial strength after 28 days of being treated, with the treatments carried out on three identified soils: Clay, silt and sand. This technique has been successfully implemented on farm roads, rural roads and highways. Thus, further investigation of stabilisation with GCP was conducted on peat, which is known as a material with high permeability and low bearing capacity behaviour. The peat samples collected are mixed at a designated percentage of OPC and 2% of GCP. The compacted and treated peat samples with OPC and GCP were prepared at the optimum moisture content, mixed thoroughly to a uniform condition using a laboratory mixer and air cured for 7 and 28 days in a single batch. The results showed that peat stabilised with GCP has an average of more than 40% of the unconfined compressive strength, qu value after 28 days of curing when compared with peat at the natural state.

The porosity-to-cement index (η/Civ) has been extensively applied to study the evolution of different types of soil stabilization. However, this index has still not been used to characterize soils cemented with crushed limestone waste (CLW). In this sense, this paper sought to analyze the applicability of the porosity-to-cement index over the unconfined compressive strength (qu) and initial stiffness at small deformations (Go) of clayey soil improved with CLW and Portland cement. In addition, a microstructural analysis (SEM and EDX tests) was also conducted. CLW addition increased soil strength and stiffness over time. Moreover, qu and Go compacted mixtures containing CLW have established a distinctive correlation. Chemical microanalyses have uncovered a complex interfacial interaction between the soil, cement, and fine CLW particles, leading to a notable reduction in porosity.

Soils from the superficial layers of the Guabirotuba formation (in Brazil) are problematic due to their expansive and low-bearing capacity. Stabilizing these soils with a calcium-based binder is a technique that must be explored. Therefore, this study aims to determine the mechanical behavior of stabilized sedimentary silts with cement and binder in various conditions. Four types of fine soils were used in deformed conditions. These soils were mixed with cement and compacted to measure their mechanical behavior. The specimens were tested in unconfined compressive and split tensile tests prepared with respect to several molding conditions: the moisture content, the curing period, durability cycles, the dry unit weight, the cement content, the cement type, and the soil type. This study was also carried out to develop a simplified approach to estimating the unconfined compressive strength (qu or UCS) and split tensile strength (qt or STS) of soil-cement or soil-cement–binder mixes. The results further demonstrate the influence of the porosity/volumetric cement index (η/Civ) on the qu- and qt-adjusted two new parameters—bo = 0.174 (dependent on cement) and k = 2.565 (dependent on the type of soil)—proposed herein for all mixtures studied. Using the proposed new parameters, a unique equation was developed to estimate the strength of the compacted blends as a function of the porosity and binder content, with an acceptance of 93% and an error close to 6%.

Applying Portland cement to soils is an excellent technique when it is necessary to improve local soil for the construction of stabilized pavement bases and to have a support layer for shallow foundations. Consoli et al. (2007, 2009, 2010) developed a rational dosage methodology for artificially cemented soils based on porosity/cement index, which can be applied to unconfined compressive strength, as well as to splitting tensile strength. Furthermore, a unique qt /qu relationship was found, independent of the cement content and voids ratio. Following the assessment of the main factors that influence the strength of artificially cemented soils, the present research aims to quantify the influence of the moisture content in the tensile and compressive strength of an artificially cemented sand. A program of splitting tensile tests and unconfined compression tests was carried out. There were tested three voids ratio (0.65, 0.73 and 0.81), four cement contents (3%, 5%, 7% and 9%) and five moisture contents (6%, 8%, 10%, 12% and 14%). The results show that the reduction in moisture content of the compacted mixture increases both the tensile and compressive strengths. Furthermore, it has been shown that qt /qu relationship was kept constant, being independent of the porosity/cement ratio and the moisture content.

This document contains the detailed results and conclusions of work carried out during a PhD to investigate the processing, production and performance of dynamically compacted cement-stabilised soil blocks suitable for sustainable low-cost building. An earlier project carried out by the author demonstrated that full-size blocks could be manufactured by dynamic compaction. It was hoped that this technique could be applied to the self-evident need for low-cost housing in the humid tropics. The apparent advantages of this process, over quasi-static compression (slow steady squeezing), have led to further investigation into the critical factors influencing the production of such building units. Initial tests on small cylindrical samples produced by both quasi-static compression and dynamic compaction provided a means of comparison and helped to develop relationships between dominant variables. These tests showed that the moisture content of the compact was a critical variable, influencing its consolidation and its final cured strength. Optimisation studies were undertaken to determine acceptable parameters for impactor mass, drop height and number of applied blows. These chosen parameters were then extrapolated to full-size block production with the necessary adjustments for practicality and cost. Full-size block production using the Test Rig indicated similar relationships as those discovered at the smaller scale, including the more effective consolidation offered by dynamic compaction. From this experience a production prototype was designed and disseminated to a collaborator in India for further trials and feasibility studies. These trials demonstrated that dynamic compaction could produce blocks with a 7-day wet compressive strength of between 3-5MPa with only 5% cement, (typical building regulations require block strength greater than 3.5MPa after 28-days). Feasibility studies there indicate dynamic compaction offers potential savings of 40% compared with local high-tech CSSB manufacture.

Soft soils are deposited globally, especially in estuarine or coastal areas. In recent years, the land resource has lessened due to rapid urbanisation and population growth around the globe. It is crucial to develop land on poor ground conditions to solve the issue of land shortage due to urbanisation. South East Queensland is a particular region where soft soils are widely deposited. More construction is expected to be carried out on its soft soil deposits as the urbanisation continues. However, the existence of soft soils can cause construction complications because of the following reasons: having high compressibility and water content, accompanied by low shear strength and permeability. Therefore, the study of the mechanical behaviour of reconstituted and stabilised soft soils is significant in geotechnical engineering practice. There are limitations in previous research regarding the properties of soft soils. For example, the common particles in soft soils are clay, silt, and sand particles. The behaviour of clay and sand particles are unique and easy to identify. However, the behaviour of silt particles lies in between the behaviours of clay and sand. It is important that some previous studies found that the behaviour of silt is not in accordance with the critical-state framework adopted for clay and sand. It is suggested that the behaviour of silts is a transitional form between clay and sand. Some silts exhibit sand-like behaviour, while some exhibit clay-like behaviour. Consequently, it is important to understand silt’s physical, mineralogical, strength and microstructural behaviour, as it is presently recognised that gaps in understanding its fundamental behaviour exist. In addition, soft soils need to be stabilised by suitable ground improvement techniques before any structure can be safely constructed on it. It is widely known that in-situ soil mixing or stabilisation (e.g., mass mixing or deep soil mixing) has been proven to be an effective ground improvement technique in improving the engineering properties of soft soils. Cement is one of the commonly used cementitious materials which can be used to treat soft soil in the application of in-situ soil mixing. It can increase the soil mix strength and decrease the water content by triggering the hydration of cement and pozzolanic reactions. The use of cement to stabilise soft soils and the behaviour of cement-stabilised soils has been extensively investigated in many previous studies. However, the use of cement can cause environmental issues as the production of cement results in high emissions of carbon dioxide (CO2). Hence, it is essential also to consider other suitable types of stabilisation additives to reduce the amount of cement used in the stabilisation of soft soil. Fly ash and a commercially available additive DuraCrete, were investigated in this study as partial replacements of cement. The behaviour of specimens stabilised by cement, fly ash-blended cement, and DuraCreteblended cement under both unconfined compressive (UC) and consolidated isotropic undrained (CIU) conditions were investigated in this study. The experimental results proved that fly ash and DuraCrete can be used as partial replacements of cement to achieve more remarkable improvement results than just cement alone in stabilising soft soils. DuraCrete is more effective compared to fly ash because the addition of DuraCrete can reduce the amount of cement needed for the stabilisation while also improving the strength of stabilised specimens. This project seeks to investigate a) the mechanical behaviour of South East Queensland soft soil stabilised by cement with different cement content; b) the effect of the presence of silt particles on the mechanical behaviour of soft soils, such as evaluating the behaviour of silty soils within the critical-state framework; c) the effect of the presence of silt particles on the mechanical and microstructural of soft soils after stabilised by cement; and d) the use of fly ash and DuraCrete as partial replacements of cement in soft soil stabilisation. A series of laboratory tests consisting of consolidated isotropic undrained (CIU) triaxial tests, unconfined compressive strength (UCS) tests, and scanning electron microscope (SEM) tests were conducted in this study to achieve these objectives. South East Queensland soft soil was collected and stabilised by cement with varying initial soil water content and cement content. The mechanical and microstructural behaviour of natural and cement-stabilised South East Queensland soft soil was investigated. Some empirical equations were derived to estimate the strength of South East Queensland soft soil specimens with different cement content. The microstructure of cement-stabilised soil specimens was also analysed and interpreted. A series of triaxial compressive tests were conducted in this study on five types of soft soils with varying clay and silt contents, and therefore the effect of silt contents on the strength and critical state behaviours of soft soils were investigated. The empirical equations were proposed to evaluate the effect of silt content on the stress paths of reconstituted soft soils under consolidated isotropic undrained triaxial tests and the critical state parameters. Based on the observations from the CIU triaxial compression tests, it can be concluded that 1. For silty soils which have a plasticity index above 29%, even the soils are classified as silt by Atterberg limit testing results, but the soils show clay-like behaviour in the critical state framework, evidenced by the corresponding normally consolidated line (NCL) and critical state line (CSL) are parallel. 2. For silty soils, which have a plasticity index between 19% and 29%, the soils show a transitional behaviour between the clay-like and sand-like behaviour, as the corresponding normally consolidated line (NCL) and critical state line (CSL) are becoming non-parallel. 3. For silty soils, which have a plasticity index lower than 19%, it shows typical sand-like behaviour. These types of soft soils were then stabilised by cement with varying cement content. A further series of unconfined compression tests were conducted for each group of cement-stabilised soil specimens. As the silt content might exhibit a different influence on the strength of cement-stabilised samples, a varying dosage of cement content was considered in this study. The experimental results indicate that silt content plays a different role in soil stabilisation under different cement contents. The effect of cement content and silt content on the microstructure development of stabilised soils were also analysed by utilising the Scanning Electron Microscope (SEM) images. With the increase of cement dosage, the number of cementitious products, such as reticulated CSH and needle-shaped ettringite, was notably increased, resulting in a denser structure. This can be attributed to the hydration of cement and the pozzolanic reactions. As for the effect of silt content, since particle size plays a significant role in microstructure development, both cement and silt contents can dramatically affect the pore size distribution. When the cement content is lower than 10%, clay platelets can fill the pore spaces and the cementitious products can enhance the inter-cluster bond strength by aggregating clay and silt platelets together to form larger and denser aggregates responsible for the strength improvement. When the cement content is between 10% and 20%, the stabilised soil strengths increase with the increase of silt content and then decrease when silt contents are higher than 50%. This is because the strength gained from cementitious product enhancement was partially countered by the increment of pore size caused by the excessive cement and silt contents. When the cement content is higher than 20%, the strength shows a negative correlation with silt content, which can be attributed to the incomplete reaction of cement due to the reduction of clay content. Regarding the partial replacement of cement by adopting fly ash and DuraCrete, the UCS and CIU testing results show that both fly ash and DuraCrete are very effective as partial replacements of cement to reduce the cement content and CO2 emission. Fly ash can the provide the highest reduction in the cement replacement content, and it can also provide the highest reduction in CO2 emission. However, at the same mixture content (e.g., 25%), the UCS of the specimens stabilised by fly ash-blended cement is lower than that stabilised by cement only. Thus, more material is needed when using fly ash to partially replace cement to maintain the same UCS. Even though, the CO2 footprint can still be reduced because the CO2 emission rate of fly ash is much lesser than that of pure cement. Therefore, fly ash is effective as a partial replacement of cement to reduce the use of cement and CO2 emission. Compared to fly ash, DuraCrete is more effective as a partial replacement of cement in some circumstances. For example, the total mixture content is reduced to achieve a target strength of 500 kPa when using DuraCrete-blended cement instead of pure cement only. The reduction in total mixture content is an essential advantage by using DuraCrete compared to using fly ash. Comparing the proportional quantities of fly ash and DuraCrete required, the quantity of fly ash required is between 6.1 times and 9.7 times the proportional quantity of DuraCrete required. Even though the use of DuraCrete can reduce the amount of cement used and reduce the total mixture content, it cannot provide as much reduction in cement as fly ash does. This is because there is a ‘saturation point’ with the DuraCrete replacement ratio. If this saturation point is exceeded, DuraCrete will not be as effective anymore, being mainly a magnesiumbased additive. Therefore, when the maximum reduction in cement is the only factor under consideration, fly ash is more suitable than DuraCrete, as it facilitates a greater reduction in cement. However, suppose both reduction in cement and the total mixture content are considered. In that case, DuraCrete might be more appropriate, as it not only reduces the use of cement but also reduces the total mixture content required. Most importantly, unlike cement and fly ash, the production of DuraCrete is not carbon-intensive. The production of DuraCrete does not produce carbon emission as it does not require a furnace, nor is it a by-product of a carbon emitting process. These critical outcomes can help engineers reliably customise the soil stabilisation design to achieve optimal strength, environmental friendliness, and cost-saving. As such, engineers can have more design options to meet the strength requirement while having the opportunity to minimise the negative impact on the environment by reducing the use of cement. They can also achieve a balance between the reduction in cement and the budget, hence the important contribution of this study.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text

This degree project is about sustainable low-cost housing in Ethiopia with a focus on CSSB-technology, which is one method of constructing houses. The project allowed me to visit Ethiopia during seven weeks in 2010, to observe, gather information and to perform tests regarding the specific subject. It is a sub-project to a larger research project initiated in 2002 at Halmstad University in an attempt to introduce low-cost housing technologies for the Kambaata Region in Ethiopia. The aim of the research project has been to develop and test new, sustainable, low-cost building technologies intended for the population, with regard to local traditions, needs and affordability.
Sustainable Low-Cost Housing for the Kambaata region in Ethiopia

Rammed earth is a monolithic construction formed by compacting processed soil in progressive layers. Rammed earth is used for the construction of load bearing walls, floors, sub base material in roadways, airport runways, taxiways, aprons, foundations and earthen bunds. Soil, sand, cement and water are the ingredients used for the preparation of cement stabilized rammed earth (CSRE) specimens. The cracking in a rammed earth structure is due to the development of tensile stresses. The tensile stresses are generated due to various causes like unequal settlement of foundation, eccentric loading and / or lateral loading such as wind pressure and earthquake on an earth structure. The cracking in a rammed earth structure causes the failure of its intended function. For example formation of crack may lead to the instability of an embankment slope. And earthen dam can be destroyed gradually by erosion of soil at the crack surface (Harison et al. 1994). Hence, it becomes important to understand the fracture behaviour of cement-stabilized rammed earth structures. Well focused studies in understanding the fracture behaviour of CSRE structures are scanty. The present work attempts to address some issues on the fracture behaviour of CSRE including size effect. Through an experimental programme material properties viz. compressive strength, tensile strength and stress-strain relationships are generated for two chosen densities, 17 and 18.5 kN/m3 of CSRE both in dry and saturated condition. Soil composition, density, cement content and moisture content of the specimen during testing influence the characteristics of CSRE. In the present investigation keeping the cement at 10%, the density is varied choosing a soil-sand mixture having optimum grading limits. The basic raw materials used are soil, sand, cement and water in the ratio of 1 : 1.5 : 0.25 : 0.34 by weight. The strength properties studied alone are inadequate to predict the mechanics of fracture due to the presence of microscopic flaws, cracks, voids and other discontinuities. Therefore, some linear elastic fracture parameters such as mode I fracture toughness (KIc), critical energy release rate (GIc), net section strength (f net) and notch sensitivity are calculated, presuming that CSRE is still a brittle material because it is yet to be confirmed that CSRE is a quasibrittle material. In fact, in the present work, it is shown that CSRE has significant amount of softening. A comprehensive experimental work has been undertaken to test CSRE beam specimens for two densities, three sizes of beam and three notch to depth ratios under three point bending (TPB) in a closed loop servo-controlled machine with crack mouth opening displacement control. Results indicate that the CSRE in dry condition exhibits a greater resistance to fracture than the saturated specimen. The variation of net section strength with the notch depth is not significant. Therefore the CSRE material is notch insensitive, implying that it is less brittle. An experimental program was undertaken to determine the nonlinear fracture parameters of beam specimens both in dry and saturated condition. The influence of moisture content, density, size of the specimen as well as notch to depth ratio of the specimen on RILEM fracture energy (G F ) are presented. The GF values increase with increase in density and size of the specimen, while they decrease with increase in notch to depth ratio. Results clearly show that the total energy absorbed by the beams (W OF ) and RILEM fracture energy (G F ) for all specimens tested in dry state are higher compared to the specimens tested in saturated state, indicating that the dry specimen offers higher resistance to the crack propagation. The RILEM fracture energy GF , determined from TPB tests, is said to be size dependent. The assumption made in the work of fracture is that the total strain energy is utilized for the fracture of the specimen. The fracture energy is proportional to the size of the fracture process zone (FPZ), which also implies that size of FPZ increases with increase in the un-cracked ligament (d - a) of beam. This also means that FPZ is proportional to the depth d for a given notch to depth ratio, because for a given notch/depth, (d - a) which is also is proportional to d because is a constant. This corroborates the fact that fracture energy increases with size. Interestingly, the same conclusion has been drawn by Karihaloo et al. (2006). They have plotted a curve relating fracture process zone length and overall depth the beam. In the present study a new method namely Fracture energy release rate method proposed by Muralidhara et al. (2013) is used. In the new method the plot of GF /(d - a) versus (d - a) is obtained from a set of experimental results. The plot is found to follow power law and showed almost constant value of GF /(d - a) at larger ligament lengths. This means the fracture energy reaches a constant value at large ligament lengths reaffirming that the fracture energy from very large specimen is size-independent. This Fracture energy release rate method is used to determine size-independent fracture energy GRf , based on the relationship between RILEM fracture energy and the un-cracked ligament length. The experimental results from the present work agree well with the proposed new method. Similarly, the method is extended to determine nominal shear strength τv for large size beam. Results show that for both densities GRf decrease in saturated condition, while in dry condition as the density is increased from 17 to 18.5 kN/m3 the GRf decrease by 7.58%, indicating that the brittleness increases with higher density. The τv for large size beam increases with density both in dry and saturated condition. The size effect method for evaluating material fracture properties proposed by Bazant (1984) is applied to cement stabilised rammed earth. By measuring the peak loads of 2D geometrically similar notched beam specimens of different sizes, nonlinear fracture parameters such as fracture energy (Gf ), fracture toughness (KIc), effective length of the fracture process zone (Cf ), brittleness number (β), characteristic length (l 0) and the critical crack tip opening displacement (CT ODc) are determined for both dry and saturated conditions. The crack growth resistance curves (R-curve) are also developed for dry and saturated specimens. In the size effect method, for both densities 18.5 and 17 kN/m3 the values of nonlinear fracture properties, namely G f , Cf , KIc, CT ODc and l 0 are lower for the saturated specimen compared to those of the dry specimen. In dry condition as the density is increased from 17 to 18.5 kN/m3 the Gf decreases to 13.54%, indicating that the brittleness increase with higher density. The areas under the load-displacement and load-CMOD curves are a measure of the fracture energy and these areas are low for saturated specimens. The crack growth resistance curves (R-curve) plotted using the size-effect law from peak loads are the measure of resistance against crack growth R. The value of R is high for dry specimen compared to that of the saturated specimens. During aggregate pullout or the opening of crack, the interlock or friction between the crack surfaces may cause the energy dissipation through friction and bridging across the crack. Therefore the wet friction in case of saturated specimen must be smaller resulting in more brittleness compared to the larger dry friction for dry specimen. In the present investigation the Digital Image Correlation (DIC) technique is used to study the FPZ properties in cement stabilised rammed earth. The MATLAB package written by Eberl et al. (2006) is suitably modified and used for image correlation to suit our requirements. CMOD measured using DIC technique is validated by comparison with the CMOD measured using clip gauge. The FPZ properties such as the development of FPZ and crack opening displacements at different loading points as well as the influence of notch/depth ratio on FPZ length (lFPZ ) are evaluated for both dry and saturated conditions. At peak load the lFPZ are about 0.315 and 0.137 times the un-cracked ligament length respectively for specimens tested under dry and saturated conditions. In dry and saturated states the FPZ length decreases as the ratio increases. Lower values of lFPZ in saturated specimen indicates that it is relatively more brittle compared to dry specimen.

Rammed earth is a technique of forming in-situ structural wall elements using rigid formwork. Advantages of rammed earth walls include flexibility in plan form, scope for adjusting strength and wall thickness, variety of textural finishes, lower embodied carbon and energy, etc. There is a growing interest in the construction of rammed earth buildings in the recent past. Well focused comprehensive studies in understanding the structural performance of rammed earth structures are scanty. Clear-cut guidelines on selecting soil grading and soil characteristics, assessing strength of rammed earth walls, density strength relationships, limits on shrinkage, standardised testing procedures, behaviour of rammed earth walls under in-plane and out of plane loads, etc are the areas needing attention. The thesis attempts to address some of these aspects of cement stabilized rammed earth for structural walls. Brief history and developments in rammed earth construction with illustrations of rammed earth buildings are presented. A review of the literature on rammed earth has been provided under two categories: (a) Unstabilised or pure rammed earth and (b) stabilised rammed earth. Review of the existing codes of practice on rammed earth has also been included. Summary of the literature on rammed earth along with points requiring attention for further R&D are discussed. Objectives and scope of the thesis are listed. The thesis deals with an extensive experimentation on cement stabilised rammed earth (CSRE) specimens and walls. Four varieties of specimens (cylindrical, prisms, wallettes and full scale walls) were used in the experiments. A natural soil and its reconstituted variants were used in the experimental work. Details of the experimental programme, characteristics of raw materials used in the experimental investigations, methods of preparing different types of specimens and their testing procedures are discussed in detail. Influence of soil grading, cement content, moulding water content, density and delayed compaction on compaction characteristics and strength of cement stabilised soil mixes were examined. Five different soil gradings with clay content ranging between 9 and 31.6% and three cement contents (5%, 8% and 12%) were considered. Effect of delayed compaction (time lag) on compaction characteristics and compressive strength of cement stabilised soils was examined by monitoring the results up to 10 hours of time lag. Influence of moulding water content and density on compressive strength and water absorption of cement stabilised soils was examined considering for a range of densities and water contents. The results indicate that (a) there is a considerable difference between dry and wet compressive strength of CSRE prisms, and the strength decreases as the moisture content at the time of testing increases, (b) wet strength is less than that of dry strength and the ratio between wet to dry strength depends upon the clay fraction of soil mix and cement content, (c) saturated moisture content depends upon the cement content and the clay content of the soil mix, (d) optimum clay percentage yielding maximum compressive strength is about 16%, (e) compressive strength of compacted cement stabilised soil increases with increase in density irrespective of cement content and moulding moisture content, and the strength increases by 300% for 20% increase in density from 15.70 kN/m3, (f) compressive strength of rammed earth is one - third higher than that of rammed earth brick masonry and (g) density decreases with increase in time lag and there is 50% decrease in strength with 10 hour time lag. Stress-strain relationships and elastic properties of cement stabilised rammed earth are essential for the analysis of CSRE structural elements and understanding the structural behaviour of CSRE walls. Influence of soil composition, density, cement content and moisture on stress-strain relationships of CSRE was studied. Three different densities (15.7 – 19.62 kN/m3) and three cement percentages (5%, 8% and 12% by weight) were considered for CSRE. Stress-strain characteristics of CSRE and rammed earth brick masonry were compared. The results reveal that (a) in dry condition the post peak response shows considerable deformation (strain hardening type behaviour) beyond the peak stress and ultimate strain values at failure (dry state) are as high as 3.5%, which is unusual for brittle materials, (b) modulus for CSRE increases with increase in density as well as cement content and there is 1 to 3 times increase as the cement content changes from 5% to 12%. Similarly the modulus increases by 2.5 to 5 times as the dry density increases from 15.7 to 19.62 kN/m3 and (c) the modulus of CSRE and masonry in dry state are nearly equal, whereas in wet state masonry has 20% less modulus. Compressive strength and behavior of storey height CSRE walls subjected to concentric compression was studied. The results of the wall strength were compared with those of wallette and prism strengths. The wall strength decreases with increase in slenderness ratio. There is nearly 30% reduction in strength as the height to thickness ratio increases from 4.65 to 19.74. It was attempted to calculate the ultimate compressive strength of CSRE walls using the tangent modulus theory. At higher slenderness ratios, there is a close agreement between the experimental and predicted values. The storey height walls show lateral deflections as the load approaches failure. The walls did not show visible buckling and the shear failure patterns indicate material failure. The shear failures noticed in the storey height walls resemble the shear failures of short height wallette specimens. The thesis ends with a summary of the results with concluding remarks in the last chapter.

The present investigation is focused on the thermal performance of building materials, specifically their thermal transmittance, and consequent impact on building envelope and building thermal performance. Thermal performance of building materials plays a crucial role in regulating indoor thermal comfort when suitably integrated as part of the building envelope. Studies into thermal performance of building materials are few, particularly in the context of designing building blocks to achieve a particular thermal transmittance in buildings. Such studies require both theoretical (numerical) investigations augmented with experimental investigation into material thermal performance. A unique contribution of this study has been assessing the temperature-dependent performance of building material and their influence on thermal conductivity. The thermal performance of conventional and alternative (low energy) building materials have also been investigated to assess their suitability for naturally ventilated building in salient climatic zones in India. The study has also investigated the impact of varying mix proportions in Cement Stabilized Soil Block on thermal performance. There is little evidence of such studies, involving both experimental and theoretical studies, tracing the thermal performance of building materials to building performance. The current study involves three parts: studying thermo-physical properties of building materials, building-envelope performance evaluation and case-study investigation on buildings in various climatic zones. The thermo-physical study involves understanding the role of materials mix-proportion, composition, and microstructure for its influence on building-envelope thermal performance. Studies into building envelope performance for conventional and alternative building materials, includes, steady and dynamic thermal performance parameters. As part of the study, a calibrated hot-box thermal testing facility has been tested to experimentally determine the thermal performance of building envelopes. Case-study investigation involves real-time monitoring and simulation based assessment of naturally ventilated buildings in three climatic zones of India. The study finds noticeable temperature-dependent performance for various building materials tested. However, their impact on overall thermal performance of buildings is limited for the climatic zones tested. Further, the study validates the hitherto unexplored possibility of customizing building materials for specific thermal performances.

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.

Roller-compacted concrete is a type of concrete with significantly larger fine aggregates comparing to conventional concrete. Larger fine aggregates percentage in roller-compacted concrete leads concrete mix to be non-slip and to be compacted by rollers. Roller-compacted concrete is cost-effective and easy to construct. Roller-compacted concrete can be paved by typical asphalt paver which simplifies the construction technology and makes it similar to asphalt paving technology. It also has the strength and performance of conventional concrete or even higher. Due to all the advantages, the use of roller-compacted pavement in industrial areas and low-volume rural roads is very beneficial. Some specially designed roller-compacted concrete structures with cement and special additives stabilized subgrade and or base layers showed very good performance in road. Few experimental tests were made measuring surface deflection with falling weight deflectometer (FWD). The main aim of these experimental tests is to collect deflection values from roller-compacted structure and to compare them between different seasons of the year. Such experimental tests also helps to learn more about this type of pavement structure and how it performs during spring thaw when the bearing capacity of the pavement structure is usually lower comparing to the other seasons. In these paper surface deflection measurements was conducted on local road No. 130 in Lithuania, which was reconstructed in 2021. The bearing capacity of the pavement structure was measured in August 2021 and March 2022. The results have showed that the bearing capacity of the pavement structure increased 9 months after reconstruction and that hydrothermal conditions do not affect the bearing capacity of RCC pavement structure with stabilized subbase and base layers.

An Experimental Study of the Technical Properties and Compressive Strength of Laterite Bricks Stabilised with Cement and Wood Ash 1Oladunmoye, O.M., 2Awofodu, J.O. & 3Babatunde, L.O. Department of Architecture, University of Ibadan, Ibadan. Department of Architecture, Lead City University Ibadan. Department of Architectural technology, Oke-ogun Polytechnic, Saki, Oyo State E-mails: .Bjarchimat15@gmail.com; Josephstone69@gmail.com ABSTRACT An experimental study was carried out in order to determine the compressive strength and technical properties of laterite bricks stabilized with cement, wood ash and sawdust. Cement stabilized compressed laterite bricks were tested. The compressive strength of lateritic soil based materials were determined. The objective of this paper is to determine the effect(s) of addition of cement and wood ash to lateritic soil brick on the compressive strength using four soil samples. The findings showed positive effect of the additives of cement and wood ash on increasing the compressive strength of the stabilized laterite bricks. The study showed that the optimum value for water absorption of wood ash stabilisation is at 10% C with 5% WA (19.09%) replacement and 15% C with 10% SD. The compressive strength of the different samples measured showed increase in the failure point of the brick with increase in percentage of cement and wood ash. Keywords: Technical Properties, Compressive Strength, Laterite Bricks , Cement and Wood Ash Proceedings Reference Format