Road Base Construction Research Articles

Short-term Effects of Applying Carboxylated Styrene Butadiene Emulsion-portland Cement Mixture on Road Base Construction

Short-term Effects of Applying Carboxylated Styrene Butadiene Emulsion-portland Cement Mixture on Road Base Construction

Evaluation of Durability and Permanent Deformation of Modified Road Base Construction Using Rovene<sup>®</sup> 4045 and Portland Cement Additives

Due to lack of previous study on applying polymer additives in road base construction, this research presents experimental results on the improvement of long-term road base performance by the addition of carboxylated styrene–butadiene emulsion (Rovene® 4045) and Portland cement. The specimens stabilized with Portland cement (0–6%) and Rovene® 4045 (5–10%) and then subjected to different stress sequences to study the wetting and drying (WD) and wheel tracking (WT) tests on the 7-day-cured specimens. Results of tests conducted to assess the specimens’ resistance to WD cycling showed that the addition of a 4% Portland cement–7% Rovene® 4045 mixture resulted in reductions of 86.99% in water absorption, volume changes of 88.55%, and weight changes of 92.84% relative to a sample with only 4% cement after 12 WD cycles. The permanent strain behaviour of the samples was assessed by the WT test. The results of WT test showed that the permanent deformation characteristics of the mixture were considerably improved by utilization of Rovene® 4045 modification, which resulted in reductions of 218.9% at 25 oC, and 356.8% at 50 oC in permanent strain of the mixture respectively. Therefore, this research nominates a new polymer additive having outstanding engineering properties and environmental friendly.

Chemically Stabilized Soft Clays for Road-Base Construction

Soft clays are widely distributed in Missouri, United States. Due to their relatively low strength and high compressibility, subgrade construction in soft clays has encountered many difficulties. In recent practice, the use of fly ash (FA) along with lime to tackle soft subgrade problems has shown promising results. The effectiveness of Class C FA and lime kiln dust (LKD) in clay subgrade stabilization is examined in this research. Scanning electron microscopic (SEM) analysis, proctor compaction tests, unconfined compression tests, and resilient modulus tests were carried out on the FA and LKD modified soil mixtures. Test specimens were prepared at optimum water content and tested at various curing periods. The test specimens were reconstituted by static compression. Test results revealed that the addition of Class C FA could increase the dry unit weight of the FA treated soil, enhance the unconfined compressive strength, and improve the resilient modulus. Regression equations were developed to correlate the resilient modulus with curing time. The mechanism of FA stabilization was discussed based on the SEM results and the measurement of the electrical conductivity of the FA-soil-water system. Correlations between the unconfined compressive strength and resilient modulus were developed. It is concluded that subgrade stabilization with Class C FA and LKD are cost-effective for road-base construction.

Application of aging methods to evaluate the long-term performance of road bases containing blast furnace slag materials

The long-term performance of secondary materials is becoming a challenging aspect in road construction since their future behaviour is difficult to estimate. In this study, aging is proposed as a means of exploring the long-term mechanical and physical performance of secondary materials. A Blast Furnace Slag (BFS) mixture which is routinely used in the Netherlands in road base construction, e.g. in the A32 motorway, was selected as a reference material. Twenty years after its construction, the A32 pavement structure experienced serious failure and the BFS base contributed to that. Accordingly, an aging protocol was suggested to detect at an early stage potential poor material performance. Two types of accelerated aging approaches were applied to the materials being steam aging and cyclic freezing and thawing. The results show that there is a linkage between the material performance and temperature, moisture, chemical composition and time. The response behaviour, of aged laboratory samples and the field-aged A32 base material, suggested that the aging methods did a reasonable job in detecting materials with a poor performance.

The Quality Control of Engineering Properties for Stabilizing Silty Nile Delta Clay Soil, Egypt

Clay soil with low-bearing capacities can present great problems underlying pavement and light structures due to uncertainty associated with their performance. This paper describes a sonic based testing methodology for quality control of a surface stabilized soil. From an engineering aspect, an increase in water content has a number of disadvantageous consequences: cohesion decreases, the soil swells, the alternating dry-out/shrinkage and wetting/swelling effects destroy the rock or a soil structure. Cement is mixed into the soil to increase both the strength and the usability of local soils in constructions purposes. This is to overcome the problems by strengthening the soil underlying the structure or diminishing the leads transmitted from the foundation to the soil. The compressive strength of the stabilized soil is highly dependent on the type of soil, moisture content, cement content, and compaction work, and can therefore vary significantly in the field. The authors performed the quality control by measuring the sonic and tensile strength velocity in the stabilized soil that has been correlated to compressive strength in native materials. The improvement of the soil materials by the addition of cement could make the material suitable as filling materials, foundation and/or a road base construction. The quality control for the stabilized soils was investigated using sonic measurements and strength gain. The test methods were performed to evaluate the degree of improvement achieved through the measurement of compression and shear-wave velocities of the soil under study. Scanning electron microscopy and electron dispersive X-ray analyses were performed on raw and laboratory treated for qualitative understanding the strength minerals formed during stabilization. The sonic test showed a considerable improvement with curing time and percentages of stabilizer. Mineralogical studies indicated the formation of silica and alumina hydrates along with interwoven structure of cement treated clay particles suggesting adequate mixing of the soil and binder owing to the strength of the soil materials.

Evaluation of Combined Excavation Waste and Reclaimed Asphalt Pavement Aggregates for Use in Road Bases and Sub-bases

More than 15 million tons of aggregates are imported each year to Qatar from neighbouring countries. Large quantities of waste materials (around 20 million tons/year) from excavation waste, demolition rubble and reclaimed asphalt pavement (RAP) are being generated. The main objective of this paper is to present the results on the use of combined excavation waste (EW) and RAP aggregates in the construction of road bases and sub-bases. Physical and chemical properties were determined. Different combinations of both materials were subjected to compaction and California Bearing Ratio (CBR) testing in accordance with Qatar Construction Specifications. Results indicated that, for the materials tested, it is not feasible to use excavation waste, RAP aggregates or a combination of the two materials in road bases and sub-bases. The materials failed to meet some Qatari standards such as Los Angeles abrasion, liquid limit, plasticity index and CBR specified for road construction.

The Stabilization of Weathered Dolerite Aggregates with Cement, Lime, and Lime Fly Ash for Pavement Construction

An experimental program was performed on weathered dolerite specimens stabilized by adding varying percentages of cement (4, 8, 12, and 16) % and lime (6 and 12) % and a combination of lime and fly ash (6% lime + 12% Fly ash and 12% lime + 12% Fly ash) % by dry weight of soil. The strength was examined under three different curing methods, namely, membrane curing (MBC), alternate moist-air curing (MAC), and water curing (WAC), by conducting unconfined compressive strength (UCS) tests. Simple polynomial and linear functions (regression models) were used to define the relationships between the variables investigated. Membrane curing (MBC) gave results close enough to the water curing (WAC) to indicate that it can be confidently used on the field during pavement construction. From the results obtained, for class B (interurban collector and major rural roads) pavement construction, addition of 8% cement was recommended for road base construction with stabilized WDA. Also the addition of 12 + 12% Lime and Fly Ash was recommended for road subbase construction with stabilized WDA. Stabilized WDA against the prejudiced myths would perform satisfactorily for base and subbase construction in both heavily trafficked and low volume roads with economic quantities of cement, lime, and fly ash in South Africa.

The Potentials of Portland Cement and Bitumen Emulsion Mixture on Soil Stabilization in Road Base Construction

Recycled road based material requires a stabilizing effect in order to provide a longer life to pavements. This is done by improving its strength and reduces its water vulnerability. One of the most popular techniques to achieve this is by using soil stabilization. This research aims to analyze in details the soil stabilization method which utilizes Portland cement and bitumen emulsion in improving soil properties. As a result, this will increase the pavement bearing capacity (conducted via laboratory research). The combination of Portland cement and bitumen emulsion are beneficial for the purpose of increasing the stiffness and also the elasticity of soil stabilized layer. In order to examine this, two steps were undertaken, first, by examining the Unconfined Compressive Strength (UCS) and Modulus of Elasticity (ME) on samples mixed with soil aggregates comprising Portland cement and bitumen emulsion. Next, the data collated was analysed and the graph plots were presented as to show the optimum value of Portland cement and bitumen emulsion used in soil stabilization. The major findings of this research showed the importance of soil stabilization using Portland cement and bitumen in improving pavement’s performances by increasing bearing capacity of its layer. The findings revealed that overall; the optimum value of Portland cement and bitumen emulsion utilized in base Soil stabilization method is 3% and 3% respectively. With this method, the duration time of the project can be reduced and subsequently the project cost may be also reduced.

Application of cement-treated recycled materials in the construction of a section of road in Malaga, Spain

In Spain, there is a low rate of application of recycled aggregates in construction of road bases and sub-bases. Recycled aggregates from crushed concretes (RCA) are usually used as unbound material in road structural layers. Recent studies have confirmed the possibility of applying these RCA in road bases as Cement Treated Granular Material (CTGM), which would result in greater effectiveness in terms of its mechanical behaviour as well as its durability. In this paper, it is included a research based on a real application performed in the construction of a road base, in which these RCA were applied in the production of CTGM. The results concluded that the effectiveness of those sections built using recycled aggregates was similar those constructed using natural aggregates. As a result, the application of RCA treated with cement is a real alternative in the construction of road bases and sub-bases.

Application of the Steam Aging Method to Evaluate the Long-Term Performance of Secondary Materials for Road Construction

Abstract Long-term performance of secondary materials is becoming a challenging aspect in road construction because, as a result of their benefits, they are being used on a large scale. The problem with these materials, however, is that their future behaviors are difficult to estimate. In this study, aging is proposed as a means of exploring the long-term mechanical and physical performance of secondary materials. A blast furnace slag (BFS) mixture, which is routinely used in the Netherlands in road (sub-)base construction, was selected as a reference material. A motorway in the Netherlands was used as a source of field-aged BFS materials. The base layer of this motorway suddenly experienced serious failures. To prevent similar problems, an aging method was suggested to detect potential poor material performance at an early stage. The steam aging approach was chosen and applied to the field-aged and fresh materials. This aging treatment has affected material characteristics. This showed that there is a linkage between material performance, mixture composition, and aging conditions.

Compaction Characteristics and Bearing Ratio of Pond Ash Stabilized with Lime and Phosphogypsum

Recycling of waste material is one of the effective solutions of its disposal problem. Fly ash produced by coal-based thermal power plants and phosphogypsum (PG) produced by fertilizer plants producing phosphoric acid as constituent of fertilizers, take huge disposal area and creates environmental problems. Stabilization/solidification of fly ash improves the engineering properties and reduces the environmental problem like leaching and dusting. This paper presents the laboratory test results of a Class F pond ash alone and stabilized with varying percentages of lime (4, 6, and 10%) and PG (0.5, and 1.0), to study the suitability of stabilized pond ash for road base and subbase construction. Standard and modified Proctor compaction tests have been conducted to reveal the compaction characteristics of the stabilized pond ash. Bearing ratio tests have been conducted on specimens, compacted at maximum dry density and optimum moisture content obtained from standard Proctor compaction tests, cured for 7, 28, and 45 days. Both unsoaked and soaked bearing ratio tests have been conducted. This paper highlights the influence of lime content, PG content, and curing period on the bearing ratio of stabilized pond ash. The empirical model has been developed to estimate the bearing ratio for the stabilized mixes through multiple regression analysis. Linear empirical relationship has been presented herein to estimate soaked bearing ratio from unsoaked bearing ratio of stabilized pond ash. The experimental results indicate that pond ash-lime-PG mixes have potential for applications as road base and subbase materials.

Use of natural pozzolan in stabilising lightweight volcanic aggregates for roadbase construction

The aim of this study was to explore whether marginal materials like lightweight volcanic aggregates (LVA) could economically and effectively be stabilised using natural pozzolan so as to conform to roadbase specifications. The combinations of natural pozzolan with lime; natural pozzolan with natural activator (natural gypsum); and natural pozzolan, lime and natural activator mixes were examined for their binding capabilities. Three types of natural pozzolan and two types of LVA materials from Arusha region in Tanzania were studied. Standard tests on physical, chemical and mineralogical properties of both the virgin materials and the stabilised mixes were carried out. Laboratory test results and statistical analyses show that natural pozzolan–lime binder could stabilise LVA to achieve roadbase strength requirements at a dosage of less than 2% of lime with between 10 and 30% (by mass) of natural pozzolan. Natural pozzolan–gypsum–lime binder mixes were found to develop a significantly higher unconfined compressive strength (UCS).

Use of Naturally Occurring Pozzolans for Road Construction in Tanzania

A pilot study has been conducted in Tanzania to investigate the possibility of using naturally occurring pozzolan materials as a sand stabilizing agent for road base and subbase construction. The pozzolan material investigated was to be used in the coastal area of Tanzania, which lacks good road construction materials that meet material specification requirements. The coastal area produces mainly sand and some poor-quality limestones that are not particularly suitable for road construction. Pozzolan samples collected from different parts of Tanzania were investigated. The collected pozzolan samples were mixed with lime to stabilize sand that could be used in a base or subbase course. Laboratory tests were done to determine properties of individual pozzolans and lime–pozzolan–sand mixtures. The compressive strength and split tensile tests were performed to determine the pozzolan mixtures' strength development and their suitability for road construction. Tanzanian experience with natural pozzolanic materials resulting from the Dar–Mlandizi road project will be discussed. The Dar–Mlandizi road was constructed by using sand stabilized with blast furnace slag as the base course material. The paper highlights the availability and preliminary testing of natural pozzolans in Tanzania, which resulted in follow-up testing of natural pozzolans in Denmark and the construction of a test road section in Tanzania. The pilot study can be considered an example of successful research in investigating the use of local materials for low-volume road construction.

Comparative studies of three methods for activating rejected fly ash

Pulverised fuel ash is a by-product of burning coal during the generation of electricity. In many places, the collected pulverised fuel ash has to be processed through a classifying stage before it can be used as a construction material. The rejected portion of the classifying process has remained unused due to its high carbon content and large particle size (> 45 μm). However, the rejected ash may be used in certain areas, such as in solidification and stabilisation processes of hazardous waste, and materials for road base or sub-base construction, which require relatively lower strength and reactivity. This paper presents the results of a study on the pozzolanic properties of cementitious materials prepared by blending rejected fly ash (rFA) with calcium hydroxide. The effects of adding chemical activators, elevating curing temperature, and grinding of the ash particles on the activation of rFA were compared by means of compressive strength, differential scanning calorimetry-thermogravimetric analysis, X-ray diffraction analysis and mercury intrusion porosimetry tests. The results show that the addition of Na2SO4 can significantly accelerate the strength development both at 28 and 90 days. K2SO4 is only effective at 28 days. The addition of flue gas desulphurisation sludge (a low-grade gypsum) and grinding can only increase the strength at 90 days. Pretreatment by steam curing decreases the 90 day strength of the samples. The compressive strength results correlate nicely with the results of the porosity and the thermal analysis tests. Adding chemical activators seems to be an effective and economical method to accelerate the hydration of rFA.

Utilization of Steel Slag Aggregate for Road Bases

Abstract Industrial wastes and byproducts have to be disposed off properly so that their environmental impacts are minimized. Alternatively, some of these materials can be utilized in recycling processes, manufacturing of new products, or as construction materials. This paper presents an effective way of utilizing the steel slag aggregate (SSA), which is a byproduct of the steel manufacturing process, in road construction. A comprehensive study was conducted to characterize SSA and determine the potential for its use in road bases. Testing results indicated that SSA is an environmentally safe product and has physical and chemical properties that make it an excellent candidate for road base construction. Laboratory and field data have shown the superior performance of SSA over the locally available calcareous sediments. The resulting California Bearing Ratio values are doubled and the water sensitivity is much less when using SSA instead of the local calcareous material.

Oil-Shale Fly Ash Utilization as Independent Binder of Natural Clayey Soils for Road and Airfield Base Construction

ABSTRACT This article describes physicochemical interactions of different natural clayey soils with oil-shale fly ash (OSFA) from thermal power plants, dealing with the strengthening processes of new materials. Toward this end, a range of traditional and modern research methods were used, i.e., definition of the ultimate strength under uniaxial compression and rupture by the Brazilian method, temporary changes in moisture content and linear deformation, water and frost resistance, free CaO and SO3, CaCO3, XRD, and SEM. It was established that the surfaces of the initial component (OSFA and soils) particles were dissolved in porous alkaline solutions. The dissolution products gave rise to new amorphous and crystal formations. After 28 days, the strength of the samples reached 2–12 MPa but, after 90 days, it rose to 4–31 MPa. It was found that the strength at every stage of hardening can be increased significantly by changing the proportion of the initial mixture's composition. The materials displayed very high water and frost resistance, with coefficients equaling or exceeding the 1.0 level, except the OFSA and loess combination. The materials developed are applicable for the construction of roads, airfields, and dam bases and for various types of foundations without traditional binders, such as cement, and without heating.

Influence of Portland Cement Type on Unconfined Compressive Strength and Linear Expansion of Cement-Stabilized Phosphogypsum

This technical note summarizes the results of a laboratory-testing program aimed at evaluating the engineering properties of cement-stabilized phosphogypsum mixtures for road base and subbase construction. Phosphogypsum is a solid byproduct of the production of phosphoric acid, a major constituent of many fertilizers that has chemical and radioactive properties may cause environmental problems. For every ton of phosphoric acid produced, approximately 5.0 tons of phosphogypsum are generated. This magnifies the problem of dealing with growing phosphogypsum stockpiles. The research program described herein, covered the physical characterization of phosphogypsum, and tests that uncovered the influence of cement type and content, curing time, and compaction energy on its unconfined compressive strength and expansion. The laboratory results indicate that cement-stabilized phosphogypsum mixtures have potential applications as road base and subbase materials.

Pozzolanic properties of reject fly ash in blended cement pastes

Low-grade fly ash (reject fly ash, r-FA), a significant portion of the pulverized fuel ash (PFA) produced from coal-fired power plants and rejected from the ash classifying process, has remained unused due to its high carbon content and large particle size. But it may be used in certain areas, such as in solidification and stabilization processes of hazardous waste and materials for road base or subbase construction, which require relatively lower strength and reactivity. It is therefore necessary to extend research on the properties of r-FA and explore its possible applications. This paper presents experimental results of a study on the mechanical and hydration properties of cementitious materials prepared by blending r-FA with ordinary Portland cement (OPC). Parallel mixes were also prepared with the good ash [i.e., classified fine fly ash (f-FA)] for comparison. Selective chemical activators were added to the mix to study the effects of the activators on the properties of the blend system. The results show that r-FA generally has a lower rate of hydration than f-FA particularly at the early stage of hydration. Adding Ca(OH) 2 alone almost had no effect on accelerating the hydration of r-FA. But adding a small quantity of Na 2SO 4 or K 2SO 4 together with Ca(OH) 2 significantly accelerated the hydration reaction. The results of the compressive strength measurement correlated nicely with the degree of hydration results. It was also found that water-to-binder ratio (w/b) was an important factor in affecting the strength development and the hydration degree of r-FA pastes.

Cement Stabilization of Reclaimed Asphalt Pavement Aggregate for Road Bases and Subbases

Pavement rehabilitation and reconstruction generates large quantities of reclaimed asphalt pavement (RAP) aggregate, and recycling into new asphalt paving mixtures is the predominant application. RAP acceptance in road bases and subbases has been limited, because of the lack of laboratory and field performance data. In the Sultanate of Oman, recycling of pavement materials is not practiced. A previous study conducted at Sultan Qaboos Univ. indicated that RAP-virgin aggregate mixtures could be utilized in the subbase layer rather than in the base course. This paper presents the results of a laboratory evaluation of cement stabilized RAP and RAP-virgin aggregate blends as base materials. Compaction and unconfined compressive strength tests were conducted on the following RAP/virgin aggregate mixtures: 100/0, 90/10, 80/20, 70/30, and 0/100%. Samples were prepared using 0, 3, 5, and 7% Type I portland cement and were cured for 3, 7, and 28 days in plastic bags at room temperature. A pavement design analysis of using various cement stabilized RAP-virgin aggregate mixtures as base materials was also undertaken. Results indicate that the optimum moisture content, maximum dry density, and strength of RAP will generally increase with the addition of virgin aggregate and cement. Longer curing periods will yield higher strength results. The ability of RAP aggregate to function as a structural component of the pavement is more pronounced when it is stabilized with cement rather than when blending with only virgin aggregate. A 100% RAP aggregate should not be recommended for use as a base material unless stabilized with cement. Cement stabilized RAP-virgin aggregate mixtures seem to be a viable alternative to dense-graded aggregate used in road base construction.

Immobilisation of PAH in waste materials

This paper gives an overview of the results of a research project into the possibilities of immobilising polycyclic aromatic hydrocarbons (PAH), that are present in waste materials. The results show that with hydraulic binders the waste materials can be solidified. The PAH do still leach to a relatively high extent. However, this PAH leaching can be decreased by more than a factor 10 by means of the addition of a specific additive. The immobilisation product fulfils technological requirements for the use as a road base construction material, such as compressive strength.