Performance of pyroclastic rocks from Abakaliki Metropolis (southeastern Nigeria) in road construction projects

A total of 15 samples from the Abakaliki pyroclastic rock bodies were subjected to petrographic and mechanical analyses to determine the suitability of the rock type as a road aggregate. Results indicate that the Abakaliki pyroclastic rock yield aggregates with marginal performance in road projects. Although the aggregates meet a number of road stone requirements (i.e., ten percent fines and their ability to absorb water), they fail to meet other key road stone requirements. Whilst their aggregate impact values, Los Angeles abrasion values, and flakiness index are generally above the recommended limits, petrographic analyses reveal appreciable amounts of shaley to muddy lithic fragment and volcanic glassy groundmass. These detrimental constituents and marginal laboratory test results would likely translate to long term poor field performance where the pyroclastic aggregate is used for road construction. This study suggests that utilization of the Abakaliki pyroclastic rock as an aggregate, especially for road construction, requires informed caution, particularly when the material is exposed to climatic extremes (high volume of rainfall and high and fluctuating temperature) as is the case in the tropics.     

Relation entre les caracteristiques des granulats et les proprietes des materiaux qu'ils permettent d'elaborer. Recherches en laboratoire et sur chantier

The introduction of the report presents data concerning the evolution of the traffic in the Cracow District between 1965 and 1983, and the aggregates used for road construction during the same period. The most important characteristics aggregates made of crushed rocks in the district are dealt with. Mineral aggregates usually belong to II–III class, and require improvements to achieve better physico-mechanical properties and after improvement they are commonly used for roadbases, basecourses and wearing courses. This report also deals with the relations between the characteristics of aggregates and the properties of same stabilized materials:

1. Mechanical stabilization for sub-base,
2. Stabilization of aggregates with granulated slag and hydrated lime for roadbases,
3. Stabilization of aggregates with granulated slag and with cement for roadbases,
4. E. Fly-ash concrete and stabilization of sand with cement for roadbases,
5. Hot bituminous mixtures/with asphalt as a binder/for basecourses,
6. Hot bituminous mixtures/with coal tar pitch as a binder/for wearing courses.

For all stabilized materials, the main results of the laboratory tests achieved during the preparation of mixes are presented, as well as the tests realized on compacted mixtures inside the road, under the traffic. It proved that satisfactory road-bases, base-courses and wearing courses could be made of aggregate of a rather poor quality. The choice of the technique must derive from the quality of the aggregates. The permanent technical control of the laboratory is necessary at all stages: designing, realization and maintenance.     

Durability testing of basic crystalline rocks and specification for use as road base aggregate

One of the most important materials for the construction of high quality pavement layers in roads in South Africa is the Basic Crystalline group of rocks. The major deposits of these materials are associated with the dolerites and basaltic lavas of the Karoo Supergroup. Problems related to the in-service deterioration of road aggregates produced from the crushing of these materials, despite their conforming to the necessary specifications, have been experienced in southern Africa for many years. This has usually resulted in the use of more expensive materials being transported further to the road project. Twelve such materials were collected from various parts of southern Africa and tested for their durability using the standard specified tests as well as a range of non-standard and new tests. Based on the results, new test methods and tentative specification limits have been proposed for assessing and predicting the durability of basic crystalline materials obtained by crushing unweathered material sources.      

集料嵌锁型碾压混凝土刚性基层材料工程实验研究

研制了一种集料嵌锁型碾压混凝土路面基层材料,并在十漫高速公路工程中进行了工程实验研究,结果表明,这种集料嵌锁型碾压混凝土基层强度高,表面粗糙,和面层之间结合良好,在减少下面层和下基层后,其承载力仍满足设计及指标,施工进度快,具有很好的技术经济效益。     

Crushed aggregate production from centralized combined and individual waste sources in Hong Kong

Owing to the comprehensive building redevelopment programmes in Hong Kong, there is a huge volume of concrete waste generated that will soon exhaust all the available landfill areas. As such, recycled aggregate is advocated. However, the use of recycled aggregate has been confined to lower-grade applications until now, such as the lower layers of a pavement structures, e.g., capping and sub-base. The main reason is the variable behaviour of recycled aggregates collected from different sources to be crushed in a centralized recycling plant. This paper applies some international standards to classify recycled aggregates. Aggregates were collected from twelve sources, including 10 from demolition sites (Samples 1–10), one from Tuen Mun Area 38 centralized recycling plant (Sample 11) and one from ordinary virgin aggregate (Sample 12). From test results, Sample 6, akin to Sample 12 (virgin aggregate), was found to be suitable for all types of construction applications, while Samples 2 and 9 were completely unsuitable as recycled concrete aggregates for any application grade. Sample 11 (Tuen Mun Area 38 centralized recycling plant) was found only suitable for non-structural applications, such as base course and fill. It is concluded that the different sources of recycled aggregate should preferably be separately crushed and classified rather than processed in a combined form centrally which will lower its overall quality and limit its application.     

石灰粉煤灰稳定建筑垃圾的路用性能研究

对石灰粉煤灰稳定建筑垃圾混合料的强度、模量、抗冻性能等路用技术性能进行了系统的试验研究,结果表明,其各项技术性能满足现行规范的要求,可以作为各级公路的底基层或基层材料。     

The potentials of some stabilizers for the use of lateritic soil in construction

Lateritic soil was stabilized with various percentages of rice husk ash (RHA), lime and cement. Atterberg limits, standard Proctor compaction, unconfined compression and California bearing ratio tests were carried out on lateritic soil with various percentages of these stabilizers in order to examine their influence. The required amounts of ash, lime and cement were determined for economical stabilization. This paper presents the potentials of rice husk ash compared to lime and cement in lateritic soil stabilization. For road construction, it recommends 7% cement for base materials, 5% lime for sub-base materials and 18% rice husk ash for sub-base materials.     

Determination of fine aggregate angularity in relation with the resistance to rutting of hot-mix asphalt

Rutting in asphalt pavements continues to create problems for pavement agencies. One factor that has been identified in determining asphalt pavement rutting susceptibility is the fine aggregate angularity (FAA) in the asphalt aggregate mix. The aim of this study is to investigate the angularity of fine aggregate produced in Turkey and to draw the attention of design engineers to this subject. To examine the relative effect of angularity of fine aggregate on the passing time through an orifice, material was obtained from 30 different sources which represent a wide range of materials used in Turkey. This collection offered a variety of geometric irregularities. The aggregates included 4 natural sands and 26 crushed aggregates. ASTM C128 “Specific Gravity Test of Fine Aggregate” and AFNOR P18-564 “Determination of Flow Rate of Fine Aggregate” which has been adopted by AFNOR were performed on each sample. Rutting tests were then performed on four different aggregate samples which had different FAA values and which were crushed by different crusher types. Test results bring to light that factors like the mineralogical properties of the fine aggregate and the crusher type must be considered in determining the angularity of fine aggregate. Also rutting test results showed that higher FAA values increased resistance to rutting of hot-mix asphalt.     

Pre-normative research on the use of mixed recycled aggregates in unbound road sections

This paper presents and discusses the results arising from a pre-normative study aimed at determining the physical, chemical and mineralogical characteristics of mixed recycled aggregates produced from the treatment of mixed rubble for use in unbound structural layers of road. The results of this research show that the combined presence of concrete and ceramic materials induces pozzolanic reactions, which contribute to an increase in the bearing capacity of the compacted mixed recycled aggregate. From an analysis of their chemical characteristics, it can be inferred that the total sulphur compound content, the gypsum content and soluble salt contents can be regulated with reference to the water soluble sulphates test, given the high correlation that exists between those parameters. Generally, mixed recycled aggregates with ceramic material contents below 35%, organic matter contents below 0.8% and water soluble sulphate contents below 0.4% constitute a granular material that is technically feasible for use in unbound structural road sections.     

Laboratory evaluation of recycled construction and demolition waste for pavements

The wide production of construction and demolition waste and its illegal deposition are serious current problems in Brazil. This research proposes to evaluate the feasibility of using aggregate from recycled construction and demolition waste (RCDW) in pavement applications. A laboratory program was conducted by geotechnical characterization, bearing capacity and repeated load triaxial tests. The results show that the composition and the compactive effort influence on the physical characteristics of the RCDW aggregate. The compaction process has promoted a partial crushing and breakage of RCDW particles, changing the grain-size distribution and increasing the percentage of cubic grains. This physical change contributes to a better densification of the RCDW aggregate and consequently an improvement in bearing capacity, resilient modulus and resistance to permanent deformation. The results have shown that the RCDW aggregate may be utilized as coarse base and sub-base layer for low-volume roads.     

Aggregates in Hong Kong

In Sweden, studded tyres cause considerable wear on road surfacings. The properties of aggregates are known to be of importance, but lack of experience with road conditions has prevented relevant specifications. The performance of nine aggregates—in a single surface dressing—has been studied by means of small test surfacings in road E4. The flakiness of two of the aggregates was varied, too. The change of the texture depth was determined with the aid of a laser profilometer and sand-patch measurements. The former is considered to give more reliable results. After two years in service, the test surfaces have been rated by an expert panel and aggregate samples have been removed from the road after heating the binder. The changes in grading and flakiness have been analyzed. The macrosurface depths after two years and the changes of that property, not considering the first summers change, because of particle orientation and embedment going on, correlates well with the Swedish aggregate abrasion value. Also, the flakiness of the worn aggregates and reduction of that property in the road, due to traffic wear, correlate. The aggregate impact value does not correlate. However, a fair relationship exists with the aggregate crushing in the road. Obviously, most of these particles, that have been crushed by traffic stresses, can go on functioning in the surface dressing. The condition is, however, that a proper aggregate-binder adhesion exists. The aggregate flakiness is also of importance mainly as it determines the “particle layer height” of the road surfacing. A lack in the abrasion property of an aggregate can partly be compensated by improving the flakiness.     

Effects of fine aggregate content on the mechanical properties of the compacted decomposed granitic soils

Decomposed granitic soil is widely used as the subgrade material in Korea. The mechanical behavior of the soil can differ depending on the fine aggregate content of the soil. Due to particle crushing during loading and compaction, the soil may behave as either cohesive or cohesionless. In order to evaluate the effects of fine aggregate content on the mechanical properties of the compacted decomposed granite soils, the direct shear test, the triaxial shear test as well as some fundamental property tests were made by using samples with the five different fine aggregate contents of 10, 20, 30, 40, and 50% by weight. Results of the triaxial tests showed that as the percentage of the fine aggregates decreased, the cohesion decreased as well as the internal friction angle increased. In the direct shear test, the soils containing lower amount of fine aggregates exhibited that the shear strength was considerably reduced after it reached the peak value. Comparably, soils with the high fine aggregates showed that the shear strength was quite constant after the peak strength. The critical state friction parameter showed that the parameter decreased with an increase of the fine aggregate content. Results of the triaxial and direct shear tests indicated also that the fine aggregate content of 30% could be one indicator for soil materials behaving either as sand or as clay materials. Thus fine aggregate content, less than 30% by weight, could be more obtainable for the subgrade materials when leading also to the increased stability of the roads. With the lower fine aggregate content the soils then also show similar and better characteristics of sands not clays. Further studies are recommended on understanding of the mechanical behavior of the decomposed granitic soils.     

建筑废弃物再生工艺及在路基中的应用研究

在香港,所有建筑废弃物必须统一回收、分离与利用。小于50 mm的物料主要用于填土(因为含泥量高);大于50 mm的物料经破碎后,可用于道路路基工程、制砖材料,甚至混凝土结构工程;分离出来的塑料板、纤维板、木屑、纸片等废弃物则必须进行掩埋。利用破碎粘土砖取代一定量的再生混凝土集料,可配制道路基层的混合料,其级配、强度(或CBR值)均满足道路基层材料的要求。     

Use of aggregates produced from marble quarry waste in asphalt pavements

More than 95% of asphalt pavement materials (by weight) consist of aggregates. The highway and construction industries consume a huge amount of aggregates annually causing considerable energy and environmental losses. The aggregates are usually produced from neighborhood aggregate quarries or from natural aggregate sources. As a result of the increasing demands for new aggregate quarries, the general texture of earth's surface has been steadily deteriorating, causing environmental concerns. The use of marble wastes from marble quarries as aggregates might help meet the increasing demands and slow down any detrimental effects on the environment. In this study, recycled aggregates produced from homogeneous marble and andesite quarry wastes in Afyonkarahisar–Iscehisar region were compared to two other aggregate specimens currently used in Afyonkarahisar city asphalt pavements. Los Angeles abrasion, aggregate impact value, freezing and thawing, flakiness index and Marshall stability flow tests were carried out on the aggregate specimens. The test results indicate that the physical properties of the aggregates are within specified limits and these waste materials can potentially be used as aggregates in light to medium trafficked asphalt pavement binder layers.     

Reuse of waste material from decorative quartz solid surfacing in the manufacture of hot bituminous mixes

Due to the increasingly strict environmental restrictions on quarry exploitation, there are severe limitations on the use of natural aggregate for road construction. The accumulation of waste in landfills is also a pressing problem for many businesses, both from an environmental and economic perspective. This article presents the results of a research project, which studied the reuse of engineered quartz (Silestone^®) waste material as aggregate in hot bituminous mixes. After a preliminary study of the material, four bituminous mixes were manufactured, which differed in their percentage of Silestone^® waste aggregate. These mixes were applied to the surface course. Based on the highly satisfactory laboratory results obtained, the mixes were then on an actual road in Almanzora (Spain). The four mixes made from this waste material were found to meet PG-3 specifications, and consequently, were deemed suitable for road surfacing. Nevertheless, since this was the first time that this type of material has been used for this purpose, in the future it will be necessary to test the medium- and long-term mechanical behavior of the road surface.     

Some properties of A sedimentary laterite soil as engineering construction material

A sedimentary laterite soil is examined for its suitability as a construction material by the consideration of its mineralogy and basic geotechnical properties as well as its consolidation and permeability in the compacted state. Three compaction energy levels are utilised. Mineralogically, the soil contains virtually nothing undesirable while its basic geotechnical properties are those generally ascribed to non-problematic soils. The compressibility of the soil varies from moderate to low depending on the energy of compaction. It is however impervious for all the compaction energy levels. The sedimentary laterite soil constitute a good engineering construction material as it has already been successfully used as base and sub-base material in road construction. Results obtained in this study show that this laterite soil is also suitable for use as fill materials in embankment and dam construction.     

Stress distribution in unbound aggregate of road structure: influence of surface roughness and particle shape

Aggregate used for road structures has to meet requirements regarding abrasion, strength and shape. These properties are largely influenced by the crushing operation. To improve these properties the aggregate can be cubicised in a vertical-shaft impact crusher. During this process, sharp edges will be rounded and the surface will be polished, which can have negative effects on road stability. This paper presents laboratory work on the load distribution by aggregate used in the unbound layers of the road structures. The aggregate used had different surface roughness and particle shape. The equipment used was a ring chamber consisting of 15 steel rings. The chamber's diameter was 320 mm and the height was 360 mm. Using this equipment, the stability of aggregates was studied with reference to particle shape and surface roughness for six types of aggregates by measuring the horizontal and the vertical stress that appear under a vertical loading. The grain size of the aggregates used was 8–11.2 mm. The aggregate was divided into three grades of surface roughness, depending on the level of cubicisation. Each level of surface roughness was divided into two groups, one flaky and one more cubic, in order to study the influence of aggregate shape. The laboratory tests showed that aggregate shape had an influence on the aggregate stability. Surface roughness also influenced the stability, but this was not as important as the aggregate shape. Electronic Publication     

Mix design and performance analysis of asphalt concretes with electric arc furnace slag

The paper presents the results of a laboratory study, aimed at verifying the possibility to use two particular typologies of electric arc furnace (EAF) steel slags, in substitution of the natural aggregates, in the composition of wearing course asphalt concrete for flexible pavements. The experimental research has been articulated in a preliminary study of the chemical, leaching, physical, and mechanical properties of the EAF steel slag, and in the following mix design and performance characterisation of the bituminous conglomerates, through gyratory compaction tests, permanent deformations tests, Stiffness Modulus tests at various temperatures, fatigue tests and indirect tensile strength tests. All the mixtures with EAF slag have satisfied the requisites for acceptance in the road sector technical standards, thus resulting as suitable for use in the construction of road infrastructures, moreover presenting higher mechanical characteristics than those of the corresponding asphalts with full natural aggregate.     

Smectite clay identification and quantification as an indicator of basic igneous rock durability

In terms of aerial extent, basic igneous rocks are one of the most used road building materials in South Africa. This is mainly due to the fact that approximately 57% of the surface lithology in South Africa is of poor road construction quality, rendering the localized Karoo dolerite intrusions the best construction material available for many road construction projects. Historically, examples of such non-durable materials have been reported and investigated by many authors and current South African specifications specifically require consideration of this potential phenomenon. There is, however, still the need for an accurate, reasonably quick and inexpensive method of determining material durability in order to identify variations within any one aggregate source. Smectite clay content has been proposed for this task but quantification of the clay mineral content of typical Karoo basic igneous rock aggregates has been problematic in recent studies. Published works have commonly discussed reasons why quantitative X-ray diffraction analysis of clays and some of the techniques developed to qualify and quantify clays using X-ray diffraction are problematic. Recent attempts to quantify clay mineralogy as an indication of basic igneous rock aggregate durability proved inconclusive and lead to a comparative study on X-ray diffraction results obtained using different techniques and by different laboratories. The findings confirmed what that literature suggested and also revealed that proposed specifications based on smectite content are not feasible due to quantification accuracy exceeding some of the proposed limits.