Natural Aggregates at Makkah Governate, Western Saudi Arabia

 Natural coarse and fine aggregates which accumulated along six selected wadis in the region of Makkah were assessed both qualitatively and quantitatively. The six wadis were Numan, Al-Yamanyah, Al-Shamyah, Hwarah, Alaf and Faydah. More than 440 aggregate samples were collected and their physical, mechanical and chemical properties determined. Petrographic studies on the gravel samples were undertaken to characterise the aggregate types. The results were compared with ASTM and British Standard specifications. The aggregates were generally within the acceptable limits for use in concrete although there were the relatively high values of chloride, sulphate and total dissolved salts in the fine aggregates in Wadis Alaf, Hwarah and Faydah. Nine fine aggregate samples representing upstream, midstream and downstream deposits from these saline wadis were washed in distilled waters after which the aggregates were within the acceptable limits for structural concrete. There were indications of material which could cause alkali-silica in the coarse aggregate at Wadi Faydah. The study proved reserves of 12.5 million m³ of coarse aggregate and 23 million m³ of fine aggregate. Received: 27 May 1998 · Accepted: 18 February 1999     

Characteristics and the environmental acceptability of the natural stone quarrying waste rocks

The paper summarises the results of a study by the Geological Survey of Finland on the potential use of waste rocks from natural stone quarry production. Petrographic, chemical, mechanical and physical tests were undertaken on granite, rapakivi granite, migmatite, syenite, diorite, gabbro, anorthosite gabbro, schist and soapstone from 33 dimension stone quarries in Finland. The results indicate the waste rocks of Finnish natural stone quarries can generally be considered environmentally sound with potential uses in other industries.     

Concrete with recycled concrete aggregate and crushed clay bricks

In the last two decades, a variety of recycling methods for construction and demolition wastes (CDW) have been developed. For instance, as one of the major components in CDW, concrete rubble has been used to replace natural aggregate after being treated. This is known as recycled concrete aggregate (RCA). The property and use of RCA for structural or non-structural concrete have been extensively studied and numerous findings have been adopted in engineering practice to produce sustainable concrete. Concrete rubble, however, is inevitably mixed with other wastes such as crushed clay bricks (CCB). The level of inclusion varies depending on the original construction materials of demolished buildings. The differing properties of CCB from RCA will affect the mix design as well as the physical and mechanical properties of the resulting new concrete when the inclusion level exceeds a certain limit. Separating CCB from RCA presents an operational difficulty in practice and also has huge cost implications. Therefore, it is important to study the effect of CCB with various inclusion levels on the properties of fresh and hardened concrete. This paper reports on a study conducted to investigate the physical and mechanical properties of recycled concrete with high inclusion levels of RCA and CCB and to explore the potential or the limitation of this type of mixed recycled aggregate in primary concrete structures.     

Basic geotechnical properties,chemistry and mineralogy of some laterite soils from S.W. Nigeria

Laterite soils derived from four basement complex rocks and a sedimentary formation from Southwestern Nigeria are analysed for their basic geotechnical properties, chemistry and mineralogy. Results obtained show that the granite gneiss derived and the sedimentary laterite soils are good engineering materials. The amphibolite derived laterite soil has a linear shrinkage of 10% and contains SO ₄ ^2? ions. The quartz schist derived and the micaschist derived laterite soils contain rather high amounts of muscovite ?30% and 25% respectively. The usability of the laterite soils and the implications of the presence of SO ₄ ^2? ions and mica and the high linear shrinkage are discussed.     

An investigation into the influence of size on the mechanical properties of aggregates

Tests have been carried out according to British Standard BS 812-1975 on non-standard and standard size aggregates to study the influence of aggregate size on mechanical properties. Dolerite, granite, limestone aggregates of different sizes have been tested. No basic relations have been found between elongation index, I_E, and flakiness index, I_F, and the different aggregate sizes. Aggregate impact value, AIV, aggregate crushing value, ACV, and 10 per cent fines loads, however, are aggregate size dependent. Tests on larger aggregate sizes give higher test values, whereas tests on smaller aggregate sizes give lower values than test results for standard size aggregates. For each rock type there is a different set of sieve sizes, from those recommended in BS 812-1975, which give the same values as the standard sieve sizes. Additionally, relations have been determined for the mechanical test results for the different size aggregates.     

废弃混凝土再生系列材料用于预拌混凝土中的试验研究

通过对废弃路面混凝土进行破碎,将其破碎成5～31.5mm作为再生粗骨料,代替部分天然碎石;而5mm以下的颗粒通过掺入一定激发剂后粉磨,作为再生掺合料代替矿粉掺入到混凝土中。本文对再生系列材料用于预拌混凝土中的各项力学性能和耐久性能进行了试验和研究,对促进行业节能减排,推动建筑垃圾应用于工程实践有一定的指导意义。     

Effects of microfissures on the engineering properties of the marble at Wadi Lisb,Saudi Arabia

The marble at Wadi Lisb was investigated in detail in order to assess its engineering properties and to examine the effect of the microfissures on these properties. The marble is white with some dark bands containing the microfissures and parallel to the regional foliation direction. The samples that are cut parallel to these dark bands have better physical and mechanical properties than those cut perpendicular to them. The general effect of the microfissures on Wadi Lisb marble is similar to their effect on Al Madrakah marble indicating a regional phenomenon. During the quarrying operation, it is recommended to take the direction of the microfissures in consideration and to correct for any deviation during the slapping process.     

湖南省炎陵县花岗岩残积土的岩土工程特性

本文对花岗岩残积土的物理力学性质、岩土工程特性进行了详细分析,希望为同类工程提供借鉴。     

Thermal deterioration of high-temperature granite after cooling shock: multiple-identification and damage mechanism

Cooling shock has a significant thermal deterioration (TD) on the physical and mechanical properties of rocks in high-temperature conditions, which is a critical concern for the engineering application of the cyclic hydraulic fracturing technique in an enhanced geothermal system (EGS). In this work, cooling shock tests were carried out on granite samples to evaluate the actual TD of high-temperature rocks by cooling shocks, and multiple test methods were used to explore the effect of TD on the corresponding physical and mechanical properties of high-temperature granite. Some core conclusions from the study are as follows: (1) The wave velocity and apparent resistivity (AR) can reflect the thermal damage effect of cooling shocks on high-temperature granite. Notably, the higher the temperature of granite, the more significant change in wave velocity and AR. (2) The stress-strain curve tends to be smooth with the granite temperature increases and the cooling shocks intensify, the quiet period of acoustic emission (AE) events is lengthened, and the number is gradually reduced. (3) The TD effect of the cooling shock tends to be more significant for the samples at temperatures above 550 °C, and the peak stress continues to decrease with cooling shock strengthen. Furthermore, thermal stress is the main cause of TD to high-temperature granite. This study has the potential to guide the use of the cooling shock effect in extraction applications of geothermal engineering.

     

Performance of mortar and concrete made with a fine aggregate of desert sand

At this moment there is no national specification concerning the application of desert sand with very fine grain. To be able to apply desert sand to mortar and concrete in civil engineering, mortar and concrete made of Tenggeli desert sand and Maowusu sandy land sand have been tested in order to clarify their engineering characteristics. Based on the determined chemical composition and the physical characteristics of desert sand, the mechanical properties of mortar and concrete made of two types of desert sand as fine aggregate were investigated. The results of the tests indicate that desert sand can be used as a fine aggregate in mortar and concrete for general civil engineering.     

再生细骨料混凝土材料性能与结构行为研究评述

国内外采用再生粗骨料制备再生骨料混凝土技术已较为成熟,已有成功的示范工程应用,在一定程度上缓解了工程对天然粗骨料的需求。然而,占再生骨料总质量约4%～60%的再生细骨料难以高效利用,造成资源浪费,加剧天然砂短缺趋势。文章基于大量的文献研究,旨在深入剖析再生细骨料混凝土材料与结构性能,揭示包括工作性能、力学性能和结构行为在内的再生细骨料混凝土性能特征,找出内在劣化规律,提炼再生细骨料混凝土应用和研究的目标和方向,为安全推广再生细骨料混凝土应用提供理论基础和研究依据。研究表明,再生细骨料的微观孔隙是造成再生细骨料混凝土性能复杂性的主要原因;再生细骨料对混凝土的工作性能和力学性能有不利影响,但通过调整水灰比和减水剂用量等方式,可以达到良好的工作性能和力学性能;相比相同抗压强度等级的天然骨料混凝土,再生细骨料混凝土的抗拉强度和弹性模量较低;再生细骨料混凝土构件的正截面承载能力与天然骨料混凝土构件相近,但其抗剪性能和与钢筋的锚固性能有待进一步研究。     

基于力学性能的吸附砂浆界限含量分析

基于再生粗骨料吸附砂浆定量分析及文献数据,研究吸附砂浆含量变化与再生粗骨料物理性能之间的关系,以及再生粗骨料取代率为100％的再生混凝土在不同吸附砂浆含量下的力学性能演化规律;以吸附砂浆含量为自变量、力学性能为因变量、目标强度为限值,利用数学方法确定吸附砂浆界限含量.研究发现:随着吸附砂浆含量的增加,再生粗骨料的物理性...     

Influence of parent concrete on the properties of recycled aggregate concrete

This paper discusses first the properties of recycled aggregates derived from parent concrete (PC) of three strengths, each of them made with three maximum sizes of aggregates. The relative physical and mechanical properties of fresh granite aggregate are discussed. Using these nine recycled aggregates, three strengths of recycled aggregate concrete (RAC) were made and studied. Typical relationship between water–cement ratio, compressive strength, aggregate-cement ratio and cement content have been formulated for RAC and compared with those of PC. RAC requires relatively lower water–cement ratio as compared to PC to achieve a particular compressive strength. The difference in strength between PC and RAC increases with strength of concrete. The relative evaluation of tensile and flexural strengths and modulus of elasticity has also been made.     

Effect of aggregate type on properties of hardened self-consolidating lightweight concrete (SCLC)

In this study, the effects of aggregate type on the physical and mechanical properties of hardened self-consolidating concrete produced with lightweight aggregate (SCLC) were investigated. In experiments, three coarse lightweight aggregate (LWA) types, pumice, volcanic tuff and diatomite, and normal limestone aggregate were used. Different combinations of water to binder ratio and superplasticizer dosage levels were prepared for the SCLC mixtures. The total powder content (cement and mineral additives) was constant in the experiments. Physical properties such as thermal conductivity, dry unit weight, porosity and capillarity; mechanical properties such as compressive and splitting tensile strength, modulus of elasticity and abrasion resistance were determined in hardened condition. The results, in general, showed that SCLC with LWA in lower unit weight has lower mechanical and physical properties except for thermal properties when compared to properties of SCC.     

基于实际分布的花岗岩颗粒流模拟几何模型

岩石通常由不同组分组成,这些组分之间的类别差异与相互作用决定了岩石的宏观物理力学性质。以花岗岩为例,使用灰度阈值分割技术确定岩石中细观组分的具体类别与实际位置,使用平行连接表征颗粒间的胶结物,使用簇粒和聚粒分别表征黑云母、长石和石英,建立了考虑细观组分实际类型和分布的花岗岩颗粒流数值模拟的几何模型。结果表明:使用数字图像处理所得组分类型和位置可以作为建立数值模拟几何模型的基本数据;不同组分可以使用簇粒和聚粒来表征;不同组分的细观物理力学参数对花岗岩宏观力学行为有较大影响。由于细观组分的实际分布与细观物理力学性质控制了岩石的变形破坏过程,本文方法为研究岩石材料力学行为提供了一条新的研究途径。     

再生混凝土基本物理力学性能试验再研究与分析

通过实验,对再生骨料的物理性能做了研究,分析了其与天然骨料产生差别的原因,并对再生混凝土的基本力学性能进行了再研究,与天然混凝土作对比后,指出配制混凝土时天然骨料可被再生骨料部分取代配得满足强度要求的混凝土材料,达到节约骨料资源,废物再利用的目的。     

泉州地区花岗岩残积土地质特征与岩土工程评价

泉州地区广泛分布的花岗岩残积土,由变质-混合岩、酸性-中酸性火山岩和花岗岩风化而成,是一种成分复杂、物理力学指标变化区间很大的特殊性土体,其工程性质主要受母岩及其风化程度的影响,与风化残积物中的成分、结构,特别是粗颗粒含量关系密切,并具有随深度规律变化的特征。本文所称的花岗岩属花岗岩类岩石,包括变质-混合花岗岩、酸性-...     

建筑固废物再生粒料基层混合料的性能研究

在研究天然集料(NA)、再生混凝土集料(RCA)、再生砖渣与混凝土集料(RBCA)物理力学性质的基础上,开展了不同RCA掺量(质量分数,下同)及掺30%砖渣的混合料CBR(California bearing ratio)试验,探讨了压实度、含水率对混合料动回弹模量的影响.结果表明:RCA掺量越大,混合料CBR值与动回弹模量均越大;掺入30%砖渣后,混合料CBR值与动回弹模量均降低明显,表明工程应用中应适当控制砖渣掺量;压实度对RCA混合料的动回弹模量影响最大,对RBCA混合料的影响次之,对NA混合料的影响最小;含水率对NA混合料的动回弹模量影响较小,而对RCA、RBCA混合料的影响较大.该研究可为建筑固废物混合料用作道路结构层提供参考.     

中天山特长隧道花岗岩段岩爆预测判据选取研究

针对南疆铁路吐库二线中天山特长隧道花岗岩段特点,对岩爆预测判据选取进行了研究,确定了中天山隧道隧址区的花岗岩岩性物理力学指标、开挖段洞壁应力分布以及合适的岩爆预测判据等关键技术问题。