水泥混凝土路面的施工和质量控制

水泥混凝土因其具有施工方便,性能可根据设计调整,抗压强度高,耐久性好,与钢筋等材料的协调性好等优点,被广泛应用于土木工程建筑中。在现代道路与桥梁中,水泥混凝土路面是一种常用的路面结构。但是由于施工质量,气候条件,以及随着重载货运车辆的快速增长,使许多水泥混凝土路面出现了断板、局部沉陷等结构性的损坏;因此,水泥混凝土路面病害,一直影响和困扰水泥面的使用和发展。通过对水泥混凝土路面施工中的一些问题进行分析和治理,提出一些看法。

混凝土路面施工的质量控制

由于混凝土具有施工方便、抗压强度高、耐久性好等优点,被广泛应用于土木工程建筑中。本文主要阐述对混凝土路面的施工质量控制的一些看法。

水泥混凝土路面的养护维修技术应用分析

在我国的路面形式中,水泥混凝土是一种最为高级的材料形式,在近几年来,得到了较大的推广与使用。但在广泛的使用过程中,也出现了一定问题,主要是早期的结构损坏性。这种问题的产生对日常的交通生活有一定的不利影响。因此,进行水泥混凝土路面的养护与维护是十分必要的。本文对水泥混凝土的路面进行了一定研究,提出了针对早期结构性损坏的解决办法,希望能够对以后的水泥混凝土路面的养护维修起到一定的借鉴作用。

公路水泥混凝土路面的施工技术和质量管理

随着我国改革开放的深入，经济快速发展，在各级路面施工中，水泥混凝土路面具有强度高、节省水泥、收缩裂缝少、抗冻和抗渗透能力强、施工进度快、极具及配套极具构造简单、操作方便、价格低廉的优点．所以水泥混凝土路面得到了广泛的应用。然而随着应用广泛的同时，也出现了一系列的问题．大多数水泥混凝土路面难以达到很长的使用年限．在使用过程中也会出现一些严重的缺陷，如：路面的早期断裂、错台边角破损、平整度及粗糙度差等，这些问题不仅对行车磨损带来危害，而且路面的修复费用高，修复难度大，本文从多个角度讨论合理施工的措施，以确保路面工程的质量。

水泥混凝土路面施工质量的控制

分析了水泥混凝土材料质量对公路施工的影响,并阐释了水泥混凝土路面施工质量几个方面的问题。

浅谈混凝土路面断板因素及预防措施

本文主要论述水泥混凝土路面产生断板的因素及预防断板产生的措施,提高混凝土质量,延长混凝土路面使用寿命。

水泥混凝土路面施工应注意的问题

针对当前的道路建设中水泥混凝土的应用问题,分析了水泥混凝土路面的施工技术,结论表明,提高道路工程的施工质量和管理,对于解决道路工程建设中的水泥混凝土路面问题具有重要的意义。

探析农村公路水泥混凝土路面施工技术

随着社会经济的不断发展,以及新农村建设工作的推进,我国农村经济建设工作也取得了较好的发展成绩。目前来说,在农村公路建设工作践行上,也有越来越多的建设项目。在开展农村公路水泥混凝土路面施工的过程中,路面工程是否有出色的品质往往会直接影响农村公路工程的建设效果。为此本文在观点研究的过程中,立足当前农村公路水泥黄凝土路面施工技术进行了观点的研究和分析,基于此提出农村公路水泥混凝土路面的施工方案,为提升农村公路水泥混凝土路面的施工品质,确保农村公路有更长的使用时间提供支撑和帮助。

浅谈水泥混凝土路面病害原因及防治措施

本文针对水泥混凝土路面病害的原因从三个大的方面进行分析,并从每个大的方面提出相应的防治措施。

Mechanical properties of pervious cement concrete

Compressive and flexural strength,fracture energy,as well as fatigue property of pervious cement concrete with either supplementary cementitious materials (SCMs) or polymer intensified,were analyzed.Test results show that the strength development of SCM-modified pervious concrete (SPC) differs from that of polymer-intensified pervious concrete (PPC),and porosity has little effect on their strength growth.PPC has higher flexural strength and remarkably higher flexural-to-compressive strength ratio than SPC at the same porosity level.Results from fracture test of pervious concrete mixes with porosity around 19.5% show that the fracture energy increases with increasing the dosage of polymer,reflecting the ductile damage features rather than brittleness.PPC displays far longer fatigue life than SPC for any given failure probability and at any stress level.It is proved that two-parameter Weibull probability function describes the flexural fatigue of pervious concrete.

Possibility of Sea Water as Mixing Water in Concrete

In the near future, fresh water will be very difficult to get and scarce. It is said that in 2025 half of the mankind will live in the areas where fresh water is not enough. Also, UN and WMO （World Meteorological Organization） are predicting five billion people will be in short of even drinking water. Also, in the present, there are some areas where sea water or chloride contained sand are used as mixing water with or without intension. The authors believe that the possibilities of using sea water as mixing water in concrete should be investigated seriously. In this paper, the authors would like to show various possibilities of using sea water as mixing water in RC （reinforced concrete） members. The possibilities are shown as follows： （1） mixed with pozzolanic materials （Blast furnace slag powder, etc.） expecting to fix the free chloride ion; （2） Mixed with corrosion inhibitor; （3） reinforced with stainless steel or corrosion resistant reinforcement; and （4） used in very dry or submerged conditions.

Analysis of Waste in the Production of Concrete Blocks---A Case Study in the Goias Industry

An ever more demanding consumer market and the need for companies to be more competitive have led organizations to try to eliminate waste. This research is a case study which presents a proposal for intervention in order to improve performance of a pre-cast concrete block factory in outer Goihnia. As a first step, waste in the production process was identified through analysis of data on time involved in each step of the process. Then, applying the concepts of lean production, a list of activities was drawn up with a view to eliminating non-value-added work, identifying waste, decreasing cycle time, streamlining the production process and increasing the flexibility and transparency of the process. From the results, it was possible to identify the sources of waste and provide management with information for strategic decisions about production. Finally, various suggestions were made with a view to eliminating or mitigating bottlenecks in the production process.

Current State of High 120 m Concrete Dam Bratsk Hydroelectric Power Plant

The research object was high 120 m concrete gravity dam of the Angara Bratsk hydroelectric power plant. The state of the concrete dam is estimated based on the results of continuous supervision performed by site personnel as well as periodic monitoring. According to the classification of the interrelations in the system ＂concrete-environment＂, there were selected some important parts of dams and a comprehensive analysis of concrete was executed on these parts. Concerning the complex research of concrete, a combination of full-scale tests with core-sampling has been proposed. Core samples tests had an object to study the deep concrete layers and to determine the specific indicators such as strength, density, porosity, comparative diameter of capillary pores, CaO content in cement stone and others. Obtained findings and recommended criteria can be applied when selecting technologies for constructing dams that guarantee their durability in the north.

High-Volume Fly Ash Concrete-A Relevant Step to Sustainable Development

HVFA （high-volume fly ash） concrete could be a sustainable way for by-product utilization to conserve natural resources and protect environment. HVFA concrete can play the role of a high-performance material that may be comparable to the conventional Portland cement concrete. The results of the research programme concerning the relationships between the composition of concrete （w/b ratio, fly ash content and type of cement） and their physical and mechanical properties are presented and discussed in the paper. It is found that the introduction of high-volume fly ash into concrete has caused a decrease in compressive strength at the early age of storage. The significant increase in strength was observed between 28 days and 90 days of curing. The high-volume fly ash concretes were characterized with lower water absorbability and sorptivity than control concrete.

Lightweight Concrete Using Local Industrial By-product

Construction is one of the largest users of energy, material resources and water and it is a formidable polluter. One of the major materials used in construction is concrete and ordinary concrete contains about 12% cement which is a major producer of greenhouse gas in the world. The use of waste materials as partial replacement of cement in concrete reduces greenhouse gases, frees up land fill space, and reduces raw materials consumption. This contributes towards sustainable development, as in a sustainable society, nature is not subject to systematically increasing concentrations of substances extracted from the earth＇s crust. This research work explores the possibility of replacing some percentage of cement in concrete with marble sludge powder to produce lightweight concrete. This was achieved by determining the compressive strength and some hardened properties of concrete like sorptivity and carbonation with marble sludge. The results so far have been able to prove that lightweight concrete can be produced when some percentage of cement is replaced with this waste.

Production and Properties of Superplasticized Concrete

The objective of this research is to study the effect of grinding powdered superplasticizer, Portland cement, sand, and silica fume on the properties of fresh and hardened concrete. Lose Angeles Machine was used to grind these constituents. The program was arranged to determine the effect of cycles＇ number, superplasticizer type and dosage, silica fume dosage and condition, and gravel to sand ratio on properties of concrete. Naphthalene sulphonated formaldehyde （NSF） superplasticizers in the forms of liquid and powdered were used. Silica fume may be grinded with the other constituents （grinded）, or added to concrete mixer （normal）. The water/cement （w/c） ratio varied from 0.35 to 0.55 to achieve a constant slump （50-90 mm）. Slumps, bulk density and mechanical properties of concrete were measured. Scanning electron microscope （SEM） was also used to show the differences between traditional and superplasticized concrete. The results showed that grinding the mixture enhances fresh and hardened concrete properties. It is also observed that grinding the mixture for 500 cycles is more effective than other numbers of grinding. In addition, superplasticized concrete exhibits compressive strength higher than traditional one at varied ages. Moreover, using powdered superplasticizer has a remarkable effect on enhancing concrete properties rather than using it in a liquid form. A dosage of 1% by weight of cement gave the highest results of compressive strength. Silica fume has an essential role in improving concrete strength and durability since it acts as very efficient void filler and as a super pozzolana. SEM observations illustrate that grinding the mixture enhances transition zone （TZ） properties and makes it denser. On the other hand, grinded mixture can be packaged in bags and transported for use in crowded cities, and so, enhances quality control, since the only requirement to obtain superplasticized concrete is to add water and gravel. This technique has many benefits such as; saving cement, labor and noise, high quality control, and enhancing concrete permeability and durability. There are many fields of application of superplasticized concrete such as; in locations which are not easily accessible by ordinary concreting techniques, in repairing and strengthen, thin coating, and for small projects when ready mix supply is not feasible.

Experimental Study on the Use of Trass as a Supplementary Cementitious Material in Pervious Concrete

Abstract： The purpose of this paper is to evaluate the suitability of using trass as a supplementary cementing material in pervious concrete. OPC （Ordinary Portland Cement） was replaced in the concrete mix by 15%, 25% and 35% weight percentages and the results were compared with reference mixtures with 100% Portland cement. The variables in this study were trass content, aggregate size and water to cement ratio. Sixteen eases of concrete mixtures were tested to study physical and mechanical properties of hardened concrete, including porosity, permeability, compressive strength, splitting-tensile strength and flexural strength at various ages. Results indicated that mechanical properties of the pervious concrete marginally decreased with the increased content of trass when compared to the reference mixtures. However, at later ages the differences were insignificant.

Creep of Concrete in Contemporary Code-Type Models

The paper presents and compares the conventional models for creep in cement concrete included in the ACI （American Concrete Institute） guide, Eurocode 2 andfib （International Federation for Structural Concrete） Model Code 2010. For the presentation and comparison of the creep models, creep coefficients are developed. The main factors affecting the prediction of creep in concrete are outlined, comparing the influence of concrete grade, environmental conditions, member size and loading conditions. Most of the conventional models currently used for creep in cement concrete develop the code-type procedures and are calibrated for normal- and high-strength concretes. They enable a more accurate analysis and better assessment of the time-dependent deformation of concrete structures at the design stage. Their complexity is significantly reduced and a range of influencing parameters are excluded from the models for simplicity and easy adaptation. The comparison of the models shows that thefib Model Code 2010 model is more consistent and calibrated to avoid shortcomings in the previous models.

Concrete Based on Fly Ash Alumosilicate Polymers

Concretes on the basis of the alumosilicate polymer can be prepared by alkali activation （NaOH, sodium water glass） of waste brown coal fly ash. The preparation is possible： （1） by using a short-term heating of the concrete mix （to 80 ℃）; or （2） by allowing the mix to harden spontaneously at a temperature of 20 ℃. The concretes prepared by short-time heating attain high strength values after their preparation; the values are comparable to those characterizing concretes obtained on the basis of Portland cement. The strength development of concretes hardening at 20 ℃ is substantially less steep but, nevertheless, the strength attained after about 60 days is practically identical with that of the concretes exposed to a short-time heating. The shrinkage of concretes prepared by short-time heating is very small as compared with the concretes allowed to harden spontaneously; the shrinkage of latter concretes is larger than that of the concretes on the basis of Portland cement. The concretes on the basis of alumosilicate polymer exhibit much better resistance to the corrosive action of the environment as compared with those prepared on the basis of Portland cement.

Experimental Study of Concrete Column Shape Modification Using Fiber Reinforced Polymer Composite Shells and Expansive Cement Concrete

Fiber Reinforced Polymer （FRP） composites are an effective material for strengthening circular concrete columns. The effectiveness of FRP confinement for square and rectangular columns is greatly reduced due to stress concentrations at the sharp comers and loss of the membrane effect at the fiat sides of the cross-section. Shape modification can eliminate the effects of column comers and flat sides, and thereby restore the membrane effect and improve the compressive behavior of FRP-confined square and rectangular concrete columns. Shape modification using chemical post-tensioning, achieved by using expansive cement concrete, is described and several mix designs for obtaining the optimal level of expansion are presented. In addition, parametric studies regarding the optimal geometry of the shape-modified cross-section are presented utilizing the analytical model.