水土混凝土表面防护技术

水土混凝土表面防护技术１饱和Ｃａ（ＯＨ）２溶液处理试件经饱和溶液Ｃａ（ＯＨ）２处理后，透气系数降低３７．６％，主要原因是饱和溶液Ｃａ（ＯＨ）２。渗透到混凝土的孔隙中，堵塞毛细孔，降低孔隙率。另外，Ｃａ（ＯＨ）２可以提高表面混凝土的碱性。２水玻璃溶液处...

水土对混凝土硫酸盐腐蚀评价方法的改进意见

在水中具有多种化学组分,部分组分对混凝土材料具有腐蚀性,对于工程防腐蚀具有一定的积极作用。在本文中,将就水土对混凝土硫酸盐腐蚀评价方法的改进进行一定的研究。

水工混凝土的碱骨料反应问题

全面比较了水工混凝土与普通混凝土的差异,系统地分析了这些差异在碱骨料反应方面所导致的不同行为。在此基础上发现当碱骨料反应发生时,水工混凝土比普通混凝土有更大的危险性。同时也对在普通混凝土基础上得出的一些评判方法及判据、混凝土安全碱含量等控制指标能否用于水工混凝土提出疑问。

水工混凝土结构损伤的特点和原因浅析

本文较详细地分析了我国水工结构损伤的特点和原因，所得出的结论和建议可为我国水工结构的使用、维修、防护以及耐久性设计提供一定的参考。

粉煤灰水工混凝土施工工艺探讨

论述了原状粉煤灰水工混凝土的特点 ,通过对其材料的选择、配比、拌合、养护工艺的调整与监控 ,有效地提高了混凝土的抗渗、抗冻、物理力学性能及耐久性 。

东部沿海地区水工建筑物混凝土的腐蚀与防护

调查发现江苏省淮海农场的水工建筑物混凝土腐蚀严重 ,几乎每座水工建筑物混凝土都因表面脱落而露出石子 ,严重的露出钢筋。造成沿海地区水工建筑物混凝土腐蚀的主要由冻融、海水浸蚀、冰凌撞击和冰凌的膨胀压力等多种因素 ,但无论是哪种原因 ,都是在设计标号偏低或施工较差的混凝土表面发生的 ,因此 。

日产IHI拌和楼混凝土最佳拌和时间试验

位于三峡左岸98．7m的混凝土拌和系统，装有日产强制式2×45001IHI楼。为确保混凝土拌和系统质量，曾进行过多项参教试验，在混凝土中既要掺粉煤灰，又要掺复合剂，还要接碎冰。为探索生产这种混凝土拌和物的均匀性与其最佳拌和时间，进行了拌和物在不同拌和时间下的考核、混凝土测温试验、坍落度试验和含气量试验。结果表明，拌和时间延长至110s为最佳拌和时间。

论如何加强水工建筑混凝土的施工质量

随着混凝土结构在工程使用越来越广泛,很多质量问题也亟需解决。在建筑工程中,可以发现,混凝土施工过程中最容易出现的问题就是混凝土出现裂缝。所以,相关部门需要重视混凝土施工过程可能出现的问题,并且采取相应的措施提高混凝土的施工质量。文章主要阐述了提高水土建筑工程的混凝土的施工质量的预防措施。

硅粉在水利工程上的应用

结合白石水库、阎王鼻子水库硅粉混凝土的试验研究，介绍了硅粉的性质、硅粉对混凝土性能的影响，阐述了硅粉改变混凝土性能的机理及其在水利工程上的应用。

JM—Ⅶ型减水剂在特细砂砼的应用研究

本文介绍了JM-Ⅶ增强型减水剂对细砂、特细砂砼的作用和在沙坡头导流明渠工程中的应用。

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.

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.

Pore Water Pressure Arising during Pile Drilling in Sand

The pile working load depends on the imperfections which may be taken place in pile-soil system, during pile construction, among many other factors. This subject attracted the researcher＇s attention world wide in the last decades. Types of imperfections either geotechnical or structural are documented in literature and well explained. Nevertheless, the influence of these imperfections in pile load calculations is still ambiguous. The work presented herein is devoted to study soil disturbance during construction of piles using continuous flight auger, CFA. The study of soil disturbance due to drilling needs some evidence. The source of this evidence is field observations collected from four different construction sites, which are documented in this paper. The study concluded that the disturbed zone of soil by CFA has a conical shape and extending laterally to a distance equivalent to ten times of the pile diameter around the auger at the cutting bits and has an inclined surface of4：1 （vertical ： horizontal）. Furthermore excess pore water pressure was induced in soil in the vicinity of pile drilling. Due to this excess pore water pressure, 3.5% to 6.5% of piles constructed by CFA showed percolation of water from the top of the piles through fresh concrete. Also, subsidence of fresh concrete in pile hole was recorded in few of the constructed piles. Pile loading tests showed that the percolation of water and/or subsidence of fresh concrete have not appreciable influence on the load-displacement characteristics of the piles. Moreover, percolation of water at pile heads.

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.