UWB水下不分散混凝土絮凝剂Underwater anti-washout concrete Admixture

一、基本组成及性能
　　UWB水下不分散混凝土絮凝剂是由水溶性高分子聚合物、表面活性物质等复合而成的粉末状砼外加剂，具有很强的抗分散性和较好的流动性，实现水下混凝土的自流平、自密实，抑制水下施工时水泥和骨料分散，并且不污染施工水域。加入UWB的水下砼，在水中落差0.3～0.5m时，其抗压强度可达同样配比时陆上混凝土强度的70％以上。
　　采用表1配合比时水下砼在水中0.4m落差时性能如表2、表3所示：

[ 应用实例 1]
　　　　　　　　　　　　　 絮凝剂在水下不分散混凝土中的应用

一、试验材料
水泥： PO42.5 水泥，细度 3500 ㎝ 2 /g ， 28d 抗压强度 48.6MPa ；
砂：Ⅱ区中砂，细度模数 2.8 ，含泥量 2.7% ；
石子：石灰岩碎石，粒径 5 ～ 20 ㎜，连续级配，含泥量 0.4% ；
外加剂：絮凝剂；
水：自来水
二、混凝土配比
水泥 430 ㎏ /m 3 ，砂率 40% ，絮凝剂掺量 2.5% （ C × % ），流动性控制：塌落度大于 22 ㎝，塌扩度 40 ～ 50 ㎝。
三、试验结果与分析

表 1 搅拌时间对水下不分散混凝土流动性能的影响

从表 1 可以看出，絮凝剂配制的混凝土，搅拌时间在 75s 时，塌扩度值基本趋于稳定。
继续对不同搅拌时间下的水下不分散混凝土体系的抗分散性进行研究，结果见表 2 ：
　　　　　　　　　　　 表 2 搅拌时间对水下不分散混凝土抗分散性能的影响

从表 2 可以看出，絮凝剂配制的混凝土，搅拌时间在 75s 时抗分散性能基本趋于稳定。
综合表 1 表 2 数据可以看出，当流动性稳定时，抗分散性能同样稳定。絮凝剂配制的混凝土需搅拌 75s 以上。

表 3 絮凝剂配制的水下不分散混凝土水陆强度比

从表 3 可以看出，絮凝剂配制的水下不分散混凝土 7d 水陆强度比达到 0.79 ， 28 天水路强度比达到 0.85 。
首先采用了泵送剂对流动性损失的测定方法进行了比较，结果见表 4 ：

表 4 絮凝剂配制的水下不分散混凝土流动性静态损失

从表 4 可以看出，采用泵送剂标准（认为是在静停状态下）测定流动性损失时，絮凝剂水下不分散混凝土 2h 以内还能保持 45 ㎝以上的塌扩度。
模拟混凝土泵车进行动态搅拌，流动性损失见表 5

表 5 絮凝剂配制的水下不分散混凝土流动性动态损失

从表 5 可以看出，在动态情况下，絮凝剂配制的水下不分散混凝土 2h 流动性基本无损失。
通过对流动性损失的研究，絮凝剂由于流动性静停或动态的损失都很小，可以适用于各种工艺。

表 6 不同的胶结料用量水下不分散混凝土物理力学性能

四、结论
絮凝剂正常掺量可控制在 2.0% ～ 3.0% 范围。配制的水下不分散混凝土搅拌时间控制 75s 即可满足要求；其塌扩度能保持 2h 基本不损失。抗分散性能明显提高， 28d 水陆强度比可达到 85% 以上。在水泥用量 400 ～ 480 ㎏ /m 3 之间时即可满足 20 ～ 30MPa 的水下混凝土设计强度要求。

Special Construction Material
Non-dispersible Underwater Concrete Admixture

Introduction
　　 Dewater of hydraulic structures for construction and repair is difficult and expensive. In recent years, as concrete structures in harbor, bridge, and marine construction has become larger in the scale, the need for non-dispersible (or antiwashout) underwater concretes (UWB) to assure correct underwater placement has been increasing.
　　 Non-dispersible Under-Water Concrete (UWB ) can be placed and self-leveled and self-compacted at any place under water. It is mainly a special admixture called flocculent made the underwater concrete, which are composed of water-soluble high polymers, inorganic mineral powders, superplasticizers and other admixtures .The following effects are produced when the UWB flocculent is used in Concrete:

　　[1]. Cohesiveness, mobility and self-leveling characteristics are increased. No pollution in water.
　　[2]. High plasticity and suitable viscosity, and self-compacting in water.
　　[3]. When the concrete is allowed to free-fall through water,there is hardly any segregation. No bleeding
　　[4]. Retardation in setting and less change in flow with time when placed in water
　　[5]. Good bond with old concrete and less strength loss in water.

Application of the UWB flocculent
（ 1 ） Antiwashout
　　 The major requirements for the UWB are antiwashout or segregation resistance, flowability, self-leveling ability and bleeding control. The UWB concrete are produced by the addition of polymeric admixtures, namely flocculent or antiwashout admixtures, at ratios of 1.0 to 3.0% by weight of cement in the mix during the mixing of ordinary cement concrete.
　　 By using the polymer admixture, the ordinary concrete, which can't resist water washing, can be changed into the non-dispersible underwater concrete, which has very well workability and very high anti-washing ability. The UWB concrete is now an essential part of diversity and great reliability of underwater civil engineering wor k.

（ 2 ） Pumping property
　　 Non-dispersible concrete can be pumped easily, this is realized by adjusting the slump flow of the fresh concrete. Generally, 200m is the pumping distance.

（ 3 ） Save the construction cost
　　 Non-dispersible concrete can be poured into water filled form without a tremie pipe to produce dense structural repairs. This type of material has particular advantages over conventional concrete both in terms of the quality of the repairs produced and the reduction in placement cost associated plant and diver manpower requirements.

Application areas
In a word, the applications of the UWB concrete are outline below:
•  Gap filling work, taking advantages of its flow properties;
•  High-quality underwater concrete, particularly where material segregation is a concern;
•  Construction work where particular attention must be paid to the prevention of water pollution;
•  Underwater reinforced concrete structures;
•  Corrosion-protecting linings for steel pipe piles and steel sheet piles;
•  Consolidation of stones and ruffle mounds;
•  Disaster recovery work, repairs, and reinforcement work.

Market and Benefit
　　Non-dispersible(antiwashout) underwater concrete is quite different in concept from conventional concrete. Many real construction projects showed that the effect of this concrete is not only to greatly improve the reliability of concrete placed under water (both fresh and salt water), but it has remarkable effects on environmental preservation in the construction area; fish can even observe the work.
　　 Substantial advances have been made in underwater concrete technology with our nearly 20 years experience in this field. The development of better understanding of material properties and mix proportioning practices affect the performance of underwater concrete. Generally, using UWB technology can save the comprehensive cost 20% or more.

Items on technical service in place

1.Technical data

2 、 MUHU is dedicated to researching, developing and producing various cconcrete additives, and providing relevant technical services.

3 、 If our UWB admixture was used, We will responsible for technical service in place. We can solve various problems with the builders and owner of the construction project together according to the requirement of concrete compressive strength, water cement ratio, pump placing and slump retention and the filed circumstances.

 Appearance, Packaging, Handle and Storage
Appearance
　　 UWB flocculent or antiwashout admixtures, is solid and stable powder, packed into sacks which are made of kraft with plastic film liner. Net weight of each sack is 25.0 ± 0.2kg .

Packaging and Handling
　　 Care should be taken during handling operation in order to avoid damage and rain-drenched. Protect from physical damage.   Handle with care and do not open toughly in  order to avoid dust. 
Storage
　　 The products should be stored in a suitable dry building.  Around 2 years of storage period is recommended for these products.  For storage periods in excess of  2 year, the products should be retested prior to use. Store in a cool, dry, ventilated area  away from sources of heat, moisture and incompatibilities.

Disposal Considerations
　　 Whatever cannot be saved for recovery or recycling should be managed in an appropriate and approved waste facility. This material may exhibit one or more characteristics of a hazardous waste and require appropriate analysis to determine specific disposal requirements. Processing, use or contamination of this product may  change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container or sacks and unused contents is in accordance with federal, state and local requirements.