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

一、基本組成及性能
　　UWB水下不分散混凝土絮凝劑是由水溶性高分子聚合物、表面活性物質(zhì)等復(fù)合而成的粉末狀砼外加劑，具有很強的抗分散性和較好的流動性，實現(xiàn)水下混凝土的自流平、自密實，抑制水下施工時水泥和骨料分散，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時，其抗壓強度可達同樣配比時陸上混凝土強度的70％以上。
　　采用表1配合比時水下砼在水中0.4m落差時性能如表2、表3所示：

[ 應(yīng)用實例 1]
　　　　　　　　　　　　　 絮凝劑在水下不分散混凝土中的應(yīng)用

一、試驗材料
水泥： PO42.5 水泥，細度 3500 ㎝ 2 /g ， 28d 抗壓強度 48.6MPa ；
砂：Ⅱ區(qū)中砂，細度模數(shù) 2.8 ，含泥量 2.7% ；
石子：石灰?guī)r碎石，粒徑 5 ～ 20 ㎜，連續(xù)級配，含泥量 0.4% ；
外加劑：絮凝劑；
水：自來水
二、混凝土配比
水泥 430 ㎏ /m 3 ，砂率 40% ，絮凝劑摻量 2.5% （ C × % ），流動性控制：塌落度大于 22 ㎝，塌擴度 40 ～ 50 ㎝。
三、試驗結(jié)果與分析

表 1 攪拌時間對水下不分散混凝土流動性能的影響

從表 1 可以看出，絮凝劑配制的混凝土，攪拌時間在 75s 時，塌擴度值基本趨于穩(wěn)定。
繼續(xù)對不同攪拌時間下的水下不分散混凝土體系的抗分散性進行研究，結(jié)果見表 2 ：
　　　　　　　　　　　 表 2 攪拌時間對水下不分散混凝土抗分散性能的影響

從表 2 可以看出，絮凝劑配制的混凝土，攪拌時間在 75s 時抗分散性能基本趨于穩(wěn)定。
綜合表 1 表 2 數(shù)據(jù)可以看出，當流動性穩(wěn)定時，抗分散性能同樣穩(wěn)定。絮凝劑配制的混凝土需攪拌 75s 以上。

表 3 絮凝劑配制的水下不分散混凝土水陸強度比

從表 3 可以看出，絮凝劑配制的水下不分散混凝土 7d 水陸強度比達到 0.79 ， 28 天水路強度比達到 0.85 。
首先采用了泵送劑對流動性損失的測定方法進行了比較，結(jié)果見表 4 ：

表 4 絮凝劑配制的水下不分散混凝土流動性靜態(tài)損失

從表 4 可以看出，采用泵送劑標準（認為是在靜停狀態(tài)下）測定流動性損失時，絮凝劑水下不分散混凝土 2h 以內(nèi)還能保持 45 ㎝以上的塌擴度。
模擬混凝土泵車進行動態(tài)攪拌，流動性損失見表 5

表 5 絮凝劑配制的水下不分散混凝土流動性動態(tài)損失

從表 5 可以看出，在動態(tài)情況下，絮凝劑配制的水下不分散混凝土 2h 流動性基本無損失。
通過對流動性損失的研究，絮凝劑由于流動性靜停或動態(tài)的損失都很小，可以適用于各種工藝。

表 6 不同的膠結(jié)料用量水下不分散混凝土物理力學(xué)性能

四、結(jié)論
絮凝劑正常摻量可控制在 2.0% ～ 3.0% 范圍。配制的水下不分散混凝土攪拌時間控制 75s 即可滿足要求；其塌擴度能保持 2h 基本不損失?？狗稚⑿阅苊黠@提高， 28d 水陸強度比可達到 85% 以上。在水泥用量 400 ～ 480 ㎏ /m 3 之間時即可滿足 20 ～ 30MPa 的水下混凝土設(shè)計強度要求。

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.