This investigation evaluates: 1) the influence of silica fume content on the strength and resistance to wear of 3-, 7-, 28-, and 91-day moist-cured concretes made with 0, 5, 10, 15, and 20% silica fume replacing a portion of the fine-aggregate; and 2) the influence of various combinations of curing schemes on the strength and resistance to abrasion of the selected fine aggregate-replaced silica fume concretes. A uniform cement factor of 385 kg/m~3 (650 lb/yd~3) and a constant water-cementitious material ratio (wlcrn) of 0.325 are used in all trial mixtures. The fresh and bulk characteristics, such as slump, air content, time of setting, bleeding, unit weight, and compressive strength are obtained to characterize the selected matrixes. ASTM C 779, Procedure C, Ball Bearings, is used to evaluate the resistance to wear. The compressive strength and abrasion. resistance of the fine aggregate-replaced silica fume concretes cured under a continuous moist-curing condition and various combinations of wet-dry curing cycles are compared. The relationships among depth of wear, compressive strength, percentage of silica fume content, and curing age are also studied. Laboratory test results conclude that both the compressive strength and resistance to wear peaked at 10% silica fume content. Silica fume incorporation in concrete by way of fine aggregate replacement did not alter the samples' compressive strength when subjected to the various combinations of wet-dry curing cycles. When compared with continuous moist curing, the selected cycled wet-dry curing conditions caused a modest reduction in resistance to abrasion that varied with silica fume contents, curing cycles, and curing schedules. There was statistically a significant correlation between the dependent variable (depth of wear) and the independent variables (compressive strength, percentage of silica fume content, and curing age) for the samples aged under continuous moistcuring conditions.

    The initial density of micro-silica powder is generally 150-200 kg/m3, transport efficiency is low, not long-distance transport. Encrypted
After treatment, the density can be increased to 500-750 kg/m3. Encrypted micro-silica structure and morphology of the original state of dense micro-silica powder is basically the same, encryption is not caused by micro-morphological changes of silica particles, their particle size distribution is still 10 ~ 100nm between the surface area of silica fume remains unchanged; the same time, encrypted micro-silica powder loading and unloading efficiency, reduce storage space and an area, easy pumping, a high degree of mechanization is suitable for automatic production, on-site feeding no longer appears the phenomenon of fly ash, thus improving the working conditions.

    The concrete production process, the use of encryption is more conducive to micro-silica powder Stir well to improve overall performance of concrete and thus encrypted micro-silica fume in concrete and other building materials is becoming increasingly popular product applications.

  In order to improve the strength of concrete test blocks, technicians often use to increase usage of cement and silica fume approach. Some of the additives used in construction, while the test block did not add admixtures. Such as micro-foam agent reduces the use of mortar strength, and in the test block do not join the micro-foam agents, the actual construction for the convenience of the majority of the construction plus micro-foam agent. Therefore, with the test block is not the entity than the mix of construction projects, resulting in some super-test block up to 100%.

   Cement raw material failed  Many raw materials used in test blocks are not used in practical engineering materials, such as general engineering of cement used in 32.5, but in order to make test pieces, many of the site specifically to buy 42.5 or higher level of cement, gravel, stones of larger sizes . Of course, this test out of certain super-block, but the on-site entities, such material can never be used. 

    As the demand increases, prices rise

Into the second half of the traditional peak season for cement sales, as well as the amount of real estate starts to increase, the amount of cement prices is to continue forever? Can the performance of cement stocks continued strength?

China recently published data on the cement industry, showing that the industry continues to maintain high growth. In August the national monthly and annual cement production rose by 3.4% and 24%, following investment in fixed assets and real estate investment growth.

Relevant personnel, according to industry estimates, cement production this year will be more than 1.6 billion tons, according to an increase of 15.3% growth rate will be higher than the previous year by about 10 percentage points.

3 Zhisi Cheng total demand for cement is important impact of the real estate industry. August real estate investment and development in the Mainland and other data Juncheng chain growth, and analysts expected a whole new area will start to grow, becoming a major force in driving demand for cement.

"From the medium to long term, will show a rising trend in cement prices. First, the industry concentration continues to increase, enterprises increased bargaining power, low-cost disorderly competition reduced; Secondly, the state eliminated the backward production capacity increase in the cost of planning and environmental protection will be support prices of cement. "Yang Dongsen analyst at China Merchants Securities, said.

BNP Paribas analyst recently visited southern and central China study found that the sales of cement companies has reached 1.1-1.2 times the yield ratio, reflecting the stock is falling.

UBS strategy report released earlier holdings of the cement industry has proposed shares, preferred shares of China's building materials; UOB Kay Hian also proposed to buy Chinese building materials, cement and Sinoma shares of landscapes. (silica fume)

　　尽管水泥需求增长，但产能过剩的情况亦已引起中国政府关注。工业和信息化部此前下发《水泥行业准入条件（徵求意见稿）》，拟在多方面提高水泥行业的准入门槛，包括提高项目的资本要求、人均产能高于一定的水平的地区，不批准建新生产线等。

　　法国巴黎银行相信，草拟中的新政策即使落实，于2011年前不会对行业带来实质的影响。该行对水泥行业2010年的前景看法仍然审慎，因预期市场的供求情况将会恶化。从过去的经验看，2004年该行业的固定资产投资虽遭控制，但亦未能扭转翌年行业盈利下滑的发生。

　　“我认为在华东、华南地区，水泥价格存在上升空间。但西部地区则因为新增产能的陆续投产，後市面临压力。”招商证券的杨东森说。

　　对明年水泥业供应过剩的预期，大华继显亦持相似看法。该行相信，去年至今年上半年水泥行业固定资产投资大增，将令今、明两年分别增加2亿和2.2亿吨产能。

　　法国巴黎银行和大华继显分析师均预期，对2010年中国的水泥行业前景看法审慎，除了因新产能增加令供大于求的情况加剧外，中国的基建开支增长明年亦可能见顶，或制约水泥价格上升。

　　上个月底，工信部联合社科院工业经济研究所发布了《2009年中国工业经济运行夏季报告》，工信部总工程师兼新闻发言人朱宏任在发布会上直言，我国产能严重过剩表现得很突出。

　　其中，水泥产能过剩3亿吨，而在建水泥生产线超过200条，又将新增产能超过2亿吨，“目前全国水泥产量在增加，但是利润却在不断下降，像有一些重点水泥生产大省，如浙江、江苏、安徽、山东等省，都存在水泥产能过剩的问题。”朱宏任说。

　　“我相信这个数字是准确的。”宋志平表示，因为工信部在发布这个报告之前和社科院曾做了详细的调研。他认为，中国水泥和平板玻璃产量在今年已经达到了惊人数字，有些完全是出于从国家4万亿投资中“分一杯羹”的考虑，实际上是重复建设。

　　他同时认为，造成目前产能过剩局面的一个重要原因是尚有大量落后产能存在，比如现在有6亿吨产能是属于要被淘汰的小立窑水泥，如果将这部分落后产能淘汰掉，则过剩就不这么明显。

　　小立窑水泥厂一般是十万吨上下规模，北方水泥有限公司执行副总裁庄春来估计，全国大约有3000多家。他同时认为，三年内全部淘汰的难度也比较大，因为各地有各地的实际情况。比如有的地方人口比较分散，几万人口的区域，就一个小水泥厂足够，而建设一个新型干法水泥厂成本相比要高，产量起码要60万吨，这个地区显然用不了这么多水泥。