Compound and Engineering Application of Fiber Reinforced Concrete with Low Shrinkage

Transcription

1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Compound and Engineering Application of Fiber Reinforced Concrete with Low Shrinkage Jianfen Li 1,a, Shujin Li 1,b 1 Changzhou Key Lab of Construction Engineering Structure and Material Properties, Changzhou Institute of Technology, Changzhou a @qq.com, b @qq.com, Key words: fiber reinforced;low shrinkage concrete; compound; expansive belt Abstract: On the basis of experimental research about PVA fiber concrete, combined with the technology measures such as expansive belt, construction quality monitoring, the jointless design and construction is successfully carried out for an industry tank. The water storage test results showed that impervious performances can meet the requirements of specification and achieved desired effects. Engineering overview With the rapid development of construction industry, reinforced concrete structure appeared superlong, oversized trend, and the shrinkage in hardening process of deformation greatly increased the risk of permeable crack. For the large underground industry tank, due to the inherent property of the concrete material itself and the unique plate (shell) system and the restraint form, the requirement for anti-seepage, crack resistance of concrete is higher [1], we should take effective measures to control the non-structural cracks, ensure egineering quality. In this paper, combined with the seamless design and construction of,a large underground industry tank (165.4m long, 73.0m wide, 4.8m deep as shown in Fig.1) in Changzhou City, Jiangsu Province, through the experimental study of shrinkage compensating concrete expansion performance of PVA fiber of structural parts, different in various underground industry tank (bottom, wall panels, roof), with different low shrinkage concrete admixture quantity expansion, and expansion belt to replace post pouring belt [2,3] in original design drawings, to enhance the quality of construction monitoring technology, the jointless design and construction is successfully carried out for an industry tank. The Fig.1 Level diagram of the industry tank storage test showed that anti-seepage, crack resistance performance meeted the requirements, So far,the tank was built and put into use for more than a year, And through one cycle of the seasons, there was no seepage and crack appeared. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-05/03/16,16:35:02)

2 874 Materials and Processes Technologies V Experimental study Raw materials and mix proportion of experiment This industry tank using PO 42.5 ordinary portland cement, initial setting time is 180min, final setting time is 255min; Using sand II with fineness modulus of 2.4 and continuous grain stone with particle size of 5-20mm, crushing value 6.9% and grade I fly ash with moisture content of 0.6%, water demand ratio 91%, Addition of fly ash is to delay and reduce the heat, release time of hydration heat of cement; JM- Ⅲ improved (crack, seepage) concrete expansive agent was slightly red powder and its water reducing rate was 18.4%, PVA fiber s diameter is 20 μ m, length is 12mm, tensile strength is 1360MPa, elastic modulus is 36GPa. Considering pool wall is constrained, in order to improve its crack resistance capacity of compensation, limited expansion ratio design values were higher one grade than the bottom, with 0.9kg/m3 PVA fibers. concrete mix proportion of industry tank for various structural parts was in table 1. Table 1 The concrete mix proportion of industry tank for various structural parts(kg/m 3 ) No. cement sand gravel fly ash JM-Ⅲ water PVA iber DB QB JQD Results and analysis of experiment Low shrinkage concrete required detection of slump before molding and forming blocks of compressive strength, splitting tensile strength, permeability test. The compressive strength, splitting tensile strength test cube used side length of 150mm, three as a group, determinate intensity values after standard curing 28d. Resistance to water penetration test used seepage height method, specimen was cone with upper diameter of 175mm, and round orifice diameter of 185mm, and height of 150mm. Specimens were fixed in the 28d standard curing concrete anti permeability tester, the water pressure is stable in 24h in 1.2MPa, the observation of specimens were no seepage face. The seepage height was measured after split, used average value of a set of six test pieces as the measured value. The specimen size for expansion and drying shrinkage rate was 100mm 100mm 300mm,and middle longitudinal limiter was embedded. After forming 12h stripping, measuring the initial length; after immersion (20 ± 2) water conservation, 3D, 7d, 14d were measured in length; and then moved into temperature (20 ± 2), relative humidity (60 ± 5) constant temperature and humidity indoor to cure, determinated the length of the 28d. And the changed value in length was from arithmetic average of three specimens. All technical indexes of the concrete test were shown in table 2. The test data showed that, concrete (No. DB) in water by 14d limited expansion ratio was , greater than the requirement of the specification [4] 1.5 x The tank wall (No. QB) and the expansion belt (No. JQD) parts of concrete expansive agent content than the bottom, limited expansion ratio can also achieve the expected design requirements ( and ). The QB s splitting tensile strength withpva - doped fiber is increased by 21.6%, which played important role in improving crack resistance ability. Table 2 The test technical indexes of various structural parts concrete of industry tank No. Rate of limited expansion and shrinkageε( 10-4 ) 3d 7d 14d 28d slump (mm) Compressive strength of 28d(Mpa) splitting tensile strength (MPa) DB QB JQD seepage height (mm)

3 Advanced Materials Research Vols Pressure permeability test data showed that, with the addition of PVA fiber concrete (QB) slab, seepage height ratio (DB) was decreased by 44%, because of the presence of concrete mixture bleeding to some extent, and characteristics of pore structure of concrete was improved in micro. At the same time, PVA fiber has characteristics of high strength, high modulus of elasticity, and has good hydrophilicity, can absorb small amounts of free water surface of the fiber, the bond strength to cement matrix was high. Through smeared crack effect of chaos fiber, the formation of matrix plastic shrinkage crack was inhibited. the ability of early cracking and compressive resistance of concrete was improved. Jointless design-construction and quality monitoring for the fiber reinforced concrete industry tank The combination of PVA fiber and expansion zone setting is applied in this industry tank, and the jointless design and continuous construction is successfully carried out, improve crack resistance of seepage. This project used expansion belt instead of post cast band in the additional stress concentration, enhanced compensation ability of contraction stress on temperature Jointless construction technology for the fiber reinforced concrete industry tank 1) The compounding requirements of PVA fiber reinforced concrete with low shrinkage was more stringent, therefore, experimental study was carried out before construction. Concrete mixing Stations was required in strict accordance with the experimentally determined, especially adding amount of expansive agent and fiber, the measurement devices were required very accurately, corrected before opening test, checked in use. 2)Vibrating mixing: the mixing time for concrete mixed with PVA fiber was extension than ordinary concrete of 60s. The concrete vibration should be uniform, dense, strictly control the vibration time, no vibration, vibration, leakage less vibration. The two vibration technology, plastering machine or manual wiping pressure were required 3 times to the surface of concrete before the final setting, in order to prevent surface cracks appeared. 3)Slump test: slump should meet the construction requirements, casting time interval should not exceed 1.5h, free fall distance should be controlled within 2m when pouring concrete. 4)Casting sequence: the construction method of taking stratified, hierarchical piecewise continuous casting top for slab concrete [5]. Time interval of adjacent concrete construction remain before the initial set of concrete, to avoid construction cold joints. 5)Curing: concrete pouring should be completed before the initial setting time, watering moist curing timely, ensure the hardening smoothly; Especially the wall and ceiling after pouring, curing period was not less than 14D. Leakage detection for the industry tank through water storage test After completing construction of this industry tank, anti permeability testing qualified according to the specification [6] before specimens in backfill soil, and the on-site sampling, compression concrete under the same curing condition were qualified too. This tank had a total of 3 cells, sequence storage test produces were tank one, tank two, pond in two production. each cell was filled with water, the first charged to the pool bottom construction joint, after checking the bottom plate and the construction joints with good quality of anti leakage. Determined water filling level by level scale, continue to water filling to 1/3 design water level as the first filled with water, second filled to 2/3 design water level, third filled to design water level, adjacent water filling time interval of two was 24h. Each tank area was required filling to design water level continuing 24h, then determinating of water leakage. 6 testing points for each cell, using water level probe (accuracy 0.1mm). Interval of each detection point between the initial and end reading was 24h, average reading of 6 testing points was accepted finally. Leakage detection results were shown in table 3.

4 876 Materials and Processes Technologies V Table 3 The water test leakage detection results of the underground industry tank percentage Lattice of tank water storage actual water Allowed water level(m) leakage(l/m 2. d) leakage(l/m 2 permited. d) (%) production tank middle tank production tank Seen from the storage test results, the actual water leakage was only 56%~60% allowed water leakage, mate the design and usage requirements. Conclusion 1) The splitting tensile strength for fiber reinforced concrete with low shrinkage was improved to a greater degree, which played an important role in anti cracking ability. 2) The expansion band was instead of post pouring belt to realize continuous casting, improved the integrity of the structure, especially on the waterproof requirement of industry tank. 3) Storage test showed that, impervious and anti crack performance mate design requirements. Up to now, the tank was built and put into use for more than a year, experienced four-season temperature cycle, there was no seepage crack. Acknowledgements This work was financially supported by the Science and Technology Project of the Ministry of Housing and Urban-Rural Development (2013-K4-37). References [1]Xinzhou Zhang: Petroleum refinery engineering Vol.35 (2005), p [2]Xiaoyong Nie,Ming NI: Zhejiang construction,vol.35 (2008),p [3]Pingyang Yie: Shanxi architecture,vol.47 (2009),p [4]JGJ/T : Technical specification for application of shrinkage-compensating concrete [S]. [5]Xiaozhu Luo,Tieli Cheng,Shaolian Lu: Zhejiang construction, Vol.26 (2009) p [6]SH/T :Specification for construction and acceptance of Petrochemical industry concrete pool[s].

5 Materials and Processes Technologies V / Compound and Engineering Application of Fiber Reinforced Concrete with Low Shrinkage /