Complex multifunctional additive (further, CA) which consists of aluminum powder, surfactant, salt-electrolyte (NaNO3) and calcium sulfate hemihydrate (CaSO4·0.5H2O) is proposed for ensuring necessary properties of anchoring grouts based on alkali-activated portland cement (further, AAPC) presented by the system «ordinary portland cement clinker - sodium metasilicate». Specified consistency of fresh AAPC mortar along with it strength after hardening are provided by water reducing due to application of modified polyethylene glycol characterized by stability of molecular structure in AAPC hydration medium. CA influence on shrinkage mitigation in AAPC mortar is explained both water-reducing effect and gas release with volume increasing during formation of dispersive-coagulation structure. Expansion of crystallization-condensation structure is ensured due to stress of calcium hydrosulfoaluminate 3CaO·Al2O3·3CaSO4·32H2O and calcium hydronitroaluminate 3CaO·Al2O3·Ca(NO3)2·10H2O which form due to presence of CaSO4·0,5H2O and NaNO3 in CA. Time matching of gas release with structure formation insures dense microstructure due to filling of pores by hydrated phases that causes lower excess stress during crystallization. CA ensures necessary performances of AAPC anchoring grout: consistency 190 mm; workability retention time 15 min; tensile strength in bending / compressive strength 6.1 / 25.7 MPa and 12.9 / 68.5 MPa in 1 d and 28 d agreeably; adhesion 0.9 MPa; linear extension up to +0.37 mm/m.
The paper is devoted to mitigation of steel reinforcement corrosion in alkali-activated slag cement (further, AASC) concretes, based on soluble sodium silicates (further, SSS's), obtained from high consistensy concrete mixes. Enhancement of AASC fine concretes crack resistance due to modification by complex shrinkage-reducing additives (further, SRA's) based on surfactants and trisodium phosphate Na3PO4 . 12H2O (further, TSP) was proposed for mitigation of steel reinforcement corrosion. SSS's were presented by sodium metasilicate (silica modulus 1.0, dry state) and water glass (silica modulus 2.9, density 1400 kg/m 3 ). In case of sodium metasilicate the application of SRA composition "ordinary portland cement clinker -TSP -sodium lignosulphonate -sodium gluconate" provides enhancement of crack resistance starting from early age structure formation with restriction of drying shrinkage from 0,984 to 0,713 mm/m after 80 d. The effect is caused by reduction of water and by higher volume of crystalline hydrates. In turn, SRA presented by compositions "TSP -glycerol" and "TSP -glycerol -polyacrylamide" provide enhancement of AASC fine concretes fracture toughness during late structure formation with increasing ratio of tensile strength in bending to compressive strength up to 37 -49 % if compare with the reference AASC when water glass is used.
Проаналiзовано сутнiсть проблеми власних деформацiй лужних цементiв (ЛЦ), ускладнення якої пов'язано з пiдвищеним вмiстом гелеподiбних гiдратних новоутворень. Як приклади розглянуто типи цементiв дiаметрально протилежнi за композицiйною будовою i вiдповiдно за вмiстом гелеподiбних фаз при гiдратацiї-лужний портландцемент (ЛПЦ) i шлаколужний цемент (ШЛЦ). Запропоновано пiдходи до формування ефективної структури штучного каменя, протидiючою деформацiям усадки, шляхом втручання в структуроутворення при використаннi комплексiв мiнеральних i органiчних сполук. Такi сполуки в складi комплексних органо-мiнеральних добавок сумiсно впливають на iнтенсифiкацiю кристалiзацiйних процесiв, формування ефективної порової структури та морфологiю гiдратних фаз при зменшеннi вмiсту води в штучному каменi. В якостi iнгредiєнтiв запропонованих комплексних добавок-модифiкаторiв розглянуто солi-електролiти рiзного анiонного типу та анiоноактивнi поверхнево-активнi речовини. Виявлено, що для модифiкацiї ЛПЦ найбiльш ефективною є система «сiль-електролiт-поверхнево-активна речовина». Показано, що модифiкацiя ЛПЦ комплексною добавкою цiєї системи на основi NaNO 3 забезпечує зменшення усадки з 0,406 до 0,017 мм/м. Натомiсть використання Na 2 SO 4 забезпечує цьому типу лужного цементу здатнiсть до розширення в межах 0,062 мм/м. Показано, що ефект компенсованої усадки модифiкованого ЛПЦ пов'язаний з бiльшою кристалiзацiєю низькоосновних гiдросилiкатiв (CSH(В)) i гiдроалюмiнатiв кальцiю (CaO•Al 2 O 3 •10H 2 O). Додатковий ефект пов'язаний з утворенням сульфатвмiщуючого натрiєво-кальцiєвого гiдроалюмiнату (для системи на основi Na 2 SO 4) та кристалiчного гiдронiтроалюмiнату кальцiю (для системи на основi NaNO 3) з вiдповiдним напруженням мiкроструктури. В розвиток для модифiкацiї ШЛЦ запропоновано комплексну добавку системи «портландцементний клiнкер-сiль-електролiт-поверхнево-активна речовина», яка забезпечує зменшення усадки з 0,984 мм/м до 0,683 мм/м. Мiнiмiзацiя усадки модифiкованого ШЛЦ пояснено формуванням поряд з низькоосновними гiдросилiкатами кальцiю гiдроалюмосилiкату натрiю типу гмелiнiту ((Na 2 Сa)•Al 2 •Si 4 •O 12 •6H 2 O) з пiдвищеним ступенем закристалiзованостi. При цьому вiдмiчено, що структура цементного каменя характеризується пiдвищеною щiльнiстю, однорiднiстю i монолiтнiстю гiдратних новоутворень Ключовi слова: лужний цемент, сiль-електролiт, комплексна органо-мiнеральна добавка, структуроутворення, власнi деформацiї, усадка
The peculiarity of alkali-activated slag cements (further, AASC’s) is increased proper deformations, which can cause increased cracking and reduced durability of structure. The paper is devoted to manage AASC’s proper deformations. The main task was to determine the composition of complex additives (further, CA’s) in system «ordinary portland cement (further, OPC) clinker - mineral compound of different anionic type - surfactant» in presence of sodium metasilicate (further, MS) to affect on hydrated AASC performance while ensuring effective structure of artificial stone by criterion of shrinkage deformations. Comparative analysis of hydrated cement systems "OPC clinker - MS", "OPC clinker - mineral compound - MS" and "OPC clinker - mineral compound - MS - surfactant" showed that the greatest effect on reduction of proper deformations occurs when the mineral compounds relate to electrolytes, i.e. Na2SO4 and NaNO3. Hydrated system is characterized by expansion (+0,062 mm/m) in presence of Na2SO4. Almost no shrinkage is supplied by application of NaNO3 (-0,062 mm/m). The obtained CA’s were tested in AASC. CA in the system “OPC clinker - NaNO3 - surfactant” provides the initial setting 43 min, the end - 65 min with accelerated strength. Investigated AASC can be classified as non-shrinking cement. This phenomena is ensured by increasing density, homogeneity and monolithicity of hydrosilicate formations, as well as due to formation of hydroaluminosilicate structures with different morphology by inclusion of nitrate anions.
Optimization of complex shrinkage-reducing additives (further, SRA’s), consisting of ordinary portland cement clinker (further, OPC clinker), salt-electrolyte and surfactants, is provided for prevention of steel reinforcement corrosion due to shrinkage mitigation in alkali-activated slag cement (further, AASC) fine concrete. Modification of AASC by SRA included 0.3 % sodium lignosulphonate, 0.15 % sodium gluconate, 1.4 – 2.0 % NaNO3 and 6.5 - 7.7 % OPC clinker (by mass of granulated blast furnace slag) provides shrinkage reduction from 0.984 up to 0.560 – 0.605 mm/m (t=202 °С, R.H.=65 %). Unlike, SRA presented by the mentioned system with 1.50 - 1.59 % Na2SO4 and 4.0 - 4.65 % OPC clinker causes shrinkage mitigation from down to 0.625 - 0.640 mm/m. In addition, SRA with 1.80 - 2.05 % Na3PO4 and 4.0 - 4.6 % OPC clinker minimizes shrinkage to 0.713 - 0.700 mm/m. Shrinkage mitigation in modified AASC fine concrete is explained by less water, higher crystallinity of hydrated phases as well as by formation of minamiit (Na,Ca0.5)Al3(SO4)2(OH)6, calcium hydronitroaluminate ЗСаО∙А12О3∙Са (NO3)2∙10Н2О and calcium hydroxylapatite Са10(РО4)6(ОН)2 crystals versus salt-electrolyte, i.e. Na2SO4, NaNO3 and Na3PO4 agreeably. The 28 day compressive strength of modified AASC fine concrete is not less than the reference one (48.0 - 56.0 МPа).
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